Nutritional Quality of Raw, Precooked and Canned Albacore Tuna (Thunnus alalunga)

The nutritional quality of raw, precooked and canned tuna was assessed by determining the total amino acids, in-vitro protein digestibility, Computed Protein Efficiency Ratio (C-PER), Tetrahymena Relative Protein Value (RPV), and fluorodinitrobenzene reactive lysine, together with selected vitamin and mineral assays. Amino acid composition, in-vitro protein digestibility, C-PER and Tetrahymena RPV remained almost the same for the raw, precooked and canned tuna. The percent retention of FDNB-reactive lysine was 91% for the precooked tuna and 80–85% for canned tuna. Thiamin retention for the canned tuna was about 5%, while niacin and riboflavin ranged from 71–73% and 49–50% respectively. The values for Cu, Fe, K, and Ca were significantly lower in canned tuna.     

Influence of Protein Source, Type, and Concentration, and Product Form on the Protein Quality of Commercial Enteral Formulas

ABSTRACT: The total, protein, and nonprotein nitrogen, 3 amino acids (lysine, histidine, and tyrosine), available lysine, and in vitro protein digestibility in enteral formulas were determined. Available lysine and protein digestibility were lower in the liquid formulas tested than in the powdered formulas. The protein quality of the formula made from soy protein isolate (soy) was lower than that of the formulas made from casein, and the protein quality of a low-protein formula was lower than that of the standard formulas. There was a statistically significant correlation between the available lysine content and protein digestibility in the polymeric formulas. New methods are required for assessing the protein quality of formulas containing hydrolyzed proteins.     

EVALUATION OF EXTRUSION COOKED COTTONSEED/SOYBEAN BLENDS OF DIFFERENT PROPORTIONS

Cottonseed kernel/full-fat soy flour blends of different proportions were cooked in a Brady low-cost extruder. Total and free gossypol, available lysine, proximate analysis, and PER and NPU values varied directly with composition. Reduction in free gossypol as a result of extrusion was constant, and independent of composition (ca. 90%). The 25 and 50% cottonseed blends exhibited low free gossypol (within limits permitted for human consumption), high available lysine, high PER and NPU values, and amino acid patterns equalling or exceeding the FAO/WHO (1973) children's pattern, except for moderate deficiencies in total sulfur amino acids and small to negligible deficiencies in valine. Both blends resembled full-fat soy products in proximate analysis. These results indicate that extension of soy with cottonseed products up to a level of 50%, utilizing the procedure described in this work, would be feasible.     

Availability of essential amino acids from proteins. I. Beef serum albumin

Available essential amino acids from beef serum albumin were determined microbiologically, after total enzymic hydrolysis of the protein by papain, leucine aminopeptidase and prolidase. Samples of pure beef serum albumin of different moisture content were heat-treated with glucose at 90° or without it at 121°. In the enzymic digest of the protein, available essential amino acids were determined using Streptococcus faecalis, S. zymogenes and Lactobacillus arabinosus. The content of essential available amino acids was correlated with the degree of in vitro digestibility of heat-treated albumin. The amount of lysine determined by Carpenter's method with fluordinitrobenzene did not correspond to the values found for lysine by microbiological analysis with S. faecalis. Lysine reactive with fluordinitrobenzene was found in the non-digestible residue of the protein, so that the values obtained by the chemical method are probably higher than the actual amount of available lysine. The results for the trypsin digest of the albumin were similar by both methods. The availability of lysine as well as that of amino acids in general depended on the enzymic digestibility.     

Effect of Heat Treatments on In Vitro Digestibility of Delactosed Whey Protein as Determined by the Digestion Cell Technique

Diafiltered whey protein concentrates (WPC) were heated, in liquid form, under various conditions of time and temperature. Protein and amino acid digestibilities were determined by in vitro pepsin and pan-creatin digestion with continuous dialysis. Whey nitrogen digestibility decreased (P < 0.05) after heating at 121°C for 5000 sec. Heating WPC for 5000 set at temperatures below 121°C increased the digestibility of all amino acids except alanine and lysine at 75°C, and methionine and lysine at 100°C. In general, the longer was the heating period at 100°C or 121°C the lower was the amino acid digestibility. These results emphasized the importance of structural modifications brought about by heat treatments on protein digestibility.     

Effects of heat treatment on lysine in soya protein

Total lysine and available lysine were used For predicting the damage to lysine in soya protein heated with glucose and in alkali. The amounts of both types of lysine decreased during the treatments. The content of total lysine was much higher than that of available lysine. In soya protein heated with glucose, the available lysine content decreased by 78-85 % and that of total lysine by 17-40 %. In soya protein heated in alkali, available lysine decreased by 7-24% and total lysine by 7-13%. Since available lysine was more sensitive, changes in total lysine underestimated the nutritional damage.     

Browning and Amino Acid Loss in Model Total Parenteral Nutrition Solutions

The kinetics of browning and amino acid loss due to the Maillard reaction was studied in model total parenteral nutrition (TPN) systems containing glucose and either lysine, tryptophan, and cysteine alone or in combination. Cysteine systems showed the highest molar rate of browning while lysine showed the slowest rate. The molar rate of browning with all amino acids combined was significantly less than that of the sum of the individual rates, indicating interactions or inhibition. TPN electrolytes had no significant effect on the browning rate. The amino acids showed an initial rapid pseudo-first-order decrease in concentration followed by an apparent recovery and stabilization at an equilibrium concentration of about 60-80% of the original level.     

Role of sorbic acid in nonenzymic browning reactions in liquid and solid model food systems

Role of sorbic acid (SA) in browning development in model systems has been studied. In liquid model systems containing water-glycerol-glucose (WGG), water-glycerol-sucrose (WGS), 45% sucrose and 30% sucrose plus 15% glucose, SA degraded when stored at 37°C forming brown pigments. Addition of amino acids (glycine or lysine monohydrochloride) increased the rate of browning development while Cu²⁺ reduced SA degradation and browning development. In the absence of amino acids and SA, WGG and WGS systems did not brown appreciably.
In solid systems with SA adsorbed on microcrystalline cellulose, the maximum rate of browning occurred at 0.73 a_w , but maximum rate of SA loss was at 1.0 a_w . In all systems inclusion of amino acids reduced SA degradation but increased browning development. The rate of SA-induced browning was considerably higher than that caused by sugar-amino acid interactions.     

Soy Supplementation of a Maize Based Kenyan Food (Ugali)

The effects of soy-supplementation of maize meal on the nutritive value of Kenyan Ugali was determined by consideration of amino acids, available lysine, minerals, phytate, oligosaccharides, protein and in vitro protein digestibility. Supplementation at 10%, 20%, and 30% of soy flour resulted in (a) increased protein ranging from 12.6% to 19.6% (b) increased chemical score ranging from 74 to 87; (c) increase in available lysine of Ugali ranging from 2.61 to 5.11 g/ 16gN and, (d) increases in minerals, phytate, and oligosaccharides. The supplementation did not affect adversely the in vitro protein digestibility of Ugali prepared from the maize-soy blends. Supplementation up to 20% had no apparent effect on the taste preference of Ugali. The overall nutritional value of Ugali could be improved substantially by supplementation of the maize meal with 20-30% soy flour.     

Processing, Functional, and Nutritional Properties of Okra Seed Products

Okra full-fat flour, defatted flour, protein concentrate, and protein isolate were prepared from whole okra seeds (Spineless Green Velvet variety). Results of proximate analysis, amino acid profiles, in vitro protein digestibility, and calculated protein efficiency ratios (C-PER) indicated that okra products have significant potential as a viable new protein source. C-PER of okra products ranged from 2.16–2.22. Protein solubility indicated that these okra products were generally more soluble than commercial soy products. Emulsion capacity and viscosity of okra products were significantly lower than those for soy products. Overall, foam stability of soy products was consistently higher than that for okra products.     

Effect of soy flour addition and heat-processing method on nutritional quality and consumer acceptability of cassava complementary porridges

BACKGROUND: The nutritional quality of cassava complementary porridge was improved through extrusion cooking and compositing with either defatted or full fat soy flour (65:35 w/w), and product acceptability by mothers with children of the target population was evaluated. RESULTS: The protein digestibility‐corrected amino acid score (PDCAAS) of extrusion‐ and conventionally cooked composite porridges was within the recommendations for complementary foods. The kinetics of starch digestibility showed that all porridges had a rapid rate of starch digestibility, but the rate was lower when defatted soy flour was added and lowest when full fat soy flour was added. The formation of amylase‐lipid complexes as shown by X‐ray diffraction and differential scanning calorimetry can be attributed to the lower digestibility of extrusion‐cooked porridge with full fat soy flour. If fed thrice per day, extrusion‐cooked porridge with defatted or full fat soy flour would meet the energy, protein and available lysine requirements of a child aged 6–8 months receiving low or average nutrients from breast milk. All porridges were well received by Mozambican mothers who use cassava as a staple food. The mean scores for sensory liking of all porridges were 3 and above on a five‐point hedonic scale. CONCLUSION: Extrusion‐cooked cassava/soy flour porridges have good potential for use as high‐energy/high‐protein complementary foods and have acceptable sensory properties. Copyright © 2012 Society of Chemical Industry     

Nutritive value of oat and rye grain protein as influenced by nitrogen and amino acid composition

In experiments with increasing applications of nitrogen to oats and rye grown in pots, grain with widely varying N-content was obtained. In rye increasing N-concentrations were associated with decreases in the protein of lysine and several other amino acids including threonine, tryptophan, methionine and cystine, whereas glutamic acid, proline and phenylalanine increased. In oat protein the amino acid composition was less affected by increasing N-content in grain. Concentrations of most essential amino acids were higher in oat than in rye protein, especially at high N-levels. The ratio lysine + arginine/proline was higher in oat than in rye protein and did not, as in rye, decrease with increasing N-concentration. Lysine as a percentage of dry matter increased up to the highest N-level in both cereals. In rat feeding experiments true digestibility of the protein of oats and rye increased to the same extent with increasing N-concentration in grain, whereas the biological value of the protein decreased considerably in rye but only slightly in oats. Net protein utilisation decreased with increasing N-content in rye but increased in oats.     

High Vacuum Flame Sterilization of Canned Diced Tuna: Preliminary Process Development and Quality Evaluation

A preliminary study of the potential of high vacuum flame sterilizing canned diced tuna was carried out. The investigation included inoculated experimental sighting packs study at five process levels, and comparative assessment of the physical, chemical and nutritional property of the raw, precooked, high vacuum flame sterilized (HVFS) and still-retorted canned tuna. The vacuum achieved in the HVFS packs was significantly higher (P < 0.05) than the control packs. Fatty acid and amino acid composition, in-vitro protein digestibility, and the Computed Protein Efficiency Ratio (C-PER) were similar for the raw, precooked and canned tuna. Available lysine was marginally decreased by precooking, and HVFS processing caused no measurable change. However, available lysine, thiamin, riboflavin, niacin and mineral concentrations were generally lower in the retort process control canned tuna.     

Stability of Trehalose, Sucrose and Glucose to Nonenzymatic Browning in Model Systems

The rate of nonenzymatic browning was compared in freeze-dried model systems containing lysine and glucose, sucrose or trehalose at pH 2.5 and a water activity of 0.33. Rate constants for brown color formation (A420) were from 200 to 2000-fold greater for the sucrose than for the trehalose system. Some rate constants for sucrose browning approached those for glucose, indicating that extensive hydrolysis had occurred. The results indicate that use of trehalose rather than sucrose may be of value in stabilizing some systems vulnerable to nonenzymatic browning.     

大豆分离蛋白在成膜后的营养特性变化

采用胃蛋白酶和2，4，6-三硝基苯磺酸分别测定大豆分离蛋白膜的消化率和赖氨酸有效性。结果表明，蛋白质的消化率和赖氨酸有效性随成膜溶液的pH升高而下降，并因一些增加蛋白交联的物质如单宁、阿魏酸和过氧化氢的添加而降低。蛋白膜的机械性与膜蛋白消化率和赖氨酸有效性存在一定负相关，即机械性能较强的膜，其消化率和赖氨酸有效性较低。不过，玉米淀粉似乎是个例外，它在改善机械特性的同时，也保持了大豆蛋白膜的营养。由于大豆分离蛋白制备成膜后，其消化率和赖氨酸有效性下降，因此将大豆蛋白膜称为生物可降解膜似乎比称作可食性膜更科学。     

The effect of iodine salts on lipid oxidation and changes in nutritive value of protein in stored processed meats

The aim was to assess the effect of iodine salts (KI or KIO(3)) on lipid oxidation as well as changes in the availability of lysine and methionine and protein digestibility in frozen-stored processed meats. Three types of iodine salt carriers were used: table salt, wheat fiber and soy protein isolate. The results showed no catalytic effect of iodine salts on lipid oxidation in stored processed meats. The application of a protein isolate and wheat fiber resulted in the inhibition of lipid oxidation in meatballs. During storage of meat products the contents of available lysine and methionine as well as protein digestibility were decreased. The utilization of wheat fiber as an iodine salt carrier had a significant effect on the reduction of lysine losses. No protective properties were found for the wheat fiber or soy protein isolate towards methionine.     

Contribution of Sucrose to Nonenzymatic Browning in Potato Chips

The contribution of sucrose, a nonreducing sugar, to nonenzymatic browning in potato chips was investigated using a model system of buffered sugars and glycine applied to filter paper discs that were then heated in oil. It was found by fiber optic colorimetry that sucrose and the amino acid produced darkening comparable to that of reducing sugars. It is postulated that sucrose enters the reaction by thermal hydrolysis to yield glucose and fructose. Addition of glucose and glycine to potato slices by vacuum infiltration resulted in increased darkening after frying but the sugar proved to be the limiting factor in nonenzymatic browning of potato chips, emphasizing the importance of sucrose in this reaction.     

Nutritional Evaluation of Breadfruit-containing Composite Flour Products

Composite flours containing wheat, breadfruit flour and soy protein, whey or peanut meal were formulated and incorporated into western style bread and biscuits. Bread containing 10% breadfruit flour and 5% whey, and biscuits containing 10% breadfruit flour and 5% soy protein were judged most acceptable in flavor, color, and texture. Breadfruit flour contained 4.4% protein and was lower in sulfur containing amino acids and higher in lysine than wheat flour. Breadfruit containing bread and biscuits had low amino acid scores. The protein efficiency ratio (PER) of the biscuit product, however, was similar to that of the casein control while the PER of bread was significantly lower. Results suggest that acceptable products can be made with composite flours containing 10% breadfruit flour.     

Reactions of chlorogenic acid and quercetin with a soy protein isolate--influence on the in vivo food protein quality in rats

Plant phenolic compounds are known to interact with proteins producing changes in the food (e. g., biological value (BV), color, taste). Therefore, the in vivo relevance, especially, of covalent phenol-protein reactions on protein quality was studied in a rat bioassay. The rats were fed protein derivatives at a 10% protein level. Soy proteins were derivatized with chlorogenic acid and quercetin (derivatization levels: 0.056 and 0.28 mmol phenolic compound/gram protein). Analysis of nitrogen in diets, urine, and fecal samples as well as the distribution of amino acids were determined. Depending on the degree of derivatization, the rats fed with soy-protein derivatives showed an increased excretion of fecal and urinary nitrogen. As a result, true nitrogen digestibility, BV, and net protein utilization were adversely affected. Protein digestibility corrected amino acid score was decreased for lysine, tryptophan, and sulfur containing amino acids.     

Proteolytic activity,amino acid composition and protein quality of germinating fenugreek seeds (Trigonella foenum graecum L.)

This study determined the changes in proteolytic activity and trypsin inhibitor, due to germination for 120 h, and their relationships to amino acid content and protein quality. The activities of cas-ase, Hb-ase, and BAPA-ase, as well as the trypsin inhibitor of the fenugreek, increased as germination proceeded. Glutamic and aspartic acids were the richest amino acids in fenugreek seeds, followed by leucine, arginine, lysine and proline. After germination, the contents of aspartic acid, phenylalanine, tyrosine, threonine, tryptophan and valine increased, while those of glutamic acid, proline and four of the essential amino acids decreased. All the free amino acids increased after germination, while glycine decreased. Cystine, tryptophan and proline originated in a free form after germination. The chemical score, based on the essential amino acid pattern of whole egg protein, for fenugreek seeds, showed a marked decrease (21%) after germination. The in vitro pepsin, followed by pancreatin digestion, showed a slight increase for the germinated seeds. Germination of seeds lowered the C-PER, a result which indicates that the protein quality decreased.