Effects of heating and autoclaving on sorption and desorption of phosphorus in some forest soils

A number of biological and chemical processes may affect soil phosphorus availability when forest fires occur, partly as a result of heating. We describe here a laboratory experiment to study the effects of soil heating on changes in sorption and desorption of P. Autoclaving was also included as an additional treatment of moist heating under pressure. Five forest soils (two Podzols, one Arenosol, one Luvisol and one Alisol) were heated to 60°C, 120°C and 250°C or autoclaved for 30 min. They were repeatedly extracted with Bray I and analysed for inorganic and organic P fractions. The desorbed P data were fitted to an asymptotic exponential equation to obtain the desorption rate and capacity parameters. Podzol and Arenosol soils showed a quick P desorption after heating, while Luvisol and Alisol soils showed a slow desorption rate. The immediate increase in available P that occurred after heating or autoclaving originated mostly from solubilisation of microbial metabolites and soil organic components. Autoclaving decreased P sorption capacity in all soils, but the effects of heating on P sorption differed among soils. Except for one of the soils, the low P-fixing soils (Podzol and Arenosol) showed a decrease in P sorption when heated to high temperatures, whereas the high P-fixing soils (Luvisol and Alisol) showed little changes after heating. Fire intensity and soil characteristics are important factors determining short-term and long-term soil P dynamics.     

Protein quality of raw and autoclaved cowpeas: Comparison between some insect resistant and susceptible varieties

A comparative study was conducted with four improved cowpea (2 pod bug resistant and 2 susceptible) varieties to assess the effect of autoclaving at 105°C under 15 psi for 30 min on their protein quality, as measured by the levels of some antinutritional factors and performance of rats fed the different cowpea diets. Also, the relationships between antinutrients in the cowpeas and protein quality indicators were examined. Results showed that autoclaving completely eliminated trypsin inhibitor, hemagglutinin and HCN, whereas it reduced significantly (p<0.01) the levels of phytic and tannic acids in the cowpeas. In both raw and autoclaved forms, the insect susceptible cowpeas were better (P<0.05) utilized than their resistant counterparts, a condition which was attributable to lower levels of antinutrients in the susceptible varieties. In the raw cowpeas, trypsin inhibitor, hemagglutinin and HCN were significant variables affecting cowpea protein utilization, while in autoclaved samples, tannic and phytic acids were important though nonsignificant (P>0.05) factors. It was concluded that autoclaving at the above temperature and time improved the protein quality of the insect susceptible more than the insect resistant cowpea varieties.     

高直链玉米抗性淀粉制备工艺的优化研究

[目的]优化高直链玉米抗性淀粉制备工艺。[方法]以发酵所得直链淀粉含量为58％的淀粉为原料,采用压热方法通过单因素试验及4因素3水平的正交试验确定制备抗性淀粉的最佳工艺路线及工艺参数。[结果]制备抗性淀粉的最佳工艺路线及工艺参数为：压热温度135℃,压热时间40min,水分含量70％,储藏温度4℃,压热冷却循环3次。通过验证性试验验证在此条件下抗性淀粉的得率达到42．89％。[结论]为制备抗性淀粉提供了技术支撑。     

Dephytinization of wheat bran by fermentation with bakers' yeast,incubation with barley malt flour and autoclaving at different pH levels

Wheat bran is an important source of dietary fiber but also contains considerable amounts of phytic acid, which is known to impair mineral absorption. The present study was conducted to investigate the phytic acid reduction in coarse and fine wheat bran by fermentation with the different levels of bakers' yeast (3, 6 and 9%) for 8 h at 30 °C, incubation with the different levels of barley malt flour (2.5, 5.0, 7.5 and 10.0%) for 8 h at pH 5.2 and 55 °C, and autoclaving at the different pH levels (pH 5.0, 4.5, 4.0 and 3.5) adjusted with acetic acid for 2 h. The phytic acid content of the wheat bran was effectively reduced by all treatments, and the phytic acid lost was in the range of 88.4–96.9%. Without addition of yeast or malt flour, or autoclaving without pH adjustment, the phytic acid content of the bran samples was reduced at most to 44.9% of the initial amounts under the investigated conditions. Increasing the concentration of yeast or malt flour or decreasing the pH towards 3.5 did not enhance the phytic acid reduction. The most reduction occurred after 2 h of yeast fermentation and malt flour incubation, and after 30 min of autoclaving, which made up 92–98% of the total phytic acid loss. Extending the treatment periods contributed nominally to further increase in the phytic acid reduction, and the rate of the phytic acid loss decreased progressively.     

响应面法优化压热法制备莲子抗性淀粉工艺的研究

以莲子淀粉为原料,采用压热法制备莲子抗性淀粉,通过单因素试验,研究淀粉乳浓度、压热温度、压热时间和淀粉乳pH值4个因素对莲子抗性淀粉得率的影响。利用响应面法进行分析,得到莲子抗性淀粉制备的最佳工艺条件。结果表明,所得的方程达到显著水平,压热法制备莲子抗性淀粉的最佳工艺条件为：淀粉乳浓度30％,压热温度111 ℃,压热时间10 min ,淀粉乳pH值为6~7。实际测得的莲子抗性淀粉得率为41.89％±1.23％,与理论预测值基本一致。     

Effects of processing methods on the quality and acceptability of melon milk

Physicochemical and sensory characteristics of melon milksamples prepared from toasted, autoclaved, boiled andgerminated melon seeds were determined. The germinated melonmilk (GMM) had higher protein and ash contents butlower pH and viscosity than the other treated milk samples.Toasting the melon seeds improved the ash, protein, totalsolids and soluble solids of melon milk more than theboiling and autoclaving processes. The mean sensoryscores showed that the GMM was rated lower than the othertypes of processed milk samples for all the sensoryattributes evaluated. The toasted melon milk (TMM) hadhigher sensory ratings for color, mouthfeel and flavorand was generally preferred to the other treated melonmilk samples.     

Effects of various water or hydrothermal treatments on certain antinutritional compounds in the seeds of the tribal pulse,Dolichos lablab var.vulgaris L.

Effects of soaking, cooking and autoclaving on changes in polyphenols, phytohaemagglutinating activity, phytic acid, hydrogen cyanide (HCN), oligosaccharides and in vitro protein digestibility were investigated in seeds ofDolichos lablab var.vulgaris. Both distilled water and NaHCO₃ solution soaking and autoclaving significantly reduced the contents of total free phenolics (85–88%) compared to raw seeds. Autoclaving (45 min) reduced the content of tannins by upto 72%. Soaking seemed to have limited effect in eliminating phytohaemagglutinating activity, whereas autoclaving (45 min) seemed to eliminate the haemagglutinating activity completely. The reduction in content of phytic acid was found to be some what greater in distilled water soaking (28%) compared to NaHCO₃ solution soaking (22%). Only a limited loss in content of phytic acid was observed under cooking as well as autoclaving. Loss of HCN was greater under autoclaving (87%) compared to the other processes studied. Of the three sugars analysed, soaking reduced the level of verbascose more than that of stachyose and raffinose. Autoclaving reduced the content of oligosaccharides more efficiently (67–86%) than ordinary cooking (53–76%). Autoclaving improved the in vitro protein digestibility (IVPD) significantly (13%). Of all the different water and hydrothermal treatments studied autoclaving seemed to be the most efficient method in improving IVPD and eliminating the antinutrients investigated except phytic acid.     

Phytic acid,in vitro protein digestibility,dietary fiber,and minerals of pulses as influenced by processing methods

The objective of this project was to determine the effect of various types of processing on selected nutrition related parameters of commonly consumed Indian pulses and soybean. Germination reduced the phytic acid content of chickpea and pigeonpea seeds by over 60%, and that of mung bean, urd bean, and soybean by about 40%. Fermentation reduced phytic acid contents by 26–39% in all these legumes with the exception of pigeonpea in which it was reduced by more than 50%. Autoclaving and roasting were more effective in reducing phytic acid in chickpea and pigeonpea than in urd bean, mung bean, and soybean. Germination and fermentation greatly increased the in vitro protein digestibility (IVPD). IVPD was only slightly increased by roasting and autoclaving of all legumes. Germination and fermentation also remarkably decreased the total dietary fiber (TDF) in all legumes. Autoclaving and roasting resulted in slight increases in TDF values. All the processing treatments had little effect on calcium, magnesium and iron contents.