Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolus vulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AAS_IVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AAS_IVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.     

Amino acid digestibility studies of autoclaved rapeseed meals using an in vitro enzymatic procedure

An investigation of in vitro enzymatic amino acid digestibility of autoclaved rapeseed meals using the enzyme pronase is presented. A correlation coefficient of 0.991 was obtained when comparing in vitro “available” lysine with “Silcock available” lysine. Autoclaving of rapeseed meal for periods of 15, 30, 60, 120 and 180 min at 103 kPa and 120°C caused the following chemical changes. Lysine, methionine and cysteine in vitro digestibilities were markedly decreased as to a lesser extent were the other amino acids. Conversion of methionine to methionine sulphoxide occurred. Deactivation of trypsin inhibitor from 3.8 units of trypsin inhibitor/mg rapeseed for the non-autoclaved meal to zero for the 15 min autoclaved meal was observed. The in vitro enzymatic method described shows considerable promise as a technique to measure amino acid availability.     

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.     

Effect of radiation and other processing methods on protein quality of sunflower meal

The effects of gamma irradiation from a ⁶⁰Co source (10 and 20 kGy), dry heating (121 °C for 10, 20 and 30 min), autoclaving (121 °C at 103.5 kPa for 10, 20 and 30 min) and their combination on chlorogenic acid, soluble protein, available lysine and in-vitro protein digestibility of sunflower meal were studied. The moisture content of the raw sample was 78 g kg⁻¹ as is and on a dry matter basis. The meal contained 26.7 g kg⁻¹ chlorogenic acid, 330 g kg⁻¹ crude protein, 78.5% soluble protein and 2.63 g 16 g N⁻¹ available lysine. Digestibility of raw meal was 81.5%. Chlorogenic acid, soluble protein and available lysine of raw meal decreased during dry heating, autoclaving and radiation processing. The digestibility was significantly affected by processing method (P < 0.05), as well as by the time of dry heating and autoclaving. The influence of combination methods revealed that irradiation alone had a little effect on chlorogenic acid and in-vitro protein digestibility. Autoclaving plus irradiation up to 20 kGy markedly improved the digestibility (90%). Therefore, the results suggested that the combination of autoclaving for 10 min plus irradiation up to 20 kGy has a beneficial effect on the protein quality of sunflower meal with little effect on its content of soluble protein, available lysine and markedly reduced chlorogenic acid by 87%, more than other processing methods. © 1999 Society of Chemical Industry     

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.     

Digestive utilisation of protein and amino acids from raw and heated lentils by growing rats

The effect of autoclave treatment on the digestive utilisation of protein and amino acids from lentils was studied in growing rats. Twenty 3‐week‐old Wistar rats (mean live weight 59 ± 4.8 g) were fed two experimental diets (n = 10 rats per diet) consisting of raw lentils (Lens culinaris M, var vulgaris, cv magda‐20) (diet RL) or lentils autoclaved at 120 °C and 1 atm for 30 min (diet AL). An additional group of 10 animals was fed a low‐protein (4%) diet and used to estimate metabolic nitrogen and amino acid excretion. Autoclaving caused a 76% reduction in the levels of trypsin inhibitor activity, but failed to improve the faecal digestive utilisation of protein or total amino acids. Lowest essential amino acid true digestibility in diets RL and AL was found for cysteine (60.2 vs 60.1%) and methionine (68.9 vs 66.6%). The protein digestibility‐corrected amino acid score was 71.2 and 66.4% and the availability of sulphur amino acid‐corrected amino acid score was 57.1 and 52.1% for diets RL and AL respectively. Sulphur amino acids were the first limiting ones. Overall, autoclave treatment did not improve protein or total amino acid digestibility from lentils, but caused a significant improvement in leucine and lysine digestibility and a significant decrease in the digestive utilisation of tyrosine and methionine. © 2002 Society of Chemical Industry     

Nutritional, Microbiological, and Sensory Qualities of a Peanut Beverage Prepared Using Various Processes

Nutritional, microbiological and sensory qualities of peanut beverages processed at 85°C, 100°C and 121°C for 15 min and 121°C for 3 sec were determined. Heating improved the digestibility of peanut beverages, particularly those processed at 121°C for 3 sec and 85°C for 15 min. Methionine was particularly sensitive to the treatment at 121°C. The limiting amino acids were threonine, cystine, valine, lysine and tyrosine. No microbial growth was observed in products processed at 100°C and 121°C followed by storage at 4°C and 30°C for 20 days. Beverage processed at 85°C and stored at 30°C for 3 days contained an aerobic microbial population of 2.4 × 10⁴ CFU/mL. The beany flavor was least pronounced in beverages processed at 100°C for 15 min and strongest at 121°C for 3 sec.     

Nonvolatile taste compounds in cooked Chinese Nanjing duck meat following postproduction heat treatment

Abstract: Taste‐active compounds, including free amino acids, succinic acid and 5′‐nucleotides, and chemical components including moisture, pH, protein, crude fat, and sodium chloride were evaluated in cooked and packaged Chinese Nanjing ducks following heat treatments including control, 99 °C for 40 min, 108 °C for 20 min, 92 °C microwave followed by water heating, 95 °C for 30 min, 121 °C for 25 min. Heat treatment decreased (P < 0.05) the content of Alamine and moisture and reduced the pH value in muscle, but increased (P < 0.05) the protein and 5′‐nucleotides content. The 99 °C group had a significantly lower crude fat content compared with other groups (P < 0.05). The succinic acid content in the control group was significantly higher than in the 121 °C group (P < 0.05). Groups treated at higher temperatures (108 °C, 121 °C, and microwave) had similar equivalent umami concentrations and 5′‐nucleotides, free amino acids content, as well as the derived bitter and sweet taste components compared with the groups treated at lower temperatures. It can be speculated that these differences account for the enhanced flavor of the meat in the 99 °C, 108 °C, 121 °C, and microwave groups compared with the untreated control. Therefore, heat treatment at lower temperature after packaging may prolong product shelf life without any detrimental effects on taste. The results of this study indicate that it is important to use lower temperatures in this type of food processing. However, it may be possible to modify the primary processing steps to improve the content of umami‐like taste compounds such as 5′‐nucleotides. Practical Application: Heat treatment of packaged products is an effective method for eradication of microbes, therefore increasing the shelf‐life. However, such treatment can result in major changes in the sensory perception of meat products, particularly the formation of off‐flavors. This study investigated changes in taste‐active compounds in duck meat following a number of types of heat treatment.     

Rapid Rehydration Methods for Dried Beans

Rapid methods of rehydrating dried kidney, pinto or navy beans by soaking at 82°C or 93°C for 5, 10 or 30 min were compared to standard 18 hr soaking at ambient temperature. Canned beans processed 21 min at 121°C had higher drained weights and softer texture with fewer split beans than those processed 41 min at 116°C. Kidney, pinto and navy beans soaked 30 min at 82°C had higher drained weight than those soaked 30 min at 93°C. Hydration coefficient (2.07) of controls (18-hr soak) and beans soaked 82°C (1.94) or 93°C for 30 min were not different. Pre soaking 30 min at 82°C provided adequate rehydration prior to canning.     

Protein quality evaluation of Amaranthus wholemeal flours and protein concentrates

Based on the amino acid composition, Amaranthus seed protein is known to be of higher quality than most of the major cereal grains. However, protein quality does not solely depend on amino acid profile but also on its digestibility. In this study we determined amino acid composition and in vitro protein digestibility of wholemeal and isoelectric protein concentrates (IPC) from five Amaranthus genotypes. Factors most likely to influence protein digestibility such as heating and presence of antinutrients were studied. Heating increased protein digestibility in wholemeals but slightly decreased it in IPCs. Trypsin inhibitor level was negatively but weakly correlated to protein digestibility, and the level of polyphenolic compounds was negatively and significantly correlated to protein digestibility. A slight deficiency in leucine was noted for wholemeals and in lysine for IPCs. However, based on both in vitro digestibility and amino acid profile, Amaranthus proteins were confirmed to be of better quality than those of other cereals. © 1998 SCI.     

Effect of preliminary and culinary processing on amino acid content and protein quality in frozen French beans

The aim of the study was to evaluate the content of amino acids and protein quality of French bean pods. The investigated material consisted of the raw vegetable, fresh pods cooked to consumption consistency, and two kinds of frozen products stored for 12 months at ?20 °C and then prepared for consumption: frozen beans obtained using the traditional method (blanching before freezing) and frozen products of the ready‐to‐eat type (cooking before freezing). A comparison of the amino acid content in the product prepared for consumption showed that the lowest quantities were found in French beans obtained using the traditional method; products obtained using the modified technology and beans cooked directly after harvest had similar levels of most amino acids. The content of amino acids in 16 g N was less varied than in 100 g of the product. The protein in all the three products prepared for consumption as well as that in fresh bean pods hardly differs, as confirmed by the values in the essential amino acid index (EAA). The first limiting amino acid was methionine with cystine and the second was lysine.     

Changes in Selected Biochemical Components, In Vitro Protein Digestibility and Amino Acids in Two Bean Cultivars During Germination

This study investigates changes in lectin and trypsin inhibitor activity, SDS-PAGE peptide pattern, in vitro protein digestibility and amino acid composition during germination of two dry bean cultivars. Lectin activity in navy beans was reduced. Significant amounts of trypsin inhibitor activity in both navy and pinto beans remained after germination for 6 days. Glycopeptides, with molecular mass ranging from 25,000 to 27,000 daltons, from partial proteolysis of the major storage proteins were resistant to a multienzyme system. In vitro protein digestibility and amino acid composition were only slightly altered. Germination did not improve protein nutritional quality of dry beans.     

Thermal stability of black turtle soup bean (Phaseolus vulgaris) lectins

A method for determining the thermal stability of porcine thyroglobulin (PTG)-binding lectins in whole black turtle soup beans (Phaseolus vulgaris L) is described. The procedure utilises PTG-Sepharose affinity chromatography and the Folin-Ciocalteau protein assay. The majority of lectin activity in whole black turtle soup beans was destroyed by heating presoaked beans at 97.8°C for 10 min whereas unsoaked beans required 20 min of heat treatment at 97.8°C. Residual lectin activity was eliminated by thermally processing the presoaked and unsoaked beans for 25 and 50 min at 97.8°C, respectively. Thermal inactivation of the lectin in the whole seed is a biphasic, first-order reaction mechanism. Lectin-rat intestinal epithelial cell binding studies indicated the presence of a second lectin in the BTS albumin protein fraction. The lectin lacked an affinity for PTG and was inactivated by heating unsoaked whole beans for 50 min at 97.8°C.     

Effects of heat processing on the nutritional value of groundnut products. I. Protein quality of groundnut cotyledons for rats

The trypsin inhibitor activity of raw groundnut cotyledons was approximately 20% of that found in raw soyabeans but was apparently sufficient to cause significant pancreatic hypertrophy in rats receiving 15% protein from this source in their diet. Autoclaving at 121° for 0.5 h reduced the inhibitor activity to one-fifth; dry heating for the same time at this temperature reduced it to one-half. There was a tendency for 0.5 h heating, wet or dry, at 100–121° slightly to increase the net protein utilisation (NPU) value of the protein for rats. Dry heating at 121° for 4 h severely reduced NPU; fluorodinitrobenzene-available lysine in the severely heated material was similarly reduced but there was little change in the level of available methionine assessed using Streptococcus zymogenes.     

Tuna Protein Nutritional Quality Changes after Canning

Albacore tuna (Thunnus alalunga) was steamed and canned in soy bean oil and sterilized at 115°C for 55 or 90 min. Proximate composition, total amino acid and available lysine content were determined during different phases of the process. Water and protein were lost in all phases and fat content increased. There was a decrease in available lysine during cooking but no loss in total amino acids. Nutritional evaluation of the protein showed differences in biological value and net protein utilization when the canned tuna was mixed with bread flour.     

The nutritive value of egg by‐products and their potential bactericidal activity: in vitro and in vivo studies

Technical‐grade egg albumen (TA) and whole egg (WE) by‐products are produced in substantial quantities by egg‐breaking facilities across North America. TA and WE products are recovered during processing but are not approved for human consumption. Both products are known to be rich in fat, maternal antibodies, protein and lysozyme, a bactericidal enzyme. The objective of this research was to explore the potential for egg by‐products to be used as a valuable protein, energy and bactericidal supplement in animal nutrition. To improve the nutritive value of TA and WE, spray‐dried samples were heat treated at various temperatures and their digestible protein content was determined in vitro using a pepsin/pancreatin digestion/dialysis system. In addition, enhancement of lysozyme activity towards Gram‐negative bacteria (GNB) by heat or irradiation was examined. Optimal protein digestibility for TA averaged 80% following heat treatment at 105–110 °C for 10 min. In contrast, protein digestibility of spray‐dried TA was only 55%. Heat treatment (100–122 °C) of spray‐dried WE or hot room storage of spray‐dried TA and WE products at 70 °C for up to 14 days had a minimal effect on protein digestibility in vitro. Heat treatment or γ‐irradiation of lysozyme for at least 20 min at 80 °C or 0.5 kGy, respectively, increased antimicrobial activity towards GNB. When compared with either the heat or radiation control treatments, reductions in Escherichia coli and Salmonella enterica serovar Typhimurium populations increased by at least 1 and 0.5 log₁₀, respectively. In contrast, the effect of irradiation (2 kGy) on the antimicrobial activity of spray‐dried TA was less pronounced. In a feeding trial, rats fed spray‐dried TA and spray‐dried TA subjected to either radiation (1.8 kGy) or heat (80 °C, 20 min) treatment exhibited a body weight gain and protein utilisation equal to or higher than the control (casein diet). In contrast, feeding spray‐dried WE or TA and WE previously maintained in a hot room (70 °C) for 3 days had a negative effect on rat growth and protein utilisation. In the case of WE products this was substantiated by poor digestibility of essential amino acids, including lysine, threonine and, to some extent, methionine. When compared with the control treatments, inclusion of heat‐treated or irradiated TA in the rat diets reduced the population of Enterobacteriaceae. Copyright © 2006 Society of Chemical Industry     

Effect of cooking on tryptophan,basic amino acids,protein solubility and retention of some vitamins in two varieties of chick pea

Egyptian and Italian varieties of chick pea were analysed chemically to study their total constituents. The two varieties were cooked for 1 and 2 h and autoclaved for 1 h at 121°C. Their constituent basic amino acids, tryptophan, thiamin, pyridoxin and niacin, were determined.There were differences in the chemical constituents between the two varieties. Cooking decreased lysine, histidine and arginine, the effect being highly significant. Tryptophan decreased, the effect being significant. In addition, protein solubility decreased with increased cooking time.The vitamin content also decreased with increased cooking time. It is preferable to cook chick pea in an autoclave at 121°C for not more than 1 h to minimise losses in vitamins and amino acids.     

Quality of Green Beans, Bell Peppers and Spinach Stored in Polyethylene Bags

Quality attributes of packaged and unpackaged vegetables generally decreased nonlinearly during storage at 10°C or 20°C, and most of the decrease was greater at 20°C than at 10°C. Packaging reduced weight loss of green beans and spinach kept at 20°C; and reduced chlorophyll loss of green beans at 10°C and of spinach at 20°C. Ascorbic acid (vitamin C) benefited by packaging of green beans and spinach kept at 10°C. Packaging had an effect on thiamin (vitamin B₁) of only spinach held at 10°C and 20°C and had no effect on riboflavin (vitamin B₂). Loss of these quality attributes appears to be enhanced with water loss.     

Effect of rabadi fermentation on phytic acid and in vitro digestibility of barley

Rabadi, an indigenous fermented food, was prepared by mixing cereal flour with buttermilk, allowing it to ferment at 30, 35 and 40 °C for 6, 12, 18, 24 and 48 h and cooking the fermented mixture for 0.5 h with continuous stirring. Two types of rabadi were prepared i.e. autoclaved and unautoclaved. In autoclaved type of rabadi cereal flour was mixed with water, autoclaved (0.103 MPa = 15 psi for 15 min), cooled, mixed with buttermilk and fermented. As this type of rabadi was precooked prior to fermentation, hence, the fermented product did not require cooking afterwards, while in unautoclaved rabadi, barley flour and buttermilk were mixed, fermented and then cooked prior to consumption. Phytic acid was reduced drastically at all the temperatures and periods of fermentation in both autoclaved and unautoclaved type of rabadi; greater reduction occurred at higher temperature and duration of fermentation. A significant improvement in the in vitro digestibility of starch and protein was observed; maximum improvement was noticed when fermentation was carried out at 40 °C for 48 h in both the types of rabadi. Phytic acid had a significant (P < 0.05) negative correlation with digestibility (in vitro) of proteins and starch of barley flour rabadi.     

Effect of Storage Conditions and Chemical Treatments on Firmness, in Vitro Protein Digestibility, Condensed Tannins, Phytic Acid and Divalent Cations of Cooked Black Beans (Phaseolus vulgaris)

Black beans stored at 30° or 40°C and 80% relative humidity showed marked increases in firmness and decreases in in vitro digestibility of proteins. Changes in these properties were small when beans were stored at 5°C and 50% relative humidity. The adverse effects of poor storage conditions could be practically eliminated by soaking beans in salt solutions instead of water. The changes in firmness and digestibility were accompanied by changes in the detectable concentrations of tannins and phytates. Protein digestibility appears to be reduced by interactions between protein and tannins, especially high molecular weight tannins. Concentration of these tannins is affected by poly-phenol oxidase activity. Firmness increased and protein digestibility decreased as the phytic acid content decreased.