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Freeze-drying has become an important technology used to extend shelf-life and to preserve food nutritional quality. It is most recommended for high-value foods and those containing heat-sensitive ingredients. However, to our knowledge, there are significant differences in the retention of phytochemicals in various fruits and vegetables during freeze-drying, which need to be summarized and explained. Thus,the evolution of the bioactive substances and free radical scavenging abilities of fruits and vegetables based on the freeze-drying procedure will be explored in this review. Furthermore, the stability of bioactive ingredients in freeze-dried products during storage will be also deeply reviewed in this paper by comparing the presented studies in these aspects. The comprehensive review of the research progress of freeze-drying techniques and the challenges in developing freeze-dried products is discussed. The freezing step causes the degradation of phenolic compounds and also causes the release of bound phenolic compounds in correlation with the cell wall. Prolonging the drying step causes the degradation of ascorbic acid and anthocyanins in some food matrix. Generally, the faster freezing rate, the higher drying temperature, and the shorter drying time can produce freeze-dried fruits and vegetables with higher retention of phytochemicals and bioactive activity. During storage, the small pore structure causes degradation of carotene and other compounds sensitive to oxygen, and the collapse freeze-dried sample showed higher retention of those substances. [ABSTRACT FROM AUTHOR]

Anthracnose is presently recognized as one of the most important postharvest disease of mango worldwide. To control the disease, chemical fungicides for a long time was widely used among fruit farmers, but recently found that pathogen had developed increasingly resistance to it. With people's growing desire of healthy and green food, finding new and environmentally friendly biological control approach was very necessary. In this paper, we provided a kind of new antagonistic yeast which enriched the strain resources and the efficacy of Debaryomyces nepalensis against postharvest anthracnose of mango fruit and the influence on quality parameters were investigated. The results showed that the decay incidence and lesion diameter of postharvest anthracnose of mango treated by D. nepalensis were significantly reduced compared with the control fruit stored at 25 °C for 30 d or at 15 °C for 40 d, and the higher concentration of D. nepalensis was, the better the efficacy of the biocontrol was. Study also found that 1 h was the best treatment duration and antagonistic yeast inoculated earlier had good biocontrol effect on anthracnose. Meanwhile, treatment by D. nepalensis could significantly reduce postharvest anthracnose of mango, delay the decrease in firmness, TSS, TA, and ascorbic acid value, and do not impair surface color during postharvest storage. Moreover, the increase in MDA (malondialdehyde) content and increase in cell membrane permeability of fruit treated by D. nepalensis was highly inhibited. The results suggested D. nepalensis treatment could not only maintain storage quality of mango fruit, but also decrease the decay incidence to anthracnose disease. All these results indicated that D. nepalensis has great potential for development of commercial formulations to control postharvest pathogens of mango fruit. [ABSTRACT FROM AUTHOR]