Evaluation of cooking time and quality of seven diverse cowpea (Vigna unguiculata (L.) Walp.) varieties

Seven cowpea ( Vigna unguiculata (L.) Walp.) varieties, which were part of a larger collection evaluated in agronomic field trials in Botswana, were selected for characterization of cooking time and quality. Newly harvested seed was kept in the open air for 2 weeks, then stored at 4°C and 40% relative humidity for 3 months. Duplicate samples were tested for cooking time with and without 12-h prior soaking. Varieties showed differences ( P < 0.01) in cooking time and response to soaking, although the overall effect of soaking was insignificant. Cooking times ranged from 29 to 64 min without soaking and 36 to 56 min after soaking, with small-seeded varieties having the longer cooking times. The seed coat of some varieties readily became soft, but others remained tough or split before finally softening.     

Identification of sex pheromones from cowpea weevil,Callosobruchus maculatus,and related studies withC. analis (coleoptera: Bruchidae)

Female cowpea weevils,Callosobruchus maculatus, produce a sex pheromone that elicits orientation and sexual behavior in males. Bioassay-directed isolation of the sex pheromone was conducted and compounds in the active fraction were identified and synthesized. Volatiles were collected from individual virgin females by adsorption on filter paper dises and hexane extraction. A bioassay was used in which the locomotory response of single males in glass vials was recorded upon exposure to treatments or controls. Crude extracts were subjected to silica gel column chromatography with solvents of increasing polarity; all activity eluted with methanol. Activity in the highly polar methanol fraction suggested a carboxylic acid or a compound with multiple polar functionality. Acid-base partitioning of the crude extract isolated all activity in the acid fraction, confirming that the pheromone was a carboxylic acid. The acid fraction was further fractionated by preparative GC with a Carbowax column. The most active GC fraction contained the following five 8-carbon acids identified by GC-MS and comparison with synthetic candidates: 3-methyleneheptanoic acid, (Z)-3-methyl-3-heptenoic acid, (E)-3-methyl-3-heptenoic acid, (Z)-3-methyl-2-heptenoic acid, and (E)-3-methyl-2-heptenoic acid. Each of the synthetic acids was active individually for males, and combinations of two or more of the acid pheromones had an additive effect. Upwind flight responses to natural and synthetic pheromones were observed in a flight tunnel. (Z)-3-Methyl-2-heptenoic acid was previously identified as the sex pheromone for the relatedC. analis, but this and the other four acid pheromones fromC. maculatus were inactive for maleC. analis. There was no cross-attraction betweenC. maculatus andC. analis in reciprocal studies using extracted volatiles from females of both species, GC-MS analysis ofC. analis female volatiles failed to detect any of theC. maculatus compounds but did find an unidentified C-8 acid with a GC retention time different from any of theC. maculatus pheromones.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by USDA.     

声频对豇豆生长和结实的影响

植物声频技术是一项生产有机、绿色、无公害农产品的农业高新技术。研究用声频技术对豇豆进行了小样试验,考察了声频技术对豇豆生长株高、开花期以及结豆荚数的影响。结果表明,约在500Hz（BW—20 dB在300～6000Hz）主频率的声频作用下,试验组豇豆比对照组豇豆生长高度增加了21．2％,平均提前了41h开花,结豆英数平均增加了61％;同时,试验组在抗病性、提高复壮能力等方面较之对照组均表现出一定的生长优势。     

3种农药在豇豆生产过程中的消解动态

[目的]研究豇豆生产中,吡虫啉、烯酰吗啉及甲维盐3种农药在豇豆中消解残留规律。[方法]在施药及冷藏后的不同时间采集样品,采用超高效液相色谱-串联质谱法进行测定。[结果]吡虫啉、烯酰吗啉及甲维盐3种农药在豇豆保护地栽培模式下半衰期为2.3、4.3、1.6 d,露地栽培模式下半衰期为2.2、3.2、1.1 d,冷藏条件下半衰期为3.2、4.2、2.9 d。[结论]3种农药在豇豆生产中的消解较快,在豇豆生产中可合理施用。     

超高压处理对泡豇豆杀菌效果的影响

为了探求超高压杀菌在四川泡菜工业中的应用,提高其微生物安全,以泡豇豆为供试材料,研究了泡豇豆含盐量、处理压力、处理时间对超高压杀菌效果的影响,并考察了超高压处理对泡豇豆保藏性能的影响。实验结果表明:含盐量为4.2%的泡豇豆超高压杀菌效果优于含盐量6.7%,超高压技术更适用于低盐泡菜的杀菌;压力越大、处理时间越长,微生物致死率越高,但压力较时间对杀菌效果的影响更大;对样品分别采用300、400MPa处理30min,菌落总数降低的对数为5.45、5.52,且均无霉菌和酵母菌检出;300～400MPa处理可以使大肠菌群数有效得到降低,且能有效提高泡豇豆的保藏性能。     

Assessment of average exposure to organochlorine pesticides in southern Togo from water,maize (Zea mays) and cowpea (Vigna unguiculata)

Drinking water, cowpea and maize grains were sampled in some potentially exposed agro-ecological areas in Togo and analysed for their contamination by some common organochlorine pesticides. A total of 19 organochlorine pesticides were investigated in ten subsamples of maize, ten subsamples of cowpea and nine subsamples of drinking water. Analytical methods included solvent extraction of the pesticide residues and their subsequent quantification using gas chromatography-mass spectrometry (GC/MS). Estimated daily intakes (EDIs) of pesticides were also determined. Pesticides residues in drinking water (0.04–0.40 µg l^?1) were higher than the maximum residue limit (MRL) (0.03 µg l^?1) set by the World Health Organization (WHO). Dieldrin, endrin, heptachlor epoxide and endosulfan levels (13.16–98.79 µg kg^?1) in cowpea grains exceeded MRLs applied in France (10–50 µg kg^?1). Contaminants’ levels in maize grains (0.53–65.70 µg kg^?1) were below the MRLs (20–100 µg kg^?1) set by the Food and Agriculture Organization (FAO) and the WHO. EDIs of the tested pesticides ranged from 0.02% to 162.07% of the acceptable daily intakes (ADIs). Population exposure levels of dieldrin and heptachlor epoxide were higher than the FAO/WHO standards. A comprehensive national monitoring programme on organochlorine pesticides should be undertaken to include such other relevant sources like meat, fish, eggs and milk.     

Effect of saponins on the foam/flow properties of paste and physical characteristics of akara made from decorticated black‐eyed cowpeas

Akara, a deep‐fat‐fried cowpea paste product, is a popular snack food in West Africa. Foaming capacity of the cowpea paste is important for achieving a spongy light‐textured fried product. The effect of two saponins, Yucca and Quillaja, on the foaming capacity of cowpea paste was investigated. Results showed that an increase in the amount of saponin added (1, 2, 4%) resulted in a decrease in specific gravity and apparent viscosity of the cowpea paste. Addition of saponin also significantly reduced the firmness and increased the cohesiveness of the akara compared with the control. Akara made using the Quillaja saponin was less firm and more cohesive than akara made using the Yucca saponin. An increase in the amount of saponin added to the cowpea paste resulted in a darker (lower L*) and browner colour of akara. However, akara containing 1% Yucca saponin had similar colour attributes to the control but was less firm and more cohesive. Copyright © 2005 Society of Chemical Industry     

不同豇豆中酚类含量与抗氧化活性

为深入了解豇豆的营养价值,以11个不同品种的豇豆样品为原料,对其总酚含量、总黄酮含量及抗氧化活性(总还原能力、1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力、·OH清除能力)进行分析,并讨论酚类物质含量及抗氧化活性的相关性。结果表明,不同品种的豇豆酚类物质含量和抗氧化活性差异显著。在测定的样品中,新杂1号表现出最高的总酚含量(5.59 mg GAE/g)、总黄酮含量(4.12 mg CAE/g)及抗氧化活性(总还原能力和DPPH自由基清除能力);豇豆中总酚含量、总黄酮含量与总还原能力、DPPH自由基清除能力之间有极显著相关性(P0.01),与·OH清除能力之间没有显著相关性。     

Improving the nutritional quality and maintaining consumption quality of akara using curdlan and composite flour

Soybean flour and curdlan were incorporated into cowpea flour to determine their effect on lowering the fat content and on the physical properties of akara. At 20% substitution, soybean flour lowered the fat content of akara by 7.7% and increased the protein content by 28.7% without significantly affecting the firmness or the colour of akara. Addition of 1% curdlan decreased the fat content by 32.2% but significantly increased the firmness of akara and produced a darker‐coloured product. The paste moisture content of akara containing 20% soybean flour and 1% curdlan was modified to obtain product characteristics comparable with the control (100% cowpea flour) while maintaining a lower fat content. Optimum results were obtained for paste with 63% moisture content. Firmness of this modified product was similar to the control and the fat content was lower (17%) compared with the control (26%).     

Kinetics of cowpea starch gelatinization and modeling of starch gelatinization during steaming of intact cowpea seed

Steaming of cowpea seeds prevents weevil infestation during storage. Physicochemical changes such as starch gelatinization from steaming may lead to seed resistance to weevil penetration and digestion. A kinetics of starch gelatinization was constructed and incorporated in a heat and mass transfer model to quantitatively investigate starch gelatinization in intact seeds during steaming. The outer layers of steamed seeds (0.5 mm thick) were removed by a specially designed grinding device to measure degree of starch gelatinization (DG). The predicted DG in the outermost layer of seeds was found to be in good agreement with experimental data. The average relative error for DG was 14.6%.