Effects of cold storage on the chemical composition of Corcyra cephalonica eggs by 1H NMR spectroscopy

Rice moth Corcyra cephalonica eggs, frequently utilized as factitious hosts of Trichogramma wasps, are usually cold-stored for a period of time in order to meet the need of Trichogramma mass rearing. However, compounds in cold stored C. cephalonica eggs can influence the quality and quantity of Trichogramma. In the present study, we used Hydrogen-1 Nuclear Magnetic Resonance (1H NMR) spectroscopy and multivariate statistical analysis to investigate the effect of cold storage on the chemical composition of fresh rice moth eggs (U) and killed embryo eggs cold stored at 4 °C for 0 (CK), 15 (N15), 30 (N30), 45 (N45), and 60 (N60) days, respectively. A total of 56 compounds were identified and quantified for each treatment, including amino acids, nucleic acid components, organic acids, sugars, and amides. Principle component analysis (PCA) and partial least square discriminant analysis (PLSDA) demonstrated that cold storage had a pronounced effect on the chemical composition of rice moth eggs. Three groups, U and CK, N15 and N30, and N45 and N60, were classified by their components' similarity. The primary components that contributed to difference among three groups were alanine, glutamine, glucose and acetate, the concentrations of which significantly changed with the increasing of cold storage days. Thus, cold storage elicits changes in the chemical compositions of rice moth Corcyra cephalonica eggs, which may affect the growth and development of Trichogramma.