Font Size: a A A

Study On Autolysis Mechanism Of Agaricus Bisporus

Posted on:2015-05-03Degree:MasterType:Thesis
Country:ChinaCandidate:T P ZhaoFull Text:PDF
GTID:2271330461498661Subject:Food processing and safety
Abstract/Summary:PDF Full Text Request
As the most widely cultivated mushroom, Agaricus bisporus is delicious and nutritious, it’s very popular in the world. Agaricus bisporus contents 90% water or more, and it’s hard to preserve due to lacking of protecting structure and strong physiological metabolism. The hardness will be declined once the Agaricus bisporus is antolyzed. All these shortcomings seriously affect the circulation of fresh Agaricus bisporus in the market, and cause serious economic losses to the farmers. It’s necessary to study the mechanism of autolysis related substances and affecting factors, so that we can clarify its participation in major composition and the mechanism for further research and application of the regulation to reduce losses. To solve this problem, we carried out research in the following three aspects by using Agaricus bisporus as experimental materials:(1) Changes in cell wal material content and cell wal material related enzyme activity of autolysing Agaricus bisporus, (2) Changes in the process of membrane lipid peroxidation during Agaricus bisporus autolysis. (3) The effect on cell ultrastructure during Agaricus bisporus autolysis. At the same time we analyzed the correlation between these indices and autolyzed indicators, so that we can find out the most important factor of Agaricus bisporus autolysis. After that we can find out the appropriate way to extend the shelf life and improve its storage quality.The results showed that:1 The Agaricus bisporus was rapidly autolyzed when stored at 20℃. It was completely autolyzed after stored 8d. The autolysis progress can be controlled when stored at 5℃.2 The cell wall material of Agaricus bisporus was composed of chitin, β-glucan, cellulose and pectin. The chitin and β-glucan content were relatively high. The content of chitin, water-soluble pectin and EDTA-soluble pectin was increased, the content of β-glucan, cellulose and Na2CO3-soluble pectin was decreased during autolysis. Correlation analysis showed that the majority of cell wall material content and autolysis index had significant or very significant correlation. Under 20℃ storage conditions, the order of relevance:β-glucan content> hemicellulose content> cellulose content> Na2CO3-soluble pectin content> EDTA-soluble pectin content> water-soluble pectin content> chitin content. Under 5℃ storage conditions:chitin content> hemicellulose content> Na2CO3-soluble pectin content> EDTA-soluble pectin content> β-glucan content> cellulose content.3 The active oxygen metabolism balance was broken during storage. CAT, POD activity were decreased, H2O2 content and O2-.level were gradually rise. Accumulation of reactive oxygen species triggered membrane lipid peroxidation, LOX activity gradually increased, unsaturated fatty acid content decreased, MDA content in the final product of membrane lipid peroxidation gradually increased, MDA destroyed the cell membrane structure, lysosome membrane was broken, the balance between enzymes and substrates was broken too, the membrane permeability increased, the cell contents escaped from the cells which accelerated Agaricus bisporus autolysis process eventually. Correlation analysis showed that, unsaturated fatty acid content> H2O2 content> O2--generation rate> MDA content under 20℃ storage. O2-. generation rate> unsaturated fatty acid content> MDA content> H2O2 content under 5℃ storage.4 It had different factors that affceting the autolysis of Agaricus bisporus under 2 storage temperatures. We found that low temperature can suppress the progress of Agaricus bisporus autolysis, and in 20℃, the cell wall material was rapidly consumed due to cell wall material related enzymes, that lead to rapid autolysis. Agaricus bisporus has slow metabolism when it was stored in 5℃, and low temperature inhibited the activity of cell wall material related enzymes. The Agaricus bisporus was slightly browning during storage at 5℃ after 14d, and the whole progress of autolysis was not completely displayed.20℃storage was more representative, we can only explain the early period of autolysis when the Agaricus bisporus was stored at 5℃. Similarly, at 20℃, Agaricus bisporus’s membrane lipid peroxidation was more thorough and the progress was more complete. However, it can’t explain the change in membrane structure, fatty acids content, active oxygen content and activity of membrane lipid peroxidation related enzyme when stored at 5℃ which illustrated that low temperature significantly inhibited membrane lipid peroxidation occurring.5 The fresh Agaricus bisporus had dense tissue, tight connections among cells, and each cell was full of cytoplasm and organelles. Every single cell had the number of intracellular organelles which structure can be observed clearly. After 4d storage, a large number of intracellular nutrients especially pectin were consumed and the connections between cells was not tight any more. The structure of cells was relatively complete, but reduced cell wall thickness leading to changes in cell morphology. At the same time the number of intracellular organelles was declined and the structure was fuzzy, the nucleus disappeared, many vacuoles appeared. After 8d storage, Agaricus bisporus’s organization was completely lost, many cells were stacked together. The cell wall was badly damaged, and the cell contents, the distribution of cell wall fragments were scattered around the damaged cells.
Keywords/Search Tags:Agaricus bisporus, Autolysis, Cell wall material, Membrane lipid peroxidation, Ultrastructure
PDF Full Text Request
Related items