【作者】 王璐；

【导师】 周建新；

【作者基本信息】 南京财经大学 ， 食品科学， 2011， 硕士

【摘要】 小麦粉是我国人民的主要食物来源,由于其颗粒细小,与外界接触面积大,吸湿性强,导热性特差,一旦条件适宜,微生物生长繁殖,极易发热霉变,甚至产生霉菌毒素,对小麦粉的食用品质和安全构成威胁。在一定的温、湿度下,对于安全水分或接近安全水分的小麦粉,其储藏稳定性与包装材料有关,因此,本论文通过不同包装材料小麦粉的模拟储藏,研究包装材料对储藏小麦粉的微生物和品质的影响,从而选择一种能够保障储藏小麦粉品质和食用安全的包装方式。实验结果表明:(1)包装材料对储藏小麦粉水分和品质的影响70%RH,18～20℃条件下,不同包装材料储藏小麦粉的水分均有不同程度的下降,其中以布袋的水分下降最多,这与布袋的阻湿性能低,水分易挥发有关,而高阻隔包装袋凭借良好的阻湿性能,其储藏小麦粉水分最为稳定,水分下降幅度最小,仅为0.6%。纸塑袋和纳特真涂抹袋内储藏小麦粉水分分别下降0.9%和1.0%。30℃储藏的小麦粉水分的变化趋势与18～20℃的基本一致,但比同期的18～20℃储藏小麦粉水分低,原因是储藏温度高,包装材料的透湿性能增加。显著性分析表明,储藏时间对小麦粉水分为极显著影响因素,而包装材料对小麦粉水分为非显著影响因素。在70%RH条件下,不同包装材料储藏小麦粉的脂肪酸值均呈现上升趋势,但上升的幅度不同,同一包装材料下,30℃储藏小麦粉脂肪酸值比同时期18～20℃储藏小麦粉的高。储藏结束时,18～20℃以布袋包装的储藏小麦粉脂肪酸值最低,纸塑袋内小麦粉脂肪酸值最高,30℃以纳特真涂抹袋内脂肪酸值最低,高阻隔包装袋内小麦粉脂肪酸值最高。显著性分析表明,包装材料和储藏时间对小麦粉脂肪酸值为极显著影响因素,各包装材料的储藏小麦粉的脂肪酸值与储藏时间基本呈一元正线性关系,与水分、储藏时间均呈二元正线性关系。(2)包装材料对储藏小麦粉微生物区系的影响70%RH、18～20℃条件下,不同包装材料下的储藏小麦粉细菌量随着储藏时间的延长而呈现不同程度的下降,至储藏结束,由千数量级下降为百数量级,略有差异,其差异与小麦粉的水分含量有关。各包装材料下储藏小麦粉细菌量与储藏时间呈不同的一元线性负相关。30℃下,储藏开始75天,各包装材料下储藏小麦粉细菌量迅速减少,之后减少速率趋于平缓。30℃各包装材料下储藏小麦粉的细菌量较18～20℃下降速度快。方差分析表明,储藏时间对细菌量的影响是极为显著的,而包装材料对储藏小麦粉细菌量为非显著影响因素。18～20℃,各包装材料储藏小麦粉的霉菌量均呈现先上升后下降的趋势,至储藏结束时,霉菌量比初始时下降,下降幅度同样与小麦粉的水分含量有关。白曲霉始终为绝对优势菌,但比例有所不同。(3)不同包装材料下小麦粉脂肪酸值与微生物和水分相关性除30℃储藏时,布袋包装中的储藏小麦粉脂肪酸值与菌落总数呈负相关外,其它各包装材料储藏小麦粉脂肪酸值与细菌量和水分均呈现不同的二元线性关系。在18～20℃储藏时,纸塑袋包装、高阻隔包装小麦粉的脂肪酸值还与水分、霉菌量呈现二元线性关系。(4)不同储藏条件下小麦粉包装材料的选择通过对不同包装材料下储藏小麦粉相关指标平均变化速率的分析,在70%RH、18～20℃下,布袋包装储藏小麦粉水分、细菌量和霉菌量下降速率最大,而脂肪酸值的上升速率最小,因此,布袋为最适合储藏小麦粉的包装;而在70%RH、30℃下,纳特真涂抹袋为最适合储藏小麦粉的包装方式。更多还原

【Abstract】 Wheat flour is the main source of food for our people. Wheat flour has small granule,large contact area with the environment,high hygroscopicity and poor thermal conductivity characteristics. Once the conditions that microorganisms may grow and reproduce are suitable,microorganisms cause mildew of wheat flour and even produce mycotoxins which will impact seriously on the eating quality and safety of wheat flour.In a certain temperature and humidity,the stored stability of wheat flour which has or close to safe moisture content is related to packing materials. In this paper,simulated storage of wheat flour was carried out for investigating the influences of all kinds of packing materials that can guanrantee qualities and safety of stored wheat flour.The experimental results showed that:(1)Influence of packing materials on moisture content and qualities of stored wheat flourAt 70%RH and 18～20℃,the moisture content of stored wheat flour in different packing materials had different degree drop and the moisture content of wheat flour in cloth bag declined most because it was worse barrier to water transmission and moisture content was easily volatile.While the moisture content of the wheat flour in high barrier packing bag which had a good wet resistance property had the most stable and the smallest drop,only 0.6%. The moisture contents of the wheat flour in paper-plastic bag and paper -plastic bag with fungicides dropped 0.9% and 1.0% respectively.The change tendency of the moisture content of stored wheat flour at 30℃was the same as at 18～20℃,but lower than the same period of 18~20℃,because the moisture permeability of packing materials was enhanced as storage temperature was high.The variance analysis showed that storage time had very significant influence while packing materials had no significant influence on moisture content of stored wheat flour.At 70%RH,the fatty acid values of stored wheat flour in different packing materials presented a similar rising trend which was concerned with packing materials. In the same packaging material,fatty acid value at 30℃was higher than that of the same period at 18～20℃. At the end of storage,the fatty acid value of wheat flour in cloth bag was the lowest and that of wheat flour in paper-plastic was highest at 18～20℃,while the fatty acid value of wheat flour in paper -plastic bag with fungicides was the lowest and that of wheat flour in high barrier packing bag was highest at 30℃.The variance analysis showed that packing materials and storage time had very significant influence on fatty acid value. The fatty acid value of stored wheat flour had positive linear relationship with storage time and showed positive bivariate linear relationships with moisture content and storage time in a packing material. (2) Influence of packing materials on microbial flora of stored wheat flourAt 18℃,70% RH,as the time prolonged,the arobic bacterial counts of stored wheat flour in these packaging materials descended in varying degrees,and at the end of storage,the arobic bacterial counts decreased from 103 to 102,but had slightly differences which were related with moisture content.In these packaging materials, the arobic bacterial counts of stored wheat flour had negative linear relationship with storage time but in varying degrees.The arobic bacterial counts of stored wheat flour sharply descended from the beginning to 75 days and softly descended after in these four packaging materials at 30℃. The arobic bacterial counts of stored wheat flour decreased faster at 30℃than that of 18～20℃. The variance analysis showed that storage time had very significant influence and packing materials had no significant influence on the arobic bacterial counts of stored wheat flour.The mould counts of stored wheat flour in different packging materials increased first and decreased then in varying degrees.The mould counts of wheat flour stored at the end was decreased compared with at the start.The different decline was related with moisture content. A. candidus was dominant strain from beginning to end,but propotion of it had differences.(3)The correlation analysis between the fatty acid values and microorganism and the moisture content of stored wheat flour in different packing materialsThe fatty acid values of stored wheat flour in these four packing materials presented binary linear relationship with the aerobic bacterial counts and the moisture content,except the fatty acid value in cloth bag had a negative correlation with the aerobic bacterial counts at 30℃. At 18～20℃,the fatty acid values of stored wheat flour in paper-plastic bag and high barrier bag had binary linear relationships with moisture content and the mould count.(4)The choice of packaging materials in different storage conditionsThe cloth bag was the most suitable for stored wheat flour at 70%RH and 18～20℃for the stored wheat flour in cloth bag had the maximum rates of decrease in moisure content,the arobic bacterial counts and the mould counts,and had the minimum rate of increase in fatty acid value,while the paper-plastic bag with fungicides was the most appropriate for stored wheat flour at 30℃through the analysis of the average rate of change on the relevant indicators of the stored wheat flour,microbial flora.更多还原