10 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 recommen that at least 90% noodles etc. which are traditionally made from of the particles should fall between 150 um and the semolina milled from hard durum wheat(T. 340 um in size. Particles larger than 340 um durum)(cf.p.154 for milling of semo). The impede the activity of enzymes in the dough highest quality pasta products are made from 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 ized. 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
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 tetraHistorically, 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 ungelatinTraditionally, 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 (kneading/sheeting)process Drying of pasta In the traditional manufacturing process in use Finally, in the traditional process, the extruded it 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 49C, 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 eet which can then be cut into strips and the recently, drying temperatures were about 50%C trips carefully dried a temperature not above and the drying process took 14-24 h 49C 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 at55°-90° circulates round the product and rods, strips, tubes, etc. -was first introduced dries it to 17-18%m c. in about l 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 Extrusion process that follows, the pasta is rested to allow moisture 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 450-70C, 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 uired C, using shorter processing times, and It is claimed that the kneading/sheeting 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 kneading/sheeting 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
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 preand 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. Advanstructure 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 uality - and lower installation and operating -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 onditioning ( Euro. Pat. Appl. No. 0, 267, 368); asta-manufacturing industry which are directed aking partially-cooked pasta in acidified towards achieving various objectives, including water (U.S. Pat. No. 4, 828, 852 use of higher drying temperatures(Manser 1986; Abecassis et al., 1989a; Euro. Pat. Appl improvement in pasta quality, e.g. by reducing Nos0,309,413,0,322,053and0,352,876) 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); o.0,267,368;U.S.Pat.Nos42539,214and pre-drying and drying as two separate stages 4,876,104); improvement in nutritional quality, e.g. by use of superheated steam for simultaneously better retention of vitamins and other nutrients cooking and drying(U.s. Pat. No. 4, 539, 214); (Manser, 1986; Euro. Pat. Appl. No 0, 322 high-temperature after-treatment to make pre- 153) ooked 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.Nos4,828,852and4,876,104); n(U.S.Pat.No.4876,104); - reduction in drying time, with consequent extrusion into n,/cO, or into vacuum to saving in energy expenditure (abecassi 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 0,272,502and0,352,876;U.S.Pat.Nos4, dough(Euro. Pat. Appl. Nos 0, 352, 876 and 539,214and4540,592) 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 the starting material, i.e. the replacement of In some countries, e.g. France and Italy, the some(or all) of the durum semolina with other material used for making pasta must be durum cereal materials or even with non-cereal materials semolina, but other countries allow the use of (Molina et aL., 1975; Mestres et al. 1990) soft wheat flour, maize four, or various other These objectives have been addressed, and diluents. Countries which are non-wheat pr most cases attained, by modification of the ducers,e.g.many African countries, are interested traditional process in various ways, such as: in pasta made from non-wheat materials, e.g modification of the moisture content of difficult because of the lack of gluten which is the product before drying(Abecassis et al., formed when wheat is the starting material, and 1989ab) which contributes to dough development during
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 Preprocessing 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 beneficial effect to use a blend of semolina and maize flour from ich good quality pasta can be obtained, provided Glyceryl monostearate as additive the maize flour has fine granularity (less than 200 um)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 90C 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 64C, but not so high as to cause gelatiniza L-Ascorbic acid as additive tion of the starch. Other flow modifying agents 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 pigments, leading to improvement in the colour of the product by inhibiting lipoxygenase activity uncooked pasta Addition of 300 mg/kg 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 four 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 the protein is not denatured and, as a result, starch leaches out, making a gummy, mushy Doughing water temperature product, unless the pasta is immediately con tacted with extremely hot water, to set the protein The temperature of the doughing water matrix. An uncooked pasta which can withstand important. Water at 36-45.C is normally used exposure to cold water without leaching of starch cold dough making, 450-65C for a warm system may be made by the addition of low-temperature using high temperature drying, and 75-85c 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 50C, since albumen coagulates at Sulphydryl reducing agents, e.g cysteine gluta- 49C. Similarly, when ascorbic acid is added, thione, which reduce disulphide (-Ss-)bonds to the water temperature should not exceed 55C, sulphydryl groups(SH), thereby facilitating the otherwise degradation of the additive will be irreversible denaturation of the gluten, can b ccelerated. 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 74C. A modern drying process would use two
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 gelatinization 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 enmade 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 addihydrates 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 tages:drying at 71-104C for 2-4h, followed by(below 24%m c cracking may occur, while above further drying at 32-71oC for 0-120 min, but 30%mc. the dough becomes too soft and elastic with the use of a high velocity air current(150 ft'/ The sheeted dough is cut into pieces which are min), the drying times could be shortened to 15- partially dried in 10-60 sec by, e.g. infrared 30 min for the first step plus 30-120 min for the heating lamps and hot air at 204C. The produc second. Pasta made in this way can be rehydrated is then steamed and pasteurized to kill micro by soaking in cold water, and then cooked in organisms, cooled to 00-10.C and packed in about 2 min by conventional boiling or by micro- sterile trays with injection of CO2/N2(25: 75 wave energy(Euro. Pat. Appl. No 0, 352, 876). to 80: 20). Such packaged products should be storable at 4-10C for at least 120 days(U.S Cooking value of pasta Pat. No.4876,104) Cooking value' is a measure of the texture or insistency of the pasta after cooking The cooked pasta should offer some resistance to chewing but Quick-cooking pasta should not stick to the teeth. To retain these A process described for making a quick-cooking qualities and to avoid loss of nutrients, current pasta starts by making a dough from flour or procedures limit drying temperature to not above semolina of which at least 90% is derived from 60C, but such drying takes a long time- 16- durum wheat, with the addition of 0.5-5.0%by 24 h. Higher drying temperatures, while still wt of an edible emulsifier, such as glyceryl or avoiding nutrient loss and adversely affecting sorbitan monostearate, lecithin or polysorbates cooking value, can be used in a step-wise process, Water, at 79 C, is added to bring the mc.to e.g. by isothermal application of heat at temper- 22-32%. The ingredients are mixed at 76-88C2 atures between 40 and 94oC while maintaining extruded through a co-rotating twin-screw extruder the vapour pressure within the pasta(Aw) below at 60-88C. The extruder comprises three zones 0.86 a cooking zone, a venting zone, and a forming In one such drying schedule, the product zone. When passing through the venting zone, passes through eight areas in which the tempera- the material may be subjected to a degree of tures are( successively)40°,50°,60°,70°,80°,84°, vacuum(2.5-5psi) to draw off excess moisture. 94 and 70C, taking about 3 h to complete the The product can be cooked by microwave energy drying. The product, with 13%m c, is then (Euro Pat. Appl. No 0, 272, 502) cooled to 25@C(Euro. Pat. Appl. No 0, 322, 053). Another process for making rapidly rehydrat able pasta simultaneously cooks and dries the Micro-organism control extruded dough (made from semolina/four and water) by the use of superheated steam at a Control of micro-organisms in stored pasta temperature of 102-140C for 7-20 min. Th products is essential. The use of high temperature product is in an unexpanded condition and can (above 60C) drying to improve pasta product be packaged without further cutting or shaping sterility has been described (Milatovic, 1985) (U.S.Pat.No.4,539,214) Another process is described in which dough is made from flour(durum wheat semolina, or quick-cooking pasta pre-cooks a mixture of pasta whole soft wheat flour plus corn flour, rice flour flour and water in a pre- conditioner before it or potato flour) about 75 parts, with about 25 passes through an extruder with three zones parts of whole egg, but with no water. Additives cooking, venting, extruding. The temperature of such as wheat gluten, soya protein isolate, algin- the mixture is kept below 101.c in the cooking ates and surfactants may be added The dough zone to prevent the formation of darkened specks is sheeted through a series of rollers to a thickness symptomatic of burning during cooking(Euro of 0.03 in, while keeping the m.c. about 24% Pat. Appl. No. 0, 267, 368)
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 microorganisms, 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 microwave 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 temperatures 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 temperatures 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, alginates 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 rehydratable 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)