Effect Of Sugar Immersion Freezing On The Quality Of Blueberries

The effects of sugar immersion freezing on the quality andefficiency of freezing and frozen storage of blueberries were studied in this paper.We had examined the indication include texture characteristics,water distribution and migration,anthocyanin content.The changes of flavor ingredient and content of blueberry were measured by gas chromatography-mass spectrometry?GC-MS?.The frozen blueberries were stored at-20?to further explore the quality changes during the frozen storage period,which provided a theoretical basis for the application of sugar immersion freezing technology in the processing and storage of fruits and vegetables.The main findings were as follows:1.The total freezing time of the blank treatment group was the shortest?289.67s?,while the total freezing time of the xylitol treatment group was the longest?617s?.And,each treatment group had reached the category of quick-freezing.The drop loss was reduced by 39.0%due to the addition of fructose.The moisture content of blueberries was better maintained by immersion freezing in sucrose,maltose and trehalose.There were three distinct water populations in the data of multi-exponential fitting of blueberries LF-NMR T₂ transverse relaxation time.The T₂₃3 value was significantly increased by 23.6%?P<0.05?when maltose was added.The values of T₂₂2 and T₂₁1 in trehalose treatment group were 59.97ms and 11.99ms respectively.The result showed that trehalose had a good effect on cell wall water and cytoplasmic water.The maltose trreatment has a good effect on vacuolar water.The LF-NMR results were consistent with the water content results.2.The degradation of blueberry anthocyanins were restrained during immersion freezing process in glucose,fructose,and maltose solution.The formation of malondialdehyde were inhibit due to add the fructose or maltose.The mass fraction of soluble solids in the xylitol treatment group was about 15.4%.In addition to the maltose treatment group,the hardness of blueberry in the other sugar immersion freezing treated group was significantly higher than that in the blank group?P<0.05?.Starch sugar,sorbitol,trehalose,fructose and glucose treatment significantly increased the brightness value of blueberry L^*?P<0.05?,but the addition of sugar did not inhibit the reddening of frozen blueberries.3.The results of GC-MS showed that the aroma of blueberry were increased after immersion freeze-thaw treatment.The main flavor linalool substance showed a decreasing trend,trans-2-hexenal decreased sharply.The trans-2-hexenol was completely lost.The content of n-hexanal was increased,and the content of eucalyptus oil was slightly increased.Ethanol was detected in the glucose,trehalose,starch sugar treatment group which were not conducive to the maintenance of the aroma of the blueberry.4.The retention of hardness,anthocyanin content,brightness and moisture content after sugar immersion freezing treated were better than that of the blank group.The mass fraction of soluble solids increased with the storage time.The glucose treatment group had the best effect on maintaining the hardness and anthocyanin content of frozen blueberries,while the sucrose treatment group had a significant effect on maintaining the moisture content of frozen blueberries.