Saponin content of food plants and some prepared foods

Quantitative thin layer chromatography was used to estimate the saponin content of 20 common food plants and also of foods prepared from some of them. The food plants found to be richest in saponins were chickpeas (Cicer arietinum), soya beans (Glycine max), lucerne (alfalfa) sprouts (Medicago sativa) and varieties of Phaseolus vulgaris (navy beans, haricot beans, kidney beans). Saponins were not destroyed by processing or cooking. They were present in falafels (prepared from chickpeas), canned baked beans, canned broad beans and protein isolate from faba beans. However, the saponin content of a fermented soya bean product (tempe) was only half that of whole soya beans. Guar meal (Cyamopsis tetragonolobus) contains saponins but only a trace could be detected in samples of guar gum.     

Fate of oligosaccharides during production of soya bean tempe

The concentrations of the flatulence and possibly prebiotic oligosaccharides, stachyose and raffinose, as well as sucrose, glucose and fructose, were monitored during the preparation of bacteria‐free tempe made with Rhizopus oligosporus NRRL 2710. The initial soya beans contained (g [kg dry matter]⁻¹): stachyose, 30; raffinose, 11; sucrose, 57, glucose, <0.1, and fructose, <0.1. Losses of oligosaccharides during preparation of tempe were due to leaching during the hydration (100°C for 30 min), washing (60°C) and cooking stages (121°C for 10 min). The losses were (g [kg dry initial soya bean]⁻¹): hydration 45; dehulling and washing, 14, and cooking, 24. Concentrations remaining in the cooked cotyledons were (g [kg dry weight]⁻¹): stachyose, 7.0; raffinose, 2.1; sucrose, 7.2; glucose, 1.8, and fructose, 0.9, representing 17% (w/w) of the stachyose, 15% of the raffinose and 13% of the sucrose+glucose+fructose in the initial soya beans. Within the errors of measurement, concentrations of stachyose, raffinose and sucrose did not change during the fermentation but concentrations of glucose and fructose were reduced to 0.2 and 0.3 g (kg dry weight)⁻¹, respectively. The results are discussed in relation to controlling the concentrations of oligosaccharides in tempe. © 1999 Society of Chemical Industry     

混菌发酵豆豉中异黄酮含量及对小鼠肺癌细胞的抑制作用

选用高产蛋白酶菌株枯草芽孢杆菌D2和β-葡萄糖苷酶产生菌枯草芽孢杆菌U35进行单菌种、混合菌种发酵生产豆豉,测定大豆异黄酮含量及其抗肿瘤能力,分析异黄酮含量和抗肿瘤能力的关系。用HPLC法测定豆豉提取物异黄酮含量,采用MTT比色法检测异黄酮含量对细胞增殖的影响,并在荧光显微镜下观察小鼠肺癌(LLC)细胞形态变化。结果表明,D2U35混菌豆豉苷元型异黄酮含量分别比D2、U35单菌豆豉高101.95μg/mL(2.38倍)和35.48μg/mL(1.25倍),D2U35混菌豆豉对肿瘤细胞的抑制率分别比D2、U35单菌豆豉高15.79%和7.02%,说明混菌发酵不仅提高了苷元型异黄酮含量,还提高了豆豉提取物的抗肿瘤能力。对肿瘤抑制作用,苷元苷型异黄酮>总异黄酮>糖苷型异黄酮。     

响应面法优化贝莱斯芽孢杆菌发酵水豆豉的工艺条件

发酵产品的质量与微生物的产酶能力和发酵条件息息相关。为提高水豆豉的发酵品质,采用单因素法结合响应面法对一株高产豆豉纤溶酶的贝莱斯芽孢杆菌发酵水豆豉的条件进行优化,以获取最佳的发酵条件。首先利用单因素法缩小发酵时间、温度和接种量的范围,然后通过响应面法以水豆豉中的氨基酸态氮含量和豆豉纤溶酶活性为指标,确定最优发酵条件为:时间5d,温度35℃,接种量0.01%。最终发酵的水豆豉氨基酸态氮含量为8.95g/kg,豆豉纤溶酶活性为420.05IU/g,与市售相比,豆豉纤溶酶活性升高约400倍。该研究为贝莱斯芽孢杆菌发酵水豆豉提供了理论依据。     

鲜毛豆保鲜与加工研究进展

近年来,鲜毛豆因其较高的营养价值、富含膳食纤维以及独特的口感逐渐成为热门消费产品。但鲜毛豆水分含量较高,在贮藏和市场流通过程中容易发生褐变及腐烂,因此,应用贮藏保鲜技术延长鲜毛豆货架期,或者将鲜毛豆及时加工成产品,以提高其利用率是解决鲜毛豆市场供应问题的两大方式。本文对鲜毛豆在贮藏保鲜、加工技术、产品种类方面的研究现状进行了总结概括,着重介绍了鲜毛豆的气调贮藏保鲜、速冻贮藏保鲜、保鲜剂处理等保鲜加工技术,并针对鲜毛豆的油炸、干燥等多种加工工艺与各类毛豆产品进行列举,最后对鲜毛豆的发展前景进行了展望,并进一步拓展了贮藏保鲜新技术与新型毛豆产品的发展趋势,为鲜毛豆的贮藏技术及其产品的研究与开发提供一定的参考。     

Effect of environmental conditions during soya-bean fermentation on the growth of Staphylococcus aureus and production and thermal stability of enterotoxins A and B

During tempe manufacture, Staphylococcus aureus was able to survive in newly started soya-bean soaks (final pH 4.7), whereas it died during soaks with accelerated souring (final pH 4.0). No S. aureus were detected after subsequent heat treatment of soaked beans. S. aureus strain S6 could produce enterotoxins A and B if inoculated on cooked soya-beans. Its growth and enterotoxin production were not influenced by inoculation rate nor by the presence of actively growing Rhizopus oligosporus, the fungus responsible for tempe formation. Enterotoxin levels were highest after 48 h fermentation. Presence of lactobacilli (L. brevis or L. plantarum) during the tempe fermentation did not influence staphylococcal growth, but enterotoxin levels were reduced. Reduced oxygen pressure did not affect staphylococcal growth, but resulted in lower enterotoxin levels after 48 h incubation. The thermal stability of enterotoxin A in tempe was significantly lower than in Brain Heart Infusion broth of comparable pH. Heating of enterotoxin-containing tempe mash reduced enterotoxin A by 99.7% as measured with ELISA and animal feeding methods.     

Changes in the concentration of organic acids during the soaking of soybeans for tempe production

Soybeans were soaked for 24h in tap water at 30°C in preparation for tempe fermentation. Soaking was conducted under conditions that give a microbial fermentation, and in the presence of antibiotics where microbial growth was inhibited. Valeric, propionic, formic and acetic were the main acids in the beans. Their concentrations decreased progressively during soaking as they were leached from the bean into the soak-water. At the end of soaking, lactic and malic were the main acids in the beans. They were produced by microbial fermentation in the soak-water and diffused into the beans. The concentration of acids produced in the soak-water was determined by the microbial species responsible for the fermentation.     

Effects of incubation and polyphenol oxidase enrichment on colour, fermentation index, procyanidins and astringency of unfermented and partly fermented cocoa beans

Incubation of unfermented and partly fermented cocoa beans in acetate buffer, pH 5.5, at 45 °C increased yellowness, total colour differences and fermentation index value of the cocoa bean powders and decreased cocoa procyanidins (monomers to pentamers), and their astringency. Fermentation index and (–)‐epicatechin content, equivalent to those of fully fermented beans, were reached by unfermented beans after 4–8‐h incubation, but not by partly fermented beans even after 16 h. During incubation of partly fermented cocoa beans enriched with polyphenol oxidase, yellowness and fermentation index value were increased, whilst (–)‐epicatechin was decreased. Tyrosinase had a less significant effect in yellow colour formation, but showed a significant reduction of (–)‐epicatechin and increase in fermentation index compared with crude cocoa polyphenol oxidase. However, both enzymes have similar effects on procyanidin degradation and astringent taste reduction. Incubation of cocoa beans for 16 h increased the cut test score of unfermented and partly fermented beans by 50 and 30%, respectively.     

Activation of remaining key enzymes in dried under-fermented cocoa beans and its effect on aroma precursor formation

Incubation-activation of remaining key enzymes in dried under-fermented cocoa beans and its effect on aroma precursor formation has been studied using defatted unfermented and partly fermented cocoa bean powders. Results of the study showed that aspartic endoprotease, carboxypeptidase and invertase were significantly inactivated during fermentation and drying, and the effect of fermentation was significantly lower than that of drying. The enzyme activities remaining in these beans were still sufficient to carry out enzymatic reaction during incubation. Peptide patterns, resulting from incubation of unfermented and partly fermented beans powders, were quite similar to the well-fermented patterns. Meanwhile, free amino acid concentrations of the unfermented beans were significantly increased during the first 4 h of incubation and then remained constant; however, with partly fermented beans, the formation continued and the hydrophobic and total free amino acid concentrations reached the value of well-fermented beans after 24 h of incubation. Reducing sugar concentrations of both unfermented and partly fermented cocoa beans could reach the level of well-fermented beans by incubation.     

Changes in Soya Bean Lipid Profiles during Kinema Production

The influence of processing on soya bean lipids during kinema production was studied. The crude lipid (CL), free fatty acid (FFA) and phytosterol contents of raw beans were 121 g, 6·9 g and 0·8 g kg⁻¹ dry matter, respectively. After soaking and cooking the moisture content of beans increased significantly from 121 to 749 g kg⁻¹, whilst the lipid contents were unchanged. During a 2 day fermentation at 37°C, the lipid contents increased significantly as indicated by capillary column gas chromatography (GC) analysis of petroleum ether extracts of lyophilised samples of unfermented and fermented beans. The fatty acids, palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and arachidic (C20:0) acids were identified. The major fatty acid present in all samples was the essential fatty acid, linoleic acid. All of the aforementioned fatty acids (except arachidic) were liberated during fermentation by microbial lipases, yielding approximately the same proportion of fatty acids found in unfermented beans. The unsaponifiable soya bean lipids identified by GC were campesterol, stigmasterol and β-sitosterol (ratio 1·2:1:3·4). Levels of these increased during fermentation by 50–61%, but remained in approximately the same proportions.     

Effect of Germination on Chemical Composition,Biochemical Constituents and Antinutritional Factors of Soya Bean (Glycine max) Seeds

The published scientific data concerning the effects of germination on chemical composition, biochemical constituents and anti-nutritional factors of soya bean are reviewed. The amino acid profile did not change to a great extent; only a noticeable increase in aspartic acid was observed whereas there was a gradual decrease in the available lysine level and lipid content as germination progressed. Both the total protein content and the nonprotein nitrogen increased after 5 days of germination. Dietary fibres are partially degraded in germinated seeds. Germinated soya bean is an excellent source of ascorbic acid and riboflavin. Niacin contents increased distinctly after germination. Germination induced a reduction in lipase inhibitor activity. The galactosyl oligosaccharides drastically decreased in germinated seeds. After 4 days of germination, the activity of certain lectins decreased to 4% of that of ungerminated soya beans. The phytic acid in the seeds was degraded by the phytase activated during germination, thus increasing the availability of the minerals present in the germinated seeds. Germination can degrade both Kunitz soya bean trypsin inhibitor and the major Bowman–Birk soya bean trypsin inhibitor; the degradation is enhanced, if germination process lasts more than 4 days. © 1997 SCI.     

Saponin content of soya beans and some commercial soya bean products

Quantitative thin layer chromatography has been used to estimate the saponin content of whole soya beans (Glycine max L. Merrill, cv. Williams) and a number of commercial soya bean products such as protein isolates and lecithin. Saponins were present in all these materials at concentrations ranging from 56 g kg-¹ (on a dry weight basis) for whole soya beans to 3 g kg-¹ for the protein isolate ?Promine-D’?. Previous estimates indicate a saponin content of whole soya beans of only about 5 g kg-¹. It is suggested that this is an underestimate resulting from loss of material during the extraction procedures used in earlier methods of analysis.     

Changes in the concentration of carbohydrates during the soaking of soybeans for tempe production

Soybeans were soaked for 24h in tap water at 30°C in preparation for tempe fermentation. Soaking was conducted under conditions that give a microbial fermentation, and in the presence of antibiotics where microbial growth was inhibited. Sucrose, stachyose and raffinose were the main di- and oligosaccharides in the beans, and their concentrations decreased by 84, 65 and 50%, respectively, during soaking. Glucose, fructose and galactose were found in the soak-water along with lesser amounts of sucrose, melibiose, raffinose and stachyose. Glucose was the main substrate for microbial growth in the soak-water. The concentrations of mono-, di-and oligosaccharides in the beans and in the soak-water were determined by the activity of invertases and α-galactosidases endogenous to the beans, diffusion of the sugars into and out of the bean, and the species of micro-organism growing in the soak-water.     

Changes in differently processed soya bean (Glycine max.) and lima bean (Phaseolus lunatus) with particular reference to their chemical composition and their mineral and some inherent anti-nutritional constituents

The effects of 3 processing techniques: cooking, roasting and autoclaving on the proximate chemical composition, the mineral content and some inherent toxic factors of soya and lima beans were investigated. The processing techniques generally reduced the crude fibre levels and enhanced the extractable fat in the soya and lima beans. The coefficients of variability for crude fibre and ether extract due to the processing techniques of soya and lima beans were 20.9%, 16.0% and 22.3%, 38.1%, respectively. In parallel with decreased ash content in the cooked bean samples, there was a decrease in the K, Mg, Na and P levels relative to the raw bean and also relative to the other processing techniques. Mineral contents of the autoclaved bean samples were generally similar to those of the raw (unprocessed) samples. Under the processing conditions, roasting caused the highest reduction in thioglucoside content (59%) in soya bean while cooking caused the highest reduction in lima bean (78%). Trypsin inhibitor activity (TIA) ranged between 0.59 mg/g sample in the cooked soya bean and 11.6 mg/g sample in the raw bean while the corresponding values for lima bean ranged between 0.59 and 6.3 mg/g sample. Cooking and roasting caused over 90% reduction of TIA, while autoclaving caused 64-69% reduction in both bean samples. Under the assay conditions, haemagglutinating activity was not detected in the cooked and autoclaved soya and lima beans. The need to prevent both functional and nutritional damage to food proteins and other nutrients, resulting from excessive heating, was discussed.     

Enzyme activities in cocoa beans during fermentation

The activities of endoprotease, aminopeptidase, carboxypeptidase, invertase (cotyledon and pulp), polyphenol oxidase and glycosidases were studied during heap fermentation of ICS-95 cocoa beans. These enzymes are of key importance in flavour precursor formation and in pigment degradation during cocoa fermentation. Optimal extraction and assay conditions were established to characterise the enzymes reactions and to quantify and compare enzyme activities during cocoa fermentation. The enzymes exhibited large differences in pH optima and stability during fermentation. Aminopeptidase, invertase (cotyledon and pulp) and polyphenol oxidase were strongly inactivated, carboxypeptidase was partly inactivated, whereas endoprotease and glycosidases remained active throughout the fermentation. Since many enzymes are inactivated during fermentation, it is generally recognised that the actual period of enzyme action is short. Although our results confirmed total inactivation for some enzymes, we show that several key enzymes are not completely inactivated during fermentation. Therefore, some enzyme reactions can continue throughout the whole fermentation process. Only polyphenol oxidase was strongly inactivated during sun and artificial drying of the beans. The other enzymes were stable during the drying process. Enzymes like endoprotease and glycosidases are still active in properly fermented and dried beans. © 1998 SCI.     

Biochemical changes in fermenting African locust bean (Parkia biglobosa) during 'iru' fermentation

The enzymic activities and biochemical changes in the principal food constituents of African locust bean were investigated. The reducing sugar level increased from 63 mg/g to 134 mg/g during the first 24 hr but subsequently decreased. Amylase activity was not detected. The lipase activities were detectable with the peak at 48 hr after the start of fermentation. The most significant activity during the fermentation is the rapid and steady increase in the quantity of free amino acids throughout the fermentation. This is due to a consistently active proteinase activity by the fermentative microorganisms. The number and quantities of each amino acids analysed also increased in the fermented beans. Glutamic acid, valine, aspartic acid and alanine were rapidly liberated during the fermentation. The changes observed are compared with the fermentation of other protein rich seeds.     

Investigating the fermentation of cocoa by correlating denaturing gradient gel electrophoresis profiles and near infrared spectra

Raw cocoa has an astringent, unpleasant taste and flavour, and has to be fermented, dried and roasted in order to obtain the characteristic cocoa flavour and taste. During the fermentation microbial activity outside the cocoa beans induces biochemical and physical changes inside the beans. The process is complex involving activity of several different groups of microorganisms which bring about numerous biochemical and physical changes inside the beans. Due to the complexity of these processes no thorough investigations of the interactions between the microbial activities on the outside of the beans and the chemical processes inside the beans have been carried out previously. Recently it has been shown that Denaturing Gradient Gel Electrophoresis (DGGE) offers an efficient tool for monitoring the microbiological changes taking place during the fermentation of cocoa. Near Infrared (NIR) spectroscopy has previously been used to determine various components in cocoa beans, offering a rapid alternative compared to traditional analytical methods for obtaining knowledge about changes in the chemical composition of the cocoa beans during fermentation. During a number of cocoa fermentations bean samples were taken with 24 h intervals to be dried and analysed by NIR. Cocoa pulp samples taken simultaneously during the same fermentations have previously been characterised using DGGE [Nielsen, D.S., Teniola, O.D., Ban-Koffi, L., Owusu, M., Andersson, T., Holzapfel, W.H. (2007). The microbiology of Ghanaian cocoa fermentations analysed using culture dependent and culture-independent methods. International Journal of Food Microbiology 114, 168-186.]. Here we report the first study where microbiological changes during the fermentation determined using DGGE are correlated to changes inside the beans determined by NIR using multivariate data analysis. Following data pre-processing (baseline correction followed by Co-shift correction or Correlation Optimised Warping) the DGGE spectra were analysed using Principal Component Analysis (PCA). A clear grouping according to fermentation time was seen demonstrating the microbial succession taking place during the fermentation. Subsequently the DGGE spectra were correlated to the NIR spectra using Partial Least Squares regression models (PLS2). Correlations of 0.87 (bacterial derived DGGE spectra) and 0.81 (yeast derived DGGE spectra) were obtained indicating the relationship between the microbial activities in the pulp and the (bio)chemical changes inside the beans. By comparing the X-block loadings of the PLS2 models and the DGGE spectra it was possible to directly link several microbial species with changes in the NIR spectra and consequently also with changes inside the beans.     

Oxidation of polyphenols in unfermented and partly fermented cocoa beans by cocoa polyphenol oxidase and tyrosinase

Unfermented and partly fermented dried cocoa beans have an excessively astringent and bitter flavour owing to their high polyphenol content. Studies on the remaining polyphenol oxidase activity and the oxidation of polyphenols in these beans have been conducted in relation to two factors, ie incubation time (0, 1, 2, 4, 8 and 16 h) and pH of incubation (3.5, 4.5, 5.5 and 6.5). Owing to unsuccessful polyphenol oxidation during incubation of partly fermented beans, incubation–enrichment treatments were carried out by combining incubation time (0, 8, 16, 24 and 32 h) and addition of crude cocoa polyphenol oxidase and purified tyrosinase from mushroom at 88 and 8800 units g^?1 and pH 5.5. Results showed that the remaining polyphenol oxidase activities of unfermented and partly fermented dried beans were 1 and 0.08% with specific activities of 9 and 1% respectively. The polyphenols of unfermented beans were effectively oxidised by incubation at 45 °C and pH 3.5–6.5 without enzyme enrichment; while those of partly fermented beans required enzyme enrichment. Both crude cocoa polyphenol oxidase and tyrosinase could be used for enzyme enrichment, but tyrosinase seemed to be more effective. © 2002 Society of Chemical Industry     

Aroma precursors and methylpyrazines in underfermented cocoa beans induced by endogenous carboxypeptidase

Cocoa-specific aroma precursors and methylpyrazines in underfermented cocoa beans obtained from fermentation induced by indigenous carboxypeptidase have been investigated. Fermentation conditions and cocoa bean components were analyzed during 0 to 3 d of fermentation. Underfermented cocoa beans were characterized as having hydrophilic peptides and free hydrophobic amino acids much higher than unfermented ones. These 2 key components of cocoa aroma precursors may be produced from the breakdown of proteins and polypeptides by endogenous carboxypeptidase during the fermentation process. The enzyme was activated during fermentation. Polypeptides of 47, 31, and 19 kDa were observed in the samples throughout the 3-d fermentation period; however, only the first 2 polypeptides were remarkably reduced during fermentation. Since the 1st day of fermentation, underfermented cocoa beans contained methylpyrazines, a dominant group of cocoa-specific aroma. This might be due to microbial activities during fermentation, observed through a decrease of pH value and an increase of temperature of cocoa beans. The concentration of tetramethylpyrazines was significantly increased during the 3 d of fermentation. This may increase the cocoa-specific flavor to the beans.