不同保鲜环境荔枝褐变的理化指标识别方法研究

Physicochemical Indexes of Browning Identification of Litchi under Different Storing Environments

为探究理化指标识别荔枝褐变的可行性,试验获取了3种常用保鲜环境（常温保鲜、冷鲜柜保鲜和气调保鲜）荔枝贮藏过程中褐变程度,色差a＊、b＊、L＊,可溶性固形物含量（TSS）和硬度变化。常温、冷鲜柜和气调3种保鲜环境荔枝褐变指数随褐变程度逐渐增大,其中常温保鲜荔枝增大最快,冷鲜柜保鲜荔枝其次,气调保鲜荔枝较慢。理化指标色差a＊、b＊、L＊和硬度均随褐变指数增大呈减小的趋势,TSS随褐变指数增大变化不明显。采用线性判别分析（LDA）对常温、冷鲜柜和气调3种保鲜环境荔枝褐变程度识别正确率分别为96.67%、100%和100%。但冷鲜柜和气调保鲜荔枝4级与5级果LDA分析数据点较近,实际分类易发生混淆。LDA可较好地识别1级、2级、3级和4~5级荔枝果实。采用偏最小二乘回归（PLSR）建立预测模型同时对3种保鲜环境荔枝褐变程度预测时,训练集与测试集测试值与实际值的拟合决定系数R2分别为0.85和0.90,证明了不同保鲜环境荔枝通过同一个模型进行预测的可行性。试验揭示了褐变、理化指标和保鲜时间之间存在的关系,证明了通过理化指标识别褐变程度的可行性,可为水果褐变准确识别以及商品价值评价提供参考。

For exploring the feasibility of litchi browning identification based on physicochemical indexes,the browning indexes,chromatic aberration a＊,b＊and L＊value,total soluble solids content（ TSS） and hard degree of litchi in storing under three common used environments（ room temperature environment,refrigerator environment and controlled atmosphere environment） were measured. Under the above three environments,browning indexes of stored litchi were increased with the increasing storing time.However,the increasing speed of stored litchi under room temperature environment was the most fast,the refrigerator environment was the second,and the controlled atmosphere environment was the third.Physicochemical indexes,including chromatic aberration a＊,b＊,L＊value,and hard degree,were decreased with the increasing browning indexes. But the change of TSS was not obvious with the increasing browning index. The accuracy of linear discriminant analysis（ LDA） for brown degree identification of stored litchi under room temperature environment,refrigerator environment and controlledatmosphere environment were 96. 67%,100% and 100%,respectively. However,the litchi samples of4 thbrowning index were similar with those of 5thbrowning index under both refrigerator environment and controlled atmosphere environment, which may cause confusion in practical classification and identification. Thus,LDA can identify the litchi samples of 1st,the 2nd,the 3rd,the 4th~ 5thbrowning index effectively. The results of partial least squares regression（ PLSR） for stored litchi under above three environments show that fitting coefficients（ R2） of predicted value and actual value were 0. 85 and0. 90,respectively,which proves that litchi could be predicted by using the same model but under different environments. This experiment has revealed the relationships among browning indexes,physicochemical indexes and storing time,which proves the feasibility of physicochemical indexes for litchi＇s browning identification,and provides a reference for fruit＇s browning identification and value estimation.