Protein concentrates digestion

Keller, B. O., Wang, Z. P., and Li, L., Low-mass proteome analysis based on liquid chromatography fractionation, nanoliter protein concentration/digestion, and microspot matrix-assisted laser desorption ionization mass spectrometry. Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences, 782,317-329, 2002. 

Figure 2. Relationship between calcium solubility and pH after complete digestion for four soy products. Key solid line, full-fat soy flour long-dashed line, soy protein isolate short-dashed line, soy protein concentrate and dotted line, defatted soy flour...

Table I. Effects of 17o Orthophosphate, Tripolyphosphate, and Hexametaphosphate on Calcium Solubility from Ground Beef or Soy Protein Concentrate Subjected to In Vitro Gastric and Gastrointestinal Digestions...

Solubilization of fish protein concentrates, recover oil or meat scraps from inedible parts Waste product conversion to feed, digestive aid... 

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibility, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

Labeling with 2H, 13C, 15N and/or lsO can be introduced via peptide synthesis, cell culture, or hydrolysis in labeled water [88]. The heavy isotope-labeled peptide can be used as an IS to obtain quantitative measurements of the protein concentration. Typically, the protein sample of interest is digested with trypsin, and the isotope-labeled control peptides are added to the mixture. The signature peptides in the digest can be separated and quantified by HPLC-ESI-MS/MS. Alternatively, MALDI-MS can also be used for tryptic peptide determinations after some separation steps such as gel electrophoresis [89]. 

Lipids are often a nuisance in extraction of proteins. For example, in preparing leaf protein concentrate a protein-lipid complex is formed frequently affecting the protein extraction efficiency (16). Nutritionally, the complex is disadvantageous because it resists digestion by proteases (17). Shenouda and Pigott (18) found that the formation of protein-bound lipids can cause a low efficiency of extraction of protein from fish. Hydro-phobic bonding probably plays an important role in protein-lipid interactions. Mohammadzadeh-k et al. (19) reported protein interaction with completely apolar compounds such as aliphatic hydrocarbons. 

The protein efficiency ratio (PER) of sesame seed protein is 1.86 (35). The PER value can be raised to 2.9 when sesame seed protein is supplemented with lysine (36). El-Adawy (37) added sesame products including sesame meal, sesame protein isolate, and protein concentrate to red wheat flour to produce flour blends. It was found that water absorption, development time, and dough weakening were increased as the protein level increased in all blends however, dough stability decreased. Sesame products could be added to wheat flour up to 16% protein without any detrimental effect on bread sensory properties. The addition of sesame products to red wheat flour increased the contents of protein, minerals, and total essential amino acids the in vitro protein digestibility also increased significantly. 

Sunflower meal (blended with wheat flour) can be used for human nutrition. Despite their dark color, sunflower protein concentrates are of excellent digestibility. A method was proposed (147) for obtaining sunflower protein concentrates from defatted wholemeal sunflower flour, through extraction of these proteins with a basic solution. The process yields a concentrate of 71% protein (dry basis), rich in glutamic and aspartic acids. The supernatant liquid, rich in potassium and phosphorous, can be used as agricultural fertilizer. 

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 . 

Fish protein concentrate, although a good protein source nutritionally, is very insoluble this limits its use in foods. The protein can be solubilized by proteolytic enzymes, but the hydrolysate is bitter (12). It would be useful to investigate the plastein reaction for removal of the bitter taste as well as for changing the solubility properties of the digest (14). The plastein reaction is described more fully in Chapter 6 of this monograph. 

Hermansson et al. (19) determined the effects of pepsin and papain treatments on the solubility of rapeseed protein concentrate (RPC). The original RPC had a solubility of 11-12% at pH values between 4.0 and 7.0. However, hydrolysis with pepsin for 24 hr increased the solubility to 82-90% over this same pH range. On the other hand papain digestion increased the solubility to only 38-43%. 

Partial proteolysis of soybean proteins with endopeptidases has been used to remove flavor compounds and related fatty materials from soybean curd and defatted soybean flour (21). Certain soybean protein concentrates possess an undesirable beany and oxidized flavor. Treatment of soybean curd and defatted soybean flour with endopeptidases such as aspergillopeptidase A released off-flavor compounds such as 1-hexanal and 1-hexanol which could be removed from the hydrolysate by solvent extraction. The enzymically digested products had less odor, taste, and color than the starting material and were more stable to oxidative deterioration. 

Hemsley JA, Hogan JP and Weston RH (1975) Effect of high intakes of sodium chloride on the utilization of a protein concentrate by sheep. II Digestion and absorption of organic matter and electrolytes. Aust J Agric Res 26 715-727. 

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