不同冻结温度及冻融循环处理对蓝莓品质特性的影响

Effects of Different Freezing Temperatures and Freeze-thaw Cycles on Quality Characteristics of Blueberries

研究冻结温度和冻融循环次数对蓝莓果实品质的影响。以4℃冷藏为对照组,考察冻结温度在-10、-18、-25和-80℃下蓝莓硬度、可溶性固性物、可滴定酸、抗坏血酸、花青素和丙二醛含量等品质指标的短周期变化;再进行1、2、3和4次冻融循环,重复测定上述品质指标和裂果率、解冻损失率等物理指标。结果表明,较于对照组,-80℃冷冻组的可溶性固性物含量平均升高0.10%,而-10℃冷冻组平均降低0.17%;在贮藏期内,对照组的可滴定酸含量下降0.35%,而-80℃冷冻组仅下降了0.15%;冻融次数与花青素含量、丙二醛含量和裂果率呈显著正相关,与硬度和抗坏血酸显著负相关,构建品质指标与冻融次数的回归方程,蓝莓反复冻融超过2次后,回归方程的变化趋势明显。蓝莓适宜冻结贮藏,-10℃不适宜作为蓝莓的冻结温度,-80℃速冻蓝莓品质更优,蓝莓在实际冻结贮藏和加工过程中反复冻融次数不宜超过2次。

The effects of freezing temperature and freeze-thaw cycles on blueberry fruit quality were studied.Using refrigeration at 4℃as the control group,the short-period changes in the quality indexes of blueberry such as firmness,soluble solid content,titratable acid content,ascorbic acid content,anthocyanin content and malondialdehyde content were investigated at freezing temperatures of-10℃,-18℃,-25℃and-80℃.One,two,three and four freeze-thaw cycles were carried out,and the above quality indexes and physical indicators such as fruit cracking rate and thawing loss rate were determined repeatedly.The results showed that compared with the control group,the soluble solid content of the-80℃freezing group increased by 0.10%on average,whilst the-10℃freezing group decreased by 0.17%on average.During the storage period,the titratable acid content of the control group decreased by 0.35%,whilst the-80℃freezing group decreased by only 0.15%.The number of freeze-thaw cycles was significantly and positively correlated with the anthocyanin content,malondialdehyde content and fruit cracking rate,and significantly and negatively correlated with the firmness and ascorbic acid content.The regression equations of the quality indexes and the number of freeze-thaw cycles was constructed.After the blueberries were subjected repeatedly to freeze-thaw cyclefor more than twice,the changing trend of the regression equation became obvious.Blueberries are suitable for frozen storage,but-10℃is not a suitable freezing temperature for blueberries.The quality of quick-frozen blueberries at-80℃is better,and the number of repeated freeze-thaw cycles during actual frozen storage and processing should not exceed twice.