The Research Of Changes In Quality Attributes With Water State And Ice Crystals Of Mango During Glassy State Frozen Storage

As one of the most important fruits worldwide,mango is a rich in a variety of nutrients,and favored by consumers.However,due to its perishability,the post-harvest shelf life of mangoes is relatively short.At present,freezing is the most frequently used method to increase the shelf life of the mango and maintain its original quality attributes all over the world.However,it is easy to form a non-equilibrium amorphous state in the process of freezing,resulting in the instability of mango during frozen storage.The previous results showed that the glassy state storage can keep the quality of frozen food,but there is little research on the quality stability in mango during glassy state storage.Therefore,exploring the frozen preservation technology of mango has important theoretical and practical significance.In order to investigate the quality stability of mango during glassy state frozen storage,mango(Mangifera indica L.)was used in the following experiments.Firstly,the effects of different state/phase transitions on quality attributes of mango cubes during frozen storage were investigated.Mango cubes were stored at-65 ? for 4 weeks,the temperature of frozen mango was modulated from-65 ?(glassy state)to-60 0C(T<Tg',glassy state),-49 ?(Tg'<T<Tg",glassy state),-38 ?(Tg",<T<Tm",partially freeze-concentrated state),-28 ?(T>Tm' rubbery state)to reach different states and the changes in color,hardness,drip loss,total soluble solid(TSS),pH,vitamin C content,beta-carotene content,moisture content,freezable water content,water state and ice crystal size were measured every one week.Regard vitamin C as an index of nutrient quality of mango,investigate the relationship between vitamin C and water state and ice crystals of mango under different state/phase transitions during frozen storage.Secondly,in order to investigate the effects of different characteristic temperatures on the quality of mango during glassy state storage without temperature fluction,mango cubes were stored at-80 ?(T<Tg'),-60 ?(T<Tg'),-49 ?(Tg'<T<Tg"),-38 ?(Tg"<T<Tm')and-18 ?(T>Tm' for 6 months,respectively,record the changes of color,hardness,drip loss,TSS,pH,vitamin C content,antioxidant activity,moisture content,freezable water content,water state and ice crystal size,analyze the changes of mango quality(vitamin C)with water state and ice crystals,and investigate the quality stability in mango during glassy state frozen storage,which would provide theoretical basis and technical support for the processing of frozen mango.The main results are as follows.(1)Compared with partial-freeze-concentrated and rubbery state,the frozen samples stored in glassy state had higher quality in terms of colour,hardness,drip loss,pH,TSS,beta-carotene and vitamin C content after one month frozen storage under state/phase changes.The quality of mango stored below Tg ' was significantly higher than that below Tg ",which reveals that there are differences between Tg' and Tg" in the prediction of quality stability in mangoes.The quality attributes of mangoes in the glassy state without temperature fluctuations still continued to change,which indicates that continued diffusion-controlled reaction occurs in the glassy state.However,the quality of mango decreased most when the temperature fluctuation was above Tm'.The results showed that glassy state storage can keep the quality of mango,and And the glassy state without temperature fluctuation was the best storage condition.(2)It was found that glassy state showed lower free water,freezable water content and smaller ice crystal size,and thus less structural damage in mango and a higher vitamin C content than other conditions after one month frozen storage under state/phase changes.In contrast,there were the significant increase in water mobility and freezable water content,bigger pores of ice crystals and greater percentage growth rate of ice crystals in frozen mangoes subjected to temperature fluctuations above Tg" and Tm ',resulting in less vitamin C content in mangoes.And the current work indicated that glassy state storage can provide better retention of vitamin C content in mangoes during frozen storage.(3)Compared with partial-freeze-concentrated and rubbery state,the frozen samples stored in glassy state had higher quality in terms of colour,hardness,moisture content,drip loss,pH,TSS,vitamin C content,antioxidant activity,freezable water content,water state and ice crystal size after six month frozen storage.The glassy state storage at-80 ? was the best storage condition,and there was no significant diference in vitamin C content between-80 ? and-60?.The quality attributes of mango stored at-60 ? was significantly higher than that of-49 ?,which implies that there were differences between the two glass-transition temperatures in predicting the quality stability of mango,and the frozen mango was more stable below Tg' than below Tg",A gradual decrease in quality and an increase in mobility of water,freezable water content and ice crystal size of all frozen samples occured with storage time,which indicated that the rates of diffusion-limited reactions,such as recrystallization do not completely cease even in the glassy state below Tg'.In conclusion,the glassy state storage can provide better retention of quality attributes in mango,which was attributed to the lower content of free water and freezable water,and the smaller size of ice crystals,resulting in the smaller damage of mango tissue and thus the higher quality(vitamin C content)in mango.The temperature above Tg" and Tm' should be avoided as soon as possible whenever the mango was stored under state/phase transition conditions or at different characteristic temperatures for long time.