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Study On The Preservation Technology Of Green Walunt And Its Kernel

Posted on:2021-08-26Degree:MasterType:Thesis
Country:ChinaCandidate:J ZhouFull Text:PDF
GTID:2481306608454904Subject:Master of Agriculture
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The shelf life of fresh walnut is short after harvest.Green walunt is easy to be rotten and browning in the process of storage and transportation.The lack of commercial storage and preservation technology has become a key problem restricting the extension of its industrial chain.In this paper,’Liaoning No.1’fresh green walnut was used as the test material.The storage properties of fresh walnut in different harvest periods,the storage quality and physiological changes of fresh walnut in different storage methods,and the preservation during the transportation of quick-frozen walnut kernel were studied in order to provide technical guidance for the large-scale storage and processing of factory fresh walnut.The specific research results were divided into three aspects:1.The effects of different storage methods on the quality of fresh walnut were studied.The fresh walnuts were stored at 0-3℃ for 75 days with 500 mg·L-1 ethephon and 3 μL·L-11-methylcyclopropene combined with spontaneous gas conditioning.The results showed that ethylene treatment could significantly inhibit the rot rate and weight loss rate of fresh walnut fruit(P<0.05),better maintain the appearance of fresh walnut,maintain the total phenol content and polyphenol oxidase activity of green peel,slow down the decrease of soluble protein,reducing sugar and crude fat of walnut kernel,and also inhibit the increase of acid value and peroxide value of walnut oil.2.The suitable harvesting time of ’Liaoning No.1’ fresh walnut was determined.The effects of fresh walnuts harvested on August 5,15 and 25 in small school refrigerators and on August 10,20 and 30 in large company refrigerators at 0-3℃ were compared.The storage of fresh walnuts at different harvesting periods was studied by comparing the color difference,respiratory intensity,green skin rate,kerneling rate,water content,rotting rate and sensory evaluation of fresh walnuts.The results showed that the fresh walnuts harvested in the third batch in late August showed low respiratory intensity just after harvesting,and the nutrient content at the end of storage was also higher than that in the first two batches,whether in the factory pilot test or in the school laboratory.Therefore,it is speculated that the late August is the best harvesting time of ’Liaoning No.1’ green walnut.3.The preservatives for walnut kernel were screened.Simulating the packaging and logistics environment of foam boxes and ice blocks in e-commerce sales,the natural preservatives and antioxidants were used to treat the walnut kernel and stored at low temperature for 0-3℃.The results showed that:the walnut kernel packed with ice cream and foam box at 0-3℃ shelf life of 2-3 days,while the shelf life of walnut kernel treated with compound preservative was 7-8 days.The walnut kernel treated with compound preservative has better oxidation stability and antibacterial property,which can effectively prevent the oxidation of walnut kernel and prolong the shelf life of walnut kernel during low temperature storage.The preservative combination was 0.2 g·L-1 poly lysine hydrochloride,0.5 g·L-1 nisin,0.15 g·L-1 natamycinand 6 g·L-1 D-isoascorbic acid sodium.The results can be used as a re ference for the e-commerce logistics of the factory.
Keywords/Search Tags:Green walnut, harvest time, spontaneous air conditioning, ethephon, 1-MCP, walnut kernel, fresh keeping
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