| Light walnuts(Juglans regia L.)is one of the characteristic forest fruits in Xinjiang.Its fresh nuts are full,crisp and tender in taste,and fragrant in flavor,which is very popular among consumers.However,the harvest period of fresh walnuts is concentrated,the moisture content of the green skin is high,and the green skin is difficult to remove during sales,and the environment is polluted.However,during the postharvest storage and transportation of wet hard walnuts,the surface of the seed shells is prone to mold and stickiness,germination,and water loss.Although the existing technology can prolong its fresh-keeping period,it cannot guarantee its long-term sales and continuous supply.Low-temperature frozen storage can significantly prolong the storage period of fresh walnuts,but the quality of walnut kernels decreases after thawing,which cannot guarantee shelf sales,which greatly limits the application and promotion of low-temperature freezing storage technology in this field.Therefore,this paper used’Wen 185’wet hard walnut as the test material to study the effect of different freezing temperatures on the storage effect of fresh walnut,and to discuss the effect of low-pressure static magnetic field treatment on the thawing effect of fresh walnut.The effect of low-pressure static magnetic field treatment on the shelf life quality of fresh walnuts was studied,in order to screen out the suitable freezing temperature and thawing method of fresh walnuts,and to provide theoretical and technical basis for the long-term freezing storage and timely thawing sales of fresh walnuts in production.The main findings are as follows:(1)The effects of four different freezing temperatures of 0℃,-10℃,-20℃and-40℃on the storage effect of fresh walnuts were studied.The results of temperature monitoring showed that the thawing times of fresh walnuts at room temperature were 35 min,57 min and 68 min,and the thawing times at low temperature were 95 min,240 min and 325 min respectively under different freezing temperature conditions;fresh walnuts in the control group were stored for 120 days at 0℃.When the temperature reaches 75%,the mildew rate reaches 75%,and the commercial value is lost;-20℃and-40℃can significantly inhibit the loss of fruit juice of’Wen 185’fresh walnut,so that it maintains a high water content,and the color,hardness,acidity and 21 kinds of characteristic flavor substances such as price,peroxide value,V_Eand so on were kept well;when stored for 6 months,the sensory scores at room temperature and low temperature reached 2.12 and 2.09 respectively,which better maintained the quality of nucleolus.(2)The effect of low pressure static magnetic field treatment on the thawing effect of fresh walnuts was discussed.Using the visual food magnetoelectric coupling processing system,the effects of different thawing time(A),thawing temperature(B)and magnetic field strength(C)on the juice loss rate,hardness and sensory indicators of fresh walnuts after thawing were studied respectively.The thawing process parameters of each single factor were analyzed.On this basis,the response surface design software was used to analyze the influence of the interaction of various factors on the thawing effect of fresh walnuts,and the process conditions suitable for thawing of’Wen 185’wet hard walnuts were determined:The thawing time was 4 h,the thawing temperature was 4°C,and the magnetic field strength was 4 m T.(3)The effect of low-pressure static magnetic field treatment on the shelf-life quality of fresh walnuts was analyzed.After the frozen fresh walnut fruit is thawed and stored at a low temperature of 4°C for 72hours,the low-pressure static magnetic field treatment can effectively inhibit the loss of juice and the decrease of the water content of the frozen walnut fruit,so that the nucleolus remains better yellow or dark yellow,and the seed coat is easy to peel off.The fresh walnut has a clear fragrance and sensory quality of2.15.The results provide a theoretical and technical basis for the production of medium and long-term frozen fresh walnuts for timely thawing and sales. |
PDF Full Text Request