UNIT 11 RICE BASED PRODUCTS Structure

11.0 Objectives

11.1 Introduction

11.2 Breakfast Cereals

11.3 Rice Flakes

11.4 Puffed Rice/Paddy 11.4.1 Sand Puffing 11.4.2 Roller Puffing 11.4.3 Oil Puffing 11.4.4 Air Puffing 11.4.5 Gun Puffing 11.4.6 Extrusion Puffing . 11.5 Quick Cooking Rice

11,6 Fortified Rice 11.6.1 Rice Enrichment Processes

11.7 Rice Based Infant and Baby Foods 11.7.1 Pre-cooked Rice Cereal 11.7.2 Extrusion-cooked Baby Food 11.7.3 Formulated Baby Foods

11.8 Fermented Rice Products 11.8.1 Fermented Rice 11.8.2 Idli, Dosa and Dhokla 11.8.3. Ambai

11.9 Rice Noodles and Pasta 11.9.1 Traditional Method of Manufacturing Rice Noodles

11.10 Let Us Sum Up

11.11 Key Words

11.12 Some Useful References

11.13 Answers to Check Your Progress

11.0 OBJECTIVES

After reading this unit, you should be able t~:

• understand'the meaning of breakfast cereals; .

• know different value added products produced from rice;

• explain the steps for production of various rice based items;

• know important consideration in the process technology; and

• understand changes in nutrition value of the products. 89 Paddy Storage and Milling , Management 11.1 INTRODUCTION

In India, due to growing urbanization of our society the demand for fast and convenience foods has increased. Rice is processed and reprocessed into numerous kinds of such foods. Process of rice depends on grain type and textural qualities for use in various kinds of prepared and convenient type rice products such as breakfast rice cereals" quick cooking rice, baby foods etc.

Rice-based products that have been popular in India for a long time include rice flakes (poha avalakki>, popped, puffed or expanded rice, which are processed from rice or paddy; idJi, dosa, papads, vermicelli, crispies, muruku, etc., which are prepared from wet-ground rice paste or dry-ground rice flour; and fermented or deep-fried preparations made from a mixture of rice and pulses.

11.2 RICE BREAKFAST CEREALS

Rice contains a large proportion of starch. In its natural form, the starch is insoluble, tasteless, andunsuited for human consumption. To make it digestible and acceptable it ml!st be cooked. Rice breakfast cereals may be divided into two classes: those which require cooking before serving and those which are ready-to-eat directly from the package. The ready-to-eat rice cereals may be made from entire rice grain or its milled products. In prepared cereals, rice, alone or in combination with other cereals, is precooked, dried, flaked or formed into dough, then expanded or puffed and toasted. The cooking time, steam pressure, temperature of the basic materials arid toasting procedure greatly influence the quality of the final product. Flouring materials, vitamin B complex, mineral and protein containing ingredients may be added to improve the nutritive value.

Breakfast cereals can be categorized into types based on use (or) physical nature of the product:

1. Traditional cereals that require cooking- Cereals which are sold in the market as processed raw grains.

2. Instant traditional hot cereal- Cereals which are sold in the market as cooked grains and require only boiled water for preparation.

3. Ready-to-eat cereals- a group of cereals manufactured from grain products having \ been cooked and modified such that they may be subdivided into flaked, puffed or shredded products.

4. Ready-to-eat cereal mixes- Cereals combined with other grains, legumes or oil seeds and dried fruit products.

5. Miscellaneous cereal products- Cereal products which can not be included in any of the above types because of specialized process or end use. Cereal nuggets and baby foods are products which may be considered in this category.

Check Your Progress 1

Note: a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. List out the value added products from rice.

90 2. What are the important parameters affecting the final quality of processed product? Rice Based Products

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3. What are the different types of breakfast cereals? Describe briefly .

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11.3 RICE FLAKES

In the traditional process, paddy is soaked in warm water overnight, the water is drained, and the soaked paddy is roasted in hot sand for I minute ana then hand pounded or passed repeatedly through an edge runner to get the kernels flattened. There is considerable loss in this process due to breakage of kernels during flaking.

In the imp'roved technique, rice is first cooked in a rotary cooker at 8.2 to 8.6 kg/ern- pressure for 20 minutes and steam pressure is bled off to eliminate gases. Cooking is continue for I to 2 hours depending upon kind of rice used. In cooking rice it is necessary to add an agent that will prevent the cooked rice from sticking and forming lumps. Moisture after cooking should be about 33% and vacuum is applied after cooking to surface dry. After being dried to about 17 % moisture content, the cooked rice is tempered for several hours and then flaked on large smooth rolls and finally toasted. Thereafter, the blistered flakes are dried to 2-3% moisture content, cooled and packaged. The roller flakes are . used to eliminate the kernel breakage. Compared with oven-puffed rice, rice flakes tend to soften more quickly in milk.

Check Your Progress 2

Note: .a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. Describe the traditional method of preparation of flaked rice.

2. Describe the improved method of preparation of flaked rice and indicate the major difference over traditional method .

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11.4 PUFFED RICE .

Puffed rice is very popular in India as a low cost ready-to-eat breakfast cereal as well as snack because of its crispness and lightness. It is also a favourite food product made in different forms like puffed rice balls, bars and fatty pastes, chocolate (or) boiled sugar confectioneries in many countries. 91 Paddy Storage and Milling Puffing of rice grains results from the sudden expansion of water vapour (steam) in the Management interstices of starch granules during high-temperature-short-time (HTST) heating of the grains. The particle is fixed in its expanded state by the dehydration resulting from the rapid diffusion of the water vapour out of it. Puffed product should be maintained around 3 percent moisture in order to achieve the desired crispness. Puffing processes may be broadly classified into two groups: 1) atmospheric pressure processes which rely upon the sudden application of heat to obtain the necessary rapid vaporization of water, and 2) pressure drop processes which consists of suddenly transferring superheated particles into a space at lower pressure. The pressure drop may be achieved by releasing the seal on a yes el containing a product, which ha been equilibrated with high temperature steam or it may be secured by transferring the hot material from the atmosphere into an evacuated chamber. Sand puffing, air puffing, oil puffing, roller puffing and oven puffing are examples of atmospheric pressure processes while gun puffing, extrusion puffing are examples of pressure-drop processes. 11.4.1 SandPuffing

. This method is traditionally followed in India where parboiled rice grains having initial moisture content of 11-12 percent are mixed with 2 percent salt and limited water so that / moisture content of rice increases upto 16-29 percent (wb), Moistened rice grains are heated (tempering) for 30 minutes to 8 h for moisture equilibration within the grains. The treated rice grains are dried in the bright sun or by conduction heating in a hemispherical metallic container with continuous stirring until grains get dried upto 10 to 11 percent (wb). Small quantity of the rice is roasted at an optimum sand temperature between 230 to 275 QCfor 6 to 20 seconds to give puffed rice with expansion ratio of 8 to 10. The process is tedious and the production capacity is very low (2-2.5kg/hr). 11.4.2 Roller Puffing , In roller puffing, dough with moisture content of 8 to 18 percent is fed into the rolls with temperature of 190 to 440Q C. Puffed products are obtained at 6 to 7 % moisture content. The rolls are heated by radiant heat or by circulation of high temperature fluid media inside the cylinder. 11.4.3 Oil Puffing

Pre heated rice (parboiled) is puffed in vegetable oil at 200 to 220 QCtogive expansion ratio of 5 to 7. 11.4.4 Air Puffing

Blast of air at 200 to 300 QCfor 7 to 10 seconds is given to pretreated rice at IOta 12O/~ moisture content which gives puffed rice with expansion ratio of 8 to 10. 11.4.5 Gun Puffing

In this process raw milled rice and other grains can be puffed and do not need pretreatment (parboiled) before puffing which is an essential step for puffing with other technique.

Pro-moistened pearled or unpearled grains are fed into a pressure vessel, which is continuously rotated and externally heated. As the optimum pressure, varies from grain to grain, the sudden release of chamber pressure causes the superheated water to flash into steam resulting in porous structure of the puffed products. In some cases preheated grains at 272-337 "C (521 to 638 OF) are fed to the pressure vessel in which pressure is built by superheated steam upto 15.1 kg/ern" at a temperature of 241.6 QCat the gun. After a short cooking time, the gun is suddenly opened to produce puffed rice. Initial moisture content of the grains and attaining optimum pressure within minimum time are. critically important for gun puffing. 92 11.4.6 Extrusion Puffing Rice Based Products

Puffed breakfast cereals, and snacks are made by extruding superheated and pressured dough through an orifice into the atmosphere. Either single screw (or) twin screw extruders is used. The sudden expansion of water vapour in the extrudate as the excess pressure is released results in a volume increase of several times. Apparent specific volume can reach or exceed those attained by gun puffing and the process seems to have several advantages over gun puffing, such as high and continuous production rates, greater versatility in product shape, and easier control of product density. However extrusion puffing is possible for dough only and not for whole grain kernels, which is possible for gun puffing.

The rice flour mix containing a 60-75% expand able starch base is moistened with water (or) steam and equilibrated to ensure a uniform supply of extrusion material. The resultant mass is compacted by a screw revolving inside a barrel, which may be heated by steam or electrical band heaters. The thread of the screw has a progressively closer pitch as it approaches discharge. In some extruder designs, the rice premix is fed directly into the extruder. The water and/or steam are injected into the barrel and mixed with the premix. The pressurizing, shearing, and steam heating brings the dough to a temperature of around 150-175 QCand a pressure of 2.46 to 35.2 kg/ern? at the die head. Under these conditions the dough is quite flexible and easily adapts to complex orifice configurations.

The dough pieces expands very rapidly as they leave the dice orifice, and the expansion may even continue for a few seconds because the dough is hard and still flexible and water continue to boil off. The pieces are further dried in hot air oven, cooled and packed.

Check Your Progress 3

Note: a) Use the spaces given below for your answers. b) Check 'your answer with those given at the end of the unit.

1. Describe the puffing of the rice grains .

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2. What are the different processes of puffing the rice grains? Describe with examples,

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3. List th~different methods of puffing?

4. What are the major differences between gun and extrusion puffing?

93 Paddy Storage and Milling Management 11.5 QUICK COOKING RICE

It is a popular product in the United States, Japan, and several western countries. Ordinary milled rice requires 20 to 30 minutes to cook to a satisfactory culinary acceptability, depending upon variety, ageing, form of rice namely raw or parboiled, and specific textural preferences. Instant or quick cooking rice is pre-cooked, dehydrated, natural, whole grain rice, which can be prepared in very short time of about 2 to 5 minutes. The quick- cooking rice must be easily processed in mass quantities and must possess good storage stability for 6-12 months at ambient temperature. To prepare quick-cooking rice, it is necessary to pre-cook the rice and gelatinize the starch to some extent in water, steam, or both. The cooked or partially cooked rice is usually dehydrated in such manner as to retain the rice grains in a porous and open-structured condition. The finished product should consist of dry, individual kernels, be free of lumps, and have approximately one and a half to three times the bulk volume of the raw rice.

The following are the commercially useful quick-cooking processes:

1. Soak-boil-steam-dry method: Raw milled rice is soaked in water to 30% moisture at room temperature and cooked in boiling water to 50 to 60 % moisture (wb), with or without steaming. The product is further boiled or steamed to increase the moisture content to 60 to 70 % (wb) and then dried carefully to 8 to 14 % moisture to maintain a porous structure.

2. Expanded and pre-gelatinization method: Rice is soaked, boiled, steamed or pressure-cooked to gelatinize the grain thoroughly, dried at low temperature to yield fairly dense glassy grains, then expanded or puffed at high temperature to produce the desired porous structure in the final product.

3. Rolling or "bumping" method: Rice is pregelatinized as described in the previous section, rolled or "bumped" to flatten the grains and dried to a relative hard glassy . product.

4. Dry heat treatment method: Rice is exposed to a blast of hot air at 65-82QCfor 10-30 minutes, or at 272 QCfor 18 seconds, to dextranize, fissure or expand the grains. No boiling or steaming is applied. The product cooks in less time than untreated grains.

5. The freeze-thaw-drying process: Rice is precooked and then frozen, thawed, and dried, It is an expensive method.

6. Gun puffing: This process is a combination of preconditioning the rice to 20-22% moisture followed by steam cooking in a retort at 3.5-5.5 kg/ern? for 5-10 minutes. Then the product is puffed to atmospheric pressure or into a vacuum. The optimum terminal condition is at 165QCat 20-25% moisture levels.

Chemical treatments have also been used to produce quick cooking rice. In this method, rice is impregnated with a saturated solution of sodium chloride (NaCI) at about 80 QC whereby the starch is partially gelatinized; however this is not a good method.

11.5.1 Types of Quick-cooking Rice

Differences in moisture levels, precooking times and te~perature, dehydration conditions, and other processing variables result in various types of quick-cooking rice. These range from reiatively undercooked rice, requiring 10-15min of cooking time, to a good quick- cooking rice requiring 5 min preparation time. Minute Rice", a commercial rice product, can be rehydrated with hot water in a minute or two, which yields a fairly good product when boiled with water. 94 Check Your Progress 4 Rice Based Products

Note: a) . Use the spaces given belowfor your answers. b) Check your answer with those given at the end of the unit.

1. What is the difference between ordinary milled and quick-cooking rice?

2. What are the main unit operations in preparation of quick-cooking rice?

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3. What is Minute Rice"? Describe briefly .

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4.· List the commercially useful quick-cooking processes .

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11.6 FORTIFIEDRICE·

Enrichment generally refers to the restoration of vitamins and minerals lost during processing. Fortification generally means adding vitamins and minerals to foods in higher amounts than were present before processing. Fortification of ready-to-eat rice breakfast cereals with vitamins, minerals, and flavour compounds is now a very common practice. The usual approach is to add the minerals and more heat-stable vitamins such as niacin, riboflavin, and pyridoxine to the basic formula mix and then spray the more heat-liable vitamins such as vitamin A and thiamin on the product after processing. The nutrients to be added must be stable during processing and storage, and a sufficient amount is added to compensate for losses in processing and storage. 11.6.1 Rice Enrichment Processes 11.6.1.1 Powder Enrichment

Currently two forms of enrichment are used commercially in the United States. The first form is a pre-blended powder mixture of thiamin, riboflavin (if requested), niacin. or niacinamide, folic acid, and either ferric orthophosphate (white iron), ferrous sulfate (yellow iron), or reduced iron. Riboflavin and ferrous sulfate give the powder and the rice a slight off-white to yellow colour, which is undesirable to some consumers. Reduced iron has the potential to turn the rice grey to black. Ferric orthophosphate is the most popular form of iron used in the industry due to its white color and ability to blend with the white rice. However, when ferric orthophosphate is oxidized or contains excessive moisture, it can turn tan, yellow, purple and/or black

95 Paddy Storage and Milling Table 11.1 : Forms of Enrichment Showing Pre-blendedLevels Management . , Forms of Vitamin or 'Level Level Addition Enrichment Mineral (g/450gms.) (mg/g) Rate" Vitamin/or Mineral Powder Thiamin 3.20 7.05 0.06% Niacin 25.6 56.44

,'. Folic acid 1.12 2.47 Iron 33.6 ' 74.07 Filler 390.8 859.96 Vitamin/mineral Thiamin - 0.4 0.88 0.5% coated kernel Niacin 3.2 7.05

Folic acid 0.14 0.31 . Iron 2.6 5.73 Filler 447.26 986.02

a When vitamin/mineral enrichment is added at this rate, the final product will contain the Federal Standard (USA) of identity for thiamin, niacin, folic acid, and iron.

b Or 0.62 mg/g (0.06%).

c Or 5.03 mg/g (0.5%).

One of the disadvantages of powder enrichment in 'rice is that 20-1000/0 of the enrichment washes off the rice, depending on 'the amount of water used in rinsing and the application time. Other disadvantages of powder enrichment are that the vitamins and minerals are less stable during storage and after application; the uniformity of application can be a problem and may cause assay problems; and the vitamins and minerals can react easily with other food ,components. The principal advantage of powder enrichment is that the blend is less expensive than other forms of enrichment.

11.6.1.2 ' Coated-Kernel Enrichment

. ' The second form of enrichment available commercially is premixed and treated kernel- type enrichment. This "premix", as it is known in the rice industry, is a powder-blended enrichment that is applied to the milled rice grains and coated with a water-insoluble surface to retain the vitamins and minerals during rinsing.

One unique aspect of kernel-type enrichment is that the rice can be rinsed without losing the enrichment before cooking. The insoluble food-grade coating is broken down when it reaches the acid' environment, of the stomach, thereby releasing the vitamins and minerals. In addition, the vitamins and minerals are stable' and do not react with other food components, and the kernels are easy to detect and assay in the final product. Kernel-type enrichment is slightly more expensive than power-type enrichment because it is not as concentrated as powder enrichment (Table 11.1). '

11.6.1.3 Extruded Kernels

The extruded-kernel premix is prepared by mixing rice starch or flour with the vitamin and minerals powder and extruding it into simulated grains. The patented extruded enrichment product on the market, .named Ultra Rice, is produced primarily for the 96 international market. Check Your Progress 5 , Rice Based Products

Note: a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. What is the difference between enrichment and fortification?

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2. List the different methods of fortification?

3. What are the advantages and disadvantages of powder enrichment process?

4. What are the advantages of coated-kernel enrichment process?

5. 'What is Ultra Rice? Describe briefly.

11.7 RICE BASED INFANT AND BABY FOODS

Babies have unique nutritional requirements, and rice cereal is often the first solid food introduced into the baby's diet. This is because it is easily digested, hypoallergenic, low in fat, and has a bland flavour. Rice in the form of rice flour or as granulated rice is used in' the formulation of many strained baby foods. Rice flour, glutinous rice flour, and rice polishing are used in preparing baby foods. Rice flour is often used to thicken baby food products. It blends well with other ingredients such as vegetables and proteins and does not add unfamiliar ingredient names to the label.

Rice baby cereals are marketed as dry, precooked flakes for rehydration and as ready- to-eat -cereals. In ready-to-eat baby cereals, the choice of rice variety is important. Medium and short grain varieties with lower amylose contents are used to avoid retrogradation during storage, which results in formation of a very rigid gel and separation of water.

The largest use of rice in the baby food industry is in the manufacture of pre-cooked infant rice cereals. 11.7.1 Pre-cooked Rice Cereal

Pre-cooked rice cereal is frequently prescribed as an infant's first solid food. The cereal must be easily reconstituted, with milk or formula, with a minimum of lumps. 97 Paddy Storage and Milling The process for making precooked baby foods consists of preparing and cooking cereal Management slurry. The objective is to precook the rice and to convert the starch from crystalline to amorphous form. To aid in the digestion of the rice starch, amylase enzymes from an industrial 'source may be added to the slurry with accurate control

The prepared rice slurry is dried with an atmospheric drum drier The thickness of the film on the drier surface, the spacing between the drums, the temperature of the drum surface, the drum speed, and the flowing properties of the slurry are controlled with the objective of making an easy-to-digest rice product. The bulk density of the cereal is related to the thickness of the sheet coming off the dryer and the size distribution of the flakes. Because of the high starch content in rice, the apparent viscosity of the cooked rice cereal is markedly affected by a slight variation in the solids content. The solids, drum speed, and the drum temperature are adjusted to obtain a finished product of excellent quality. Packaging of the final product in selected paperboard carton containers appears to be a common practice for markets where extreme climate fluctuations are not common.

Some precooked rice cereals with strawberries or apples appear to be gaining favourable consumer acceptance. These products are prepared in a manner similar to that employed for regular precooked infant cereals. Cereal ingredients, fruit, sugar, oil, vitamins, and minerals are cooked, dried on an atmospheric drum drier, flaked, and packaged. Because of the hygroscopicity of the fruit and sugar, fruit cereals require moisture-proof packages. Some antioxidant may be incorporated in the packaging material to prolong the shelf life of the product. But special permission for such practices from the Food and Drug Administration (FDA) may be necessary because baby foods require special attention for safety seasons.

Rice based cereal may become rancid if packaged in a hermetically sealed container. The packaging material most suitable for such product is one that allows transmission of both moisture vapour and gas. Most precooked infant cereals are packed in paperboard cartons. A bleached manila liner on the interior of the carton appears to be very commonly used. The carton is wrapped with a glue-mounted, printed-paper label. The tight wrap offers sifting and insect protection to the package. 11.7.2 Extrusion-cooked Baby Food

Besides drum drying of rice baby foods, extrusion cooking is a new method for preparing baby foods. The type of extruders used, the particle size of the rice flour, the moisture content of the rice-water mixture, and the extrusion condition are some of the important factors influencing the properties of extruded rice baby foods. An example of extrusion cooked rice-based baby foods is the Kasetsart" infant food, developed by Khasart University, Bangkok, Thailand. It contains 72% rice flour and 13% full-fat soy flour and babymate. A mixture made with 75% milled rice flour and 25% dehulled mung bean is customarily used in the preparation of soups and casserole dishes. 11.7.3 Formulated Baby Foods

Rice cereal products are customarily used in the preparation of formulated baby foods. Not only is rice a food ingredient" but its use in baby foods has a significant role in the consistency of the product. The variety of rice used in these products is important to the physical properties of the final product. Long-grain rice, because of its higher amylose content, causes the product to thicken during storage (starch retrogradation) 98 and eventually produce a very rigid gel and water separation. The presence of free liquid in a product packaged in a glass container is a serious defect. 'Glutinous-rice Rice Based Products -flouris a good stabilizer for canned and frozen food products. The stability is achieved as a result of a reduction of amylose/amylopectin ratio in the product.

There is a grade of baby food designed for more advanced babies called junior grade. "Junior'tbaby foods have a coarser texture. They help the babies acquire the mouth feel of solid food. To produce the junior grade baby foods, granulated rice is incor- porated into the formulation for many junior vegetable and meat items. In the for- mulation of junior baby foods, care must be taken to avoid thin consistency after cooking, or particles can settle out to form a mat in the bottom of the jar. To' ensure uniform distribution of the junior-sized particles, modified waxy-maize starch is frequently incorporated into the product.

Check Your Progress 6·

Note: a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. What are the main features of rice baby foods?

2. List the various forms of rice used in preparation of baby foods?

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3. Wliat is the main reason to use medium and short grain varieties in preparation of ready-to-eat baby cereals?

4. List the various ingredients used in preparation of baby foods .

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5. What are the main important operations in preparation of precooked baby cereal?

6. List the parameters affect the final quality of easy-to-digest rice product in drum drying .

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99 I

Paddy Storage and Milling 7. State the reason not to use hermetic ally sealed container for packing precooked Management rice baby cereal.

8. . What are the important factors which influence the properties of extruded rice . baby foods?

9. Describe Kasetart" infant food.

10. State the reason to use long grain rice in formulated baby foods.

11. Describe Junior baby food .

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11.8 FERMENTED RICE PRODUCTS 11.8.1 Fermented Rice This product is prepared by adding water to cooked rice and incubating the mixture overnight. The water is then drained off and used for cooking vegetables or mixed with buttermilk and salt and consumed directly. The rice is mixed with curd (dahi) and salt. S. faecalis (2.7x107 per g), Pediococcus acidilactict (2.7x107 per g), and Bacillus sp. (1.6x108 per g), and Microbacterium flavum (1.1 * 108 per g) have been isolated from fermented rice. The pH decreases from 6.1 to 5.7 in 16 hr. There is no change in volume, amino nitrogen, or free sugar. 11.8.2 Idli, Dosa and Dhokla ldli is a small, white acid-leavened and steamed cake prepared by bacterial fermentation of a thick batter prepared from carefully washed rice and dehulled black-gram pulse. The rice is coarsely ground and the black-gram is finely ground. Dosa batter is very . similar to idli batter, except that the rice and black-gram are finely ground. Following' fermentation, the dosa is quickly fried as a thin, fairly crisp pancake and eaten directly. Dhokla is similar to idli except that dehulled Bengal-gram pulse is used instead of black gram pulse in its preparation. The fermented batter is poured into a greased pie pan, and steamed in the open rather than in a covered idli steamer. Fig 11.1 outlines processing 100 methodology for the preparation of idli. Wash and soak for 5-10 hrs Wash and soak for 5-10 hrs Rice Based Products

Grind finely in a mortar Grind coarsely in a mortar

Combine slurries into a thick batter and mix well I Add salt for seasoning (approximately 1% w/v)

Incubate overnight 1a warm place (30-32X:)

POUfbatter into small cups in idli cooker

Steam for IO minutes I Ready for consumption

Fig. 11.1: Flow chart for idli production

11.8.3 Ambai

Ragi, a millet flour, is combined with water to make a thick batter and fermented 14 to 16 hours. The batter is added with continuous stirring to partially (3/4th) cooked rice and .., cooking is completed. Then, following cooling, sour milk is added and the ambali is ready to eat. L. mesenteroides (1.6x109 per g), L. fermentum (1.6><109per g), and S. faecalis (8x108 per g) have been isolated from the fermentedsragi. The pH decreases from 6.4 to 4.0 and the volume increases by about 20%, indicating some C02 production. Other types of breads are prepared primarily by acid fermentation of rice flour dough, which . include Korean kichudok and Philippine puto, These products are leavened, steamed rice cakes which are similar to Indian idli, except for the fact that they do not contain any legumes. - Puto is special in that it is prepared using year-old rice and the batter is neutralized at the

midpoint of the fermentation. Fig 11.2outlines processing methodologies for the preparation of kichudok and puto.

Kichudok is prepared at the household level in Korea and is consumed on special occasions, while puto is normally consumed as a breakfast and snack in the Philippines. Puto is a common food of the lower-income group, but puto varieties containing added cheese, eggs etc., are consumed as delicacies by higher-income groups. In a number of Philippine towns, the preparation of puto is an important cottage industry.

Brem is a special snack food prepared by the acid fermentation of rice in Indonesia. It is a solid cake, with a sweet and slightly sour taste, containing over 65% of glucose .. 101 Paddy Storage and Milling Polished rice Mixed rice ~500g) Management'

Wash, soak in water Wash and soak in water (3-4 hr) • ___ 1 _ I Drain and grind Ferment'100g portion' Hang remaining I 18 hrs at room temp. portion (900g) in Mix with,rakjU and water muslin bag for 24 hrs

Liquid dough Add sugar I . Ferment overnight . I Ferment 6 hrs. I Steam in layers . I Mix and add 30-100 ml water Kichudok

Ferment 9 hrs. I Add 300 g sugar, 12 g lye 80m] water and mix I Ferment 4-5 he. I Steam for 30 min.

Puto

Figure 2. Flow chart for preparation of Korean kichudok and Philippine puto

Check Your Progress 7

Note: a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. List the traditional ingredients for preparing dhokla, idli and dosa.

2. What is the major difference between idli and dhokla?

3. Distinguish between Indian idli and Phillippin puto. ,

~. List the differences between kichudok and puto .

...... '...... 102 Rice Based Products 11.9 RICE NOODLES AND PASTA 11.9.1 Noobles (Rice "Pasta'·') Rice noodles are a popular rice product in Asia and are consumed in the form of soups (or) snack foods. They are also called bifun (bihon) or vermicelli in Taiwan, China and east southern Asia and harusame in Japan. They are usually prepared from high- amylose rice flour.

11.9.1.1 Traditiona1 Method of Manufacturing Rice Noodles Figure i1.3.111ustrates the traditional method of manufacturing rice noodles. Freshly polished rice is preferred so that rancidity in the product is minimized. Brokens can be used. to reduce the cost. Horizontal stone or concrete mills and vertical steel mills are used to wet-mill the presoaked rice. Microbial growth generally is not desirable for regular rice noodles. Nevertheless, fermentation is conducted during long-time soaking for special rice noodles in Thailand. Brokens are soaked for:three days for fermentation, which reduces the pH from 7 to 3.5, with Lactobacillus sp.' and Streptococcus sp .. The protein content decreases to 1.6,% after one day offermentation and to 1.1% after three days.

In Taiwan, extrusion has been commercially adapted to integrate the action of cooking, .kneading, and forming. .A single-screw extruder is used to partially cook the feeding flour with appropriate water content (35-40%). The precooked dough is then kneaded and formed to noodle strands via the second single-screw extruder. The extruded noodle strands are further steam cooked and then dried in an air oven. Alternatively, one extruder can be used instead of two extruders. However, pregelatinized flour or starch is needed as a binder to enhance the strength of the noodle strands. A twin-screw extruder has been used to produce rice noodles without adding pregelatinized flour or starch. The manufacture of rice noodles is then switched from a batch to a continuous process. The dry noodles are soaked "in cold water until hydrated and soft and then soaked in hot .water. The stability of the rehydrated sample is determined by observing the turbidity of the hot soaking water, and the sample is manually assessed for surface smoothness and stickiness. Excellent noodles hydrate with minimum turbidity and surface stickiness. Cooking loss has been a good index with which to assess the quality of hydrated noodles. Low cooking loss is an associate with low turbidity. Generally, cooking losses lower than 10% is desirable for good quality, clear soup.

Polished rice ----+Wet milling ----+ Dehydration ----+ Mixing& Or ' by pressing crushing Brokens ~

Forming •.••-- Kneading .•••••f---- Steam or water .--- Forming a Partially cooking dough (Balls or Cylinders)

Cooking in boiling water----- ...~• Cooking in cool water

Cooking by steam -----.~ Wet noodles ---+~Drying

~ Product .••.••f---- Packaging

Figure 11.3: Flow chart for traditional process of manufacturing rice noodles 103 Paddy Storage and Milling Traditionally, rice noodles are made from wet-milled flour, which results in environmental Management concerns due to wastewater. In response, some have tried to replace wet-milled flour with dry-milled flour. Wet-milled flour has a smaller particle size than dry-milled flours. Under the light microscope, dry-milled particles aggregate, but wet-milled particles disperse individually. The heat generated during dry milling gelatinizes the surface of the particle, which results in a sticky surface and aggregation. The dry-milled flour yields rice noodles with a cooking loss as high as 20.9%, which is much higher than that for the wet-milled product (9.2%). In addition, the surface of noodles from dry- milled flour is.much rougher than is that from wet-milled flour. The particle size of dry milled flour has been found to affect its uitability for rice noodle making. A general stamp mill yielded the smallest flour fraction of 100-150 im, which withstood heating without disintegration and was suitable for making rice noodles; The rate of water absorption by course particles is slower than that by fine particles, which results in lower degree of gelatinization and higher die pressure during twin-screw extrusion cooking. Flour smaller than 1061m was recommended for extrusion cooking of rice noodles with a degree of starch gelatinization higher than 90%.

The amylose content in rice flour has been shown to affect the quality of rice noodles. High amylose content is necessary to produce a product with fibrillar structure and to give noodles lower density and more whiteness. In Philippines, rice noodles made from \ intermediate-amylose rice (IR48) is preferred. High-amylose rice with low gelatinization temperature and hard gel consistency is preferred for making rice noodles in Taiwan. Milled rice flour with hard gel consistency (35min)and.high amylose content(30%) is used in Thailand. In Japan, rice noodles are made exclusively from indica rice with high amylose content.

Surface gelatinization of the extruded noodles improves the stability and texture upon cooking. The cooked extruded noodles lack the X-ray diffraction crystallinity of raw rice starch. The average degree of starch gelatinization of steamed, extruded noodles 'is reported to be 65-75%, with the surface 98% gelatinized and core only 55% gelatinized. Electron micrography of both raw and ~ooked rice noodles showed a honeycomb-like fiberillar network of retrograded starch, with protein interwoven in the strands.

11.9.1.2 Instant Rice Noodles

Instant rice noodles are commercially available in Asia. The claim of 'instant' indicates that the dry rice noodles can be rehydrated completely and .are ready to serve in 5 min, most in less than 3 min. The manufacturing processis similar to that discussed above. In moderri plants, a two-extruder setup is utilized to produce the product. The size or diameter of the product is a critical factor of instant rice noodles. Instant rice noodles are smaller than 0.68 mm. When the diameter of rice noodles is larger than 0.78 mm, the product cannot meet the requirement for instant rice noodles.

'll.9.J.3 Snack Food Noodles

Mitaimu (or bilabial), one kind of noodle, it eaten as a snack food. A short wet-type. noodle with a large diameter, it is eaten with syrup and ice during the summer. In Taiwan, mitaimu is also eaten with meat, green onion, or leek. Salt, monosodium glutamate, and pepper are always added' as condiments, The manufacturing of mitaimu is similar to the process for conventional rice noodles. During the mixing of flour with water, hot water can be used to gelatinize a portion of starch for binding effects. Mitaimu generally is shorter than 10 cm and has a diameter of 3-5 mm. It is very difficult to dry or rehydrate the dried mitaimu; thus, no dried product is commercially available. As is the case for rice noodles, only indica rice with high amylose content is used as the raw material. Some starches, such as corn, tapioca, and sweet potato, are added to adjust . the texture ofthe product. Sweet potato starch is used to; increase its elasticity. Corn or tapioca starch reduces its hardness. 104

.\ 11.9.1.4 Sheeted or Flat Noodles Rice Based Products

Sheeted or flat noodles are quite popular in Asia, particularly in Thailand, Japan and Taiwan. The starting material can be either dry-milled or wet-milled flour, but wet-milled is preferred in most areas. Traditionally, a drum is used to form a milk layer that is then cooked by steam. The gelatinized sheets are partially dried and cut to noodle strips. In a modem plant, an extruder is used for cooking and forming. Indica rice .with high amylose is traditionally used. Some Japanese non-waxy rice (amylose content<20%) has been successfully used to prepare sheeted or flat noodles. Corn or tapioca starch -can be used to adjust the texture of the final products. Only thin flat rice noodles (thickness-cl Smm) are dried and packed as commercial products. The wet-type product is used in most restaurants.

Check Your Progress 8 Note: a) Use the spaces given below for your answers. b) Check your answer with those given at the end of the unit.

1. List the various names & types of rice noodles .

...... , ...... ~ .

2. What are the requirements in manufacturing rice noodles? ...... " .

3. What is the advantage of using a twin-screw extruder to produce rice noodles?

...... •...... 4. How to judge the stability of rehydrated rice noodles?

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5. What are the advantages to use wet milled flour for making rice noodles than dry milled flour?

6. State the reasons to use high amylose content rice in making rice noodles .

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105 Paddy Storage and Milling 7. Describe instant rice noodles. Management

••••••••••••••••••••••••••••••••••••••••• ~ •••••••••••••••••••••••••••••••••••••• o ••••••••••••••••••••• ; ••••••••••••••••••••• \ •••••

...... , ! .

8. What are the main features of Mitaimu noodles?

9. List the starches used in manufacture of rice noodles .

• • • • • • • • • • • • •• • t •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• ~ •••••••••••••••••••••••••••••••••••

11.10 LET US SUMUP

Value addition to rice, in addition to its traditional use as a table food, helps to increase rice consumption. It is achieved through many ways: processing into products with a precise utilization (breakfast cereals, puffed rice, quick-cooking rice, noodles &. pasta, baby foods); combining multiple ingredients in 'products that promote health and well- being (fruited cereal flakes, ready mixes, for traditional foods); and improving quality by adding nutrients (fortification). Various types of processes used in value addition include puffing, extrusion, fermentation; fortification; nutrient supplementation; extend- ing the shelf-life of products through drying, canning and appropriate storage; and imparting visual appeal through roasting; freezing, toasting, baking, grinding, flaking, the use of additives (colours and flavours) and packing. 11.11 KEY WORDS

Milled Rice Paddy from which husk, germs and bran layers have been substantially removed by milling machinery, also known as raw rice.

Broken Rice Dehusked milled rice consisting of broken grain or less than 3/4th of the whole grain but not less than 1I4th.

Ready-to-eat Cereals The products which are cooked during cooking and which require no further cooking.

Puffing Sudden expansion of water vapour (steam) in the interstices of starch granules during high-temperature- short-time (HTST) heating of the grains.

'Extrusion Puffing Extruding superheated and pressurized dough through an orifice into the atmosphere. The sudden expansion of water vapour causes increase in the product volume- several times.

Quick Cooking Rice It is pre-cooked, dehydrated, natural, whole grain rice, which can be prepared in very short time of about 2 to 5 minutes. Fortification Adding vitamins and minerals to foods in higher amounts 106 than were' present before processing. Rtce Based Products 11.12 SOME USEFUL REFERENCES

1. Bor, S.L. 1980. Rice: Production and Utilization, The AVI publishing company; INC; Westport, Connecticut. -

2. Juliano, B.O.1985. Rice Chemistry and 'Iechnology, The American Association of Cereal Chemists, Inc; St.Paul, Minnesota, U.S.A

3. Dendy, AY.D. 2001.Cereals and Cereal Products: Chemistry and Technology, Aspen Publishers, Inc; Gaithersburg, Maryland.

4. Mercier Ch. & Cantarelli, C.1985. Pasta and Extrusion Cooked Foods, The Elsevier Applied Science Publishing Co., Inc; 52, Vanderbilt Avenue, New York.

5. Steinkruss, K.H. & Cullwen, R.E.1983 .Hand Book of Indigenous Fermented Food's,' Marcel Dekker, Inc; New York.

6. Champagne, E.T. 1998. Rice Chemistry and Technology, The American Association of Cereal Chemists, Inc; St.Paul, Minnesota, U.S;A

7. Robin Guy. 2001. Extrusion Cooking-Technologies and Applications, Woodhead Publishing Limited and CRC Press LLC, Abington, Cambridge CBI 6 AH, England.

11.13 ANSWERS TO CHECK YOUR PROGRESS

Check Your Progress 1 1. Breakfast cereals, rice flakes, puffed rice, quick cooking rice, fortified rice, papads, fermented rice products, rice noodles.

2. Cooking time, steam pressure, temperature of the basic materials, toasting procedure.

3. Traditional cereals that require cooking, instant traditional hot cereal, ready-to-eat cereals, ready-to-eat cereal mixes, miscellaneous cereal products. '

Check Your Progress 2 .

1. Paddy is soaked in warm water overnight, the water is drained, and the soaked paddy is roasted in hot sand for 1 minute and then hand pounding.

2. Rice is first cooked in a rotary cooker at 8.2 to 8.6 kg/ern- pressure for 20 minutes. Moisture after cooking should be about 33% and vacuum is applied after cooking to dry the surface. After being dried to about 17 % moisture content, the cooked rice is tempered for several hours and then flaked on large smooth rolls and finally toasted. The blistered flakes are dried to 2- 3% moisture content, cooled and packaged. The roller flakes are used to eliminate the kernel breakage .:

Check Your Progress 3

1. Puffing of rice grains results from the sudden expansion of water vapour (steam) in the interstices of starch granules during high-temperature-short-time (HTST) heating of the grains. '

2. Atmospheric pressure processes- sand, air, oil roller and oven puffing' Pressure drop processes- gun and extrusion puffing.

3. Sand, roller, oil, air, gun and extrusion puffing.

4. Extrusion puffing advantages- high and continuous production rates, greater versatility in product shape, and easier control of product density. However extrusion puffing is possible for dough only and not for whole grain kernels, which is possible for gun puffing. 107 Paddy Storage and Milling Check Your Progress 4 Management 1. Ordinary milled rice cooking time: 20 to 30 minutes, where as quick cooking rice cooking time: 2 to 5 minutes.

2. Precooking, starch gelatinization, steaming and dehydration.

3. A commercial rice product, can be rehydrated with hot water in a minute or two, yields a fairly mushy product when boiled with water.

4. Soak-boil-steam-dry method, expanded and pre-gelatinization method, rolling or "bumping" method, freeze-thaw-drying method.

Check Your Progress 5

1. Enrichment generally refers to the restoration of vitamins and minerals lost during processing. Fortification generally means adding vitamins and minerals to foods in higher amounts than were present before processing. • , 2. Powder enrichment, coated kernel enrichment and extruded kernels.

3. Advantages over other enrichment process are blend is less expensive. Disadvantages are 20-100% of the enrichment washes off the rice, vitamins and minerals are less stable during storage, non uniformity in application, reaction of vitamins and minerals with other food components.

4. Rice can be rinsed without losing enrichment before cooking; the insoluble food- grade coating is broken down when it reaches the acid environment of the stomach, thereby releasing the vitamins and minerals. In addition, the vitamins and minerals are stable and do not react with other food components.

5. It is produced primarily for the international market. The extruded kernel premix is prepared by mixing rice starch or flour with the vitamin and mineral powder and extruding it into simulated grains. .

Check Your Progress 6 .' 1. Easily digested, hypoallergenic, low fat and bland flavour.

2. Rice flour, glutinous rice flour, and rice polishing.

3. Medium and short grain varieties with lower amylose contents are used to avoid retrogradation durin~ storage, which results in, formation of a very rigid gel and separation of water.

4. Rice flour, rice polishing- sugar, dibasic calcium phosphate, glycerol monostearate, rice oil, thiamine, riboflavin, and niacin.

5. Preparing and cooking cereal slurry, adding amylase enzymes; drying and packaging.

6. The thickness of the film on the drier surface, the spacing between the drums, the temperature of the drum surface, the drum speed, an the flowing propeities of the slurry.

7. Rice baby cereal may become rancid if packaged in a hermetic ally sealed container.

8. Type of extruder, flour particle size, moisture content of rice-water mixture and extrusion condition. I 9. Developed by Khasart University, Bangkok contains 72% rice flour and 13% full fat soya flour and babymate.

10. Higher amylose content, product thickened during storage and very rigid gel. 108 11. Junior baby foods have a coarser texture and help the babies acquire the mouth feel Rice Based Products of solid food. To produce the junior grade baby foods, granulated rice is incorporated into the formulation for many junior vegetable and me?t items. .

Check Your Progress 7

1. Dhokla -Rice and Bengal-gram . I I Idli - Rice and black-gram Dosa - Rice and black-gram.

2. Idli- rice and black-gram, closed steaming.

Dhokla- rice and Bengal-gram, open steaming.

3. Indian Idli-polished rice, soaking, grinding, addition of salt, fermentation, steaming Puto- old milled rice, soaking, fermentation, adding sugar, fermentation, steaming

4. Kichudok-prepared household 1eveland consumed on special occasions. Puto-common food of low income group, consumed as breakfast and snack food, cottage industry. Check Your Progress 8

1. Various names of noodles: Bifun, vermicelli, and harusame.

Types of noodles: Ordinary noodles, instant noodles, snack food noodles and sheeted or flat noodles.

2. Freshly polished rice or broken rice, horizontal stone or concrete mills, pre-soaking or fermentation, cooking, kneading, forming, steam cooking and drying.

3. Produce noodles without adding pre-gelatinized flour or starch.

4. Observation of turbidity of the soaking water, manual checking of smoothness and ~tickiness, and cooking loss.

5. Wet-milled flour has a smaller particle size than dry-milled flours. The dry-milled flour yields rice noodles with a cooking loss as high as 20.9%, which is much higher than that for the wet-milled product (9.2%). In addition, the surface of noodles from dry-milled flour is much rougher than is that from wet-milled flour.

6. Produce a product with fibrillar structure, lower density and whiteness.

7. Instant rice noodles are commercially available in Asia. Instant noodles can be rehydrated completely and are ready to serve in 5 min, most in less than 3 min. The size or diameter of the product is a critical factor of instant rice noodles, Instant rice noodles are smaller than 0.68 mm.

8. Mitaimu, one kind of noodle, it eaten as a snack food. A short wet-type noodle eaten with syrup and ice during the summer. It is shorter than 10 cm and has a diameter of 3-5 mm. Indica rice with high, amylose content is used as the raw material,

9. Corn, tapioca and sweet potato starch.

109