11.1 Introduction Modified atmosphere packaging (MAP) may be defined as ‘the enclosure of food products in gas-barrier materials, in which the gaseous environment has been changed’ (Young et al., 1988). Because of its substantial shelf-life extending effect, MAP has been one of the most significant and innovative growth areas in retail food packaging. The potential advantages and disadvantages of MAP have been presented by Farber (1991), Parry (1993) and Davies (1995). Whilst there is considerable information available regarding suitable gas mixtures for different food products, there is still a lack of scientific detail regarding many aspects relating to MAP. These include: ? mechanism of action of carbon dioxide (CO 2 ) on microorganisms ? safety of MAP packaged food products ? effect of MAP on the nutritional quality of packaged food products. Current research and gaps in knowledge are discussed in the following sections. 11.2 Carbon dioxide as an antimicrobial gas The gases that are applied in MAP today are basically O 2 ,CO 2 and N 2 . The last has no specific preservative effect but functions mainly as a filler gas to avoid the collapse that takes place when CO 2 dissolves in the food product. CO 2 , because of its antimicrobial activity, is the most important component in applied gas mixtures. When CO 2 is introduced into the package, it is partly dissolved in 11 MAP, product safety and nutritional quality F. Devlieghere and J. Debevere, Ghent University, Belgium and M I Gil, CEBAS-CSIC, Spain the water phase and the fat phase of the food. This results, after equilibrium, in a certain concentration of dissolved CO 2 ([CO 2 ] diss ) in the water phase of the product. Devlieghere et al. (1998) have demonstrated that the growth inhibition of microorganisms in modified atmospheres is determined by the concentration of dissolved CO 2 in the water phase. The effect of the gaseous environment on microorganisms in foods is not as well understood by microbiologists and food technologists as are other external factors, such as pH and a w . Despite numerous reports of the effects of CO 2 on microbial growth and metabolism, the ‘mechanism’ of CO 2 inhibition still remains unclear (Dixon and Kell, 1989; Day, 2000). The question of whether any specific metabolic pathway or cellular activity is critically sensitive to CO 2 inhibition has been examined in several studies. The different proposed mechanisms of action are: 1. Lowering the pH of the food. 2. Cellular penetration followed by a decrease in the cytoplasmic pH of the cell. 3. Specific actions on cytoplasmic enzymes. 4. Specific actions on biological membranes. When gaseous CO 2 is applied to a biological tissue, it first dissolves in the liquid phase, where hydration and dissociation lead to a rapid pH decrease in the tissue. This drop in pH, which depends on the buffering capacity of the medium (Dixon and Kell, 1989), is not large in food products. In fact, the pH drop in cooked meat products only amounted to 0.3 pH units when 80% of CO 2 was applied in the gas phase with a gas/product volume ration of 4:1 (Devlieghere et al., 2000b). Several studies have proved that the observed inhibitory effects of CO 2 could not solely be explained by the acidification of the substrate (Becker, 1933; Coyne, 1933). Many researchers have documented the rapidity with which CO 2 in solution penetrates into the cell. Krogh (1919) discovered that this rate is 30 times faster than for oxygen (O 2 ) under most circumstances. Wolfe (1980) suggested the inhibitory effects of CO 2 are the result of internal acidification of the cytoplasm. Eklund (1984) supported this idea by pointing out that the growth inhibition of four bacteria obtained with CO 2 had the same general form as that obtained with weak organic acids (chemical preservatives), such as sorbic and benzoic acid. Tan and Gill (1982) also found that the intracellular pH of Pseudomonas fluorescens fell by approximately 0.03 units for each 1 mM rise in extracellular CO 2 concentration. CO 2 may also exert its influence upon a cell by affecting the rate at which particular enzymatic reactions proceed. One way this may be brought about is to cause an alteration in the production of a specific enzyme, or enzymes, via induction or repression of enzyme synthesis (Dixon, 1988; Dixon and Kell, 1989; Jones, 1989). It was also suggested (Jones and Greenfield, 1982; Dixon and Kell, 1989) that the primary sites where CO 2 exerts its effects are the enzymatic carboxylation and decarboxylation reactions, although inhibition of other enzymes has also been reported (Jones and Greenfield, 1982). MAP, product safety and nutritional quality 209 Another possible factor contributing to the growth-inhibitory effect of CO 2 could be an alteration of the membrane properties (Daniels et al., 1985; Dixon and Kell, 1989). It was suggested that CO 2 interacts with lipids in the cell membrane, decreasing the ability of the cell wall to uptake various ions. Moreover, perturbations in membrane fluidity, caused by the disordering of the lipid bilayer, are postulated to alter the function of membrane proteins (Chin et al., 1976; Roth, 1980). Studies examining the effect of a CO 2 enriched atmosphere on the growth of microorganisms are often difficult to compare because of the lack of information regarding the packaging configurations applied. The gas/product volume ratio and the permeability of the applied film for O 2 and CO 2 will influence the amount of dissolved CO 2 and thus the microbial inhibition of the atmosphere. For this reason, the concentration of dissolved CO 2 in the aqueous phase of the food should always be measured and mentioned in publications concerning MAP (Devlieghere et al., 1998). Only a few publications deal with the effect of MAP on specific spoilage microorganisms. Gill and Tan (1980) compared the effect of CO 2 on the growth of some fresh meat spoilage bacteria at 30oC. Molin (1983) determined the resistance to CO 2 of several food spoilage bacteria. Boskou and Debevere (1997; 1998) investigated the effect of CO 2 on the growth and trimethylamine production of Shewanella putrefaciens in marine fish, and Devlieghere and Debevere (2000) compared the sensitivity for dissolved CO 2 of different spoilage bacteria at 7oC. In general, Gram-negative microorganisms such as Pseudomonas, Shewanella and Aeromonas are very sensitive to CO 2 . Gram- positive bacteria show less sensitivity and lactic acid bacteria are the most resistant. Most yeasts and moulds are also sensitive to CO 2 . The effect of CO 2 on psychrotrophic food pathogens is discussed in Section 11.3. 11.3 The microbial safety of MAP: Clostridium botulinum and Listeria monocytogenes Modified atmospheres containing CO 2 are effective in extending the shelf-life of many food products. However, one major concern is the inhibition of normal aerobic spoilage bacteria and the possible growth of psychrotrophic food pathogens, which may result in the food becoming unsafe for consumption before it appears to be organoleptically unacceptable. Most of the pathogenic bacteria can be inhibited by low temperatures (<7oC). At these conditions, only psychrotrophic pathogens can proliferate. The effect of CO 2 on the different psychrotrophic foodborne pathogens is described below. A particular concern is the possibility that psychrotrophic, non-proteolytic strains of C. botulinum types B, E and F are able to grow and produce toxins under MAP conditions. Little is known about the effects of modified atmosphere storage conditions on toxin production by C. botulinum. The possibility of inhibiting C. botulinum by incorporating low levels of O 2 in the package does 210 Novel food packaging techniques not appear to be feasible. Miller (1988, cited by Connor et al., 1989) reported that psychrotrophic strains of C. botulinum are able to produce toxins in an environment with up to 10% O 2 . Toxin production by C. botulinum type E, prior to spoilage, has been described in three types of fish, at O 2 levels of 2% and 4% (O’Connor-Shaw and Reyes, 2000). Dufresne et al. (2000) also proposed that additional barriers, other than headspace O 2 and film, need to be considered to ensure the safety of MAP trout fillets, particularly at moderate temperature abuse conditions. The probability of one spore of non-proteolytic C. botulinum (types B, E and F) being toxicogenic in rock fish was outlined in a report by Ikawa and Genigeorgis (1987). The results showed that the toxigenicity was significantly affected (P<0.005) by temperature and storage time, but not by the used modified atmosphere (vacuum, 100% CO 2 , or 70% CO 2 /30% air). In Tilapia fillets, a modified atmosphere (75% CO 2 /25% N 2 ), at 8oC, delayed toxin formation by C. botulinum type E, from 17 to 40 days, when compared to vacuum packaged fillets (Reddy et al., 1996). Similar inhibiting effects were recorded for salmon fillets and catfish fillets, at 4oC (Reddy et al., 1997a and 1997b). Toxin production from non-proteolytic C. botulinum type B spores was also retarded by a CO 2 enriched atmosphere (30% CO 2 /70% N 2 ) in cooked turkey at 4oC but not at 10oC nor at 15oC (Lawlor et al., 2000). Recent results in a study by Gibson et al. (2000) also indicated that 100% CO 2 slows the growth rate of C. botulinum, and that this inhibitory effect is further enhanced with appropriate NaC1 concentrations and chilled temperatures. Listeria monocytogenes is considered a psychrotrophic foodborne pathogen. Growth is possible at 1oC (Varnam and Evans, 1991) and has even been reported at temperatures as low as 1.5C (Hudson et al., 1994). The growth of L. monocytogenes in food products, packaged under modified atmospheres, has been the focus of several, although in some cases contradicting, studies (Garcia de Fernando et al., 1995). In general, L. monocytogenes is not greatly inhibited by CO 2 enriched atmospheres (Zhao et al., 1992) although when combined with other factors such as low temperature, decreased water activity and the addition of Na lactate the inhibiting effect of CO 2 is significant (Devlieghere et al., 2001). Listeria growth in anaerobic CO 2 enriched atmosphere has been demonstrated in lamb in an atmosphere of 50:50 CO 2 /N 2 , at 5oC (Nychas, 1994); in frankfurter type sausages in atmospheres of distinct proportions of CO 2 /N 2 , at 4, 7 and 10oC (Kra¨mer and Baumgart, 1992) and in pork in an atmosphere of 40:60 CO 2 /N 2 , at 4oC (Manu-Tawiah et al., 1993). However, other authors have not detected growth in chicken anaerobically packaged in 30:70 CO 2 /N 2 , at 6oC (Hart et al., 1991); in 75:25 CO 2 /N 2 at 4oC (Wimpfheimer et al., 1990) and at 4oC in 100% CO 2 in raw minced meat (Franco-Abuin et al., 1997) or in buffered tryptose broth (Szabo and Cahill, 1998). Several investigations demonstrated possible growth of L. monocytogenes on modified atmosphere packaged fresh-cut vegetables, although the results depended very much on the type of vegetables and the storage temperature (Berrang et al., 1989a; Beuchat and Brackett, 1990; Omary et al., 1993; Carlin et al., 1995; MAP, product safety and nutritional quality 211 Carlin et al., 1996a and 1996b; Zhang and Farber, 1996; Juneja et al., 1998; Bennick et al., 1999; Jacxsens et al., 1999; Liao and Sapers, 1999; Thomas et al., 1999; Castillejo-Rodriguez et al., 2000). There is no agreement about the effect of incorporating O 2 in the atmosphere on the antimicrobial activity of CO 2 on L. monocytogenes (Garcia de Fernando et al., 1995). However, this effect could be very important in practice, as the existence of residual O 2 levels after packaging, and the diffusion of O 2 through the packaging film, can result in substantial O 2 levels during the storage of industrially ‘anaerobically’ modified atmosphere packaged food products. Most publications suggest there is a decrease in the inhibitory effect of CO 2 on L. monocytogenes when O 2 is incorporated into the atmosphere. Experiments on raw chicken showed L. monocytogenes failed to grow at 4, 10 and 27oC, in an anaerobic atmosphere containing 75% CO 2 and 25% N 2 (Wimpfheimer et al., 1990). However, an aerobic atmosphere containing 72.5% CO 2 , 22.5% N 2 , and 5% O 2 did not inhibit the growth of L. monocytogenes, even at 4oC. L. monocytogenes was also only minimally inhibited on chicken legs, in an atmosphere containing 10% O 2 and 90% CO 2 (Zeitoun and Debevere, 1991). There was no significant difference in the inhibitory effect of CO 2 , between the range of 0% and 50%, when 1.5% O 2 , or 21% O 2 was present in the atmosphere of gas packaged brain heart infusion agar plates (Bennik et al. 1995). When L. monocytogenes was cultured in buffered nutrient broth, at 7.5oC, in atmospheres containing 30% CO 2 , with four different O 2 concentrations (0, 10, 20 and 40%), the results showed that bacterial growth increased with the increasing O 2 concentrations (Hendricks and Hotchkiss, 1997). 11.4 The microbial safety of MAP: Yersinia enterocolitica and Aeromonas spp. Yersinia enterocolitica is generally regarded as one of the most psychrotrophic foodborne pathogens. Growth of Y. enterocolitica was reported in vacuum packaged lamb at 0oC (Doherty et al., 1995; Sheridan and Doherty, 1994; Sheridan et al., 1992), beef at 2oC (Gill and Reichel, 1989), pork at 4oC (Bodnaruk and Draughon, 1998; Manu-Tawiah et al., 1993), fresh chicken breasts (O ¨ zbas et al., 1997) and roast beef at 3oC but not at 1.5oC (Hudson et al., 1994). CO 2 retards the growth of Y. enterocolitica at refrigerated temperatures. The effect of CO 2 on the growth of Y. enterocolitica has been described by several authors. Some of the results are shown in Table 11.1. Oxygen also seems to play an inhibiting role on the growth of Y. enterocolitica (Garcia de Fernando et al., 1995). To ensure total inhibition of Y. enterocolitica in O 2 poor atmospheres and at realistic temperatures throughout the cooling chain, high CO 2 concentrations in the headspace are necessary. Aeromonas species are able to multiply in food products stored in refrigerated conditions. Growth of A. hydrophila has been detected at low temperatures in a 212 Novel food packaging techniques variety of vacuum packaged fresh products, such as chicken breasts at 3oC (O ¨ zbas et al., 1996), lamb at 0oC under high pH conditions (Doherty et al., 1996), and at 2oC (Gill and Reichel, 1989), and in sliced roast beef at 1.5oC (Hudson et al., 1994). Devlieghere et al. (2000a) developed a model, predicting the influence of temperature and CO 2 on the growth of A. hydrophila. Proliferation of A. hydrophila is greatly affected by CO 2 enriched atmospheres. Some reports regarding the effect of CO 2 on the growth of A. hydrophila on meat are summarised in Table 11.2. In a study by Berrang et al. (1989b), regarding controlled atmosphere storage of broccoli, cauliflower and asparagus stored at 4oC and 15oC, fast proliferation of A. hydrophila was observed at both temperatures, but growth was not significantly affected by gas atmosphere. Garcia-Gimeno et al. (1996) published the survival of A. hydrophila on mixed vegetable salads (lettuce, red cabbage and carrots) Table 11.1 Growth of Yersina enterocolitica in different atmospheres Product pH Temp. Storage Atmosphere Increase Reference type (oC) time (%O 2 / (log (days) CO 2 /N 2 ) cfu/g) Beef >6.0 2 126 0/100/0 0 Gill and 63 vacuum 2.4 Reichel 0 98 0/100/0 0 (1989) 49 vacuum 4.1 2 42 0/100/0 0 35 vacuum 5.1 5 35 0/100/0 1.9 17 vacuum 5.5 10 10 0/100/0 3.4 5 vacuum 4.0 Sliced 6.1 1.5 112 0/100/0 0 Hudson et al. roast beef 56 vacuum 4.2 (1994) 3 70 0/100/0 3.8 21 vacuum 4.7 Pork 5.57 30 0/100/0 0 Bodnaruk and (normal) 4 25 vacuum 1.7 Draughon 6.21 30 0/100/0 1.7 (1998) (high) 25 vacuum 2.6 Pork 6.0 35 0/20/80 4.1 Manu- chops 4 35 0/40/60 4.0 Tawiah et al. 35 10/40/50 4.0 (1993) 35 vacuum 4.1 Lamb 5.4–5.8 0 28 80/20/0 1.2 Doherty et al. 28 0/50/50 3.9 (1995) 28 0/100/0 1.6 28 vacuum 5.9 28 80/20/0 6.8 28 0/50/50 8.5 28 0/100/0 5.6 28 vacuum 8.1 MAP, product safety and nutritional quality 213 packaged under MA (initial 10% of O 2 -10% CO 2 , after 48h 0% O 2 -18% CO 2 ) and stored at 4oC while at 15oC a fast growth was noticed (5 log units in 24h). The combination of high CO 2 concentration and low temperature was revealed as responsible for the inhibition of growth. Bennik et al. (1995) concluded from their solid-surface model that at MA-conditions, generally applied for minimally processed vegetables (1–5% O 2 and 5–10% CO 2 ), growth of A. hydrophila is possible. Growth was virtually the same under 1.5% and 21% O 2 . The behaviour of a cocktail of A. caviae (HG4) and A. bestiarum (HG2) in air or in low O 2 -low CO 2 atmosphere was investigated in fresh-cut vegetables: no difference between both atmospheres was observed on grated carrots, a decreased growth on shredded Belgian endive and Brussels sprouts in MA but an increased growth on shredded iceberg lettuce in MA storage (Jacxsens et al., 1999). Table 11.2 Growth of Aeromonas hydrophila in different atmospheres Product pH Temp. Storage Atmosphere Increase Reference type (oC) time (%O 2 / (log (days) CO 2 /N 2 ) cfu/g) Beef >6.0 2 126 0/100/0 0 Gill and 63 vacuum 1.0 Reichel 0 98 0/100/0 0 (1989) 49 vacuum 3.1 2 42 0/100/0 0 35 vacuum 3.0 5 35 0/100/0 0 17 vacuum 3.0 10 10 0/100/0 3.8 5 vacuum 5.8 Sliced 6.1 1.5 112 0/100/0 0 Hudson et al. roast beef 56 vacuum 4.3 (1994) 3 70 0/100/0 3.1 21 vacuum 4.6 Lamb 5.4–5.8 0 45 80/20/0 0 Doherty et al. 45 0/50/50 0 (1996) 45 0/100/0 0 45 vacuum 0 5 45 80/20/0 0 45 0/50/50 0 45 0/100/0 0 45 vacuum 0 Lamb >6.0 0 42 80/20/0 0 Doherty et al. 42 0/50/50 0 (1996) 42 0/100/0 0 42 vacuum 4.1 5 42 80/20/0 4.2 42 0/50/50 1.7 42 0/100/0 0 42 vacuum 4.0 214 Novel food packaging techniques 11.5 The effect of MAP on the nutritional quality of non- respiring food products By using modified atmosphere packaging, the shelf-life of the packaged products can be extended by 50–200%, however, questions could arise regarding the nutritional consequences of MAP on the packaged food products. This section will discuss the effect of MAP on the nutritional quality of non-respiring food products while the effect of MAP on the nutritional value of respiring products, such as fresh fruits and vegetables, will be discussed in detail in the following sections. Very little information is available about the influence of MAP on the nutritional quality of non-respiring food products. In most cases, for packaging non-respiring food products, oxygen is excluded from the atmosphere and therefore one should expect a retardation of oxidative degradation reactions. Moreover, modified atmosphere packaged food products should be stored under refrigeration to allow CO 2 to dissolve and perform its antimicrobial action. At these chilled conditions, chemical degradation reactions have only a limited importance. No information is available regarding the nutritional consequences of enriched oxygen concentrations in modified atmospheres which can be applied for packaging fresh meat and marine fish. Some oxidative reactions can occur with nutritionally important compounds such as vitamins and polyunsaturated fatty acids. However, no quantitative information is available about these degradation reactions in products packaged in O 2 enriched atmospheres. 11.6 The effect of MAP on the nutritional quality of fresh fruits and vegetables: vitamin C and carotenoids During the last few years many studies have demonstrated that fruit and vegetables are rich sources of micronutrients and dietary fibre. They also contain an immense variety of biologically active secondary metabolites that provide the plant with colour, flavour and sometimes antinutritional or toxic properties (Johnson et al., 1994). Among the most important classes of such substances are vitamin C, carotenoids, folates, flavonoids and more complex phenolics, saponins, phytosterols, glycoalkaloids and the glucosinolates. The nutrient content of fruit and vegetables can be influenced by various factors such as genetic and agronomic factors, maturity and harvesting methods, and postharvest handling procedures. There are some postharvest treatments which undoubtedly improve food quality by inhibiting the action of oxidative enzymes and slowing down deleterious processes. Storage of fresh fruits and vegetables within the optimum range of low O 2 and/or elevated CO 2 atmospheres for each commodity reduces their respiration and C 2 H 4 production rates (Kader, 1986; Kader, 1997). Optimum CA retards loss of chlorophyll, biosynthesis of carotenoids and anthocyanins, and biosyntheses and oxidation of phenolic compounds. MAP, product safety and nutritional quality 215 In general, CA influences flavour quality by reducing loss of acidity, starch to sugar conversion, and biosynthesis of aroma volatiles, especially esters. Retention of ascorbic acid and other vitamins results in better nutritional quality, including antioxidant activity, of fruits and vegetables when kept in their optimum CA (Kader, 2001). However, little information is available on the effectiveness of controlled atmospheres or modified atmosphere packaging (CA/ MAP) on nutrient retention during storage. The influence of CA/MAP on the antioxidant constituents related to nutritional quality of fruits and vegetables, including vitamin C, carotenoids, phenolic compounds, as well as glucosinolates will be reviewed here. 11.6.1 Vitamin C Vitamin C is one of the most important vitamins in fruits and vegetables for human nutrition. More than 90% of the vitamin C in human diets is supplied by the intake of fresh fruits and vegetables. Vitamin C is required for the prevention of scurvy and maintenance of healthy skin, gums and blood vessels. Vitamin C, as an antioxidant, reduces the risk of arteriosclerosis, cardiovascular diseases and some forms of cancer (Simon, 1992). Ascorbic oxidase has been proposed as the major enzyme responsible for enzymatic degradation of L -ascorbic acid (AA). The oxidation of AA, the active form of vitamin C, to dehydroascorbic acid (DHA) does not result in loss of biological activity since DHA is readily re- converted to L -AA in vivo. However, DHA is less stable than AA and may be hydrolysed to 2,3-diketogulonic acid, which does not have physiological activity (Klein, 1987) and it has therefore been suggested that measurements of vitamin C in fruits and vegetables in relation to their nutritional value should include both AA and DHA. The vulnerability of different fruits and vegetables to oxidative loss of AA varies greatly, as indeed do general quality changes. Low pH fruits (citrus fruits) are relatively stable, whereas soft fruits (strawberries, raspberries) undergo more rapid changes. Leafy vegetables (e.g. spinach) are very vulnerable to spoilage and AA loss, whereas root vegetables (e.g. potatoes) retain quality and AA for many months (Davey et al., 2000). Fruits and vegetables undergo changes from the moment of harvest and since L -AA is one of the more reactive compounds it is particularly vulnerable to treatment and storage conditions. In broad terms, the milder the treatment and the lower the temperature the better the retention of vitamin C, but there are several interacting factors that affect AA retention (Davey et al., 2000). The rate of postharvest oxidation of AA in plant tissues has been reported to depend upon several factors such as temperature, water content, storage atmosphere and storage time (Lee and Kader, 2002). The effect of controlled atmospheres on the ascorbate content of intact fruit has not been extensively studied. The results vary among fruit species and cultivars, but the tendency is for reduced O 2 and/or elevated CO 2 levels to enhance the retention of ascorbate (Weichmann, 1986; Kader et al., 1989). A reduction in temperature and of O 2 concentration in the storage atmosphere have 216 Novel food packaging techniques been described as the two treatments which contribute to preserve vitamin C in fruits and vegetables (Watada, 1987). Delaporte (1971) and others observed that loss of AA can be reduced by storing apples in a reduced oxygen atmosphere. However, Haffner et al. (1997) have shown that AA levels in various apple cultivars decreased more under ultra low oxygen (ULO) compared to air storage. On the other hand, increasing CO 2 concentration above a certain threshold seems to have an adverse effect on vitamin C content in some fruits and vegetables. It has been reported that the effect of elevated CO 2 level and storage temperature and duration (Weichmann, 1986). Bangerth (1977) observed accelerated AA losses in apples and red currants stored in elevated CO 2 atmospheres. Vitamin C content was reduced by high CO 2 concentrations (10– 30% CO 2 ) in strawberries and blackberries and only a moderate to negligible effect was found for black currants, red currants and raspberries (Agar et al., 1997). Storage of sweet pepper for six days at 13oC in CO 2 enriched atmospheres resulted in a reduction in AA content (Wang, 1977). Wang (1983) noted that 1% O 2 retarded AA degradation in Chinese cabbage stored for three months at 0oC. He observed that treatments with 10 or 20% CO 2 for five or ten days produced no effect, and 30 or 40% CO 2 increased AA decomposition. Veltman et al. (1999) have observed a 60% loss in AA content of ‘Conference’ pears after storage in 2% O 2 + 10% CO 2 . There were no data available to show whether a parallel reduction in O 2 concentration alleviates the negative CO 2 effect. Agar et al. (1997) proposed that reducing O 2 concentration in the storage atmosphere in the present of high CO 2 had little effect on the vitamin C preservation. The only beneficial effect of low O 2 alleviating the CO 2 effect could be observed when applying CO 2 concentrations lower than 10%. In fresh-cut products, high CO 2 concentration in the storage atmosphere has also been described to cause degradation of vitamin C. Thus, concentrations of 5, 10 or 20% CO 2 caused degradation of vitamin C in fresh-cut kiwifruit slices (Agar et al., 1999). Enhanced losses of vitamin C in response to CO 2 higher than 10% may be due to the stimulating effects on oxidation of AA and/or inhibition of DHA reduction to AA (Agar et al., 1999). In addition, vitamin C content decreased in MAP-stored Swiss chard (Gil et al., 1998a) as well as in potato strips (Tudela et al., 2002). In contrast, MAP retarded the conversion of AA to DHA that occurred in air-stored jalapeno pepper rings (Howard et al., 1994; Howard and Hernandez-Brenes 1998). Wright and Kader (1997a) found no significant losses of vitamin C occurred during the post-cutting life of fresh-cut strawberries and persimmons for eight days in CA (2% O 2 , air + 12% CO 2 , or 2% O 2 + 12% CO 2 ) at 0oC. In studies of cut broccoli florets and intact heads of broccoli CA/MAP resulted in greater AA retention and shelf-life extension in contrast to air-stored samples (Barth et al., 1993; Paradis et al., 1996). Retention of AA was found in fresh-cut lettuce packaged with nitrogen (Barry-Ryan and O’Beirne, 1999). They suggest that high levels of CO 2 (30–40%) increased AA losses by conversion into DHA due to availability of oxygen in lettuce (Barry-Ryan and MAP, product safety and nutritional quality 217 O’Beirne, 1999). This fact has also been shown in sweet green peppers (Petersen and Berends, 1993). The reduction of AA and the relative increase in DHA could be an indication that high CO 2 stimulates the oxidation of AA, probably by ascorbate peroxidase as in the case of strawberries (Agar et al., 1997) and of spinach (Gil et al., 1999). Mehlhorn (1990) demonstrated an increase in ascorbate peroxidase activity in response to ethylene. High CO 2 at injurious concentrations for the commodity may reduce AA by increasing ethylene production and therefore the activity of ascorbate peroxidase. Ascorbate oxidase from green zucchini fruit, which catalyses the oxidation of AA to DHA, has been found to be unstable and to lose activity below pH 4 (Maccarrone et al., 1993). This could partially explain the lower DHA content of the strawberries (pH 3.4–3.7) and the higher DHA content of the persimmons (pH 5.4–6.0) (Wright and Kader, 1997a) as well as the tendency of some vegetables at pH near to neutral to lose AA during storage (Gil et al., 1998b). In conclusion, the loss of vitamin C after harvest can be reduced by storing fruits and vegetables in atmosphere of reduced O 2 and/or up to 10% CO 2 as Lee and Kader (2002) have reported. CA conditions do not have a beneficial effect on vitamin C if high CO 2 concentrations are involved, although the concentrations above which CO 2 affects the loss of AA must be estimated for each commodity (Kader, 2001). 11.6.2 Carotenoids Carotenoids form one of the more important classes of plant pigments and play a crucial role in defining the quality parameters of fruit and vegetables. Their role in the plant is to act as accessory pigments for light harvesting and in the prevention of photo-oxidative damage, as well as acting as attractants for pollinators. The best documented and established function of some of the carotenoids is their provitamin A activity, especially of -carotene. A-Carotene and -crytozanthin also possess provitamin A activity, but to a lesser extent than does -carotene. Many yellow, orange or red fruit and root vegetables contain large amounts of carotenoids, which accumulate in the chloroplast during ripening or maturation. In some cases, the carotenoids present are simple, e.g. - carotene in carrot or lycopene in tomato, but in other cases complex mixtures of unusual structures are found, e.g. in Capsicum. Carotenoids are found in membranes, as microcrystals, in association with proteins or in oil droplets. In vivo, carotenoids are stabilised by these molecular interactions, that are also important in determining the bioavailability of the carotenoids. Plant materials do not contain vitamin A, but provide carotenoids that are converted to vitamin A after ingestion. Provitamin A carotenoids found in significant quantitites in fruits may have a role in cancer prevention by acting as free radical scavengers (Britton and Hornero-Mendez, 1997). Lycopene, although it has no provitamin A activity, has been identified as a particularly effective quencher of singlet oxygen in vitro (Di Mascio et al., 1989) and as an anticarcinogenic (Giovannucci, 1999). Carotenoids are unstable when exposed 218 Novel food packaging techniques to acidic pH, oxygen or light (Klein, 1987). The effect of controlled and modified atmospheres on the carotenoid content of intact fruits has not been well studied. Modified atmospheres including either reduced O 2 or elevated CO 2 are generally considered to reduce the loss of provitamin A, but also to inhibit the biosynthesis of carotenoids (Kader et al., 1989). Reducing O 2 to lower concentrations enhanced the retention of carotene in carrots (Weichmann, 1986). The carotene content of leeks was found to be higher after storage in 1% O 2 + 10% CO 2 than after storage in air (Weichmann, 1986). Few studies on the effect of CA storage on the provitamin A carotenoid content of fresh-cut products have been published. Wright and Kader (1997b) found for sliced peaches and persimmons, that the limit of shelf-life was reached before major losses of carotenoids occurred. Low changes in carotenoids have been observed in minimally processed pumpkin stored for 25 days at 5oC in MAP (Baskaran et al., 2001). Petrel et al. (1998) found no changes on the carotenoid content of ready to eat oranges after 11 days at 4oC in MAP (19% O 2 + 5% CO 2 and 3% O 2 + 25% CO 2 ). In addition, the content of -carotene in broccoli florets increased at the end of CA storage (2% O 2 + 6% CO 2 ) and remained stable after returning the samples to ambient conditions for 24 h (Paradis et al, 1996). Lutein, the major carotenoid in green bean tissue, also showed an accumulation after 13 days of CA storage (1% O 2 + 3% CO 2 ) and in these conditions retained carotenoids up to 22 days at 8oC (Cano et al., 1998). However, Sozzi et al. (1999) have observed that CA of 3% O 2 and 20% CO 2 both alone and together with ethylene prevented total carotenoid and lycopene biosynthesis on tomato. After exposing the fruits to air, total carotenoids and lycopene increased but were in all cases significantly lower than those which were held in air. 11.7 The effect of MAP on the nutritional quality of fresh fruits and vegetables: phenolic compounds and glucosinolates 11.7.1 Phenolic compounds There is considerable evidence for the role of antioxidant constituents of fruits and vegetables in the maintenance of health and disease prevention (Ames et al., 1993). Epidemiological studies show that consumption of fruits and vegetables with high phenolic content correlates with reduced cardio- and cerebrovascular diseases and cancer mortality (Hertog et al., 1997). Recent work is also beginning to highlight the relation of flavonoids and other dietary phenolic constituents to these protective effects. They act as antioxidants by virtue of the free radical scavenging properties of their constituent hydroxyl groups (Kanner et al., 1994; Vinson et al., 1995). The biological properties of phenolic com- pounds are very variable and include anti-platelet action, antioxidant, antiinflamatory, antiumoral and oestrogenic activities, which might suggest their potential in the prevention of coronary heart diseases and cancer (Hertog et al., 1993; Arai et al., 2000). MAP, product safety and nutritional quality 219 In the last few years there has been an increasing interest in determining relevant dietary sources of antioxidant phenolics and red fruits such as strawberries, cherries, grapes and pomegranates have received considerable attention due to their antioxidant activity. However, storage under CA/MAP conditions has been focused on keeping the visual properties and few studies have been made on the effect on the nutritional quality. Generally an increase in phenolics is considered a positive attribute and enhances the nutritional value of plant product. However, many secondary metabolites typical of wild species of fruits or vegetables have toxic effects although they are not considered here. In addition, the organoleptic and nutritional characteristics of fruit and vegetables are strongly modified by the appearance of brown pigments. Oxidative browning is mainly due to the enzyme polyphenol oxidase (PPO) which catalyses the hydroxylation of monophenols to o-diphenols and, in a second step, the oxidation of colourless o-diphenols to highly coloured o-quinones (Va′mos- Vigya′zo′, 1981). The o-quinones non-enzymatically polymerise and give rise to heterogeneous black, brown or red pigments called melanins decreasing the organoleptic and nutritional qualities (Toma′s-Barbera′n et al., 1997; Toma′s- Barbera′n and Espin, 2002). Controlled atmospheres and modified atmosphere packaging (MAP) can directly influence the phenolic composition as reflected in the changes observed in anthocyanins. Carbon dioxide-enriched atmospheres (>20%) used to reduce decay and extend the postharvest life of strawberries induced a remarkable decrease in anthocyanin content of internal tissues compared with the external ones (Gil et al., 1997). Holcroft and Kader (1999) related the decrease in strawberry colour under CO 2 atmosphere, with a decrease of important enzyme activity involved in the biosynthesis of anthocyanins, phenylalanine ammonialyase (PAL; EC 4.3.1.5) and glucosyltransferase (GT; EC 2.4.1.9.1). A moderated CO 2 atmosphere (10%) prolongs the storage life and maintains quality and adequate red colour intensity of pomegranate arils (Holcroft et al., 1998). However, the arils of pomegranates stored in air were deeper red than were those of the initial controls and of those stored in a CO 2 enriched atmosphere. Modified atmospheres can also have a positive effect on phenolic-related quality, as in the case of the prevention of browning of minimally processed lettuce (Saltveit, 1997; Gil et al., 1998b). In addition, modified atmosphere packaging of minimally processed red lettuce (2–3% O 2 + 12–14% CO 2 ) decreased the content of flavonol and anthocyanins of pigmented lettuce tissues when compared to air storage (Gil et al., 1998b). The increase of soluble phenylpropanoids observed in the midribs of minimally processed red lettuce after storage in air was avoided under MAP. When minimally processed Swiss chard was stored in MAP (7% O 2 + 10% CO 2 ), no effect was observed on flavonoid content after eight days cold storage when compared to that stored in air (Gil et al., 1998b). In addition, the total flavonoid content of fresh-cut spinach remained quite constant during storage in both air and MAP atmosphere (Gil et al., 1999). 220 Novel food packaging techniques Abnormal browning frequently occurs when fruits are stored in very low oxygen atmospheres. Extended treatment in pure nitrogen enhances the appearance of brown surfaces in fruits, which then rot rapidly when they are returned to air (Macheix et al., 1990). These observations are probably the result of cell disorganisation under anaerobiosis, but may also be related to variations in phenolic metabolism. There is a decrease in all phenolic compounds (e.g. anthocyanins, flavonols, and caffeoyl tartaric and p-coumaroyl tartaric acids) in both skin and pulp of grape berries rapidly brought under anaerobiosis in CO 2 enriched atmosphere (Macheix et al., 1990). Anaerobiosis generally appears to be harmful for the fruit products formed, with the frequent appearance of unwanted browning or loss of anthocyanins. In contrast, this treatment becomes necessary in the case of removal of astringency from persimmon fruit by means of an atmosphere of CO 2 or N 2 . These treatments result in the production of acetaldehyde, and deastringency is due to the insolubilisation of kaki-tannin by reaction with the acetaldehyde (Haslam et al., 1992). 11.7.2 Glucosinolates Brassica vegetables, such as cabbage, Brussels sprouts, broccoli and cauliflower are an important dietary source for a group of secondary plant metabolites known as glucosinolates. The sulphur-containing glucosinolates are present as glucosides and can be hydrolysed by the endogenous plant enzyme myrosinase (thioglucoside glucohydrolase EC 3.2.3.1). Myrosinase and the flucosinolates are physically separated from each other in the plant cell and therefore hydrolysis can only take place when cells are damaged, e.g. by cutting or chewing (Verkerk et al., 2001). The hydrolysis generally results in further breakdown of glucosinolates into isothiocyanates, nitriles, thiocyanates, indoles and oxazolidinethiones. Glucosinolate degradation products contribute to the characteristic flavour and taste of Brassica vegetables. Glucosinolates and their biological effects have been reviewed in detail (Rosa et al., 1997). Indol-3-ylmethylglucosinolates, which occur in appreciable amounts in several Brassica vegetables, are of interest for their potential contribution of anticarcinogenic compounds to the diet (Loft et al., 1992) and so broccoli has been associated with a decreased risk of cancer based on several beneficial properties such as the level of vitamin C, fibre and glucosinolates. The glucosinolate content in Brassica vegetables can vary depending on the variety, cultivation conditions, harvest time and climate. Storage and processing of the vegetables can also greatly affect the glucosinolate content. Processes such as chopping, cooking and freezing influence the extent of hydrolysis of glucosinolates and the composition of the final products (Verkert et al., 2001). There are a few reports describing the effects of storage on the glucosinolate content; for instance the storage of white and red cabbage for up to five months at 4oC which does not seem to affect the levels of glucosinolates (Berard and Chong, 1985). However, there is still little information about the influence of MAP, product safety and nutritional quality 221 CA/MAP on total or individual glucosinolate content of Brassica vegetables but an increase in total glucosinolate content was reported in broccoli florets when stored in air or CA while the absence of O 2 with a 20% CO 2 resulted in total loss (Hansen et al., 1995). 11.8 References AGAR I T, STREIF J and BANGERTH F (1997), ‘Effect of high CO 2 and controlled atmosphere on the ascorbic and dehydroascorbic acid content of some berry fruits’, Postharvest Biol Technol, 11, 47–55. AGAR I T, MASSANTINI R, HESS-PIERCE B and KADER A A (1999), ‘Postharvest CO 2 and ethylene production and quality maintenance of fresh-cut kiwifruit slices’, J Food Sci, 64, 433–40. AMES B M, SHIGENA M K and HAGEN T M (1993), ‘Oxidants, antioxidants and the degenerative diseases of ageing’, Proc Natl Acad Sci USA, 90, 7915–22. ARAI Y, WATANABE S, KIMIRA M, SHIMOI K, MOCHIZUKI R and KINAE N (2000), ‘Dietary intakes of flavonols, flavones and isoflavones by Japanese women and the inverse correlation between quercetin intake and plasma LDL cholesterol’, J Nutr, 130, 2378–83. BANGERTH F (1977), ‘The effect of different partial pressures of CO 2 , C 2 H 4 , and O 2 in the storage atmosphere on the ascorbic acid content of fruits and vegetables’, Qual Plant, 27, 125–33. BARRY-RYAN C and O’BEIRNE D (1999), ‘Ascorbic acid retention in shredded iceberg lettuce as affected by minimal processing’, J Food Sci, 64, 498– 500. BARTH M M, KERBEL E L, PERRY A K and SCHMIDT S J (1993), ‘Modified atmosphere packaging affects ascorbic acid, enzyme activity and market quality of broccoli’, J Food Sci, 57, 954–7. BASKARAN R H, PRASAD R and SHIVAIAH K M (2001), ‘Storage behaviour of minimally processed pumpkin (Cucurbiat maxima) under modified atmosphere packaging conditions’, Eur Food Res Technol, 212, 165–9. BECKER Z E (1933), ‘A comparison between the action of carbonic acid and other acids upon the living cell’, Protoplasma, 25, 161–75. BENNICK M H J, SMID E J, ROMBOUTS F M and GORRIS L G M (1995), ‘Growth of psychrotrophic foodborne pathogens in a solid surface model system under the influence of carbon dioxide and oxygen’, Food Microbiol, 12, 509–19. BENNICK M, VAN OVERBEEK W, SMID E and GORRIS L (1999), ‘Biopreservation in modified atmosphere stored mungbean sprouts: the use of vegetable- associated bacteriogenic lactic acid bacteria to control the growth of Listeria monocytogenes’, Letters in Applied Microbiology, 28, 226–32. BERARD L and CHONG C (1985), ‘Influences of storage on glucosinolate fluctuations in cabbage’, Acta Hort, 157, 29–44. BERRANG M, BRACKETT R and BEUCHAT L (1989a), ‘Growth of Listeria monocytogenes on fresh vegetables stored under a controlled atmosphere’, 222 Novel food packaging techniques J Food Prot, 52(10), 702–5. BERRANG M, BRACKETT R and BEUCHAT L (1989b), ‘Growth of Aeromonas hydrophila on fresh vegetables stored under a controlled atmosphere’, Applied and Environmental Microbiology, 55, 2167–71. BEUCHAT L and BRACKETT R (1990), ‘Survival and growth of L. monocytogenes on lettuce as influenced by shredding, chlorine treatment, modified atmosphere packaging and temperature’, Journal of Food Science, 55(3), 755–8, 870. BODNARUK P W and DRAUGHON F A (1998), ‘Effect of packaging atmosphere and pH on the virulence and growth of Yersinia enterocolitica on pork stored at 4 degrees’, Food Microbio, 15(2), 129–36. BOSKOU G and DEBEVERE J (1997), ‘Reduction of trimethylamine oxide by Shewanella spp. under modified atmospheres in vitro’, Food Microbiol, 14, 543–53. BOSKOU G and DEBEVERE J (1998), ‘In vitro study of TMAO reduction by Shewanella putrefaciens isolated from cod fillets packed in modified atmosphere’, Food Additives and Contaminants, 15(2), 229–36. BRITTON G and HORNERO-ME ′ NDEZ D (1997), ‘Carotenoids and colour in fruit and vegetables’, in Phytochemistry of Fruit and Vegetables, F A Toma′s- Barbera′n, R J Robins (eds), Oxford, Oxford University Press. CANO P, MONREAL M, DE ANCOS B and ALIQUE R (1998), ‘Effects of oxygen levels on pigment concentrations in cold-stored green beans (Phaseolus vulgaris L. Cv Perona)’, J Agric Food Chem, 46, 4164–70. CARLIN F, NGUYEN-THE C AND ABREU DA SILVA A (1995), ‘Factors affecting the growth of L. monocytogenes on minimally processed fresh endive’, Journal of Applied Bacteriology, 78, 636–46. CARLIN F, NGUYEN-THE C, ABREU DA SILVA A and COCHET C (1996a), ‘Effects of carbon dioxide on the fate of L. monocytogenes, of aerobic bacteria and on the development of spoilage in minimally processed fresh endive’, International Journal of Food Microbiology, 32, 159–72. CARLIN F, NGUYEN-THE C and MORRIS C (1996b), ‘The influence of the background microflora on the fate of Listeria monocytogenes on minimally processed fresh broad leaved endive’, Journal of Food Protection, 59(7), 698–703. CASTILLO-RODRIGUEZ A, BARCO-ALCALA E, GARCIA-GIMENO R and ZURERA- COSANO G (2000), ‘Growth modelling of Listeria monocytogenes in packaged fresh green asparagus’, Food Microbiology, 17, 421–7. CHIN J H, TRUDELL J R and COHEN E N (1976), ‘The compression-ordering and solubility-disordering effects of high pressure gases on phospholipid bilayers’, Life Sciences, 18, 489–98. CONNOR D E, SCOTT V N and BERNARD D T (1989), ‘Potential Clostridium botulinum hazards associated with extended shelf-life refrigerated foods: a review’, J Food Safety, 10, 131–53. COYNE F P (1933), ‘The effect of carbon dioxide on bacterial growth with special reference to the preservation of fish. Part II’, J Soc Chem Ind (London), MAP, product safety and nutritional quality 223 52, 19–24. DANIELS J A, KRISHNAMURTHI R and RIZVI S S H (1985), ‘A review of effects of carbon dioxide on microbial growth and food quality’, J Food Prot, 48, 532–7. DAVEY M W, VAN MONTAGU M, INZE ′ D, SANMARTIN M, KANELLIS A, SMIRNOFF N, BENZIE I J J, STRAIN J J, FAVELL D and FLETCHER J (2000), ‘Plant L ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing’, J Sci Food Agri, 80, 825–60. DAVIES A R (1995), ‘Advances in modified-atmosphere packaging’, in New Methods in Food Preservation, G W Gould (ed.), London, Blackie Academic and Professional, 304–20. DAY B P F (2000), ‘Chilled storage of foods, principles’, in Encyclopaedia of Food Microbiology, R K Robinson, C A Batt and P D Patel (eds), San Diego, Academic Press, 403–10. DELAPORTE N (1971), ‘Effect of oxygen content of atmosphere on ascorbic acid content of apple during controlled atmosphere storage’, Lebens Wiss Technol, 4, 106–12. DEVLIEGHERE F and DEBEVERE J (2000), ‘Influence of dissolved carbon dioxide on the growth of spoilage bacteria’, Lebens Wiss Technol, 33, 531–7. DEVLIEGHERE F, DEBEVERE J and VAN IMPE J (1998), ‘Concentration of carbon dioxide in the water-phase as a parameter to model the effect of a modified atmosphere on microorganisms’, Int J Food Microbiol, 43, 105–13. DEVLIEGHERE F, LEFEVERE I, MAGNIN A and DEBEVERE J (2000a), ‘Growth of Aeromonas hydrophila on modified atmosphere packaged cooked meat products, Food Microbiol, 17, 185–96. DEVLIEGHERE F, GEERAERD A H, VERSYCK K J, BERNAERT H, VAN IMPE J H and DEBEVERE J (2000b), ‘Shelf life of modified atmosphere packaged cooked meat products: addition of Na-lactate as a fourth shelf-life determinative factor in a model and product validation’, Int J Food Microbiol, 58, 93– 106. DEVLIEGHERE F, GEERAERD A H, VERSYCK K J, VANDEWAETERE B, VAN IMPE J and DEBEVERE J (2001), ‘Growth of Listeria monocytogenes in modified atmosphere paced cooked meat products: a predictive model’, Int J Food Microbiol, 18, 53–66. DI MASCIO P, KAISER S and SIES H (1989), ‘Lycopene as the most efficient biological carotenoid singlet oxygen quencher’, Arch Biochem Biophys, 274, 532–8. DIXON N M (1988), Effects of CO 2 on Anaerobic Bacterial Growth and Metabolism, PhD thesis, University College of Wales, Aberystwyth. DIXON N M and KELL D B (1989), ‘The inhibition by CO 2 of the growth and metabolism of micro-organisms’, J Appl Bacteriol, 67, 109–36. DOHERTY A, SHERIDAN J J, ALLEN P, MCDOWELL D A, BLAIR I S and HARRINGTON D (1995), ‘Growth of Yersinia enterocolitica O:3 on modified atmosphere packaged lamb’, Food Microbiol, 12(3), 251–7. DOHERTY A, SHERIDAN J J, ALLEN P, MCDOWELL D A, BLAIR I S and HARRINGTON D 224 Novel food packaging techniques (1996), ‘Survival and growth of Aeromonas hydrophilia on modified atmosphere packaged normal and high pH lamb’, International Journal of Food Microbiol, 28(3), 379–92. DUFRESNE I, SMITH J P, JIUN-NI-LIU and TARTE I (2000), ‘Effect of headspace oxygen and films of different oxygen transmission rate on toxin production by Clostridium botulinum type E in rainbow trout fillets stored under modified atmospheres’, J Food Safety, 20(3), 157–75. EKLUND T (1984), ‘The effect of carbon dioxide on bacterial growth and on uptake processes in bacterial membrane vesicles’, Int J Food Microbiol, 1, 179–85. FARBER J M (1991), ‘Microbiological aspects of modified atmosphere packaging technology – a review’, J Food Prot, 54, 58–70. FRANCO-ABUIN C M, ROZAS-BARRERO J, ROMERO-RODRIGUEZ M A, CEPEDA-SAEZ A and FENTE-SAMPAYO C (1997), ‘Effects of modified atmosphere packaging on the growth an survival of Listeria in raw minced beef’, Food Sci and Technol Int, 3, 285–90. GARCIA DE FERNANDO G D, NYCHAS G J E, PECK M W and ORDONEZ J A (1995), ‘Growth/survival of psychrotrophic pathogens on meat packaged under modified atmospheres’, Int J Food Microbiol, 28, 221–31. GARCIA-GIMENO R, SANCHEZ-POZO M, AMARO-LOPEZ M and ZURERA-COSANO G (1996), ‘Behaviour of Aeromonas hydrophila in vegetables salads stored under modified atmosphere at 4 and 15C’, Food Microbiol, 13, 369–74. GIBSON A M, ELLIS-BROWNLEE R C L, CAHILL M E, SZABO E A, FLETCHER G C and BREMER P J (2000), ‘The effect of 100% CO 2 on the growth of non- proteolytic Clostridium botulinum at chill temperatures’, Int J Food Microbiol, 54, 39–48. GIL M I, HOLCROFT D M and KADER A A (1997), ‘Changes in strawberry anthocyanins in response to carbon dioxide treatments’, J Agric Food Chem, 45, 1662–7. GIL M I, FERRERES F and TOMA ′ S-BARBERA ′ N F A (1998a), ‘Effect of modified atmosphere packaging on the flavonoids and vitamin C content of minimally processed Swiss chard (Beta vulgaris subsp. Cycla)’, J Agric Food Chem, 46, 2007–12. GIL M I, CASTAN ? ER M, FERRERES F, ARTE ′ S F and TOMA ′ S-BARBERA ′ N F A (1998b), ‘Modified-atmosphere packaging of minimally processed Lollo Rosso (Lactuca sativa)’, Z Lebensm Unters Forsch, 206, 350–4. GIL M I, FERRERES F and TOMA ′ S-BARBERA ′ N F A (1999), ‘Effect of postharvest storage and processing on the antioxidant constituents (flavonoids and vitamin C) of fresh-cut spinach’, J Agric Food Chem, 47, 2213–17. GILL C O and REICHEL M P (1989), ‘Growth of the cold-tolerant pathogens Yersinia enterocolitica, Aeromonas hydrophila and Listeria mono- cytogenes on high-pH beef packaged under vacuum or carbon dioxide’, Food Microbiol, 6, 223–30. GILL C O and TAN K H (1980), ‘Effect of carbon dioxide on growth of meat spoilage bacteria’, Appl Environ Microbiol, 39, 317–19. MAP, product safety and nutritional quality 225 GIOVANNUCCI E (1999), ‘Tomatoes, tomato-based products, lycopene and cancer: review of the epidemiologic literature’, J Natl Cancer Inst, 91, 317–31. HAFFNER K, JEKSRUD W K and TENGESDAL G (1997), ‘ L -ascorbic acid contents and other quality criteria in apples (Malus domestica Borkh) after storage in cold store and controlled atmosphere’, Postharvest Horticultural Series No 16, University of California, E J Micham (ed.). HANSEN M, MOLLER P, SORENSEN H and CANTWELL M (1995), ‘Glucosinolates in broccoli stored under controlled atmosphere’, J Amer Soc Hort Sci, 120, 1069–74. HART C D, MEAD G C and NORRIS A P (1991), ‘Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat’, J Appl Bacteriol, 70, 40–6. HASLAM E, LILLEY T H, WARMINSKI E, LIAO H, CAI Y, MARTIN R, GAFFNEY S H, GOULDING P N and LUCK G (1992), ‘Polyphenol complexation’, in Phenolic Compounds in Food and Their Effect on Health I, C T Ho, C Y Lee, M T Huang (eds), Washington, DC, American Chemical Society. HENDRICKS M T and HOTCHKISS J H (1997), ‘Effect of carbon dioxide on the growth of Pseudomonas fluorescens and Listeria monocytogenes in aerobic atmospheres’, J Food Prot, 60, 1548–52. HERTOG M G L, FESKENS E J M, HOLLMAN P C H, KATAN M B and KROMHOUT D (1993), ‘Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen elderly study’, The Lancet, 342, 1007–11. HERTOG M G L, SWEETNAM P M, FEHILY A M, ELWOOD P C and KROMHOUT D (1997), ‘Antioxidant flavonols and ischaemic heart disease in a Welsh population of men. The Caerphilly study’, Am J Clin Nutr, 65, 1489–94. HOLCROFT D M and KADER A A (1999), ‘Carbon dioxide-induced changes in color and anthocyanin synthesis of stored strawberry fruit’, HortSci, 34, 1244–8. HOLCROFT D M, GIL M I and KADER A A (1998), ‘Effect of carbon dioxide on anthocyanins, phenylalanine ammonia lyase and glucosyltransferase in the arils of stored pomegranates’, J Amer Soc Hort Sci, 123, 136–40. HOWARD L R and HERNANDEZ-BRENES C (1998), ‘Antioxidant content and market quality of jalapeno pepper rings as affected by minimal processing and modified atmosphere packaging’, J Food Quality, 21, 317–27. HOWARD L R, SMITH R T, WAGNER A B, VILLALON B and BURNS E E (1994), ‘Provitamin A and ascorbic acid content of fresh pepper cultivars (Capiscum annuum) and processed jalapenos’, J Food Sci, 59, 362–5. HUDSON J A, MOTT S J and PENNEY N (1994), ‘Growth of Listeria monocytogenes, Aeromonas hydrophila and Yersinia enterocolitica on vacuum and saturated carbon dioxide controlled atmosphere packaged sliced roast beef’, J Food Prot, 57(3), 204–8. IKAWA J T and GENIGEORGIS C (1987), ‘Probability of growth and toxin production by non-proteolitic Clostridium botulinum in rockfish fillets stored under modified atmospheres’, Int J Food Microbiol, 4, 167–81. JACXSENS L, DEVLIEGHERE F, FALCATO P and DEBEVERE J (1999), ‘Behaviour of 226 Novel food packaging techniques Listeria monocytogenes and Aeromonas spp. on fresh cut produce packaged under equilibrium modified atmosphere’, J Food Prot, 62, 1128–35. JOHNSON I T, WILLIAMSON G M and MUSK S R R (1994), ‘Anticarcinogenic factors in plant foods: a new class of nutrients’, Nutr Res Rev, 7, 175–204. JONES M V (1989), ‘Modified atmospheres’, in Mechanisms of Action of Food Preservation Procedures, G W Gould (ed.), Elsevier Science, 247–84. JONES R P and GREENFIELD P F (1982), ‘Effect of carbon dioxide on yeast growth and fermentation’, Enzyme & Microbial Technol, 4, 210–84. JUNEJA V, MARTIN S and SAPERS G (1998), ‘Control of L. monocytogenes in vacuum-packaged pre-peeled potatoes’, J Food Sci, 63, 911–14. KADER A A (1986), ‘Biochemical and physiological basis for effects of controlled and modified atmospheres on fruits and vegetables’, Food Technol, 40, 99–100, 102–4. KADER A A (1997), ‘Biological bases of O 2 and CO 2 effects on postharvest-life of horticultural perishables’, Postharvest Horticultural Series No 18, University of California, M E Saltveit (ed.). KADER A A (2001), ‘Physiology of CA treated produce’, 8 th International Controlled Atmosphere Research Conference, Rotterdam, Oosterhaven. KADER A A, ZAGORY D and KERBEL E L (1989), ‘Modified atmosphere packaging of fruit and vegetables’, Crit Rev Food Sci Nutr, 28, 1–30. KANNER J, FRANKEL E, GRANIT R, GERMAN B and KINSELLA J E (1994), ‘Natural antioxidants in grapes and wines’, J Agric Food Chem, 42, 64–9. KLEIN B P (1987), ‘Nutritional consequences of minimal processing fruits and vegetables’, J Food Qual, 10, 179–83. KRA ¨ MER K H and BAUMGART J (1992), ‘Bru¨hwurstaufschnitt hemmung von Listeria monocytogenes durch eine modifizierte atmospha¨re’, Fleisch- wirtschaft, 72, 666–8. KROGH A (1919), ‘The rate of diffusion of gases through animal tissues with some remarks on the coefficient of invasion’, J Physiol, 52, 391–408. LAWLOR K A, PIERSON M D, HACKNEY C R, CLAUS J R and MARCY J E (2000), ‘Non- proteolytic Clostridium botulinum toxigenesis in cooked turkey stored under modified atmospheres’, J Food Prot, 63, 1511–16. LEE S K and KADER A A (2002), ‘Preharvest and postharvest factors influencing vitamin C content of horticultural crops’, Postharvest Biol Technol, 20, 207–20. LIAO C and SAPERS G (1999), ‘Influence of soft rot bacteria on growth of Listeria monocytogenes on potato slices’, J Food Prot, 62, 343–8. LOFT S, OTTE J, POULSEN H E and SORENSEN H (1992), ‘Influence of intact and myrosinase-treated indolyl glucosinolates on the metabolism in vivo of metronidazole and antipyrine in rat’, Food Chem Toxicology, 30, 927–35. MACCARRONE M, D’ANDREA G, SALUCCI M L, AVIGLIANO L and FINAZZI-AGRO A (1993), ‘Temperature, pH, and UV irradation effects on ascorbate oxidase’, Phytochemistry, 35, 795–8. MACHEIX J J, FLEURIET A and BILLOT J (1990), Fruit Phenolics, Boca Raton, MAP, product safety and nutritional quality 227 Florida, CRC Press. MANU-TAWIAH W, MYERS D J, OLSON D G and MOLINS R A (1993), ‘Survival and growth of Listeria monocytogenes and Yersinia enterocolitica in pork chops packaged under modified gas atmospheres’, J Food Sci, 58, 475–9. MEHLHORN H (1990), ‘Ethylene-promoted ascorbate peroxidase activity protects plants against hydrogen peroxide, ozone and paraquat’, Plant Cell Envrion, 13, 971–6. MOLIN G (1983), ‘The resistance to carbon dioxide of some food related bacteria’, European J Appl Microbiol Biotechnol, 18, 214–17. NYCHAS G J E (1994), ‘Modified atmosphere packaging of meats’, in Minimal Processing of Foods and Process Optimization, an Interface, R P Singh, F A R Oliveira (eds), London CRC Press, 417–36. O’CONNOR-SHAW R E and REYES V G (2000), ‘Use of modified-atmosphere packaging’, in Encyclopedia of Food Microbiology, R K Robinson, C A Batt, P D Patel (eds), San Diego, Academic Press, 410–15. OMARY M, TESTIN R, BAREFOOT S and RUSHING J (1993), ‘Packaging effects on growth of Listeria innocua in shredded cabbage’, Journal of Food Science, 58, 623–6. O ¨ ZBAS Z Y, VURAL H and AYTAC S A (1996), ‘Effect of modified atmosphere and vacuum packaging on the growth of spoilage and inoculated pathogenic bacteria on fresh poultry’, Z Lebensm Unters Forsch, 203, 326–32. O ¨ ZBAS Z Y, VURAL H and AYTAC S A (1997), ‘Effects of modified atmosphere and vacuum packaging on the growth of spoilage and inoculated pathogenic bacteria on fresh poultry’, Fleischwirtschaft, 77, 1111–16. PARADIS C, CASTAIGNE F, DESROSIERS T, FORTIN J, RODRIGUE N and WILLEMOT C (1996), ‘Sensory, nutrient and chlorophyll changes in broccoli florets during controlled atmosphere storage’, J Food Qual, 19, 303–16. PARRY R T (1993), ‘Introduction’, in Principles and Applications of Modified Atmosphere Packaging of Food, R T Parry (ed.), Glasgow, Blackie Academic and Professonal, 1–18. PETERSEN M A and BERENDS H (1993), ‘Ascorbic acid and dehydroascorbic acid content of blanched sweet green pepper during chilled storage in modified atmospheres’, Z Lebens Unters Forsch, 197, 546–9. PETREL M T, FERNa′NDEZ P S, ROMOJARO F and MART?′NEZ A (1998), ‘The effect of modified atmosphere packaging on ready-to-eat oranges’, Lebensm Wiss Technol, 31, 322–8. REDDY N R, PARADIS A, ROMAN M G, SOLOMON H M and RHODEHAMEL E J (1996), ‘Toxin development by Clostridium botulinum in modified atmosphere- packaged fresh Tilapia fillets during storage’, J Food Sci, 61, 632–5. REDDY N R, ROMAN M G, VILLANUEVA M, SOLOMON H M, KAUTTER D A and RHODEHAMEL E J (1997a), ‘Shelf life and Clostridium botulinum toxin development during storage of modified atmosphere-packaged fresh catfish fillets’, J Food Sci, 62, 878–84. REDDY N R, SOLOMON H M, YEP H, ROMAN M G and RHODEHAMEL E J (1997b), ‘Shelf life and toxin development by Clostridium botulinum during storage 228 Novel food packaging techniques of modified-atmosphere-packaged fresh aquacultured salmon fillets’, J Food Prot, 60, 1055–63. ROSA E A S, HEANEY R K, FENWICK G R and PORTAS C A (1997), ‘Glucosinolate in crop plants’, Hort Rev, 19, 99–215. ROTH S H (1980), ‘Membrane and cellular actions for anesthetic agents’, Federation Proceedings, 39, 1595–9. SALTVEIT M E (1997), ‘Physical and physiological changes in minimally processed fruits and vegetables’, in Phytochemistry of Fruit and Vegetables, F A Toma′s-Barbera′n, R J Robins (eds), Oxford, Oxford University Press. SHERIDAN J J and DOHERTY A (1994), ‘Growth of Yersinia enterocolitica on modified atmosphere packaged lamb’, Proceedings 40th International S.Iia.13. Congress on Meat Science Technology, The Hague, Holland. SHERIDAN J J, DOHERTY A and ALLEN P (1992), Improving the Safety and Quality of Meat and Meat Products by Modified Atmosphere and Assessment by Novel Methods, FLAIR 89055 Interim. 2 nd year report, EEC SGXII, Brussels. SIMON J A (1992), ‘Vitamin C and cardiovascular disease: a review’, J Am Coll Nutr, 11, 107–25. SOZZI G, TRINCHERO G D and FRASCHINA A A (1999), ‘Controlled-atmosphere storage of tomato fruit: low oxygen or elevated carbon dioxide levels alter galactosidase activity and inhibit exogenous ethylene action’, J Sci Food Agric, 79, 1065–70. SZABO E A and CAHILL M E (1998), ‘The combined affects of modified atmosphere, temperature, nisin and ALSO-T-M 2341 on the growth of Listeria monocytogenes’, Int J Food Microbiol, 43(1/2), 21–31. TAN K H and GILL C O (1982), ‘Physiological basis of CO 2 inhibition of a meat spoilage bacterium, Pseudomonas fluorescens’, Meat Sci, 7, 9–17. THOMAS C, PRIOR O and O’BEIRNE D (1999), ‘Survival and growth of Listeria species in a model ready-to-use vegetable product containing raw and cooked ingredients as affected by storage temperature and acidification’, International Journal of Food Science and Technology, 34, 317–24. TOMA ′ S-BARBERA ′ N F A and ESPI ′ N J C (2002), ‘Phenolic compounds and related enzymes as determinants of quality in fruit and vegetables’, J Sci Food Agric, 81, 853–76. TOMA ′ S-BARBERA ′ N F A, GIL M I, CASTAN ? ER M, ARTA ′ S F and SALTVEIT M E (1997), ‘Effect of selected browning inhibitors on harvested lettuce stem phenolic metabolism’, J Agric Food Chem, 45, 583–9. TUDELA J A, ESPI ′ N J C and GIL M I (2002), ‘Vitamin C retention in fresh-cut potatoes’, Postharvest Biol Techno, in press. VA ′ MOS-VIGYA ′ ZO ′ L (1981), ‘Polyphenol oxidase and peroxidase in fruits and vegetables’, CRC Crit Rev Food Sci Nutr, 15, 49–127. VARNAM A H and EVANS M G (1991), Foodborne pathogens: an Illustrated Text, London, Wolfe Publishing. VELTMAN R H, SANDERS M G, PERSIJN S T, PEPPELENBOS H W and OOSTERHAVEN J MAP, product safety and nutritional quality 229 (1999), ‘Decreased ascorbic acid levels and brown core development in pears (Pyrus communis L. cv. Conference)’, Physiol Plant, 107, 39–45. VERKERT R, DEKKER M and JONGEN W M F (2001), ‘Postharvest increase of indolyl glucosinolates in response to chopping and storage of Brassica vegetables’, J Sci Food Agric, 81, 953–8. VINSON J A and HONTZ B A (1995), ‘Phenol antioxidant index: comparative antioxidant effectiveness of red and white wines’, J Agric Food Chem, 43, 401–3. WANG C Y (1977), ‘Effects of CO 2 treatment on storage and shelf life of sweet pepper’, J Amer Soc Hortc Sci, 102, 808–12. WANG C Y (1983), ‘Postharvest responses of Chinese cabbage to high CO 2 treatments or low O 2 storage’, J Amer Soc Hortc Sci, 108, 125–9. WATADA A E (1987), Vitamins, New York, Marcel Dekker. WEICHMANN J (1986), ‘The effect of controlled-atmosphere storage on the sensory and nutritonal quality of fruits and vegetables’, Hort Rev, 8, 101– 27. WIMPFHEIMER L, ALTMAN N S and HOTCHKISS J H (1990), ‘Growth of Listeria monocytogenes Scott A, serotype 4 and competitive spoilage organisms in raw chicken packaged under modified atmospheres and in air’, Int J Food Microbiol, 11, 205–14. WOLFE S K (1980), ‘Use of CO and CO 2 enriched atmospheres for meats, fish and produce’, Food Technol, 34, 55–9. WRIGHT K P and KADER A A (1997a), ‘Effect of slicing and controlled-atmosphere storage on the ascorbate content and quality of strawberries and persimmons’, Postharvest Biol Techno, 10, 39–48. WRIGHT K P AND KADER A A (1997b), ‘Effect of controlled-atmosphere storage on the quality and carotenoid content of sliced persimmons and peaches’, Postharvest Biol Technol, 10, 89–97. YOUNG L L, REVERIE R D and COLE A B (1988), ‘Fresh red meats: a place to apply modified atmospheres’, Food Technol, 42(9), 64–6, 68–9. ZEITOUN A A M and DEBEVERE J M (1991), ‘Inhibition, survival and growth of Listeria monocytogenes on poultry as influenced by buffered lactic acid treatment and modified atmosphere packaging’, Int J Food Microbiol, 14, 161–70. ZHANG S and FARBER J (1996), ‘The effects of various disinfectants against L. monocytogenes on fresh-cut vegetables’, Food Microbiol, 13, 311–21. ZHAO Y, WELLS J H and MARSHALL D L (1992), ‘Description of log phase growth for selected microorganisms during modified atmosphere storage’, J Food Proc Engin, 15, 299–317. 230 Novel food packaging techniques