Effects Of Different Freezing And Thawing Methods On The Eating Quality Of Soft-boiled Chicken

The quality of frozen meat is closely related to the freezing and thawing methods.In the process of freezing,the formation of ice crystals damages the tissue and cell of meat.Likewise,during the thawing,there would be fat oxidation,juice loss,color and flavor deterioration as well as microbial proliferation,etc.So it is necessary to use proper freezing and thawing methods to minimize the loss and keep the quality of meat.The new freezing and thawing technique refers to using novel instrument to change the traditional way which uses air as the medium to freeze materials.The novel thawing technique refers to using mechanical instrument technique that is different from the traditional thawing method.Compared with the traditional thawing method,the new one has a faster thawing speed,lower energy consumption,and can better maintain the quality of meat dishes.This thesis investigated the application of room temperature thawing,water immersing thawing,microwave thawing,ultrasonic thawing,air blast freezing,liquid nitrogen quick freezing and immersion chilling and freezing methods,aiming to provide theoretical reference for the companies to choose the proper method.The main research contents and results are shown below:1.Effects of different freezing methods on the eating quality of soft-boiled chickenThis chapter demonstrated the effects of three freezing methods on the quality of softboiled chicken.Air blast freezing(-18℃),immersion chilling and freezing(-35℃)and liquid nitrogen quick freezing(-110℃)methods were applied to the fresh cooked soft-boiled chicken.After the center of the chicken temperature reached-18℃,put it in a-18℃ freezer for one month.Then the products were thawed overnight in a 4℃ cold storage,and various indexes were determined.The results showed that liquid nitrogen quick freezing and immersion chilling and freezing methods can significantly increase the freezing velocity,their velocities are about 60 and 15 times of that of the air blast freezing method.As for the thawing loss,the liquid nitrogen quick freezing and immersion chilling and freezing method reduces from 6.39% to 3.82% and 3.16%.Both liquid nitrogen flash freezing and immersion chilling and freezing methods can keep the color of the food,delay the decline of p H and fat oxidation in the freezing process.Compared with air blast freezing and immersion chilling and freezing methods,liquid nitrogen quick freezing can better maintain the taste(umami,sweetness and richness)of the soft-boiled chicken.Liquid nitrogen quick freezing and immersion chilling and freezing methods inhibited the quality deterioration of the soft-boiled chicken caused by air blast freezing method.2.Effects of different thawing methods on the eating quality of soft-boiled chickenThis chapter evaluated the effects of four thawing methods on the eating quality of softboiled chicken.Room temperature thawing,water immersing thawing,microwave thawing and ultrasonic thawing methods were applied on the soft-boiled chicken which has been frozen by air blast freezing method for one month,and various indexes were determined.The results showed that microwave thawing and ultrasonic thawing methods can shorten the thawing time,significantly improved the thawing efficiency,about 3 and 7 times than that of room temperature thawing respectively,reduced the content of malondialdehyde of room temperature thawing,The contents of malondialdehyde in water immersing thawing,microwave thawing and ultrasonic thawing is 1.28,0.99,0.76 and 0.43 mg/kg,meanwhile,microwave and ultrasonic thawing can keep the food color,improve the taste of the freezethaw chicken,and inhibit the loss of flavor substance caused by room temperature thawing method.But the juice of the food largely lost,and the proportion of free water is high after thawing use these methods.Water immersing thawing can better maintain the color,p H and taste(umami,sweetness and richness)of the chicken.It also can keep the loss of thawing at the lowest level.Compared with room temperature thawing,it has a certain inhibitory effect on fat oxidation,however the thawing rate of it is much lower than that of microwave thawing and ultrasonic thawing methods.Room temperature thawing method is not proper for keeping the quality characteristics of soft-boiled chicken.In conclusion,for the soft-boiled chicken that needs to be frozen after production,it can be frozen by different methods according to the different sales channels and purpose.As for the one which is short for time,and has a high quality requirement,it is recommended to use the liquid nitrogen quick freezing method with high cost but most efficient.As for the one has to be frozen for a long time,immersion chilling and freezing method can be used instead of air blast freezing method,which is economical and has a good freezing effect.For the air blast frozen soft-boiled chicken,the thawing method can be selected according to the different freezing time,and the different destinations of the products.For example,microwave thawing and ultrasonic thawing methods can shorten the thawing time to improve the production efficiency.These two methods also can improve fat oxidation and taste.So they are suitable for the soft-boiled chicken that has been frozen for a long time.Water immersing thawing method can significantly reduce thawing loss,so it can be used for the soft-boiled chicken with short freezing time and no serious color deterioration.