Study On Processing Quality Changes During Potato Storage

Qingshu No.9,Qingshu No.168,Kexin No.1,Jizhang No.8,Zhuangshu No.3 and Longshu No.6 were used as the raw materials in this research.To study its dry matter,starch,reducing sugar,texture,browning rate and potato starch particle morphology,crystal structure,amylose content,transparency,solubility,swelling degree,starch gel texture in the storage time of 0-180 d,and the activities of polyphenol oxidase(PPO),starch phosphorylase,amylase and granule bound starch synthase(GBSS)in potato were measured.Analyzed the change rule of each index over time and carry out correlation analysis,and evaluated the processing suitability of potato in the quality state during storage.The following results were obtained:1.During the storage period,the contents of dry matter and starch in potato showed a trend of increase-decrease-increas-decrease;and contrary to reducing sugar content;the hardness value of fresh and cooking potato showed a linear decreasing trend.The L* value decreases during the entire storage period,but at the time of determination at each measuring point the rate of browning varies.2.During the storage period,the potato starch particles were oval or round,smooth surface,complete particles,no cracks,particle size in the range of 20-80μm;the crystal structure of starch particles showed a typical B-type crystal,and the particle morphology and crystal structure did not change with the change of storage time.The amylose content and the texture characteristics of starch gel showed a trend of increase first and then decrease.Transparency during the storage period shows a “V” trend.Solubility showded a trend of increasing first and then decreasing,and swelling did not change significantly with storage time,but was opposite on the change of starch content.3.The PPO and GBSS activity of potato showed a trend of increasing first and then decreasing during storage.Starch phosphorylase and amylase were less active in tuber dormancy and have higher activity when tubers begin to germinate.Then,with the growth of shoots,the activity of starch phosphorylase and amylase begins to decrease.4.Correlation analysis showed that there was a significant positive correlation between dry matter and starch.There was a positive correlation between reducing sugars and amylases.There was a positive correlation between fresh potato hardness and dry matter content.There was a significant positive correlation between fresh potato firmness and potato mud hardness.There was a negative correlation between the lightness L* value and PPO activity.There was a highly significant positive correlation between amylose content and GBSS activity.5.During the early storage period,the potato had higher dry matter and starch content and lower reducing sugar content.At this time,the potato was suitable for the production of whole potato powder,potato starch and fried food processing.During the middle storage period,the potato was suitable for the production of potato mud baked products.During the middle and late period of storage,the dry matter content had lowest,at this time the potato was suitable for canned industrial processing.At the end of storage,it was no longer suitable for processing.From the perspective of starch characteristics,the content of amylose was high when stored for 30-90 days,and it was suitable for processing vermicelli and vermicelli products.The degree of starch swelling was higher when stored for 30-60 days,and it was suitable for fillers,emulsifiers,etc.The transparency of starch in the early stage of storage was relatively large,and it was suitable for use in food processing such as beverages and jellies.