Levels Of Trypsin Inhibitor Activity Research Articles

Effects of thermal processing on the nutritional and antinutritional properties of African yam bean (Sphenostylis stenocarpa) seed flours

The study was carried out to evaluate the effects of thermal processing treatments on nutrient and antinutrient contents of African yam bean seed flours. The African yam bean seeds were sorted, cleaned and divided into five equal lots of one kilogram each. Four lots were processed into boiled, blanched, roasted and autoclaved African yam bean flours, while the last lot was processed raw and used as control. The flour samples obtained were analysed for proximate, mineral, vitamin and antinutrient contents using standard methods. The proximate composition of the samples revealed that the flours had a range of 6.14-11.24% moisture, 8.18-14.37% crude protein, 3.06-4.61% fat, 2.04–3.32% ash, 3.18–3.56% crude fibre, 62.90–76.98% carbohydrate and 350.57–368.50 kJ/100g energy, respectively. The mineral composition of the samples showed that the flours contained 128.81–174.16 mg/100g calcium, 88.86–212.20 mg/100g, potassium, 134.71–166.77 mg/100g phosphorus, 89.17 – 122.76 mg/100g, magnesium, 14.28–18-11 mg/100g iron and 3.24–5.59 mg/100g zinc, respectively. The vitamin composition of the flours were 1.15–1.37 mg/100g ascorbic acid, 1.15–135 mg/100g thiamine, 1.19–1.55 mg/100g niacin, 1.34–1.85 mg/100g riboflavin, 1.09–1.29 mg/100g folic acid, 1.37–1.95 mg /100g vitamin A and 1.27–1.66 mg/100g vitamin E, respectively. The results showed that the roasted and autoclaved African yam bean flours generally had higher crude protein, fat, ash, crude fibre, mineral and vitamin contents than the boiled and blanched flour samples compared to the raw sample. The antinutrient composition of the flours also showed that the levels of trypsin inhibitor activity, tannin, phytate, oxalate, saponin and haemagglutinin of the samples were significantly (p<0.05) reduced by boiling, autoclaving roasting and blanching treatments compared to the raw sample. However, the study revealed that the processed African yam bean flours have the potentials to be used as nutrient dense ingredients in the preparation of a wide range of food products than the raw sample especially in both underdeveloped and developing countries where the problems of protein-energy malnutrition and micronutrients deficiencies are prevalent.

Disclosing the Nutritional Quality Diversity of Portuguese Common Beans—The Missing Link for Their Effective Use in Protein Quality Breeding Programs

The common bean (Phaseolus vulgaris L.) represents a sustainable and affordable source of protein, namely, to populations with vegetarian dietary habits. Despite the national germplasm genetic diversity, little is known about the Portuguese accessions’ nutritional and protein quality, leading to their underuse in breeding programs. To fill this gap, a representative collection (106 accessions) was cropped under two contrasting environments (traditional versus heat stress) and evaluated in terms of nutritional quality by near-infrared spectroscopy. Protein quality was assessed, under the stressful environment, considering the individual amino acid contents and the activity of trypsin inhibitors through mass spectrometry (LC-MS/MS) and spectrophotometry, respectively. On top of strong genotypic control, the nutritional composition (protein, fat, fiber, moisture and ash) was also highly influenced by the environment and by genotype × environment interaction, with a clear nutritional quality ranking change for the accessions in heat stress conditions. Classified into three clusters, the accessions from the cluster with the highest individual amino acid and protein contents also showed higher trypsin inhibitor activity (TIA). Since different levels of TIA had no translation into contrasting protein digestibility, breeders focusing on common beans’ protein quality improvement, especially under challenging warming climate conditions, may take advantage of this group of accessions.

АКТИВНОСТЬ ИНГИБИТОРОВ ТРИПСИНА В СЕМЕНАХ ФАСОЛИ ОБЫКНОВЕННОЙ (PHASEOLUS VULGARIS L.) ИЗ КОЛЛЕКЦИИ ВИР: ИЗМЕНЧИВОСТЬ И ИСХОДНЫЙ МАТЕРИАЛ ДЛЯ СЕЛЕКЦИИ

Background. An important trend in modern common bean breeding is the improvement of grain quality, including by reducing the content of anti-nutrients, so it is important to identify accessions that are free of inhibitors or contain minimal amounts of them. The search for samples with high content of inhibitors is also relevant, since inhibitors play a crucial role in the functioning of the basic biochemical mechanisms that determine and regulate the physiological state of the cell. Materials and methods. Presented here are the results of biochemical and field screening of 141 common bean accessions (Phaseolus vulgaris L.) of different ecogeographic origin from the collection of VIR. Various sets of accessions were grown at VIR's experimental stations - Krymsk Experiment Breeding Station, branch of VIR (Town of Krymsk); Pushkin and Pavlovsk Laboratories of VIR (City of St. Petersburg) - in 2000-2003. Field study of economically valuable traits was carried out according to VIR's methods. Trypsin inhibitor activity (TIA) was calculated at the biochemical laboratory of VIR by spectrophotometry. The program Statistica 7.0. (StatSoft, Inc., USA) was used for statistical analysis. Results. TIA assessment in the seeds of common bean accessions showed that the mean value of the trait varied depending on the country of origin and the year of study. The results of the correlation analysis showed that the values of correlation coefficients were unstable over the years of study, and did not allow us to reveal stable relationships between TIA in bean seeds and meteorological conditions (-0.39 ≤ r ≤ 0.41), morphological (0.03 ≤ r ≤ 0.23) and economically valuable (-0.05 ≤ r ≤ 0.21) traits. The analysis of variance showed that the content of trypsin inhibitors in seeds depends more on the genetic properties of plants (effect-size percentage is 88.6%), less on weather conditions (12.24-20.16%), the year of reproduction (20.16%) or origin (18.87%), and only to a small extent on the place of reproduction (10.76%). Conclusions. The study helped to find 8 sources of low TIA ( 13 mg/g). Accessions combining high seed protein content (> 30%) with low (< 7 mg/g) or medium (7-9 mg/g) TIA levels were also identified. Those accessions can be included in future breeding programs. The lowest mean TIA values were observed in the accessions from Azerbaijan (7.55), Madagascar (8), Costa Rica (8.05), and Denmark (8.98), while high mean TIA was manifested by the accessions from Bhutan (17.8), Russia (13.4), Kenya (13.2), and Sweden (12, 97). The correlation analysis failed to reveal stable interrelations between TIA and meteorological conditions or morphological and economically valuable traits. The TIA level basically depends on the genetic properties of plants.

In Vitro Digestibility of Rapeseed and Bovine Whey Protein Mixtures.

Partial replacement of animal protein sources with plant proteins is highly relevant for the food industry, but potential effects on protein digestibility need to be established. In this study, the in vitro protein digestibility (IVPD) of four protein sources and their mixtures (50:50 w/w ratio) was investigated using a transient pepsin hydrolysis (1 h) followed by pancreatin (1 h). The protein sources consisted of napin-rich rapeseed (Brassica napus L.) protein concentrates (RPCs; RP1, RP2) prepared in pilot scale and major bovine whey proteins (WPs; α-LA, alpha-lactalbumin; β-LG, beta-lactoglobulin). IVPD of individual protein sources was higher for WPs compared to RPCs. The RP2/β-LG mixture resulted in an unexpected high IVPD equivalent to β-LG protein alone. Protein mixtures containing RP1 showed a new IVPD response type due to the negative influence of a high trypsin inhibitor activity (TIA) level. Improved IVPD of RP1 alone and in protein mixtures was obtained by lowering the TIA level using dithiothreitol (DTT). These results showed that napin-rich protein products prepared by appropriate processing can be combined with specific WPs in mixtures to improve the IVPD.

Comparative analysis of nutritional quality of five different cultivars of sweet potatoes (Ipomea batatas (L) Lam) in Sri Lanka.

Nutritional attributes of flours obtained from five different cultivars of sweet potato roots commonly available in Sri Lanka showed significant differences in the tested parameters. The starch level ranged between 33% and 64% on the dry basis and the extractability from fresh tubers was governed by the quantity of starch. The crude fiber level ranged between 2.1% and 13.6% on dry basis and the highest level was observed in swp7 (CARI 273) and resistant starch ranged from 14.2% to 17.2%. Higher percentage of resistant starch from total starch was found in Wariyapola red (swp1) cultivar resulting in lower digestion level while higher levels of digestion was evident in cultivars with lower levels of resistant starch with high level of total starch. Low levels of calcium and significant levels of iron were found in the five cultivars studied. Crude protein level was in the range of 1.2–3.3% on dry basis and trypsin inhibitor activity level (TIA) was significantly different (P > 0.05) in the cultivars studied while heating resulted in a significantly high reduction in the TIA level than in unheated condition. Polygonal or round shaped starch granules were in the range of 16.8–23.5 μm and low level of starch digestion was shown in cultivars containing larger granules. Total amylose content lies in the range 15.4–19.6% and cultivars having higher percentage of amylose showed higher level of in vitro pancreatic digestion (Pallepola [swp4] and swp7). The starch digestibility of sweet potato flour was in the range of 36–55% and the highest digestion was observed in swp7. Orange fleshed cultivars (swp4 and swp7) were comparatively rich in nutrients and digestibility than the other three studied cultivars.

Nutritive Evaluation of Lysine- and Methionine-Supplemented Raw Vs Heat-Processed Soybean to Replace Fishmeal as a Dietary Protein Source for Grey Mullet, Mugil cephalus, and Milkfish, Chanos chanos

Two experiments were conducted to study the effect of methionine- and lysine-supplemented raw and hydrothermically processed full-fat soybean as a dietary protein source on growth performance, digestibility, and digestive enzyme activity in grey mullet, Mugil cephalus (mean BW 0.55 g), and milkfish, Chanos chanos (mean BW 3.83 g). Eight isocaloric (gross energy about 18.27 kj g−1) and isonitrogenous (crude protein about 40%) diets (1–4 = raw soybean based; 5–8 = processed full-fat soybean based) were formulated. A fishmeal-based diet was used as the reference/control diet. Growth performance, nutrient retention, feed conversion ratio (FCR), and protein digestibility in fishes correlated well with the trypsin inhibitor activity levels of the diets. Carcass phosphorous levels were significantly (P < 0.05) higher in fish fed the fishmeal control diet. Irrespective of the fish species, significantly (P < 0.05) lower levels of total ammonia excretion and reactive phosphate production (mg kg−1 BW d−1) were recorded where the fish were fed processed full-fat soybean diets compared with the fish fed fishmeal or raw soybean diets. Among these diets, the best growth performance and the lowest levels of metabolic waste were obtained in fishes fed the methionine- and lysine-supplemented processed soybean-based diets containing no fishmeal.

Effect of treatment with α‐galactosidase, tannase or a cell‐wall‐degrading enzyme complex on the nutritive utilisation of protein and carbohydrates from pea (Pisum sativum L.) flour

AbstractThe effect of treatment with α‐galactosidase, tannase or a cell‐wall‐degrading enzyme complex under optimal conditions of pH, temperature and length of incubation time on the chemical composition and nutritive utilisation of protein and carbohydrates from pea (Pisum sativum L.) flour was studied. Soaking of pea flours in combination with enzyme treatment led to reductions of 77–90% in the levels of α‐galactosides, and of 60–80% in the levels of trypsin inhibitor activity, increasing the content of total available sugars, which was highest in the pea flour treated with the cell‐wall‐degrading enzyme complex. All the treatments assayed caused a significant improvement in daily food intake, whereas the nutritive utilisation of protein was not increased in any of the pea products tested when compared to the raw pea flour. However, all the soaking and enzymatic treatments led to a significant improvement in daily weight gain associated with a higher dietary intake of food and total available sugars. Copyright © 2007 Society of Chemical Industry

Comparison of white flakes and toasted soybean meal partly replacing fish meal as protein source in extruded feed for rainbow trout ( Oncorhynchus mykiss)

An experiment was carried out to study the nutritional value of solvent extracted, toasted soybean meal (SBM) and solvent extracted, untoasted soy “white flakes” (WF) partly replacing high-quality fish meal (FM) in extruded diets for rainbow trout. Particularly, we wanted to find out if feed extrusion provides sufficient heat to reduce the soybean trypsin inhibitor activity (TIA) to a tolerable level in diets for trout. Three diets were produced: a control diet with 490 g FM kg − 1 (FM diet), a diet with 290 g FM and 250 g SBM kg − 1 (SBM diet), and a diet with 290 g FM and 250 g WF kg − 1 (WF diet). Each diet was fed to three groups of trout for 63 days. The TIA levels in the SBM and WF diets after extrusion were 0.6 and 2.1 mg (g dry matter) − 1 , respectively. Feed intake was lower ( P < 0.05) in trout fed the SBM and WF diets than in those fed the FM diet, resulting in reduced growth and poorer feed conversion. The diets did not significantly affect whole-body content of dry matter, protein and fat, or carcass yield, total gut weight, or weight of pyloric, mid and distal intestine. Trout fed the WF diet had higher stomach weight than trout fed the FM diet. Liver weight, plasma cholesterol and triacylglycerol were lower in trout fed the SBM and WF diets than in those fed the FM diet. Apparent digestibility of nitrogen was lower for the WF diet than for the FM diet and intermediate for the SBM diet. The SBM and WF diets caused lower digestibility of fat and most amino acids and lower nitrogen retention than the FM diet. Moderate morphological abnormalities were found in the distal intestine of trout fed the SBM and WF diets. Bile acid concentration in chyme was lower in fish fed the SBM and WF diets than in fish fed the FM diet, except for the proximal pyloric region and the posterior distal intestine. Trypsin activity in chyme of the distal intestine was higher and leucine amino peptidase activity in intestinal wall tissue was lower in trout fed the SBM and WF diets than in trout fed the FM diet. In conclusion, both SBM and WF had a negative influence on growth and feed conversion compared with the FM diet. Extrusion did not influence soy-related challenges such as reduced fat digestibility, and morphological and enzymatic changes. However, extrusion was sufficient to lower TIA in the diets to an acceptable level for rainbow trout.

Radiation induced variability of seed storage proteins in soybean [ Glycine max (L.) Merrill

Soybean variety VLSoy-2 was irradiated with 250 Gy gamma rays to induce variability. A large number of mutants affecting morphological characters were identified and characterized. True breeding mutants obtained were used for studying the variation in seed storage proteins. The mutants M-231, M-17 and M-291 lacked the A 3 subunit of glycinin (11S) protein. Among the three, two mutants M-231 and M-17 were also characterized by the lack of α and α′-subunits of β-conglycinin (7S). In addition, the mutant M-291 also showed low levels of trypsin inhibitor activity (TIA) and low levels of α and α′-subunits of 7S protein.

Identification and stability of trypsin inhibitor isoforms in pea ( Pisum sativum L.) cultivars grown in New Zealand

Trypsin inhibitor activity (TIA) of 17 spring-sown field pea cultivars grown in New Zealand ranged from 0.33 to 0.75 TIU/mg DM. These values were much lower than those reported for most European pea cultivars. After soaking and cooking, values fell by 42–91%, with an average reduction of 78% (0.07–0.19 TIU/mg DM). After heat treatment, the residual percentage of TIA was negatively correlated to the amount of TIA in the raw seed. Six to ten trypsin isoinhibitors were observed in each cultivar of the raw extracts, with isoelectric points ranging from 4.6 to 7.6. Only three of the isoinhibitors, with isoelectric points of 5.1, 5.9 and 7.6, remained after heat treatment. Pea cultivars with high TIA levels in the raw seed may be more suitable as processing peas because cooking substantially reduces TIA levels, suggesting that adverse effects of consuming TIA would be limited. Conversely, raw peas with low TIA levels would be more suitable for use as animal feed. Cultivars that contain more unstable isoforms may require less heat treatment, therefore retaining their nutritional value be more suitable for human consumption and use as animal feed, and have reduced processing costs.

Effects of variability in trypsin inhibitor content of soya bean meals on true and apparent ileal digestibility of amino acids and pancreas size in broiler chicks

Variability in the nutritional value of processed soya bean meal (SBM) and full fat soya bean (FFSB) currently restrict its use in diets for non-ruminant livestock. Two metabolism trials determined the amino acid digestibility and effect on pancreas size in young broilers of eight commercially obtained products. Trypsin inhibitor (TI) values varied from 1.1 to 3.6 mg/g but were all within the tolerated range of trypsin inhibitor activity (TIA). The results of the trials reported demonstrated that the coefficients of digestibility for individual amino acids varied widely between samples (e.g. coefficient of ileal apparent digestibility (CIAD), for lysine was from 0.755 to 0.884 for SBM and 0.778 to 0.848 for FFSB) but did not correlate with TIA levels, indicating other factors also affect amino acid digestibility of FFSB and SBM. Pancreas to body weight ratio (PBWR) increased with rate of soya inclusion in both the SBM (from 2.25 to 2.44 g pancreas/kg body weight) and the FFSB (from 2.19 to 2.40 g pancreas/kg body weight). The linear increase in pancreas size with increasing TIA intake suggested a dose dependent response that should be considered in feed formulation.

Influence of processing of full fat soya beans included in diets for piglets: II. Digestibility and intestinal morphology

The objective of the current experiment was to investigate the effect of inclusion of differently micronized (Trial 1) and extruded (Trial 2) full fat soya beans (FFSB) on ileal and total tract apparent digestibility of FFSB in piglets. Histological examinations of the small intestine mucosa were also conducted. Data for coefficient of total tract apparent digestibility (CTTAD) revealed no differences for the effect of steam ( S) or heat ( H) in Trial 1 ( P > 0.05). However S × H was significant for CCTAD for crude protein (CP) ( P = 0.002). Full steam high cook (FSHC), full steam low cook (FSLC) and low steam high cook (LSHC) diets maintained similar villus height (VH) and no effect of S or H or S × H was observed at both jejunum and ileum, while only the S × T interaction was significant ( P = 0.008) for crypt depth (CD). Trypsin inhibitor activity (TIA) content of the FFSB and the TIA daily intake influenced the VH/CD ratio ( P < 0.05); values were reduced progressively from 3.52 for the FSHC diet to 2.86 for the LSLC. In Trial 2 CTTAD for dry matter (DM), gross energy (GE) and CP were not related to the different extrusion temperatures investigated ( P > 0.05). Coefficients of ileal apparent digestibility (CIAD) for the 150 °C extruded FFSB (E-FFSB) diets were consistently lower for ileal DM, GE and EE, and they were significantly related to the different extrusion temperatures investigated ( P = 0.042, P = 0.050 and P = 0.028, respectively) compared to 90 °C E-FFSB diets. VH was consistently higher for the low TIA diet (150 °C E-FFSB) and CD was correlated to the FFSB TIA levels and TIA daily intake at the same site ( P < 0.05). When digestibility coefficients were regressed against the levels of TIA in FFSB no relationships were observed ( P > 0.05) for both trials. Thermal processing of the FFSB did not therefore affect digestibility while small intestinal structure, as expressed by VH and CD values, was not affected to any significant extent. Villus atrophy was not related to feed intake. However villi dimensions were associated with the dietary daily TIA intake. Combined results from both trials suggest that adequate inactivation of the anti-nutritional factors (ANFs) resulted in an increased VH and a lower TIA intake was associated with a higher mean VH. It is thus intake and not dietary concentration of TIA which is the major factor influencing responses.

Fermentation of Vigna sinensis var. carilla Flours by Natural Microflora and Lactobacillus Species

Natural fermentation and an inoculum containing 10% (vol/vol) Lactobacillus fermentum or Lactobacillus plantarum were used to obtain fermented flours from Vigna sinensis L. var. carilla seeds that had been washed with distilled water and dried at 55°C for 24 h. To optimize the fermentation parameters (lactic acid bacterium level, bean flour concentration, and fermentation time), several small-scale fermentation processes were carried out. On the basis of the results obtained, fermentor-scale bean fermentation by microorganisms present on the seeds (natural fermentation [NF]) or by inoculation with L. plantarum (PF) was carried out at 37°C for 48 h with a concentration of 300 g of bean flour per liter. The fermented flours (NF and PF) were also autoclaved. The levels of α-galactosides, inositol phosphates, trypsin inhibitor activity (TIA), soluble carbohydrates, starch (total and available), total available carbohydrates, thiamin, and riboflavin were determined for the processed cowpea flours, and microbiological studies were also carried out. The beans' levels of α-galactosides, TIA, and inositol hexaphosphate decreased by 95, 50, and 85%, respectively, for the NF flour and by 87, 27, and 85%, respectively, for the PF flour, while inositol pentaphosphate and inositol tetraphosphate were present in both fermented flours. The sucrose content decreased, and glucose, fructose, and galactose appeared as a result of fermentation. The levels of total available sugars and thiamin decreased by 2 and 12% and by 69 and 43%, respectively, while the riboflavin content increased by 106 and 94% for NF and PF flours, respectively. When NF and PF cowpea flours were heated in an autoclave for 20 min, TIA decreased further (by 80 and 56%, respectively). According to the chemical and microbiological results obtained in this study, fermentation with L. plantarum and autoclaving is an excellent process by which to produce a new functional food from the seed of a cheap legume (Vigna sinensis L. var. carilla).

Relationship between physicochemical and cooking properties, and effects of cooking on antinutrients, of yellow field peas (Pisum sativum)

AbstractThe relationship between the physicochemical and cooking properties of yellow peas was examined in this study. A positive correlation was found between seed weight and water hydration capacity. The Peleg model, which was modified, could be used to describe the water absorption characteristics of peas and could be used to predict the rate of water absorption in the initial water absorption period. Cooking time could be measured objectively using the Mattson cooker. Cooking time was found to decrease with an increase in water hydration capacity. Hardness of cooked peas, measured using a texture analyser, was negatively correlated with both seed weight and water hydration capacity. Seed coats had a significant effect on water hydration and cooking quality of peas. Peas with relatively thin seed coats exhibited higher water hydration capacity, shorter cooking times and softer texture after cooking. The effects of soaking and cooking on trypsin inhibitor activity (TIA) and oligosaccharide levels in peas were also studied. Cooking was more effective than soaking in reducing TIA levels and oligosaccharides (raffinose, stachyose and verbascose) in peas. Copyright © 2003 Society of Chemical Industry

The effect of drying on unsaturated fatty acids and trypsin inhibitor activity in soybean

A study was conducted to assess and compare the effect of forced convection drying (FC) and microwave assisted drying (MW) on some unsaturated fatty acids and trypsin inhibitor activity (TIA) in soybeans. Samples were collected at regular intervals during drying at 60 °C (for food purposes), 40 °C (for seed purposes) and 100 °C (to simulate harsh conditions). All samples were dried to a final moisture content (MC) of 10 or 13% before being analyzed. Treated samples contained significantly lower quantities of unsaturated fatty acids ( P<0.05) per unit dry matter than untreated samples and MW was less destructive to fatty acids and TIA than FC. Although fatty acid destruction was more rapid at higher temperatures, the extent of degradation was dependent on both the drying temperature and drying time. Soybeans dried using FC contained acceptable low levels of TIA, making them adequately processed for food purposes, but suffered greater degrees of fatty acid degradation. Soybeans dried using MW retained higher levels of (TIA). Recoveries were >84%.

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

AbstractThe 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

Biochemical changes during storage of sweet potato roots differing in dry matter content

Abstract Changes during storage were investigated in carbohydrate level, digestibility, α-amylase, trypsin inhibitor activity and pasting properties of roots of six genotypes of sweet potato ( Ipomoea batatas (L.) Lam) differing in dry matter content. Most genotypes showed a slight decrease in starch content during 0–180 days of storage, but in the genotype Hi-dry, it decreased substantially. Alpha-amylase activity increased during the first 2 months of storage, followed by a decrease with continued storage to a level similar to that at harvest. The decline in starch content was correlated with α-amylase activity in the first 60 days storage ( r =0.80, P =0.06). Trypsin inhibitor activity (TIA) in the fresh roots varied among genotypes from 3.90 to 21.83 U/mg. Storage had little influence on TIA level. There was considerable genotypic variation in digestibility, with up to 27% reduction in digestibility after 120 days in storage. Glucose and sucrose concentration increased early in storage and then remained fairly constant. Storage reduced flour pasting viscosities, with up to nearly a 30% decline in peak viscosity.

Effect of temperature and time during steam treatment on the protein quality of full‐fat soybeans from different origins

Soybeans (Glycine max) of Argentinian and Chinese origin were steam-processed at 102°C, 118°C and 136°C for various durations with the use of a laboratory-scale steam toaster. Samples of raw and processed soybeans were analysed for dry matter (DM), crude protein (CP), trypsin inhibitor activity (TIA), protein dispersibility index (PDI) and reactive lysine content. Chinese raw soybeans showed higher levels of CP, TIA and PDI, and a lower level of reactive lysine than Argentinian raw soybeans (366 vs 357 g kg−1, 20.6 vs 15.2 mg g−1, 87.6 vs 85.6% and 17.4 vs 19.4 g kg−1, respectively). Both the TIA and PDI of the two soybean samples were decreased following a logarithmic pattern with the lengthening of the heating time when beans were steam heated at various temperatures. The reduction rates for TIA and PDI, however, were different between the two origins of soybeans. Chinese soybeans required a longer time or a higher temperature to reduce their TIA to a safe level in comparison with Argentinian soybeans. In the case that the beans were heated at 136°C, the difference in PDI between Chinese and Argentinian soybeans was smaller. It is concluded that the two soybeans origins need different processing conditions to improve their protein properties. © 1998 SCI.

Effect of temperature and time during steam treatment on the protein quality of full-fat soybeans from different origins

Soybeans (Glycine max) of Argentinian and Chinese origin were steam-processed at 102°C, 118°C and 136°C for various durations with the use of a laboratory-scale steam toaster. Samples of raw and processed soybeans were analysed for dry matter (DM), crude protein (CP), trypsin inhibitor activity (TIA), protein dispersibility index (PDI) and reactive lysine content. Chinese raw soybeans showed higher levels of CP, TIA and PDI, and a lower level of reactive lysine than Argentinian raw soybeans (366 vs 357 g kg−1, 20.6 vs 15.2 mg g−1, 87.6 vs 85.6% and 17.4 vs 19.4 g kg−1, respectively). Both the TIA and PDI of the two soybean samples were decreased following a logarithmic pattern with the lengthening of the heating time when beans were steam heated at various temperatures. The reduction rates for TIA and PDI, however, were different between the two origins of soybeans. Chinese soybeans required a longer time or a higher temperature to reduce their TIA to a safe level in comparison with Argentinian soybeans. In the case that the beans were heated at 136°C, the difference in PDI between Chinese and Argentinian soybeans was smaller. It is concluded that the two soybeans origins need different processing conditions to improve their protein properties. © 1998 SCI.

Comparative evaluation of non-toxic and toxic varieties of Jatropha curcas for chemical composition, digestibility, protein degradability and toxic factors

Four varieties of Jatropha curcas which originated from Nicaragua (Cape Verde and Nicaragua toxic varieties cultivated in Managua), Nigeria (a wild variety from Ife; toxicity unknown) and Mexico (a wild non-toxic variety collected from Papantla) were studied. The average seed weight was 0.69, 0.86, 0.53 and 0.65 g for Cape Verde, Nicaragua, Ife-Nigeria and non-toxic Mexico varieties, respectively. The kernel to shell ratio in seeds was relatively similar (62.7:37.3 for both Cape Verde and Nicaraguan, 60:40 for Ife-Nigerian and 63.5:36.5 for non-toxic Mexican). The shell of the seeds composed mainly of fiber (>83% neutral detergent fiber) and very little crude protein (CP < 6%). The kernels were rich in CP (22.2–27.7%) and lipid (53.9–58.5%). The meal (defatted kernels) had a CP content of 57.3, 61.9, 56.1 and 64.4% for Cape Verde, Nicaragua, Ife-Nigeria and non-toxic Mexico varieties, respectively, and about 90% of this CP was true protein. The pepsin insoluble nitrogen was from 5.5 to 7%. The amino acid composition of meals from Cape Verde, Nicaragua and non-toxic Mexico varieties was similar. The levels of essential amino acids except lysine were higher than that for the FAO reference protein. The meal from the toxic variety (Cape Verde) did not have any anti-fermentative activity on rumen microbes. The estimated digestible organic matter (DOM) and metabolizable energy (ME) for the shells were low (26.2–27.1% and 2.4–2.8 MJ kg −1), whereas these values for Jatropha meals were 77.3–78.4% and 10.7–10.9MJ kg −1. For commercially available (heat-treated) soyabean meal, DOM and ME were 87.9% and 13.3MJ kg −1, respectively. The in-vitro rumen degradable nitrogen (% of total nitrogen) for meals from Cape Verde, Nicaragua, Ife-Nigeria and non-toxic Mexico varieties was 43.3, 37.7, 38.7 and 28.9, respectively, and for the soyabean meal it was 80.9%. Tannins, cyanogens, glucosinolates and amylase inhibitors were not detected in meals of any of the four varieties. A small amount of tannins were present in shells (2.0–2.9% as tannic acid equivalent). High levels of trypsin inhibitor activity (18.4–26.5 mg trypsin inhibited g −1), lectin (51–102; inverse of the minimum amount in mg ml −1 of the assay which produced haemagglutination in presence of 10 mM Mn 2+) and phytate (7.2–10.1%) were observed in the meals. The concentrations of phorbol esters in kernels of Cape Verde, Nicaragua and Ife-Nigeria varieties were 2.70, 2.17 and 2.30mg g −1, whereas kernels of non-toxic Mexican had a very low level (O.11 mg g −1) of phorbol esters.