不同预处理对杏鲍菇片真空冻结品质的影响

Effect of different pretreatments on quality of vacuum frozen Pleurotus eryngii slices

为探索切片厚度、烫漂处理、外源水添加量等不同预处理条件对真空冻结杏鲍菇品质的影响,分析切片厚度与真空冻结失水率的关系,对烫漂、不烫漂两组物料添加不同比例的外源水后进行真空冻结对比试验。结果表明,随着切片厚度增加,杏鲍菇片真空冻结失水率呈递减趋势,为保证物料不失水而所需的外源水添加量与切片厚度之间呈现极显著的负线性关系(R^2=0.98,P<0.01)。不烫漂组杏鲍菇片解冻汁液流失率均显著高于烫漂组(P<0.01),主要是由于其解冻前相对较高的含水率所致。烫漂组杏鲍菇片总损失率和相对电导率均显著高于不烫漂组,且均整体上随外源水添加量的增加而逐渐减小。外源水添加量可显著降低杏鲍菇片真空冻结失水率(P<0.05),当外源水添加量低于20%时,不烫漂组杏鲍菇片真空冻结失水率显著高于烫漂组(P<0.05),当外源水添加量高于25%时则相反。随着外源水添加量的增加,不烫漂组杏鲍菇片解冻汁液流失率整体呈增加趋势,而烫漂组解冻汁液流失率当外源水添加量高于10%时无显著性差异(P>0.01)。显微结构观察表明,烫漂处理对杏鲍菇细胞网络结构产生一定破坏作用,而真空冻结前添加外源水可不同程度上降低物料组织内部水分蒸腾作用,减少对细胞组织结构的破坏。生产真空速冻杏鲍菇片时,推荐预处理条件为:切片厚度3 mm,90℃热水烫漂1 min,冻结前外源水添加量为30%。该研究结果可为食品真空冻结技术实践应用提供参考。

Vacuum freezing is an advanced technique for quick freezing and has attracted increased attention worldwide.Compared with traditional freezing,vacuum freezing has advantages of fast cooling rate,short freezing period,and uniform cooling effect.Existing studies on vacuum freezing are limited to liquids,drugs and solid foods.Pleurotus eryngii is rich in protein,polysaccharides and essential amino acids,and a quick freezing can keep it fresh and maintain the nutrients.One concern over the vacuum freezing is its mass loss,but it could be ameliorated by pre-treatments such as adding exogenous water prior to freezing.This paper investigate the efficacy of several pre-treatments,including slicing thickness,blanching and adding exogenous water,on the quality of vacuum-frozen Pleurotus eryngii.The relationship between slicing thickness and water loss ratio after vacuum-freezing was studied,and the impact of adding exogenous water and blanching on vacuum-freezing results was experimentally examined.The results showed that increasing slicing thickness reduced the water-loss ratio,and that the amount of exogenous water that was required to reach a zero-water loss after thawing was negatively correlated to the slicing thicknesses at significant level(P<0.05),with a determination coefficient of 0.98.Adding exogenous water could partially or completely compensate the evaporation loss.When the adding exogenous water was less than 20%,water loss from the Pleurotus eryngii slices without blanching was significantly higher than that with blanching,while the opposite was true when the adding exogenous water exceeded 25%(P<0.05).The loss ratio of the vacuum-frozen Pleurotus eryngii slices after thawing without blanching was significantly higher than that with blanching(P<0.01),indicating that blanching might have significantly reduced the moisture in the vacuum-frozen samples as they were positively correlated to the loss ratio after thawing(P<0.01).The loss ratio after thawing without blanching increased with the added exogenous water,yet no significant difference was found between the loss ratio with blanching when the added exogenous water was more than 10%(P>0.01).The total loss ratio and the relative electrical conductivity of the Pleurotus eryngii slices with blanching were significantly higher than those without blanching,and they all decreased with the increase in the added exogenous water.Microstructure analysis revealed that blanching damaged the cell network in tissues,and adding exogenous water prior to vacuum-freezing could reduce water evaporation from the tissues,thereby ameliorating cellular structure damage.In summary,our results suggested that the optimal pre-treatment for vacuum-freezing the Pleurotus eryngii slices were:slicing at3 mm of thickness,blanching with 90°C hot water for 1 minute,and adding 30%of exogenous water.