核桃青果皮栲胶提取工艺优化及其品质评价

Optimization of extraction technology and evaluation of tannin extracted from walnut green peel

【目的】探究核桃青果皮栲胶提取的最佳工艺及其鞣制效应,提高核桃副产物资源利用率。【方法】以核桃青果皮为试验材料,以单宁含量为评价指标,在浸提剂、液固比、提取温度、提取时长单因素试验基础上,采用Central Composite Design响应面试验,优化核桃青果皮栲胶提取工艺,并使用核桃青果皮栲胶对新鲜猪皮进行鞣制,对鞣制后猪皮的质构特性和收缩温度进行测定,评价栲胶鞣制效应。【结果】在乙醇体积分数48%、液固比62︰1、提取温度46℃、提取时长68 min等条件下,通过离心、抽滤、浓缩和喷雾干燥工艺后,核桃青果皮提取液中单宁含量为10.98 mg/g,核桃青果皮栲胶得率为26.96%,与预测值11.125 mg/g相近,回归方程拟合良好,结果准确可靠。4种因素对单宁含量的影响由大到小依次为乙醇体积分数、提取温度、提取时长、液固比。此外,核桃青果皮栲胶成品单宁含量为61.75%±2.50%,不溶物含量为4.75%±0.50%,水分不大于10%,pH为3.93±0.10,总色值为28.25±2.87。与新鲜猪皮和浸酸猪皮相比,经栲胶鞣制后猪皮的收缩温度分别提高了14.25、21.45℃,弹性分别增加了71.67%、58.46%,硬度分别增加了6.17、1.41倍,剪切力分别增加了2.93、1.23倍,表明核桃青果皮栲胶具有较好的鞣制效果。【结论】核桃青果皮栲胶具有较好的鞣制效应,可作为一种新型的栲胶原料。

【Objective】To explore the optimum extraction parameters and tanning action of tannin extract from walnut green peel,improve the utilization of walnut by-product resources.【Method】Walnut green peel was selected as test material,the tannin content was used as the response value,based on single factor tests,extractants,liquid-to-material ratio,extraction time,extraction temperature were tested to explore the optimum extraction parameters by response surface test of central composite design.Fresh pigskin was tanned with walnut green peel tannin extract,and its texture profile and shrinkage temperature were measured to evaluate the tannin extract tanning effect.【Result】The optimal conditions of tannin extract from walnut green peel were as follows:ethanol concentration was 48%,liquid-to-material ratio was 62︰1,extraction temperature was 68℃,and extraction time was 46 min.Under this condition,after centrifugation,suction filtration,concentration and spray drying processes,the tannin content in the green walnut peel extract was 10.98 mg/g,and extraction rate of tannin extract was 26.96%,which was close to the simulated value of 11.125 mg/g,indicating that the regression equation was fitted well with the actual situation,and the result was accurate and reliable.The four influence factors of tannin content on the yield were as follow:ethanol concentration>extraction temperature>extraction time>liquid-solid ratio.In addition,the tannin content of walnut green peel tannin extract product was 61.75%±2.50%,the insoluble content was 4.75%±0.50%,the moisture content was less than 10%,the pH value was 3.93±0.10 and the total color value was 28.25±2.87.Compared with fresh pigskin and pickled pigskin,the shrinkage temperature of pigskin tanned with tannin extract increased by 14.25℃and 21.45℃,elasticity increased by 71.67%and 58.46%,hardness increased by 6.17 times and 1.41 times and the shearing force increased by 2.93 times and 1.23 times,respectively.These suggested that the walnut green peel tannin extract had a better tanning action.【Conclusion】Walnut green peel tannin extract has an excellent tanning action,and it could be used as a new type of tannin extract raw material.