Optimizing microencapsulation of peanut sprout extract by response surface methodology

This study was carried out to optimize conditions for peanut sprout extract microencapsulation by response surface methodology (RSM). The coating materials of microencapsulation were medium-chain triacylglycerol (MCT) for primary emulsion, and whey protein concentrates (WPC), maltodextrin (MD) and gum Arabic (AG) for secondary emulsion. The yield of microencapsulation of peanut sprout extract was investigated with respect to four variables (ratio of core and coating materials, concentration of primary emulsifier, ratio of W/O emulsion and secondary coating materials and concentration of secondary emulsifier) in RSM. The optimal conditions for microencapsulation of peanut sprout extract were 1:2 as the ratio of core material to coating material, 1.25% (w/v) of primary emulsifier concentration, 1:1.23 as W/O emulsion to secondary coating material, 1.21% (w/v) as secondary emulsifier concentration and 30% (w/w) as WPC concentration for spray drying. In conclusion, the microencapsulation of peanut sprout extract under the optimized conditions by RSM ensures the smaller size (3–7 μm) of microcapsules with the highest yield reaching to 98.74%.     

Effect of extraction conditions on the yield and purity of ulvan extracted from Ulva lactuca

A study of the influence of extraction conditions (pH: 1.5 and 2; temperature: 80 °C and 90 °C; extraction time: 1–3 h), on the yield, chemical composition and purity of the sulphated cell wall polysaccharides ulvan, extracted from the green seaweed Ulva lactuca and precipitated by alcohol is carried out. The alcohol precipitate yields varied from 21.68% to 32.67% (%dw/dw) depending on the pH. At pH 2, the alcohol precipitate yields and the uronic acid recovery from extract juice are higher than those obtained at pH 1.5. Other compounds than ulvan such as cellulose, hemicellulose, proteins and ash are solubilized from the cell walls of Ulva lactuca at both pH, and they are precipitated with alcohol. The alcohol precipitate obtained from different extraction conditions has high uronic acid (20.37%–23.60%) and neutral sugar content (20.09%–29.12%), especially when the conditions (pH, temperature) are drastic. It contains rhamnose (13.35%–15.59%), glucose (2.90%–10.97%), and xylose (2.36%–2.73%). A decrease in the molecular weight of ulvan was observed at acid pH, and for long extraction times. The presence of proteins (1.94%–2.32%) and inorganic material (33.36%–47.15%) in alcohol precipitate prove the lower purity of ulvan extracted and shows that ulvan precipitation with ethanol is not specific.     

黑曲霉菌丝体活力对α-L-鼠李糖苷酶发酵的影响

α-L-鼠李糖苷酶是工业上一种重要的水解酶。为了方便地优化和监控α-L-鼠李糖苷酶的发酵生产过程,在5 L发酵罐水平研究黑曲霉菌丝体活力与α-L-鼠李糖苷酶产量之间的关系,菌丝体活力采用TTC-脱氢酶法进行测定。实验结果表明,在发酵过程中维持适宜的菌丝体活力对α-L-鼠李糖苷酶的产量非常重要:当摇瓶种子菌丝体活力达到最大值0.388 U/mL时,对应的5 L发酵罐中α-L-鼠李糖苷酶的产量最大;控制发酵过程的pH恒定于5.5,可以有效延缓菌丝体活力下降速度,使α-L-鼠李糖苷酶的产量提高28.7%;当搅拌转速低于400r/min或通气量低于0.3 vvm时,发酵24～36 h的菌丝体活力大幅下降,α-L-鼠李糖苷酶的产量显著降低。因此,可以将菌丝体活力作为α-L-鼠李糖苷酶发酵工艺优化和生产过程控制中一项重要的监控参数。     

反应条件对双醛山药淀粉醛基含量的影响

以山药淀粉为原料,高碘酸盐为氧化剂制备双醛山药淀粉,考察了反应温度、反应时间、pH值、淀粉浆液质量分数,高碘酸钠与淀粉葡萄糖单元的摩尔比对醛基含量的影响。实验结果表明,制备醛基含量大于90%的双醛淀粉的适宜工艺条件为:反应温度40℃,反应时间4 h,pH值为4.0,淀粉浆液质量分数为20%,高碘酸钠与淀粉葡萄糖单元摩尔比为1.1:1,在此条件下醛基含量高达97.5%。     

两种放牧方式对绒山羊肉抗氧化系统的影响

以草场放牧、山地放牧两种方式下的绒山羊背最长肌为实验材料,测定背最长肌的色泽、肌红蛋白含量、 丙二醛含量、氧合肌红蛋白相对含量、高铁肌红蛋白相对含量、抗氧化酶活力和总抗氧化能力等指标并进行比较分 析。结果表明：草场放牧绒山羊肉的红度、过氧化氢酶活力、谷胱甘肽过氧化物酶活力和自由基清除率均显著高于 山地放牧（P＜0.05）;草场放牧绒山羊肉亮度、黄度、高铁肌红蛋白相对含量、丙二醛含量均显著低于山地放牧 （P＜0.05）,但两种放牧方式绒山羊肉的肌红蛋白含量、氧合肌红蛋白相对含量、超氧化物歧化酶活力和总抗氧 化能力没有显著差异（P＞0.05）。在草场放牧条件下,绒山羊能摄食大量绿色牧草,并且有适宜的运动量,增加 了抗氧化酶的活力和肉色稳定性,自由基的产生和清除达到了平衡,从而使其肉品的抗氧化能力高于山地放牧。     

原纸挤出涂布时耐热离型纸结合强度预测

合成革离型纸生产时,需要在原纸上挤出涂布DX820 TPX树脂以得到耐高温的离型纸。挤出涂布时,关系到纸膜结合强度的主要工艺参数是:螺杆转速x1、电晕功率x2、气隙高度x3、压区压力x4。为了找到挤出涂布时的主要工艺参数与纸膜结合强度之间的非线性回归模型,基于部分量纲消除的方法,设计了38种方案的解释变量组合。结果表明:选择x12x32/x2、x12x4作为解释变量组合的方案时回归,所得关联式的最大拟合误差为0.6122%。根据得到的关联式进行敏感度分析,定量计算表明:气隙高度对纸膜结合强度的影响呈现非线性关系。高精度关联式的建立,达到了根据螺杆转速、电晕功率、气隙高度、压区压力预测纸膜结合强度的目的。     

浓香型大曲中优势蛋白酶产生细菌的分离及产酶条件研究

对浓香型大曲中蛋白酶产生细菌进行分离,并对其最适产酶条件进行研究。采用酪素培养基,从大曲中分离出5株产蛋白酶菌株,筛选出酶活力最高的菌株,其酶活为53.40 U/mL。以小麦为固体培养基,从pH值、培养基水分含量、碳源添加量、氮源添加量、接种量、培养温度和培养时间等方面研究此菌株的最适产酶条件。结果表明,在水分含量65%、初始pH6.0、蔗糖添加量6%、硫酸铵添加量1%、接种量12%、温度40℃,培养时间5 d的条件下,其酶活可达262.18 U/mL,为菌种复筛时的4.91倍。     

山杏仁多肽的制备及清除自由基能力研究

以DPPH自由基清除率为指标,对风味蛋白酶酶解脱脂山杏仁的工艺进行研究。在单因素实验的基础上,采用二次回归正交旋转组合设计对其酶解工艺进行优化。建立脱脂山杏仁酶解液的DPPH自由基清除率与蛋白酶用量、酶解温度及酶解pH,3个实验因素的正交回归模型方程,通过频率分析法得到酶解最佳工艺条件:蛋白酶用量0.50%,酶解温度55℃,酶解pH7.2,酶解时间4h,最佳条件下酶解液的DPPH自由基清除率为56.8%。在此条件下,山杏仁蛋白酶解液清除DPPH自由基的IC50值为4.18mg/mL。经过超滤分离获得不同分子量的抗氧化多肽,用DPPH自由基清除率评价其抗氧化性,得分子量小于5ku的肽清除DPPH自由基能力最强。