Specific role of endopeptidases in modulating the nature of protein digestion products

The impact of various endopeptidases on the nature of protein digestion products was measured with the digestion cell technique. After a 30 min pepsin pre-digestion, casein and rapeseed concentrates were hydrolyzed with various amounts of pancreatin, trypsin and/or chymotrypsin. This hydrolysis was performed in a dialysis tube (molecular weight cut-off 1000) with continuous collection of the digested material. The addition of pure trypsin or chymotrypsin to pancreatin (Enzyme:Substrate 125) did not change the digestibility of casein. Only a higher pancreatin level (Enzyme: Substrate 112.5) increased the total protein digestibility without affecting the amino acid spectra. Rapeseed digestibility was markedly increased by the addition of pure trypsin to pancreatin. Lysine and arginine, target amino acids of trypsin, were favored at the expense of chymotrypsin and elastase target amino acids. Supplementation of pancreatin with, chymotrypsin enhanced rapeseed digestibility without affecting the relative amino acid digestibility. The impact of a higher pancreatin ratio (Enzyme: Substrate 112.5) was similar to that of enriched pancreatin but the rate of amino acid release was modified. The differences between protein sources were mainly attributed to protein structure.     

Effect of Cooking Procedures and Storage on Starch Bioavailability in Common Beans (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.)

Common commercial beans were cooked using two procedures: under pressure (autoclaving) and traditional cooking. Total starch extraction was higher in beans cooked with the traditional procedure (41.69–42.81%) than in the autoclaved samples (37.04–38.16%) and did not change during storage at 4 °C. However, available and total resistant starch levels in vitro were not influenced by the cooking procedure or storage. Retrograded resistant starch content was higher in beans cooked with the traditional process (2.65–2.79%) than in autoclaved beans (1.62–1.94%). The initial in vitro -amylolysis rate in freshly cooked beans was higher in the autoclaved preparation than in the beans cooked by the traditional process, but final hydrolysis indices (90 min) were similar for both samples. None of the bean samples showed statistical differences in -amylolysis behavior (=0.05) after storage at 4 °C for 96 hour.     

Quality attributes of fermented yam flour supplemented with processed soy flour

Pretreated soy flour was used to replace 10, 20, 30 and 40% of fermented yam flour as a protein supplement. The effect of the supplementation on the physicochemical and sensory properties of amala, a popular West African food made from rehydrated yam flour, was investigated. Blanching (10 min in boiling water) and subsequent fermentation (24 h) as pretreatment methods produced flour that was lighter in color than the unfermented samples. Protein content of the yam-soy mixture increased from 3.5% in the control to 19.7% for 40% soy fortification. Water binding capacity increased from 212.6 g/100 g for the yam flour control to 257.3 g/100 g for the blend with 40% soy flour. However, swelling capacity and solubility were adversely affected with increased soy flour addition as dough became sticky and soft. There was no significant difference in color, taste, flavor or overall acceptability when compared with the control up to 20% soy substitution. Dough with 20% soy flour is a possibility for increasing the protein content of yam flour in human feeding.     

Yield andin vitro nutritional quality of some leguminous seed protein isolates

Seed protein concentrates (SPC) were extracted from 4 leguminous species and the extractabilities of total N (nitrogen), protein N and SPC determined. In addition, composition, calorie value andin vitro enzymatic digestibility of these SPCs was analysed. Results indicate the promising nutritional potential of these SPCs.     

Properties of starch and dietary fibre in raw and processed quinoa (Chenopodium quinoa,Willd) seeds

We investigated certain properties of starch in raw and in heat-treated samples of quinoa, properties that are of importance to the nutritional quality of an infant food currently being developed. Scanning electron microscopy of the starch in raw seeds showed polygonal granules (0.6 to 2.0 µm diameter) to be present both singly and as spherical aggregates. Thermograms (DSC) of the flours showed one transition phase for gelatinisation of the starch and another for the amylose-lipid complex. The gelatinisation temperature of the starch was 67°C. Cooked samples manifested the highest degree of gelatinisation (97%), followed by the drum-dried (96%) and autoclaved (27%) samples. Separation of the starch on a SEPHAROSE CL-2B column showed the quinoa starch to be affected by the heat treatment, manifesting changes in the degree and extent of degradation. The amylograph viscosity of the quinoa flour showed no distinct peak for pasting, but the viscosity remained constant after gelatinisation. Cooking and autoclaving modified the viscosity of the paste. The drum-dried sample manifested a higher initial viscosity at 25°C. Thein vitro digestibility of raw quinoa starch determined by incubation for 60 min with -amylase was 22%, while that of autoclaved, cooked and drum-dried samples was 32%, 45% and 73%, respectively. Saponins did not affect the digestibility of the starch, though they tended to increase the amylograph viscosity. The total dietary fibre content in the cooked sample (11.0%) was significantly lower than that in the autoclaved (13.2%), drum-dried (13.3%) or raw samples (13.3%), while the insoluble dietary fibre fraction in the samples did not change with heat treatment. However, as compared with that of raw quinoa, the soluble dietary fibre fraction was reduced significantly both by cooking (0.9%) and by autoclaving (1.0%).     

Rabadi fermentation of wheat: Changes in phytic acid content andin vitro digestibility

Fermentation of raw as well as autoclaved wheat flour with buttermilk at 30, 35 and 40°C for 6, 12, 18, 24 ad 48h significantly decreased the level of phytic acid; maximum decrease was observed at 40°C for 48h. Starch as well as protein digestibility (in vitro) improved with an increase in temperature and period of fermentation. Phytic acid had a significant (P<0.05) negative correlation with digestibility (in vitro) of both starch and protein ofrabadi.     

Formulation,acceptability, chemical composition and in vitro digestibility of novel snack food and meat ball analogue

Potato purée and wheat flour were blended at ratio of 7:1 w/w with 2 parts per weight of soybean protein concentrate (SPC) and/or faba bean-protein micellar mass (PMM). Two snack foods were formulated and deep fried. Spices, onion, parsley and chicken stock were added to the aforementioned two recipes to formulate meat ball analogues. Data revealed good acceptability of all products. Moreover, they can be considered as a good source for some essential amino acids; protein (26%); lipids (20%); carbohydrates (48%) and minerals. The in vitro digestibility ranged between 61.0% and 66.9%.     

A comparison of in vivo and in vitro estimates of protein digestibility of native and thermally processed vegetable proteins

Research was performed to determine the suitability of the rapid multienzymatic assay for in vitro protein digestibility estimation by using a group of native and thermally processed vegetable proteins which constitute the staple foods in developing countries. The in vitro digestibility was assessed by measuring the extent to which the pH of the protein suspension dropped when treated with a multienzyme system consisting of trypsin, chymotrypsin, and peptidase for 10 min, andStreptomyces griseus protease for 10 min more. The best correlation occurred between in vivo rat protein digestibility and the pH of the protein suspension after 15 min enzymatic treatment. The response of different types of proteins to the multienzyme assay was different, and thus distinct equations were derived for the in vitro digestibility estimation of the samples assayed. The first group included nonprocessed cereal grains and oilseeds, and cereal grain-leguminous seed mixtures. The second group was formed by leguminous seeds, and the third by thermally processed cereal and oilseed products. Although highly significant correlations between in vivo and in vitro estimates for the three groups were found, important differences occurred in the group of processed samples; therefore, more research is required with these types of samples.     

Evaluation of pumpkin seed products for bread fortification

Pumpkin seed products (raw, roasted, autoclaved,germinated, fermented, pumpkin protein concentrate and pumpkin proteinisolate) were incorporated into wheat flour to produce blends with proteinlevels of 15, 17, 19 and 21%. Dough properties were evaluated by afarinograph; loaves of breads were evaluated by a taste panel for crustcolor, crumb color, crumb texture, flavor, and overall quality. Resultsindicated that pumpkin seed products can be added to wheat flour up toa 17% protein level for raw, roasted and autoclaved pumpkin meal, 19%level for germinated, fermented and pumpkin protein concentrate and21% level for pumpkin protein isolate without a detrimental effecton dough or loaf quality. On the other hand, the addition of pumpkin seedproteins resulted in increasing protein, lysine and mineral contentscompared to the control. While lysine and tryptophan were the first andsecond limiting amino acids in the control bread, tryptophan and lysinewere the first and second limiting amino acids for raw, roasted, autoclaved,germinated and fermented pumpkin meal; valine and lysine and valine andtotal sulfur amino acids were the first and second limiting amino acids forpumpkin protein concentrate and isolate, respectively. In vitro protein digestibility improved when the pumpkin seed proteinswere added.     

Seed protein yield from someCrotalaria spp andin vitro nutritional quality of that fromC. juncea

Seed Protein Concentrates (SPC) of 6 species ofCrotalaria were extracted and the extractabilities of SPC, total N and protein N determined. SPC of high yielding species (C. juncea) was analysed for the contents of amino acids, ash, phosphorus, sugar, starch, fibre and calories, as well as forin vitro digestibility. Results indicate the promising potential ofC. juncea for SPC yield.     

Chemical changes during the fermentation of African locust-bean (Parkia filicoidea Welw) seeds for production of ‘Daddawa’

African locust-bean (Parkia filicoidea Welw) seeds were allowed to ferment under natural conditions and the chemical changes occurring during the fermentation were studied. Chemical analysis of fermented and unfermented beans showed a marked decrease in the total sugar content; crude and true protein levels all increased. The results of the chemical analyses indicate that fermentation resulted in protein enrichment of the fermented locust bean (daddaw). Fermentation also imparts a characteristic flavour and odour to the beans.     

Effects of processing on protein nutritive quality of coconut Cocos nucifera products

Pared, comminuted and blanched coconut meat was freeze-dried at25 ^°C for 24 hours and pulverized. Whole coconut meal wassolvent extracted with n-hexane to yield a defatted meal while full-fatcoconut protein concentrate (FFC-PC) containing 27.60% protein wasprepared by alkali extraction of undefatted meal followed by isoelectricprecipitation. Defatted coconut meal had a significantly (p 0.05)lower crude fat but higher protein content than whole coconut meal.Similarly, FFC-PC had a significantly (p 0.05) higher proteinbut lower carbohydrate content than whole coconut meal and defattedcoconut meal. Whole coconut meal, defatted coconut meal and FFC-PChad PERs of 1.98, 2.18 and 2.48 respectively, with NPRs of 2.86, 3.28and 3.92, respectively. Protein digestibility values of 88.75%, 89.30%and 94.02% were obtained for whole coconut meal, defatted coconutmeal and full-fat coconut protein concentrate, respectively. Growthresponse of animals showed that FPC-PC was superior to all other testdiets.     

Nutritional evaluation of chickpea and germinated chickpea flours

The ability of seed germination to increase the nutritional quality of chickpea was studied. Chickpea flours germinated for 0, 24 and 48 h were evaluated nutritionally by determination of protein efficiency ratio (PER), net protein ratio (NPR), digestibility and essential amino acid availability in vivo. A significant increase in ascorbic acid was observed during germination. PER and NPR values indicated that germinated chickpea flours compared favorably to casein. Protein digestibility decreased as germination time increased. Essential amino acid availability did not change after 24 h of germination, but a small decrease was observed after 48 h. The increase in some amino acids during germination may account for the observed increase in PER for the germinated flours. Seed germination enhanced significantly the nutritional quality of chickpea protein and substantially increased the ascorbic acid level.Contribution No. 4359, Arizona Agricultural Experiment Station, University of Arizona, Tucson, AZ 85721, USA.     

Chemical composition and nutritional quality of five peanut cultivars grown in Pakistan

Four high yielding imported and one local peanut cultivar, grown under local soil and climatic conditions, were compared for their chemical composition and nutritional quality. The local cultivar Kurram contained the maximum protein (28.3%) and the imported cultivar No. 45 contained the maximum oil content (49.5%). K, Mg, P, Fe, Zn, Cu and Mn were present in nutritionally significant and comparable amounts in all the cultivars. Lysine was the first limiting amino acid in all the cultivars. The chemical scores and net protein utilization (operative) values were higher for the imported than local cultivar while net dietary protein calories percent (NDP Cal%) values showed only minor variations among the five cultivars. Significant differences (P<0.05) were observed for protein, oil, Na, K, Ca, P and Zn contents of all the cultivars. Roasting (150°C, 1/2 h) decreased the lysine, threonine, methionine, cystine, arginine, tryptophan and tyrosine contents but increased the protein, oil, ash, fiber, mineral elements (except Na and C1), aspartic acid, serine, glutamic acid, proline and phenylalanine contents.     

Studies on weaning diets in Nigeria: 2 protein sources

Protein isolates were extracted from melon, groundnut, and soybean cakes in an aqueous system that could potentially yield both oil and protein from oilseeds quantitatively. Protein isolates obtained were 91.2, 78.6 and 79.5% of the total protein content of melon, groundnut and soybean cakes respectively. Both cakes and isolates were assessed in a rat bioassay while breadfruit, cassava, and corn starch were also investigated as sources of carbohydrate. Results showed that there were no significant differences between feed intake, weight gain and PER of rats fed the cake and the protein isolates except in soybean. Weight gain, PER and NPR were highest in cassava-soybean protein isolate diet followed by cassavacasein diet (control) while performance was only moderate with melon- and groundnutcassava diets. With melon protein isolate, cassava and breadfruit were better carbohydrate sources than corn starch. In simulated weaning diets, cassava-sucrose-melon-soybean protein isolate based diet performed better (weight gain 33.4 g, PER 1.63, NPR 2.23) than a commercial weaning food (weight gain 30.6 g PER 1.57, NPR 2.18) while replacement of sucrose and cassava at 30% by breadfruit yielded a cost effective diet with good performance (weight gain 29.4 g, PER 1.51, NPR 2.12). Diets where soybean protein served as the sole source of protein or breadfruit, white and yellow maize ogi served as the main source of carbohydrate performed only moderately.     

Isolation and characterization of nanocrystalline cellulose from different precursor materials

Nanocrytalline cellulose (NCC) was isolated using cellulose extracted from two different precursor materials: Eucalyptus globulus and rice straw. The two ground precursor materials were autoclaved with a 10 % NaOH solution at 120 °C for 3 h. The alkali-treated precursor materials were bleached using sodium chlorite/acetic acid and sodium hypochlorite. The bleached precursor materials were acid-hydrolyzed in 65 % (w/w) sulfuric acid at 45 °C for 30-120 min. The changes in the chemical composition of the two precursor materials were studied before and after bleaching by Fourier transform infrared spectroscopy according to the NREL report and TAPPI standards. Hydrolyzates were characterized by X-ray diffractometry, thermogravimetric analysis, Zeta-potential analysis, and transmission electron microscopy. The results revealed that the physical properties of NCC were strongly dependent on the acid-hydrolysis time.     

Effect of sesame seed proteins supplementation on the nutritional,physical, chemical and sensory properties of wheat flour bread

Sesame products (sesame meal, roasted and autoclaved sesame meal, sesame protein isolate and concentrate) were added to Red wheat flour to produce blends at protein levels of 14, 16, 18 and 20 percent. Dough properties were studied using a Brabender Farinograph. Loaves were prepared from the various blends using the straight dough procedure and then evaluated for volume, crust and crumb colour, crumb texture, flavour and overall quality. The water absorption, development time and dough weakening were increased (p<0.05) as the protein level increased in all blends; however, dough stability decreased. Sesame products could be added to wheat flour up to 18 percent protein level (sesame protein isolate) and up to 16 percent protein level (other sesame products) without any observed detrimental effect on bread sensory properties. No significant differences (p>0.05) were recorded in loaf volume between control and breads containing sesame protein isolate (up to 18 percent protein level) and either autoclaved sesame meal or sesame protein concentrate (up to 14 percent protein level). Addition of sesame products increased the content not only of protein but also minerals and total essential amino acids, especially lysine. The addition also improved in-vitro protein digestibility.     

Effect of fermentation on sorghum protein fractions and in vitro protein digestibility

Changes in pH, titratable acidity, total soluble solids and proteins ofDabar sorghum (Sorghum bicolor (Linn) Moench.) during naturalfermentation at 37 ^°C for up to 36 h were monitored. The pH ofthe fermenting material decreased sharply with a concomitant increase in the titratable acidity. Total soluble solids increased with progressivefermentation time. The crude protein and non-protein nitrogen slightlyincreased during the last stages of fermentation. The in vitroprotein digestibility markedly increased as a result of fermentation.The globulin plus albumin fractions increased significantly (p 0.05)during the first 8 h of fermentation. Kaffirin fraction decreasedduring the first 8 h of fermentation but increased sharply as fermentationprogressed. Cross-linked kaffirins fluctuated during the fermentationprocess. Glutelin like protein, which was the minor fraction, trueglutelins, the second most abundant fraction, together with non-extractableproteins fluctuated during the fermentation process.     

The USDA trypsin inhibitor study. III. Sequential development of pancreatic pathology in rats

Weanling male, Wistar rats (40 per diet) were maintained on 15 diets which provided 4 graded trypsin inhibitor (TI) levels (93, 215, 337, and 577 mg/100g diet) repeated at 3 levels of protein (10%, 20%, and 30%). Raw and heated (toasted) soy flour provided 10% protein in the diet, while casein was added to increase the protein level to 20% and 30%. Three diets containing only casein as the protein source, at 10%, 20%, and 30% were included. Histologic changes occurring in the pancreas were evaluated in approximately 5 rats from each diet at 3 month intervals, beginning at 6 months, for 22 months. Criteria for the diagnosis of the observed histologic changes in the pancreas are discussed. Ultrastructure of the endocrine cells in the gastrointestinal mucosa was also examined.Pancreatic acinar cell density, as determined morphometrically, was reduced throughout the study in rats fed the 577 mg TI/100 g diet, indicating hypertrophy at the cellular level. Nodular hyperplasia was observed in the first sacrifice group at 6 months. Incidence of the lesion was positively related to both time of exposure and level of dietary TI. Acinar adenoma was first observed at 18 months and was most prevalent in rats fed the highest concentration of TI.Endocrine cells of the duodenal mucosa which contain cholecystokinin (so-called I cells) contained a denser population of secretory granules in animals fed the high TI diet compared with I cells from control animals, leading to the speculation that production and secretion of cytoplasmic hormones was increased in TI treated rats.Reference to a company and/or product named by the Department is only for purposes of information and does not imply approval or recommendation of the product to the exclusion of others which may also be suitable.     

Effect of cooking on protein solubility profiles of faba beans (Vicia faba L.) grown using different nutritional regimes

A field experiment was carried out to study the effect ofcooking on protein solubility profiles of mycorrhizal inoculated, phosphorusand sulphur fertilized faba beans under two water regimes. The resultsindicated that cooking significantly (p 0.05) increasedthe G₃-glutelin fraction as well as the insoluble protein butsignificantly (p 0.05) decreased the globulin and albuminfractions; prolamin, G₁-glutelin and G₂-glutelin fractionswere slightly increased. Mycorrhizal inoculation and mycorrhiza +phosphorus + sulphur fertilization significantly (p 0.05) increased albumin content. All fertilizer treatments significantly (p 0.05) decreased the insoluble protein.