Using biological metabolites as biomarkers to predict safety and quality of whole and minimally processed spinach

This study investigated the possible linkage between spinach metabolic biomarkers and their safety and quality during minimally processing and storage. Spinach leaves were treated following the basic minimal processing practices treatments (minimally processed, whole washed, and whole unwashed) and packaged in plastic bags. Significant changes (p < 0.05) in various metabolites biomarkers, physical properties and microbial counts were recorded during the 15 days of refrigerated storage. The contents of vitamin C and polyphenols decreased by 47.82% and 31.62%, respectively, while pH increased from 6.21 ± 0.04 to 6.62 ± 0.04. Furthermore, physical examination revealed significant (p < 0.05) decline in greenness and crispness and increase in yellowness and brownness. Most importantly, CO₂ increased gradually and the volatile compounds such as 2-methyl furan, 1-octen-3-ol and 3-octadien-3-one started to emerge after 8 days of storage, while (E)-2-pentenal, (E)-2-hexanal and (Z)-2-hexen-1-ol disappeared. These changes in volatile compounds correlated with the significant (p < 0.05) increase (4.93 log CFUg^-1) in the microbial counts and hence can be considered as metabolite markers of quality and safety of spinach.