Miscellaneous
Miscellaneous:
Quality and Quality Factors in Wheat :
The wheat quality is judged according to its functional usage and the quality requirement differs from agency to agency involved in production, processing, and utilization viz. by the farmers, the millers, the bakers and the consumers respectively. Accordingly the farmers want to get higher yield, the millers need maximum yield of good quality flour, and the bakers need more volume of bread with good crumb structure. Similarly the consumers’ interest is in the color and quality of flour which may make best and attractive chapattis, poories, parathas etc. Thus the wheat quality becomes personal and subjective and therefore, it is difficult to define precisely. However, few aspects have been described as under:
Physical aspects of quality assessment.
The physical aspects consist of following factors:
Purity:
The quality of the finished products largely depends upon the cleanliness of the wheat grains. Thus the grains free from dust, stones, foreign material and parts of the nodes and rachis make the best milling material for processing into various products. The purity may be determined by purity tests after separating out various materials present in the bulk of wheat. The purity percent may be worked out by calculating the relative part of pure wheat out of the bulk sample taken and multiplied by hundred:
Purity per cent Weight of pure wheat 100
= --------------------------------- X
Weight of bulk sample
Moisture:
It is a single factor which affects the milling quality, the keeping quality etc. of the wheat grains. It may be determined by drying a known quantity of sample to constant moisture at 1300C or by a moisture meter. The ideal moisture for best storage and processing is 120C.
Physical characteristics of grains:
Physical characters of grains include color, size, plumpness and weight of grains. Usually the color of the grain may be amber, whitish or red, the size may be small, medium or very large and the texture may be soft to medium hard. Depending upon these characteristics the grains may be divided as follows:
Category 1: Very large, plump and amber type (used for better atta making).
Category 2: Medium sized plump and bright grains.
Category 3: Small grains, shriveled or diseased.
For domestic consumption, the grains, of first category are most preferred as they give better atta of high recovery and chapattis prepared from this atta becomes very attractive.
Similarly the healthier grains are supposed to be the best for quality point of view. The grain weight is measured by weighing either 1000 grains (test weight), or 100 seeds (seed index).
Kernel hardness is the resistance of grains in splitting by applied pressure. It is generally measured by determining the Pearling Index. For peraling inde3x 20 g grain sample is taken in a laboratory pearler and it is pearled for about one minute. The pearled material is taken over a 30 mesh sieve and shaken for 20 times. The peraling index is calculated by using the following equation:
Pearling Index 20 - material left in sieving 100
= --------------------------------- X
20
Based on the results the grains may be divided or classified as:
Pearling Index Texture of the grain
Below 29 percent hard wheat
29-40 percent semi hard
41-50 percent cent soft
Above 50 percent very soft
Nutritive aspects of quality assessment:
This aspect includes the chemical tests for nutritive value viz. protein mineral percent, amino acids, carbohydrate etc. as these are factors that govern the chapatti making and baking qualities of the grains. The range of variation of these constituents normally observed in different wheats as follows:
Starch - 60-68 per cent
Protein - 8-15 per cent
Fat - 1.5-2.0 per cent
Sugar - 2-3.0 per cent
Cellulose - 2.0-2.5 per cent
Mineral Matter - 1.5-2.0 per cent
In addition to these, vitamins A, B1, B2 Nicotinic acid and E (∞- tocopherol) are also present.
Protein. Proteins are main constituent of the body cells and carry out many vital functions viz. promotion of growth, production of metabolic and digestive enzymes and blood proteins, production of hormones and antibodies, etc. its deficiency causes serious nutritional disorders in infants and adults such as loss of body weight, stunted growth, diarrhea. Etc.
Amino acids. Protein is carrier of amino-acids hence it is essential to upgrade the protein along with increasing content of amino-acids by genetic means. Amino-acids like glutamic acid, prolone, alanine and aspartic acid. The essential amino-acids like lysine,m phenylalanine, methionine, threonine, leucine, isoleucine and valine formed about 24-30 percent of total amino acids. It is observed that the concertration og glutamic acid was relatively low in brain and resultant atta, while flour had the highest percentage of glutramic acid and proline.
Fats. Fat on its complete digestion, gives out more than double the energy per unit weight of either protein or carbohydrate. It also supplies fat soluble vitamins like A,B,E and K besides supplying fatty acids viz. linoleic, linolenic and arachidonic acids needed by body.
Carbohydrates. They include starch, sugars which supply energy after their break down into glucose that is absorbed by the blood stream. In ordinary Indian diets carbohydrates supply about 50-80 percent of the calories which are obtained from cereal.
Minerals. The important minerals supplied by wheat flour are Ca, P,K, Fe etc.
Vitamins. These are organic substances that are present in minute quantities in the wheat products. Usually vitamins A,B,c and D are the most commonly occurring ones.
Industrial aspects of quality assessment of wheat:
This includes milling quality, biscuit making and bread making qualities of wheat. These qualities are discussed below:
(a) Milling quality: Milling quality represents the recovery percent of flour from wheat. In early years of wheat improvement, the newly evolved varieties were sent to U.K for testing their milling qualities and it was noticed that the wheat varieties evolved in India were hardly meeting the requirement of whole meal or atta but now with the increased production the roller flour milling industries are spreading very fast in the country. Consequently, the newly evolved varieties are now extensively tested for milling quality. The recovery of straight run flour, in general, varied from 60 to 77 percent. The wheat varieties, based on their flour recovery, have been classified into following group:
Low-Giving less than 65 percent flour yield.
Medium-Giving less than 65 to 69.9 percent flour yield.
High-Giving 70 percent and above flour yield.
Process of milling: Before milling wheat is tempered by adding water about 24 to 48 hours earlier to milling so that the moisture of grains comes around 14.0 percent. The quantity of water to be added for tempering may be calculated as:
Quantity of water needed 100 - original moisture
g of wheat
= ----------------------------- X
100 – Required moisture
Quantity of water needed= *.
It is done to make wheat mellow which allows better separation of bran from the endorsperm by causing the bran-coat to be tougher and flake during milling rather than powdering. Normally Buhler and brabender mills are used for experimental milling of large and small sized samples. In quadrumatic junior brabender the grains flow from the adjustable feeder gate to the break rolls and after the grains are reduced here, they directly pass to the reduction rolls which have very fine corrugations. Thus the final grinding operation takes place in reduction rolls from where the grinding stock drops into rotating sifter reel for separation of flour from the brain.
From the milling process the semolina or macaroni, maida etc. are prepared and recovery is calculated for quality assessment of various varieties.
(b) Bread making quality: From the experimental results, reported from U.K, it was concluded that the order Indian commercial wheat varieties were not good for baking purposes. In the past there was very limited demand for baked products in India especially for bread but the ever increasing demands now for the baked products resulted in a rapid development for baking industries in recent years. Thus the breeders are trying to identify and evolve varieties of superior baking quality. The flour is subjected to extensive baking and dough tests. The loaves are assessed for baking characters viz. volume, general appearance, symmetry of form, color, and texture of crust and crumb, taste, flavor, crumbliness, compressibility and keeping quality. The best varieties for bread-making purposes are Sharbati Sonara. Heera, Moti, UP 310, UP 319, K 65, K 68, WG 357, Deccan Queen, Narbada-4 and Hyb 65, etc.
(c) Biscuit-making quality: Soft and weak flour having low water absorbing capacity along with low protein content is preferred for biscuit-making puroses. The gluten of the flour should be plastic so that it may be stretched without much shrinkage. Lerma Rojo and Chhoti Lerma have been found to be the most promising amongst the new plant types.
Domestic or consumers’ aspects of quality assessment:
The consumer’s interest in the quality factor of wheat is to get soft, amber colored and good chapattis, pooris or parathas to which they may relish and enjoy the most. Nearly 90 percent of the wheat produced in the country is being used for consumption as chapati, therefore, our wheat breeders are giving much emphasis to produce varieties having superior chapatti-making quality. It is observed that for good chapatti-making quality the whole-meal (atta) should have high water absorbing capacity, the dough made out of atta should be medium strong, elastic, extensible and non-sticky. The chapatti prepared from the dough should have creamish white color and should puff well while cooking. Besides, these charaters, the chapattis should be soft, smooth and pliable for at least 4 to 6 hours. These characters may be obtained from the wheat having 10-12 percent protein, 30-40 ml sedimentation value and 100-150 ml. Pelshenke values. The dough should have stability of 100 mm to 130 mm, Baking strength 15 cm2 or 25 cm2, extensibility less than 150 mg maltose equivalent per 10g of whole-meal. Wheat varieties like Sharbati Sonara, Arjun, Janak, Pratap, WG 357, WG 377 and Pb. C 306 are found to have all the said characters and possess the best chapatti-making quality.
Storage behavior of wheat grains:
The grains are eaten up by the store pests if they have more than 12 percent moisture in them. It is observed that there are certain varieties like Sonalika, Raj 821, etc. which have rough grain surface and they are the first to be damaged by the pests, thus it becomes a varietal character also.
Factors affecting the quality of Wheat
Quality of wheat grains is an important factor in fixing the price of wheat or in subjective evaluation of wheat varieties. It is greatly affected by several factors which need to be given due attention. Following are some of them:
Genetic factors.
The varieties differ in their quality characters viz. according to their characteristics someone are good for baking purposes (those varieties which have 14 mm to 103 mm stability, 38 mm to 155 mm extensibility, 1.4 cm2 to 30 cm2 elasticity, 3.6 cm2 to 3.8 cm2 baking strength and 0.59 to 5.27 L/P ratio extensibility/stability). The important varieties having such characters are K 64, K 65, K 68, NP 876, NP 880 and NP 887 etc. Similarly varieties like Lerma Rojo, Safed Lerma, Chhoti Lerma are good fore biscuit-making as they posses lower values for stability, elasticity, baking strength and deformation work. Based on L/P ratio the dough has been classified as shoft, balanced and extensible dough types. Varieties having L/P ration less than 0.85 are included in shot dough group and are fit for making doughtnuts, crackers etc. These varieties are Pb. C. 303, Rs 31-1 and NP 858. Dough with L/P ratio of 0.85 to 1.35 is found to be good for homemade bread and chapati-making purposes. The varieties of this group are NP 824, NP 871, NP 890, NP 891, Pb.C.273 and Kalyan Sona etc. The extensible dough has a L/P ratio of more than 1.35 and is supposed to be of the best quality for making industry. The varieties of this group are Sharbati Sonara, HD 2122, UP 310, UP 319 and Hyb. 65 etc.
Effect of location on quality of wheat.
The wheat samples collected from various locations of the country by All India Co-ordinated Wheat Improvement Project showed a significant variation in the protein content and lysine percentage in then sample even in the same variety. It was found that the wheat grown in Maharashtra, Gujarat, Peninsular India and parts of M.P. under high fertility status analysed for 12 to 14 percent protein which are much higher than those grown in other locations. Thus it is clear that ecology also governs the quality of wheat grains. It was noticed that the crop having shorter duration, gave lower yield and higher protein and lysine content in them.
Effect of fertilization on the protein content and quality of wheat.
Amongst the nutrients nitrogen is the most important which affects the quality of the wheat grains? It increases about 2-6 percent protein in grains depending upon the varieties viz. tall and dwarf varieties it is observed that with increase in the protein content the relative percentage of lysine is found to be decreased while prolamin was increased. The nitrogen fertilization, in general decreased the content of protein, glycine, tyrosine and lysine content does not affect the chapatti quality characters viz. water –absorption, puffing, texture and sweetishness.
In case of durum wheat it is found that at low nitrogen levels these varieties show yellow berry or soft grains. This softness spoils the quality of semolina or macaroni.
Effect of grinding methods on quality characters of wheat.
Studies were made in different grinding methods viz. roller mills, power-driver stone chakki, hand-driven stone chakki, and water-mill in which It was observed that nicotinic acid (niacin) content suffered over the original wheat sample which was 11 percent in hand-chakki and 21 to 23 percent in the other three cases. The losses in thiamine (B1) content were 13.8, 22.5, 43.2 and 53.5 percent in hand chakki, water-mill, power-driver cahkki and milli attas respectively. Beside those losses, the diastatic enzymes also get destroyed to greater extent in mill attas is perhaps the higher temperature developed during the milling process. The temperature recorded in the delivery sprouts was 154.F in power-driven stone chakki and in other cases it varied from 82 to 89.F.
Effect of agronomic practices on the quality characters of wheat.
The agronomic practices like time of sowing, irrigation, weed control etc. affect the yield and development of grains which ultimately affect the yield and quality of such grains. The recovery of Atta (whole meal) from the grains, thus produced, is also found to be very poor because of larger proportion of brain in them. Therefore, the timely sowing irrigation at critical growth stages, control of weeds etc. are essential for the reduction of quality grains.