Effect of different storage temperatures on the quality and metabolic changes of fresh macadamia nuts
摘要
【Objective】This study aimed to explore the effects of different storage temperatures on the quality and metabolic changes of fresh macadamia (Macadamia spp.) nuts, elucidating the mechanisms by which storage temperature influences the physiological metabolism of the nuts, thereby providing a theoretical basis for extending the shelf life of fresh macadamia nuts and maintaining its post-harvest quality.【Methods】In this experiment, fresh green-peel kernels (XQ) and shelled kernels (XK) were used as the main test materials, which were packaged in PE bags and stored under different temperatures (25℃,4℃, -18℃), and divided into 6 groups:25XQ,4XQ, -18XQ,25XK,4XK, -18XK, and samples were taken after 0,7,14,21,28,35, and 42 days of storage. The moisture content, protein content, crude fat content, color difference, energy metabolism level, polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) enzyme activities, and malondialdehyde (MDA) content were determined. Experimental data were collected and collated by Microsoft Excel 2016, graphed with Origin 2022, and one-way analysis of variance (ANOVA) was performed with SPSS 27.0 software (P<0.05).【Results】The results showed that 4℃was the optimal temperature for preserving the moisture content, crude fat content, and protein content of fresh macadamia kernels. On day 0, the kernels exhibited a relatively high initial moisture content (approximately 23.43%), with crude fat and protein contents of about 59.34% and 6.13%, respectively. When stored at room temperature (25℃), the crude fat content of 25XQ ranged from 58.80% to 61.73%, while its protein content varied between 6.04% and 6.38%. For 25XK, the crude fat content ranged from 59.34% to 72.15%, and the protein content ranged from 6.13% to 7.45%. In contrast, under 4℃storage, the crude fat and protein contents ranged from 59.34% to 62.05% and 6.13% to 6.41%, respectively. Similarly,4XK maintained crude fat content between 59.34% and 64.34%, an