Hard-to-Cook Defect in Cowpeas: Storage-Induced and Treatment-Induced Development

Cowpea seeds with a range of hard-to-cook (HTC) levels induced by storage at various temperatures/relative humidities/times were subjected to heat incubation in water and/or soaking in CaCl_2. For control seeds, the hardening effect of Ca soaking was greatly increased by incubation at 60-85°C before soaking, but not after. For aged seeds, Ca soaking alone evoked a great increase in hardness whereas incubation slightly enhanced hardening. Trivalent cations induced HTC less effectively than divalent cations; univalent ions suppressed HTC. EDTA soaking completely reversed while EGTA partially reversed HTC state of aged seeds. HTC state in cowpeas apparently develops via two stages: an increase in cation-uptake capacity within cotyledons induced by moderate heat or adverse storage, followed by divalent cation binding.     

草鱼饲喂蚕豆过程中肌肉质构特性和化学成分变化及其关联性研究

研究草鱼饲喂蚕豆过程中草鱼质构特性和化学成分的变化及关联性,确定草鱼脆化开始和达到商品脆性的时间。随饲喂时间的延长,草鱼肌肉的硬度、咀嚼性显著增大,硬度在饲喂80天后,基本与普通鲩鱼相同,鱼肉开始脆化,继续饲喂20天,硬度达到商品鱼的脆化标准。咀嚼性和弹性在饲喂80天时基本稳定,且熟制的背肌肌肉弹性随饲喂时间的延长显著增加,回复性在饲喂40天达到最大值。草鱼背肌粗蛋白、基质蛋白、胶原蛋白、碱溶性蛋白含量随饲喂时间的延长显著增加,均在饲喂100天时达到峰值。水分含量基本呈下降趋势,在饲喂20天时最大。粗脂肪、可溶性固形物、水溶性蛋白和盐溶性蛋白在饲喂40~60天时达到最大值。草鱼腹肌化学成分的含量变化与背肌基本一致。经相关性分析,草鱼肌肉质构特性的变化与粗蛋白、碱溶性蛋白、胶原蛋白和基质蛋白含量的变化显著相关。     

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.     

Effect of the Hard-to-Cook Phenomenon on Some Physicochemical Properties of Bean Starch

Two bean varieties of outstanding agronomic performance were seeded, harvested and a portion stored for 135 days under high temperature and humidity. These varieties were Negro Qro and Canario with black and light yellow seeds, respectively. Hard-to-cook (HTC) defect developed in aged seeds as assessed by the Mattson cooker and Instron texturemeter. Fresh and HTC beans were used in order to determine physicochemical changes in starch and to evaluate its contribution in textural defects. The damaged starch content, water absorption and swelling were higher for isolated starches from HTC seeds than for the controls. Starch damage was generated by enzymatic attack and/or by mechanical action during milling. Pasting properties examined with the Brabender viscograph showed that peak viscosity increased and stability and retrogradation capacities declined after storage. These results might be ascribed to the starch damage and also to changes undergone by the residual impurities of isolated starches. In agreement with the previous observations, scanning electron microscopy of starch isolated from HTC samples revealed the presence of some swollen granules and many others with fissures, while those from controls had smooth surfaces and with no evidence of damage. Differential scanning calorimetry (DSC) evaluations showed that gelatinization temperatures and transition enthalpies were not significantly influenced by storage; results in agreement with birefringence studies. It is suggested that the changes in the starch from defective seeds were not sufficient to modify the gelatinization performance.     

Changes in Selected Chemical and Antinutritional Components during Tempeh Preparation Using Fresh and Hardened Common Beans

A tempeh-type fermented product was prepared from fresh and hard-to-cook (HTC) common beans. Fermentation decreased fat and fiber content and increased soluble solids, total and soluble proteins, soluble carbohydrates and pH of both bean samples. About 12% of solids were reduced during 72 hr fermentations. Results suggested that Rhyzopus oligosporus was capable of hydrolyzing the trypsin inhibitor and phytic acid of the substrate. Lectin and tannin contents decreased as a result of treatments applied during substrate preparation. Fresh and HTC beans may be converted by this fermentation technique into products of higher quality.     

Relationship of Loss of Membrane Functionality and Hard-to-Cook Defect in Aged Beans

Microsomal membranes were prepared from fresh beans (Phaseolus vulgaris) and from samples kept 9 mo at various temperatures and humitidies. Increasing storage severity produced progressively hard-to-cook (HTC) beans as well as higher solids loss and lower water-holding capacity during soaking. Membrane phase transition temperature (PTT), calcuated from spin label electron paramagnetic resonance data, also increased and showed a highly significant (r = 0.997) correlation with cooked hardness. Fatty acid analysis of membrane lipids demonstrated higher PTT values were due to a significant increase in proportion of saturated fatty acids. These data reflect membrane deterioration during aging that could explain solids loss and water-holding capacity changes. Changes in the membrane may be the primary event in initiation of the HTC defect.     

小利马豆淀粉理化性质的研究

以马铃薯和玉米淀粉为对照,采用湿磨法制备小利马豆淀粉,通过理化检测方法测定其淀粉特性,研究小利马豆淀粉的基本理化性质。结果表明:小利马豆淀粉颗粒多为椭圆形,表面光滑,大小不一,粒径为5.46～37.58μm,平均为18.36μm;小利马豆淀粉糊的透明度为30.89%,凝沉作用强于马铃薯淀粉糊和玉米淀粉糊,其淀粉的膨胀度和溶解度随着温度升高而增加;小利马豆淀粉凝胶的硬度、弹性、胶着性和咀嚼性高于马铃薯和玉米淀粉;与马铃薯和玉米淀粉相比,小利马豆淀粉的糊化温度低,为63.60℃,容易糊化,峰值黏度高,但破损值大,热糊稳定性差,回生值大,冷糊稳定性差,易老化。     

Changes in Chemical Composition of Winged Bean (Psophocarpus tetragonolobus L.) during Seed Development

Three cultivars of winged bean were analyzed for total dry matter, crude fat, nitrogenous constituents, phosphorus, calcium, magnesium, zinc, iron, copper and cooking behavior at different stages of seed maturity. Accumulation of dry matter, crude fat and nitrogen occurred during seed development whereas nonprotein nitrogen and tryptophan contents decreased significantly. Reduction in poly-phenol content was observed at all the stages of seed development. There was a significant decrease in total phosphorus content with concomitant increase in the proportion of phytate phosphorus throughout the seed development. In matured seeds, phytate phosphorus accounted for 66—73% of total phosphorus. A reduction in zinc content was noticed in all the cultivars studied. In contrast, calcium, magnesium, iron and copper contents of seeds of different stages of maturity did not exhibit marked differences.     

Chemical and Enzymic Changes During the Fermentation of Bacteria-Free Soya Bean Tempe

Amounts of dry matter, ash, protein, free ammonia, crude lipid, glyceride–glycerol, free fatty acids, free glycerol, glucosamine, protease activity and lipase activity were monitored during the fermentation of bacteria-free tempe made with acidified soya bean cotyledons and Rhizopus oligosporus NRRL 2710 at 30°C. During the phase of mycelial growth (0–32 h) the total dry matter decreased by approximately 10% (w/w), accounted for by losses of crude lipid (3% of initial dry matter), protein/amino acids (0·5%), and unidentified compounds (6·5%). During the phase of mycelial senescence (60–180 h), decrease in dry matter (12% of initial dry matter) was due almost entirely to loss of crude lipid. Lipase activity and the production of free fatty acids occurred from the earliest stages of the fermentation. The production of only small amounts of free glycerol indicates that triglycerides were primarily hydrolysed to partial glycerides and free fatty acids. Protease activity and production of free ammonia were also detected at the earliest stages of the fermentation. During the phase of mycelial senescence, amounts of crude lipid and glycerol decreased in the absence of fungal growth, possibly due to the activity of enzymes released from senescent mycelium.     

豆渣不同菌种发酵后成分变化的研究

用根霉、毛霉、米曲霉菌分别对一定量的豆渣进行发酵,对发酵前后6个时期豆渣的营养成分、酶活力进行分析,结果表明,发酵后豆渣的品质明显提高。豆渣中氨基酸态氮的含量均升高;豆渣中的可溶性总糖含量也明显提高,脂肪含量有所降低。豆渣中蛋白酶活力及淀粉酶活力在发酵前期为最大值,随着时间的延长逐步降低,且毛霉产蛋白酶能力较强,最大值达到96.4 U/g,而根霉产淀粉酶能力较强,最大值达到13.2 U/g。     

Hard-to-Cook Phenomenon in Beans: Structural Changes During Storage and lmbibition

Dry black beans stored at high temperatures (41°C) and humidities (75%, 100%) for short time periods showed alterations in attachments between plasmalemma and cell wall as well as disintegration of organelles and inclusions of the cytoplasm. Although those structural changes did not affect the mode of water penetration into aged beans, as determined by autoradiography, electron micrographs clearly revealed structural differences between fresh and aged beans during imbibition.     

Hard-to-Cook Phenomenon in Beans: Changes in Protein Electrophoretic Patterns During Storage

Effect of storage at elevated temperature and relative humidity on black bean cotyledon proteins was examined by polyacrylamide gel electrophoresis (PAGE) at pH 3.1. Electrophoregrams of acetic acid extracts of dehulled ground cotyledons of beans with storage-induced hardness showed concomitant changes with storage time. The changes were accelerated by higher temperature and humidity.     

回用纤维表面的物理和化学变化

研究了硫酸盐浆、酸性亚硫酸盐浆、氢氧化钠浆、碱性亚硫酸盐浆1次回用后纤维的形态、纤维表面的物理及化学变化。结果表明,纸张经1次回用后,回用浆中细小纤维的含量明显增加,纤维平均长度变化不大,纤维的柔软性降低,卷曲指数和扭结指数下降;电镜分析显示,回用纤维的表面和原纤维的表面特征相似,密实光滑,但与原纤维表面相比,回用纤维暴露出较多的S2层,即纤维表面部分复合胞间层在回用过程中脱落;实验的4种浆料经回用后,纤维表面的O/C原子比均下降,氢氧化钠浆的O/C原子比下降得最多达22%,而酸性亚硫酸盐浆O/C原子比只下降3.4%。     

Reversibility of the Hard-to-Cook Defect in Dry Beans (Phaseolus vulgaris) and Cowpeas (Vigna unguiculata)

The hard-to-cook defect, assumed to be a permanent condition in legume seeds, can be reversed. Dry beans (Phaseolus vulgaris) and cowpeas (Vigna unguiculata) which had developed the hard-to-cook defect when stored at 29°C, 65% RH had progressively shorter cooking times after additional storage at 6.5°C, 71% RH. This would suggest that the mechanism(s) leading to development of the defect should be easily reversed. The ability to reverse the hard-to-cook defect in legume seeds would provide several economic and nutritional benefits.     

生姜酵素理化成分、风味物质及抗氧化性分析

对生姜酵素理化成分、风味成分及抗氧化性进行检测分析.结果 表明,生姜酵素的pH值为3.80,总酸为2.91 g/100 g,乙醇含量为0.82 g/100 g,可溶性固形物含量为24.4％,乳酸含量为2.6× 103 mg/l00 g,总酚含量达到5.77 μg/μL.利用气相色谱-质谱(GC-MS)联用技术分析鉴定出...     

醇化过程中烤烟片烟化学成分的变化

研究了福建和云南烤烟片烟在醇化过程中还原糖、淀粉、总氮、烟碱、挥发碱、挥发酸含量及pH值的变化。结果表明 ,片烟的还原糖、烟碱、挥发碱含量及pH值均随着醇化的进行呈持续降低趋势 ;挥发酸含量则逐渐增加 ;总氮含量无明显变化 ;淀粉含量在醇化过程中的变化与供试片烟的产地、等级(配方 )有关。     

叶丝滚筒干燥过程中化学成分的动态变化特征研究

利用批处理式滚筒干燥试验装置,以两种烤烟、一种白肋烟为原料,研究了叶丝滚筒干燥过程中含水率、总植物碱、还原糖、总糖、石油醚提取物等含量随干燥处理时间的动态变化特征,同时对比分析了滚筒壁温对上述指标变化特征的影响。结果表明:①叶丝干燥过程含水率的变化规律符合菲克第二定律,实验所用烤烟的传质有效扩散系数(De)均小于白肋烟。滚筒壁温升高,3种叶丝De值均增大,但上部叶De值的变化较中部叶小;②随干燥时间延长,总植物碱和还原糖含量均呈近似线性下降,随滚筒壁温升高,其下降速率增大;③总糖含量除在160℃干燥结束阶段急剧下降外,整体变化规律不明显;④石油醚提取物含量在不同条件下均有相似的变化规律,其含量随干燥过程的进行呈先升高后降低的趋势,峰值区间均在含水率为8%~2.5%时。     

Matching Changes in Sensory Evaluation with Physical and Chemical Parameters

Changes in pistachio nuts induced by roasting and salting processes, evaluated by both sensory and instrumental analyses are reported, looking for a match in both methods. Dried (DP), roasted (RP), and salted–roasted pistachios (SRP) were studied, including four groups of sensory attributes, six basic chemical parameters, complemented by volatile organic compounds (VOCs) and breaking force. Multivariate statistics helped with data interpretation, enabling correlations between two groups of variables. Key results show that the perception of roasting is associated with increased amounts of α-pinene and 3-carene in RP and SRP, while DP are associated with higher amounts of limonene, moisture, and bitterness. Sensory and puncture test measurements (texturometer) showed opposite results, which could be explained considering the loss of plasticity in RP and SRP. Current results present a novel approach for the evaluation of changes in the perception of pistachio quality by consumers, supported by both sensory and instrumental analyses using multivariate statistics for data evaluation.