Soya protein concentrate

Cell recovery presents a problem in algal culture, as centrifugation (the most effective method) can be prohibitively expensive (Table 4.2). Methods such as flocculation with calcium hydroxide and sedimentation can be employed for feed purposes. Waste water is recycled and recovered cells are dried preferably by drum drying, which breaks up cell walls making the product easier to digest by humans. The product contains 40-50% protein and 4-6% nucleic add, and has been produced in relatively snudl quantities at a selling price 4-10 kg (1990 prices). This compares to soya protein concentrate (70% protein) and milk powder (36% protein) at about 3 kg . 

Soya protein concentrates are produced by solvent extraction and removal of insoluble carbohydrate. Protein concentration is of the order of 70 per cent. During processing, antigenic and antinutritional substances are removed and the materials are suitable for inclusion in calf milk replacers and baby pig diets. 

Table 16.29. Composition of soya protein concentrate and isolate (%)...

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. 

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... 

Ingredients. All ingredients were obtained commercially along with compositional information and consisted of corn starch (National Starch, Bridgewater, NJ), whey protein concentrate (WPC) and sodium caseinate (SC) (Leprino Foods, Denver, CO), defatted soy flour (DSF) (Archer Daniels Midland, Decatur, IL), soy protein concentrate (SPC) (Central Soya Company, Fort Wayne, IN), and gluten (G) (Ogilvie Mills Ltd., Montreal, Canada). 

The three proteins chosen for this study are a mildly produced soy protein isolate, kindly provided by Central Soya, a commercially available sodium caseinate (DMV, Holland) and a whey protein concentrate (WPC) obtained by ultrafiltration (UF) and spray drying of cheese whey. Analysis of the proteins is given in (4) and (11). The present protein products have been investigated , when dispersed in distilled water and in 0.2 M NaCl solution at pH 7 denoted as (0 - 7) and (0.2 - 7), respectively. 

Beetroot red (E 162), available as liquid beetroot concentrate and as beetroot concentrate powders, is suitable for products of relatively short shelf life, which do not undergo as severe heat treatment as meat and soya protein products, ice cream, and gelatin desserts. 

Figure 2. Time-dependence of the interfacial pressure, 49, for three curves. They represent WPC dispersed in (0.2-7) adsorbing at the A/W and the soya bean oil/water (0/W) interfaces at a subphase concentration of 10" and 10 wt%, respectively, and a soya protein isolate adsorbing at the A/W-interface at a subphase concentration of 10 wt%.

For the soya proteins this happens at a concentration of about 10 2 wt% and for the other two proteins atwlO" wt%. 

With a few exceptions, most of the detailed research has been performed on relatively few proteins. Of these, the caseins (a , B and k) and whey proteins P-lactalbumin and B-lactoglobulin) predominate. This is principally because these proteins are readily available in pure and mixed forms in relatively large amounts they are all quite strongly surfactant and are already widely used in the food industry, in the form of caseinates and whey protein concentrates or isolates. Other emulsifying proteins are less amenable to detailed study by being less readily available in pure form (e.g., the proteins and lipoproteins of egg yolk). Many other available proteins are less surface active than the milk proteins, for example, soya isolates (49), possibly because they exist as disulfide-linked oligomeric units rather than as individual molecules (50). Even more complexity is encountered on the phos-phorylated lipoproteins of egg yolk, which exist in the form of granules (51), which themselves can be the surface-active units (e.g., in mayonnaise) (52). 

Figure 4 Average particle diameter as a function of protein concentration for emulsions made using 20% soya oil and caseinate at different concentrations. Below a concentration of about 0.5% caseinate, the size of droplets is dependent upon the concentration of casein above this, the concentration depends on the conditions of homogenization.

The protein sources, a soybean protein isolate (Promine F, Central Soya, Chic.) and a rapeseed protein concentrate (prepared by FRI-71 process at the Food Research Institute, Agriculture Canada, Ottawa) were suspended (10% W/V) in 0.1 N NaOH and heated at 60 C for 4 or 8 h with continuous agitation. Treatment was stopped by the rapid addition of 6 N HCl followed by cooling, adjustment of pH to 4.5, and centrifugation for 15 min at... 

Table 1.44. Amino acid composition (weight-%) of plasteins with high tyrosine and low phenylalanine contents from fish protein concentrate (FPC) and soya protein isolate (SPI)...

Sodium Azide is often used (at 0.01% concentration) as an anti-bacterial preservative. The same concentration should be present in an all the buffers against which the sample is dialyzed (see below). Soya Bean trypsin inhibitor is often added to protein samples at 10 pg/ml, but not usually to dialysis buffers. 

It has long been the aim to relate the properties of the extruded product or half-product to the state of the extrudate as it leaves the die. We have noted that this is often attempted via the apparent viscosity of the melt but must fail if mixes are regarded as simple power law fluids. Elasticity in melts is easily demonstrated as die swell, caused by elastic normal forces. This occurs with many cereal flours and protein/carbohydrate mixes (e.g., soya flour, grits and concentrates) and does not involve puffing, or gas expansion. It occurs immediately after the die and may relax before the structure is set. Nonetheless, die swell expansions of up to 200% have been recorded (Guy and Home 1998). 

The defatted toasted soya flour can be upgraded to a concentrate (70 % protein) by removing soluble material by leaching with water, or better still, with aqueous alcohol. This removes the oligosaccharides, sugars with 2-5 hexose units, i.e. sucrose, raffinose, stachyose and verbascose. Of these, the last three are recognised as flatus factors since it has been demonstrated that their metabolism involves intestinal gas production. 

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