Effects of precise temperature control on the storage quality and aroma components of fresh goji fruit

Abstract: Goji (Lycium barbarum L.) is one of the most popular medicinal plants, particularly as a typical nutritional fruit supplement rich with bioactive compounds. However, fruits browning, taste loss, and storage intolerance often occur during postharvest, because of tender and juicy tissue. Among them, the temperature is one of the most significant factors to maintain the quality and extend the shelf life of fruits. It is necessary to place fruits in a constant temperature environment after harvest since temperature fluctuations and variation tend to induce product quality deterioration. This study aims to investigate the effect of precise temperature control on storage quality and aroma components of fresh goji fruits. Three treatments of storage temperature at 0℃ were also set, including foam box (CK), foam box + cool storage agent (ice temperature), as well as the precise temperature control box and cool storage agent (phase temperature). The temperature was real-time recorded in different cabinets to evaluate the storage quality. Principal component analysis (PCA) was used to evaluate the aroma components of goji. Results showed that the foam box containing the self-made refrigerant performed better at ambient temperature, compared with that with the ice. Temperatures in the box of CK, ice, and phase temperature group were (0.12±0.17), (-0.04±0.07) and (-0.05±0.04)℃, respectively, during the whole storage period. A cold accumulator provided a cold source in the box to maintain a low-temperature environment. The temperature distribution was more uniform in the precision temperature control box, while the maintenance time of low temperature was longer than before, due to the excellent performance of heat preservation. The time of mildew and rot in the CK group, ice, and phase temperature group were 10, 20, and 40 d, respectively. At the storage of 40 d, the rot rate in the phase temperature group were 4.11%, much lower than 14.85% in the CK group. Chromatic aberration ΔE was lower than 3, while Brightness L value reached 34.12. The content of soluble solid, titratable acid, Vitamin C conten, carotenoid were 0.65 percentage, 0.03 percentage, 4.34 mg/100g, 2.90 mg/g higher than CK group, respectively. Correspondingly, the treatment in the phase temperature group inhibited the increase of decay rate and weight loss rate, indicating the delay of ΔE and L, as well as a higher soluble solid, titratable acid, VC, and carotenoid content. The principal component analysis demonstrated that the goji quality in three groups was in the order of phase temperature group, ice temperature group and CK group. Moreover, the contents of favorable aroma components, such as lycium aldehydes and terpenoids, were relatively higher in the storage under precise temperature control. Consequently, the ice and phase temperature storage was the most effective in the long-term preservation of goji, where the color change of goji was delayed to facilitate the release of volatile substances, while effectively prolonging the storage period of goji to 30 days. The finding can be greatly beneficial to guide the preservation of goji fruits.