<i>Relationship between stress relaxation characteristics and quality of Chinese cabbage (Brassica pekinensis L.)</i>

Abstract

Abstract. Stress relaxation experiment, as a typical static rheological test, is one of the most important evaluation tools for the viscoelastic performance and quality characteristics of materials for agriculture products. Comprehensive testing and evaluation using stress relaxation characteristics to describe the rheological changes of Chinese cabbage (Brassica pekinensis L.) under storage conditions ( 12 days at 20 ℃) were presented in this context. Generalized Maxwell model was used to analyze the stress relaxation characteristics of Chinese cabbage and the correlation analysis between stress relaxation characteristics parameters and quality characteristics (firmness, moisture, soluble solids content, and vitamin C) was made to establish models for quality prediction of Chinese cabbage which was verified. The results of stress relaxation test show that the viscoelastic properties and relaxation process were well evaluated by four-term Maxwell model (R2 ＞ 0.9998). There existed a certain correlation (p ＜0.05) between the parameters of the stress relaxation model of Chinese cabbage, while the regression models established had the best fitting effect on firmness (R2 = 0.982, p = 0.022), followed by vitamin C content (R2 = 0.958, p = 0.070) and moisture content (R2 = 0.912, p = 0.191), but less effect on soluble solids content (R2 = 0.791, p = 0.217). The coefficients of determination between the predicted and measured values of firmness, soluble solids content, vitamin C content and moisture content were 0.936, 0.593, 0.625 and 0.284, respectively. The results corroborated the relationship between stress relaxation characteristics and quality properties, which explored a method to predict and evaluate the quality of Chinese cabbage by stress relaxation parameters, as well as provided a theoretical basis for low-damage storage and quality evaluation of Chinese cabbage. Furthermore, no attempt was made to apply rheological parameters of intact s to evaluate and predict apple quality.