Effects of Osmo-dehydration on Quality Attributes of Mangoes during Frozen Storage
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Abstract:
The effects of osmotic dehydration pretreatment on the freezing time and the quality attributes of frozen mangoes were investigated. Mangoes were dehydrated in mixed osmotic solutions (sucrose: glucose: fructose, 3.6:1:3) at three concentrations (30%, 40%, and 50%, m/m) for 2 h at 30 ℃, and then stored at -18 ℃for six months. The results revealed that the freezing time of the osmo-dehydrofrozen samples was 6.3~13.8% lower than that of the conventional frozen samples. Moreover, osmotic dehydration pretreatment improved the quality attributes of frozen mango in terms of color (total color difference reducing by 12.5~36.8%), hardness (increasing by 35.8~65.5%), drip loss (reducing by 11.3~44.5%) and vitamin C content (increasing by 21.2~134.8%) compared to the untreated ones after six months of frozen storage. Pretreatment with higher solution concentration showed smaller alterations in the quality attributes of samples. Through comprehensive analysis, dehydration in osmotic solution of 40% concentration was considered as the optimum pretreatment condition for frozen storage. In addition, the quality was better maintained in shaded side (firmer) of mangoes than the sun-exposed side (softer). With progression of storage time, mangoes pretreated by osmotic dehydration showed less reduction than the untreated ones. The current study indicates osmotic dehydration enhances both freezing rate and quality attributes of frozen mango.
