Soya protein

Normal ad libitum diet supplemented with 38 g soya protein/day (38 mg/day genistein) for 6 months Postmenopausal women (n = 6)... 

SAQ 4.15 Use the data in the Resource Material to answer the following question. It is 1977. The bacterial SCP from methanol plant referred to in Table 4.9 does not produce protein at a price that competes with soya protein. By how much would the cost of methanol have to fall in order that the protein from such a plant can be produced competitively with soya protein You can assume i) that the SCP processes referred to in Tables 4.7 and 4.9 to 4.15 are of 2 x 10s tons annual capacity, ii) that yield on methanol is 0.5kg biomass per kg methanol, iii) bacterial SCP contains 60% protein. 

If methanol costs are discounted altogether, the remaining production cost of bacterial protein is still 0.36 kg 1, ie more than the cost of soya protein. At these levels the particular SCP process in question is clearly not competitive. 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

Fig. 1. Relationship between reactor mean velocity gradient and particle size for isoelectric soya protein precipitate. Open symbols represent precipitate diameter for 50% oversize Closed symbols represent precipitate diameter for 90% oversize [51]...

ANASTASIA J V, BRAUN B L and SMITH K T (1990) General and histopathological results of a two-year study of rats fed semi-purified diets containing casein and soya protein. Food Chem Toxicol. 28 (3) 147-56. 

Soya Proteins. Early attempts to make albumen substitutes from soya protein also ran into problems. A bean flavour tended to appear in the finished product. A solution to these problems has been found. Whipping agents based on enzyme modified soy proteins are now available. The advantage of enzymatic modification is that by appropriate choice of enzymes the protein can be modified in a very controlled way. Chemical treatment would be far less specific. In making these materials the manufacturer has control of the substrate and the enzyme, allowing the final product to be almost made to order. The substrates used are oil-free soy flakes or flour or soy protein concentrate or isolate. The enzymes to use are chosen from a combination of pepsin, papain, ficin, trypsin or bacterial proteases. The substrate will be treated with one or more enzymes under carefully controlled conditions. The finished product is then spray dried. 

In use these soya based products, unlike egg albumen, do not coagulate. They must be used in conjunction with egg albumen or another coagulating material if coagulation is needed. The soya-based proteins have the advantage that they have approximately twice the whipping capacity of egg albumen. The modified soya protein is used by dispersing it directly in two to three times its own weight of water. It is not necessary to pre-soak this material, unlike egg albumen. 

These products are made by adding protein to flour. While whey protein, soya protein, casein and yeast can be used the protein normally employed is pure vital wheat gluten. 

Two miCTonutrients of particular concern in vegan diets are vitamin B,2 and iron which are normally obtained from meat. A dietary supply of vitamin B,2 can be ensured from sources such as yeast extracts or soya protein. 

Soya protein - [BIOPOLYMERS - ANALYTICALTECPENIQUES] (Vol 4) -centrifugal separation of [SEPARATION - CENTRIFUGALSEPARATION] (Vol21)... 

TMP Cattaneo, A Feroldi, PM Toppino, C Olieman. Sample preparation for selective and sensitive detection of soya proteins in dairy products with chromatographic and electrophoretic techniques. Neth Milk Dairy J 48 225 -234, 1994. 

In this report various chemical and in vivo methods are compared in their ability to assess nutritional damage in various model soya proteins representing mainly the Maillard-type modification of lysine. 

Model protein samples. Isolated soya protein (Purina Brand Assay Protein RP 100 ) was employed in these studies and found to contain on a dry matter basis 96% crude protein, 1.4% ash, 0.2% crude fiber, and 2% N-free extract. This material was used to prepare 48 samples, which were heated in airtight metal containers ( 250-ml ) at temperatures of 90, 110, 130° C for 0.5, 1, 2, and 4 h respectively. 

The samples were prepared by a mixture of 90 parts of soya protein with 10 parts of tap water or of 80 parts of soya protein with 10 parts of glucose and 10 parts of tap water or instead of glucose an equivalent amount of lactose or xylose according to their molecular mass compared on water-free basis to the glucose. In this way for instance the lactose samples contained 71 g soya protein, 19 g lactose and 10 g tap water. 

A further 3 samples were prepared by heating equal masses of isolated soya protein and tap water in open vessels for 24 h at either 95, 138, or 160° C. 

Figure 1. Comparison of the sensitivity of the various chemical procedures to lysine damage in a variety of heat-treated model soya protein samples. (All lysine data are given in g/16 g of N) Key - —, unheated —, heated alone — —, with glucose with xylose and--------------------------, with lactose.

The highest concentrations of nickel in individual foods occur in tea, soya protein and herbs.40 Other foods with elevated levels are pulses, cocoa products and some nuts. Nickel has been found in crops at levels of <0.01 to 1.5 mg/kg, with the highest concentrations in broad beans and Bmssels sprouts. Studies of nickel in marine fish and shellfish have shown that concentrations are low in fish in general, but that levels in shellfish average 0.61 mg/kg, with higher mean... 

Bitter peptides from peptic soya protein hydrolysates... 

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