IO
Pasta and Whole Grain Foods
Pasta Cooking quality of pasta
Pasta is the collective term used to describe Particle size of the semolina is an important
products such as macaroni, spaghetti, vermicelli, characteristic: it is recommended that at least 90%
noodles etc. which are traditionally made from of the particles should fall between 150 pm and
the semolina milled from hard durum wheat (T. 340 pm in size. Particles larger than 340 pm
durum) (cf. p. 154 for milling of semo). The impede the activity of enzymes in the dough
highest quality pasta products are made from (Milatovic, 1985). Good quality of the pasta
durum wheat alone, but other hard wheat, e.g. may be defined as the ability of the proteins to
CWRS or HRS, can be substituted, but only at form an insoluble network capable of entrapping
the expense of quality. The Plate wheat Taganrog swollen and gelatinized starch granules (Feillet,
used for puffing (cf. p. 87) is not liked for pasta 1984), and is thus related to the composition of
as it tends to yield a brownish-coloured product. the protein. A strong correlation (+0.796) has
Durum wheat grown in Britain has been success- been found between pasta cooking quality and
fully used for pasta, although parcels with high acid-insoluble residue protein (Sgrulletta and De
alpha-amylase activity are unsuitable. U.K.- Stefanis, 1989); a highly significant correlation
grown durum wheat will probably be blended in was also found between good cooking quality and
small quantities into a grist in which imported the total sulphydryl plus disulphide (SH + SS)
durum wheat will predominate. content of glutenins extracted by sodium tetra-
Historically, pasta products are believed to decanoate solution (Kobrehel and Alary, 1989;
have been introduced into Italy from China in Alary and Kobrehel, 1987), and also with certain
the 13th century, but were first produced low mol. wt glutenin subunits, particularly the
in Europe in the 15th century, in Germany band 45 of the electrophoretic pattern. On the
(Pomeranz, 1987). other hand, poor cooking quality was associated
with the 42 band, and it is suggested that
this association could be a useful indicator for
Degree of cooking
the breeding of durum wheat for pasta-cooking
Pasta products, as sold, could be described as qualities (du Cros and Hare, 1985; Autran et al.,
‘uncooked’, ‘partially cooked’, or ‘fully cooked’ 1989).
(pre-cooked), depending on the degree to which In uncooked pasta, the protein is largely
the protein is denatured and the starch gelatinized. undenatured, and most of the starch is ungelatin-
Traditionally, pasta products are prepared in ked. The processing conditions of dough moisture
an uncooked state, because dry, uncooked pasta content and extrusion temperature were carefully
can be stored at room temperatures for long controlled to prevent protein denaturation and
periods while maintaining its highly glutinous starch gelatinization.
properties.
233
234 TECHNOLOGY OF CEREALS
Traditional (kneadinglsheeting) process Drying of pasta
In the traditional manufacturing process in use Finally, in the traditional process, the extruded
at the beginning of the 20th century, a dough is product is dried to about 12.5% m.c. In Italy,
first made by mixing semolina and water to give drying might be done outdoors, but elsewhere
a moisture content of about 30% in the dough. special equipment is used in which the temperature
A moisture content of 30% is needed to ensure and relative humidity of the air can be carefully
that the viscosity of the dough is low enough to controlled. The rate of drying must be correct:
avoid the use of excessive pressure within the drying at too low a rate could lead to the
extruder. The dough is then kneaded, brought development of moulds, discoloration and souring,
to a temperature of about 49"C, and is then whilst drying too rapidly could cause cracking
extruded through a hydraulic press to form a thin ('checking' in the U.S.A.) and curling. Until
sheet which can then be cut into strips and the recently, drying temperatures were about 50"C,
strips carefully dried. A temperature not above and the drying process took 14-24 h.
49°C is necessary to prevent cooking the product A three-stage drying process, comprising pre-
and avoid denaturing the protein. A modification drying, sweating, and drying, has been described
of this process, in which the dough was extruded (Antognelli, 1980). In the pre-drying stage, air
through special dies to make shaped products - at 55"-90"C circulates round the product and
rods, strips, tubes, etc. - was first introduced dries it to 17-18% m.c. in about 1 h. Moisture
about 50 years ago (Pomeranz, 1987). migrates from the centre to the periphery, where
it evaporates, resulting in a marked moisture
gradient in the product. In the sweating period
that follows, the pasta is rested to allow moisture
Extrusion process
equilibration between the inner core of the pasta
In the extrusion process, the moisture content and the surface to occur. In the drying stage,
of the dough would be about 28% and the diminishing periods of hot-air circulation alternate
extrusion temperature, i.e. the temperature of the with periods of sweating. Temperatures in the
extrusion barrel, would be around 54"C, low drying stage are 45"-70"C, and the total drying
enough to avoid cooking the product. The extru- time is 6-28 h.
sion barrel would be provided with a jacket in In the late 1970s, the processing of macaroni
which water could be circulated to maintain the was improved by drying at temperatures above
required temperature. 60"C, using shorter processing times, and
It is claimed that the kneadingkheeting process sterilizing the product during drying.
has the advantage of producing a springy, elastic A rapid drying process using microwave energy
texture in the product, leading to good eating has been described (Katskee, 1978). A pre-drying
quality, while advantages claimed for the extru- stage uses hot air at 71"-82°C to reduce the m.c.
sion process are that it produces a pasta with a of the pasta to 17.5% in 30 min. In the microwave
firmer texture in a larger variety of shapes, that stage that follows, the product is fully dried to
it is more efficient and less time-consuming, and the target m.c. in 10-20 min. The microwave
that the extruded dough has a lower moisture system operates at about 30 kW, an air temperature
content requiring a shorter drying time to complete of 82°C and 15-20% r.h. The final, or cooling and
the preparation of the pasta. However, pasta equalization stage, operated at 70-80% r.h.,
made by the extrusion process lacks the laminated brings the total drying time up to 1.5 h. Advan-
structure and desirable eating qualities of pasta tages claimed for the microwave drying process,
made by the kneadingkheeting process, and the besides the considerable saving of time, include
colour of the pasta is less appealing (U.S. Pat. space-saving, improved product quality - cooking
No. 4,675,199).
quality, colour enhancement, and microbiological
PASTA AND WHOLE GRAIN FOODS 235
- modification of the temperature of the doughing
water, the temperature in the cooking zone,
and the extrusion temperature (Milatovic ,
1985; Euro. Pat. Appl. Nos 0,267,368 and
Recent processing changes 0,288,136);
Within the last 20 years or so,
numerous - Partially Pre-cooking the dough by Pre-
processing changes have been introduced to the conditioning (Euro. Pat. Appl. No. 0,267,368);
pasta-manufacturing industry which are directed - soaking partially-cooked pasta in acidified
towards achieving various objectives, including water (U.S. Pat. No. 4,828,852);
the following:
- use of higher drying temperatures (Manser,
1986; Abecassiset al., 1989a; Euro. Pat. Appl.
- improvement in pasta quality, e.g. by reducing Nos 0,309,413, 0,322,053 and 0,352,876);
cooking loss, avoidance Of cracking, imprOV- - back-mixing the dough, combined with high
ing the colour of the product, elimination of drying temperature (Brit. Pat. Spec. No.
dark specks, destruction of micro-organisms, 2,151,898; U.S. Pat. No. 4,540,592);
improving the appearance and firmness of - venting the product between the cooking and
the product (Milatovic, 1985; Manser, 1986; the forming zones (Euro. Pat. Appl. No.
Abecassis et al., 1989a; Euro. Pat. Appl. 0,267,368);
No. 092679368; U.S. Pat. Nos 4,539,214 and - pre-drying and drying as two separate stages
4,876,104); (Milatovic, 1985);
- improvement in nutritional quality, e.g. by - use of superheated steam for simultaneously
better retention of vitamins and other nutrients cooking anddrying (U.S. Pat.No. 4,539,214);
(Manser, 1986; Euro. Pat. APPl. No. 0,322, - high-temperature after-treatment to make pre-
153); cooked pasta (Abecassis et al., 1989a,b;
- improvement in shelf-life of the product (U. S. Mestres et al., 1990; U.S. Pat. No. 4,830,866);
Pat. Nos 4,828,852 and 4,876,104); - pasteurization (U.S. Pat. No. 4,876,104);
- reduction in drying time, with consequent - extrusion into N~/c~~ or into vacuum to
saving in energy expenditure (Abecassis, improve storability (Euro. Pat. Appl. No.
1989b);
0,146,510; U.S. Pat. No. 4,540,590);
- faster-cooking Products, e.g. a rapidly - use of extrusion cooking instead of ordinary
rehydratable pasta, or a microwave-cookable extrusion (U.S. Pat. No. 4,540,592);
Product (Euro. Pat. APPl. Nos 0,267,368, - use of additives, e.g. emulsifiers, in the
0,272,502 and 0,352,876; U.S. Pat. Nos 4, dough (Euro. Pat. Appl. Nos 0,352,876 and
539,214 and 4,540,592); 0,288,136).
- a ready-to-eat pasta, or an instant pre-cooked
pasta (U.S. Pat. Nos 4,540,592 and 4,828,852).
Use of non-wheat materials
Another objective has been the diversification
In some countries, e.g. France and Italy, the
of the starting material, i.e. the replacement of
material used for making pasta must be durum
some (or all) of the durum semolina with other
semolina, but other countries allow the use of
cereal materials or even with non-cereal materials
soft wheat flour, maize flour, or various other
(Molina et al., 1975; Mestres et al., 1990).
diluents. Countries which are non-wheat pro-
These objectives have been addressed, and
ducers, e.g. many African countries, are interested
in most cases attained, by modification of the
in pasta made from non-wheat materials, e.g.
traditional process in various ways, such as:
maize, sorghum. Preparation of such pasta is
- modification of the moisture content of difficult because of the lack of gluten which is
formed when wheat is the starting material, and
which contributes to dough development during
quality - and lower installation and operating
costs.
the product before drying (Abecassis et al.,
1989a,b);
236 TECHNOLOGY OF CEREALS
mixing and extrusion, and thus prevents disag- system is restricted to preparation of pasta from
gregation of the pasta during cooking in boiling semolina or flour having more than 32% wet
water (Feillet, 1984; Abecassis et al., 1989a). It gluten content. This system produces the most
has been suggested that the lack of gluten can be rapid hydration of gluten and gelatinization of
overcome by blending pregelatinized starch or the starch, but of course cannot be employed if
corn flour before adding water and mixing, or by ascorbic acid is included, because the latter
gelatinizing some of the starch during mixing or decomposes at these temperatures and has no
extruding (Molina et al., 1975). A compromise is beneficial effect.
to use a blend of semolina and maize flour, from
which good quality pasta can be obtained, provided
Glyceryl monostearate as additive
the maize flour has fine granularity (less than
200 pm) and a low lipid content (not higher than The use of glyceryl monostearate as a flour
2% on d.b.). By submitting the dried pasta to modifier is proposed in order to permit the
thermal treatment at 90°C for 90-180 min, a extrusion of the dough at a lower m.c., viz. 28%,
blend of 70 maize flour: 30 durum wheat semolina than is customary in making uncooked pasta. The
was found to be satisfactory (Mestres et al., 1990). temperature of the dough at extrusion is above
54"C, but not so high as to cause gelatiniza-
tion of the starch. Other flow modifying agents
L-Ascorbic acid as additive
suggested are whey solids and sulphydryl reducing
The use of L-ascorbic acid as an additive for substances such as L-cysteine, glutathione, sodium
improving the quality of pasta has been suggested bisulphite or calcium sulphite at levels of 0.025-
(Milatovic, 1985). Ascorbic acid, which is oxidized 0.1% by wt (Euro. Pat. Appl. No. 0,288,136).
to dehydroascorbic acid, a strong reducing agent,
inhibits the destruction of naturally occurring
Prevention of starch leaching from
uncooked pasta
pigments, leading to improvement in the colour
of the product by inhibiting lipoxygenase activity.
Addition of 300 mglkg of L-ascorbic acid to the High temperature (above 74°C) drying of pasta
doughing water improved the colour of the pasta causes denaturation of the protein, thereby en-
made from all soft wheat flour or from 50 soft trapping the starch and rendering the pasta stable
wheat flour: 50 semolina, and also reduced the to starch leaching in the presence of cold water.
loss of solid matter and protein from the cooked If dried at the lower, traditional, temperature,
product. the protein is not denatured and, as a result,
starch leaches out, making a gummy, mushy
product, unless the pasta is immediately con-
Doughing water temperature
tacted with extremely hot water, to set the protein
The temperature of the doughing water is matrix. An uncooked pasta which can withstand
important. Water at 36"-45"C is normally used for exposure to cold water without leaching of starch
cold dough making, 45"-65"C for a warm system may be made by the addition of low-temperature
using high temperature drying, and 75"-85"C coagulatable materials such as albumin, whole
for very warm processing. If egg is an addi- egg, whey protein concentrates, but preferably
tive, the doughing water temperature should egg white, added at a level of 0.5-3.0% by wt.
not exceed 50"C, since albumen coagulates at Sulphydryl reducing agents, e.g. cysteine, gluta-
49°C. Similarly, when ascorbic acid is added, thione, which reduce disulphide (-SS-) bonds to
the water temperature should not exceed 55"C, sulphydryl groups (-SH), thereby facilitating the
otherwise degradation of the additive will be irreversible denaturation of the gluten, can be
accelerated. In the warm system, the gluten added at levels of 0.02-0.04% by wt: their addi-
hydrates rapidly, reducing the length of the tion is essential at drying temperatures below
dough preparation time. Use of the very warm 74°C. A modern drying process would use two
PASTA AND WHOLE GRAIN FOODS 237
(below 24% m.c. crackingmay occur, while above
30% m.c. the dough becomes too soft and elastic).
The sheeted dough is cut into pieces which are
partially dried in 1040 sec by, e.g. infrared
heating lamps and hot air at 204°C. The product
is then steamed and pasteurized to kill micro-
organisms, cooled to O"-lO"C and packed in
sterile trays with injection of C02/N2 (25:75
to 80:20). Such packaged products should be
storable at 4"-10"C for at least 120 days (U.S.
Pat. No. 4,876,104).
stages: drying at 71"-104°C for 24 h, followed by
further drying at 32"-71"C for 0-120 min, but
with the use of a high velocity air current (150 ft3/
rnin), the drying times could be shortened to 15-
30 min for the first step plus 30-120 min for the
second. Pasta made in this way can be rehydrated
by soaking in cold water, and then cooked in
about 2 min by conventional boiling or by micro-
wave energy (Euro. Pat. Appl. No. 0,352,876).
'Cooking value ' of pasta
'Cooking value' is a measure of the texture or
consistency of the pasta after cooking. The cooked
pasta should offer some resistance to chewing but
should not stick to the teeth. To retain these
qualities and to avoid loss of nutrients, current
procedures limit drying temperature to not above
60"C, but such drying takes a long time - 16-
24 h. Higher drying temperatures, while still
avoiding nutrient loss and adversely affecting
cooking value, can be used in a step-wise process,
e.g. by isothermal application of heat at temper-
atures between 40" and 94°C while maintaining
the vapour pressure within the pasta (A,) below
0.86.
In one such drying schedule, the product
passes through eight areas in which the tempera-
tures are (successively) 40", 50", 60", 70", SO", 84",
94" and 70"C, taking about 3 h to complete the
drying. The product, with 13% m.c., is then
cooled to 25°C (Euro. Pat. Appl. No. 0,322,053).
Micro-organism control
Control of micro-organisms in stored pasta
products is essential. The use of high temperature
(above 60°C) drying to improve pasta product
sterility has been described (Milatovic, 1985).
Another process is described in which dough
is made from flour (durum wheat semolina, or
whole soft wheat flour plus corn flour, rice flour
or potato flour) about 75 parts, with about 25
parts of whole egg, but with no water. Additives
such as wheat gluten, soya protein isolate, algin-
ates and surfactants may be added. The dough
is sheeted through a series of rollers to a thickness
of 0.03 in, while keeping the m.c. about 24%
Quick-cooking pasta
A process described for making a quick-cooking
pasta starts by making a dough from flour or
semolina of which at least 90% is derived from
durum wheat, with the addition of 0.5-5.0% by
wt of an edible emulsifier, such as glyceryl or
sorbitan monostearate, lecithin or polysorbates.
Water, at 79"C, is added to bring the m.c. to
22-32%. The ingredients are mixed at 76"-88"C,
extruded through a co-rotating twin-screw extruder
at 60"-88"C. The extruder comprises three zones:
a cooking zone, a venting zone, and a forming
zone. When passing through the venting zone,
the material may be subjected to a degree of
vacuum (2.5-5 psi) to draw off excess moisture.
The product can be cooked by microwave energy
(Euro. Pat. Appl. No. 0,272,502).
Another process for making rapidly rehydrat-
able pasta simultaneously cooks and dries the
extruded dough (made from semolindflour and
water) by the use of superheated steam at a
temperature of 102"-140"C for 7-20 min. The
product is in an unexpanded condition and can
be packaged without further cutting or shaping
(U.S. Pat. No. 4,539,214).
A process to eliminate darkened specks in a
quick-cooking pasta pre-cooks a mixture of pasta
flour and water in a pre-conditioner before it
passes through an extruder with three zones:
cooking, venting, extruding. The temperature of
the mixture is kept below 101°C in the cooking
zone to prevent the formation of darkened specks
symptomatic of burning during cooking (Euro.
Pat. Appl. No. 0,267,368).
238 TECHNOLOGY OF CEREALS
Pre-cooked pasta
A method of preparing instant, pre-cooked
pasta is disclosed in U.S. Pat. No. 4,540,592.
The pasta dough is completely gelatinized in a
co-rotating, twin-screw extrusion cooker, incorp-
orating at least one high-shear back-mixing cook-
ing zone, and using high temperature and pressure
so that the final product rehydrates to a cooked
pasta instantly in hot water.
Shelf-stable, pre-cooked pasta
preparation of a pre-cooked product which is
shelf-stable for long periods is described (U. S.
Pat. No. 4,828,852). The starting material can
be durum semolina or flour, soft wheat flour, corn
flour, pregelatinized corn flour, rice flour, waxy
rice flour, pre-cooked rice flour, potato flour, pre-
cooked potato flour, lentil flour, pea flour, soya
flour, kidney or pinto beans, Mung bean flour,
corn starch, wheat starch, potato starch, pea
starch etc. A dough of 2628% m.c. is extruded
to make pasta of 1.0-2.0 mm thickness. The pasta
is then boiled in acidified water (using acetic,
malic, fumaric, tartaric, phosphoric or adipic, but
preferably lactic or citric acid) and then soaked
those containing egg, additional gluten or other
additives) to conform to the following standard:
protein 11.5% (min.), m.c. 12.5% (max.) when
packed, ash 0.60-0.85°/~. Degree of acidity and
colour are also specified.
~~~~~~~~
c~~~~~~~ is a type of pasta product made in
Algeria from a durum semolina and water paste
which is dried and ground. The product is size-
graded, and is similar in size to that of very
coarse semolina. Thus prepared, the couscous has
exce11ent keeping qualities-
Pasta composition
semolina in the U.K. is shown in Table 10.1.
pasta ConsumPtion
The per capila consumpt~on of pasta products
in 1989 was (in kg) 21 in ~~~l~, 6 in F~~~~~,
G~~~~~, portugal, switzerland, 5 in G~~~~~~ FR,
4 in Sweden, 3.5 in ~~~~~i~ and the u.K., 3 in
spain, 2 in Finland and Ireland, 1.5 in ~~l~i~~,
The composition of pasta made from durum
in Water acidified to pH 3.84.3 to 6l-68% m.C.
The partially cooked pasta is drained and then
Denmark and The Netherlands, and 0.2 in N~~~~
(European Food Marketing Directory, 1991).
coated with an acidified cream at pH 4.14.4.
The acidification gives a better shelf life, and
thickens the cream to improve coating. The Rice substitutes
product is then flush-packaged with an inert gas,
or is vacuum packaged. Finally, the containers
are sealed and heated to 9Oo-100"C for 20-40 min
to complete the cooking of the pasta.
U. K. Code of Practice
A Code of Practice for dry pasta products in
the U.K. requires all pasta products (other than
Bulgur
Bulgur consists of parboiled whole or crushed
partially debranned wheat grains, and is used as
a substitute for rice, e.g. in pilaf, an eastern
European dish consisting of wheat, meat, oil and
herbs cooked together. The ancient method of
producing bulgur, which is referred to as Arisah
TABLE 10.1
Nutrients in Pasta* (per lOOg)
Carbohydrates, g 75 Thiamin, mg 0.09 Calcium, mg 10
Protein, g 12 Riboflavin, mg 0.1 Iron, mg 1.2
Lipoprotein, g 1.8 Niacin, mg 2.0 Phosphorus, mg 144
Calories 380
* Source: Home Economics 1972, Dec.: 24.
PASTA AND WHOLE GRAIN FOODS 239
in the Old Testament, consists of boiling whole grain lightly milled, and the product sieved to
wheat in open vessels until it becomes tender. separate large from small bulgur (Certel et al.,
The cooked wheat is spread in thin layers for 1989).
drying in the sun. The outer bran layers are During the soaking and cooking stages, a
removed by sprinkling with water and rubbing proportion of the vitamins and other nutrients
by hand. This is followed by cracking the grains present in the outer layers of the grain are
by stone or in a crude mill. mobilized, and move to the inner part of the
A product resembling the wheat portion of the grain, in a similar way to that described for
pilaf dish was developed in the U.S.A. in 1945 parboiled rice (q.v.). Thus, removal of the outer
as an outlet for part of the U.S. wheat surplus. layers of the grain, after soaking, cooking and
In one method of manufacture of bulgur, described drying, does not much reduce the nutritive value
by Schafer (1962), cleaned white or red soft of the bulgur.
wheat, preferably decorticated, is cooked by a Bulgur is sent from the U.S.A. to peoples in
multistage process in which the moisture content the Far East, as part of the programme of
is gradually increased by spraying with water and American aid to famine areas. In 1971,227,000 t
raising the temperature. Eventually, when the of bulgur were produced in the U.S.A., of which
m.c. has reached 40%, the wheat is heated at 5% was used domestically, the remainder being
94°C and then steamed for 1.5 min at 206.85 used in the Foods for Peace Program. The staple
kN/m2 (30 lb/in2) pressure so that the cooked food of people in these areas had always been
product is gummy and starchy. The starch is boiled rice; the process of breadmaking was
partially gelatinized. The m.c. is then reduced to unknown; wheat and wheat flour were therefore
about 10% by drying with air at 66"C, and the unacceptable foods. Bulgur provided a cheap
dried cooked wheat is pearled or cracked. One food that was acceptable because it could be
brand of the whole grain product is called Redi- cooked in the same way as rice and superficially
wheat in the U.S.A.; the crushed is Cracked- resembled it. The level of bulgur exports from
Bulgur (Nouri, 1988). the U.S.A. for the food aid programme is now
Other processes for making bulgur are reviewed about 250,000 t per year (Certel et aE., 1989).
by Shetty and Amla (1972). Bulgur can be stored for 6-8 months under
In a continuous system used in the U.S.A. for a wide range of temperature and humidity condi-
the production of bulgur, the wheat is soaked in tions, and its hard and brittle nature discourages
a succession of three tanks in which the m.c. is attack by insects and mites.
raised progressively to 25-30% during 3.54 h
Nutritive value
in the first tank, to 3540% m.c. during 2.5 h in
the second and to 45% m.c. during 2-2.5 h in
the third, giving a total soaking time of 8 h. The The nutritive value of bulgur is similar to that
grain is then cooked with steam at a pressure of the wheat from which it is made. Fat, ash and
of 1.5-3 bar for 70-90 sec and then dried to crude fibre levels are slightly lower, but protein
10-11% m.c. The outer layers are removed, the level is unchanged. Retention of thiamin and
TABLE 10.2
Nutrients in Bulgur* (per 100 g)
Carbohydrates, 75.7 Thiamin, mg 0.28 Phosphorus, mg 430
Protein, g 11.2 Riboflavin, mg 0.14 Potassium, mg 229
Fat, g
1.5 Niacin, mg 5.5 Magnesium, mg 160
Energy, kcal 354 Vitamin B6, mg 0.32 Calcium, mg 22.6
Pantothenic acid, mg 0.83 Iron, mg 7.8
Folacin, mg 0.038 Zinc, mg 4.4
Iodine, mg 14
* Source: Protein Grain Products International, Washington, D.C.
240 TECHNOLOGY OF CEREALS
niacin is about 98% of the original, that of in addition the nutritive value of the milled rice
riboflavin about 73%. Iron and calcium contents is increased by this treatment, because the water
are slightly increased, while phosphorus content dissolves vitamins and minerals present in the
is decreased by the parboiling process. The hulls and bran coats and carries them into
nutrient composition of bulgur is shown in Table the endosperm. Thus, valuable nutrients which
10.2. would otherwise be lost with the hulls and bran
Bulgur of acceptable quality has also been in the milling of raw rice are retained by the
prepared from triticale (Singh and Dodda, 1979) endosperm. It has been shown that rice oil
and from maize (Certel et al., 1989). migrates outwards during parboiling: therefore in
The consumption of bulgur in Turkey is esti- parboiled rice the oil content of the milled kernel
mated at 20-30 kg/head/annum. Turkey is said is lower, and bran content higher, than in raw
to export about 100,000 t of bulgur per annum rice.
(Certel et al., 1989). By gelatinizing the starch in the outer layers
of the grain, parboiling seals the aleurone layer
and scutellum so that these fractions of the grain
are retained in milling to a greater degree in milled
WURLD Wheat
Peeled bulgur wheat is a light-coloured, low- parboiled than in milled raw rice (Hinton, 1948).
fibre bulgur, made to resemble rice by removal Parboiling toughens the grain and reduces the
of the bran in a lye-peeling operation. The wheat amount of breakage in milling. Moreover, par-
grain is treated with sodium hydroxide, and the boiled rice is less liable to insect damage than is
loosened bran removed by vigorous washing with milled raw rice, and has an improved storage life.
water. The grain is then treated with warm dilute
Con version
acetic acid to restore the surface whiteness, and
dried. This treatment leaves the aleurone layer
intact. Peeled bulgur made from a red wheat is Conversion of rice is the modern commercial
known as WURLD wheat, a U.S. Department development of parboiling. In the H. R. Conver-
of Agriculture Western Utilization Research sion Process, wet paddy is held for about 10 min
Laboratry Develpment (Shepherd et al., 1965). in a large vessel which is evacuated to about 635
mm (25 in) of mercury. The paddy is then steeped
for 2-3 h in water at 75-85°C introduced under
a pressure of 552-690 kN/m2 (80-100 lb/in2). The
Ricena
Ricena is a rice substitute, originating in steeping water is drained off and the paddy is
Australia, made from wheat by a relatively in- heated under pressure for a short time with live
expensive patented process which gives a yield of steam in a steam-jacketed vessel. The steam is
about 65% (Brit. Pat. No. 1,199,181). The wheat blown off, and the pressure in the vessel reduced
is washed, cleaned, steamed under pressure and to 711-737 mm (28-29 in) of vacuum. The
dried. The product sells at the price of low-grade product is then vacuum dried to about 15% m.c.
rice, although the protein, iron and vitamin B1 in the steam-jacketed vessel, or it can be air-
contents of ricena exceed those of milled rice. dried at temperatures not exceeding 63°C. After
cooling, the converted paddy is tempered in
bins for 8 h or more to permit equilibration of
moisture, and is then milled.
In the Malek process, paddy is soaked in water
at 38°C for 4-6 h, steamed at 103.4 kN/m2 (15
lb/in2) pressure for 15 min, dried and milled. The
product is called Malekized rice.
Redistribution of thiamin (vitamin B1) in rice
parboiled by the Malek process was investigated
Parboiled rice
The parboiling (viz. part-boiling) of rice is an
ancient tradition in India and Pakistan, and
consists of stepping the rough rice (paddy) in hot
water, steaming it, and then drying it down to a
suitable moisture content for milling. The original
purpose of parboiling was to loosen the hulls, but
PASTA AND WHOLE GRAIN FOODS 241
by Hinton (1948). By microdissection of raw and this problem. If the steep water is maintained at
Malekized rice grains, followed by microanalysis a temperature of 65"C, the steeping time can be
of the fractions, Hinton showed that the thiamin limited to 4 h, and odour development is avoided.
content of the endosperm adjoining the scutellum The soaking conditions must be chosen care-
increased from 0.4 to 5.2 iu/g, while that of the fully so as to hydrate the grain sufficiently for it
scutellum decreased from 44 to 9 iu/g,and that to be gelatinized on subsequent heating, but so
of the pericarp/aleurone from 10 to 3 iu/g. as to avoid splitting the hull - which leads to
The thiamin content of the whole endosperm excessive hydration and leaching of nutrients.
increased from 0.25 to 0.5 iu/g. The redistribu- Rate of hydration increases with temperature of
tion of thiamin was due to the inward passage the steeping water, but above about 75°C the
of water through the thiamin-containing layers rate of hydration increases so rapidly that splitting
rendered permeable by heat to the vitamin. of the hull occurs. Thus, the solution is to limit
In a process called double-steaming, raw paddy the moisture level in the grain to 30-32% either
is presteamed for 15-20 min and then steeped in by soaking at 70°C or lower, or by starting the
water for 12-24 h. The water is drained off, and soaking at 75°C and allowing the material to
the product is steamed again and then dried. cool naturally during soaking. This method
Parboiling may induce discoloration of the gives the fastest hydration without complications
grains or development of deteriorative flavour (Bhattacharya, 1985).
changes. A suggested remedy for reducing flavour A process devized by F. H. Schule GmbH does
changes is steeping in sodium chromate solution not involve steaming. Rough rice is soaked for
(0.05%). It has been shown that the additional 2-3 h in water at a medium temperature while
chromium present in the milled rice is not absorbed the hydrostatic pressure is raised to 4-6 kg/cm*
when the rice is consumed, and thus poses no by admitting compressed air. The pressure is
health hazard (Pillaiyar, 1990). A remedy suggested released, and the rice is cooked in water at about
for bleaching is steeping in sodium metabisulphite 90°C. The rice is then pre-dried in a vibratory
solution (0.32%), but this treatment lowers the drier and subsequently dried by three passes
availability of thiamin. through columnar driers with successively decreas-
If steeping time exceeds about 8 h, the steep ing air temperature (Bhattacharya, 1985).
water tends to develop an off odour which is A high-temperature, short-time process for
picked up by the rice. The odour is due to the parboiling rice has been described (Pillaiyar,
activity of anaerobic bacteria in the steep water. 1990). Paddy steeped to about 24% m.c. is simul-
Various methods have been suggested to avoid taneously parboiled and dried in a sand-roaster
TABLE 10.3
Nutrient Composition of Rice* (gl1OOg)
Product Moisture Protein Fat Crude fibre Carbohydrate Ash Calories
Brown rice 12 7.5 1.9 0.9 76.5 1.2 360
White rice 12 6.7 0.4 0.3 80.1 0.5 363
Parboiled rice 10 7.4 0.3 0.2 81.1 0.7 369
(mg/lOOg)
Product Ca P Fe Na K Thiamin Riboflavin Niacin Tocopherol
Brown rice 32 221 1.6 9 214 0.34 0.05 4.7 29
White rice
Unenriched 24 94 0.8 5 92 0.07 0.03 1.6 -
Enriched 24 94 2.9 5 92 0.44 - 3.5 -
Enriched 60 200 2.9 9 150 0.44 - 3.5
* Source: U.S. Dept. Agric., Agricultural Research Service, Agricultural Handbook 8 (1963).
Parboiled rice
242 TECHNOLOGY OF CEREALS
in which the paddy is mixed with hot sand
and remains in contact with the sand for about
40 set, after which the sand and the rice are
separated by sieving. During this process the rice
loses about 10% of moisture.
For a comprehensive survey of other processes,
see Bhattacharya (1985).
AUTRAN, J. C., AIT-MOUH, 0. and FEILLET, P. (1989)
Thermal modification of gluten as related to end-use
properties. In: Wheat is Unique, pp. 563-593, POMERANZ,
Y. (Ed.). Amer. Assoc of Cereal Chemists Inc. St. Paul
MN. U.S.A.
BHATTACHARYA, K. R. (1985) Parboiling of rice. In: Rice:
Chemistry and Technology, Ch. 8, pp. 289-348, 2nd edn.
JULIANO, B. 0. (Ed.). Amer. Assoc. of Cereal Chemists
Inc. St. Paul MN. U.S.A.
BRITISH PATENT SPECIFICATION NOS 2,151,898 (back-mixing
of dough); 1,199,181 (ricena).
CERTEL, V. M., MAHNKE, S. and GERSTENKORN, P. (1989)
Bulgur-nichte eine turkishe Getreide spezialitat. Muhle
Mischfuttertechnik, 126(6 July): 414-416.
DE CARO, L., RINDI, G. and CASELLA, C. (1949) Contents
in thiamine, folic acid, and biotin in an Italian converted
rice. Abst. Commun. 1st Int. Cong. Biocha. 31.
Du CROS, D. L. and HARE, R. A. (1985) Inheritance of
gliadin proteins associated with quality in durum wheat.
Crop Sci. 25: 674-677.
European Food Marketing Directory, 2nd edn (1991) Euro-
monitor plc., London.
EUROPEAN PATENT APPLICATIONS Nos 0,1463 10 (extrusion
into N2/C02); 0,267,368 (quick-cooking pasta); 0,272,
502 (quick-cooking pasta); 0,288,136 (shaped pasta
products); 0,322,053 (drying Pasta); 0,352,876 (shelf-
stable, microwave-cookable pasta).
FEILLET, P. (1984) Present knowledge on biochemical basis
of pasta cooking quality. Consequence for wheat breeders.
Sci. Aliment. 4: 551-566.
HINTON, J. J. C. (1948) Parboiling treatment of rice. Nature,
Land. 162: 913-915.
HOUSTON, D. F. (1972) Rice: Chemism and Technology.
JULIANO, Inc. St. Paul B. 0. MN. (Ed.) U.S.A. Amer. Assoc. of Cereal Chemists
KATSKEE, A. L. (1978) Microwave macaroni drying. Macaroni
KIK, M. C. (1943) Thiamin in products of commercial rice
milling. Cereal Chem. 20: 103.
Material Thiamin Riboflavin Niacin KIK, M. C. and VAN LANDINGHAM, F. B. (1943) Riboflavin
in products of commercial rice milling and thiamin,
Paddy rice 3.540 0.4-0.5 52.3-55.0 riboflavin and niacin content of rice. Cereal Chem. 20:
Converted parboiled rice 1.9-3.1 0.3-0.4 31.2-47.8 563-569.
Milled, polished,
KOBREHEL, K. and ALARY, R. (1989) The role of a low
non-parboded rice 0.4-0.8 0.15-0.3 14.0-25.0 molecular weight glutenin fraction in the cooking quality
of durum wheat pasta. J. Sci Food Agrk. 47: 487-500.
* Sources: Kik (1943); Kik and van Landingham (1943). MANSER, J. (1986) Einfluss von Trocknungs-Hochst-
Temperaturen auf die Teigwarenqualitat. Getreide Mehl
Brot. 40: 309-315.
MESTRES, C., MATENCIO. F. and FAURE, J. (1990) Optimizing
process for making pasta from maize in admixture with
durum wheat. J. Sci. Food Agn'c. 51: 355-368.
MILATOVIC, L. (1985) The use of L-ascorbic acid in improving
the quality of pasta. Int. J. Vitam. Nutr. Res. Suppl. 27:
MOLINA, R. MAYORGA, I., LACHANCE, P. and BRESSANTI,
R. (1975) Production of high protein quality pasta products
using semolina-corn-soya-flour mkture. 1. Influence of
thermal processing of cOrn flour on pasta quality, cereal
Chem. 52: 240-247.
NOURI, N. (1988) Bulgur4in Beitrag zur Vollwert-und vege-
tarischen Ernahrung. Getreide Mehl Brot. 42: 317-3 19.
PILLAIYAR, P. (1990) Rice parboiling research in India.
Cereal Foods Wld 35: 225-227.
Consumption
Parboiled or converted rice is readily consumed
in India and Pakistan, while in the U.S.A. it is
used as a ready-to-eat cereal, as canned rice,
and as a soup ingredient. Elsewhere, however,
parboiled rice is not popular.
Nutrient value
Specimen figures for the chemical composition
of brown rice, white (polished) rice and parboiled
rice are given in Tab1e 10.3; the vitamin contents
of milled (unconverted) and parboiled (converted)
rice are shown in Tab1e 'Oa4' The fo1ic acid 'On-
tent of rice is increased from 0.04 to 0.08 pg/g by
conversion, whilst that of the polishings is reduced
from 0.26-0.40 to 0.12 pg/g (De Car0 et al, 1949).
TABLE 10.4 J. June: 12.
Vitamin Contents of Rice* (pglg)
References
ABECASSIS, J., FAURE, J. and FEILLET, p. (19894 Improve-
ment of cooking quality of maize pasta products by heat
treatment. J. Sci. Food Agric. 47(4): 475485.
P. (198913) Effect of moisture content of pasta during high
temperature drying. Getreide Mehl Brot 43(Feb): 58-62.
ALARY, R. and KOBREHEL, K. (1987) The sulphydryl Plus
disulphide content in the proteins of durum wheat and its
relationship with the cooking quality of pasta. J. Sci. Food
Agric. 39: 123-136.
ANTOGNELLI, C. (1980) The manufacture and applications
of pasta as a food and as a food ingredient: a review J.
Food Technol. 15: 125.
ABECASSIS, J., CHAURAND, M., METENCIO, F. and FEILLET,
345-36 1.
PASTA AND WHOLE GRAIN FOODS 243
POMERANZ, Y. (1987) Modern Cereal Science and Technology, Further Reading
Ch. 20: Extrusion products. VCH Publishers Inc., NY.
SCHAFER, W. (1962) Bulgur for underdeveloped countries. ANON. (1987) Bulgur wheat production. Am. Milh Process.
SGRULLETTA, D. and De STEFANIS, E. (1989) Relationship AUTRAN, J. C. and GALTERIO, G. (1989) Association between
between pasta cooking quality and acetic acid insoluble electrophoretic composition of proteins, quality character-
protein of semolina. J. Cereal Sci. 9: 217-220. istics and agronomic attributes of durum wheats. 11.
SHEPHERD, A. D., FERREL, R. E., BELLARD, N. and PENCE, Protein-quality associations. J. Cereal Sci. 9: 195-215.
J. W. (1965) Nutrient composition of bulgur and lye- JULIANO, B. 0. (Ed.) (1985) Rice: Chemistry and Technology,
peeled bulgur. Cereal Sci Today 10: 590. 2nd edn. Amer. Assoc. of Cereal Chemists Inc. St. Paul
SHETTY, M. S. and AMLA, B. L. (1972) Bulgur wheat. J. MN. U.S.A.
Fd. Sci. Technol. 9: 163. LICHODZIEVSKAJA, I. B., BRANDO, E. E., CHIMIZOV, J. I.,
SINGH, B and DODDA, L. M. (1979) Studies on the prepara- MUCHIN, M. A., TOLSTOGUZOV, V. B., MUSCHIOLIK, G.
tion and nutrient composition of bulgur from triticale. J. and WEBERS, V. (1989) Herstellung von Teigwaren aus
Food Sci. 44: 449. Backmehl unter Andwendung von Polysaccharid-Zusatn.
U.S. PATENT SPECIFICATION NOS 4,539,214 (rapidly rehydrat- Nahrung 33: 191-201.
able pasta); 4,540,590 (extrusion into vacuum); 4,540,592 MORGAN, A. I. Jr, BARTA, E. J. and GRAHAM, R. P. (1966)
(pre-cooked pasta); 4,675,199 (extrusionkompression WURLD wheat - a product of chemical peeling. North-
process); 4,828,852 (shelf-stable, pre-cooked pasta); west Miller 273(6): 40.
4,830,866 (pre-cooked pasta); 4,876,104 (long shelf-life
pasta).
Milling 139: 688. 92(10): 17-18.