Abstract: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 controlled atmosphere environment were 96.67%, 100% and 100%, respectively. However, the litchi samples of 4th browning index were similar with those of 5th browning 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~5th browning 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 and 0.90, 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.
