市售真空包装大米拆封后品质变化研究

Research on Quality Changes of Vacuum-Packed Rice Sold in the Market After Unsealing

大米是中国人的主食之一,居民采购的真空包装大米在拆封至全部食用完毕,期间的品质如何变化目前鲜有研究。研究在我国多个储粮生态区的大型连锁超市随机采集了42份真空包装大米,调查发现市售大米包装质量多为5 kg,保质期以12和18个月为主,粳米平均水质量分数14.4%,最高达15.6%,籼米水质量分数略低,平均在13.5%。42份真空包装大米拆封后在25℃、65%RH的环境进行模拟储藏,统计分析了3个月储藏期内大米食味品质和外观品质的变化,以及害虫和霉菌的感染情况。结果显示,在食味品质方面,储藏3个月后,59.52%(25/42)样品的食味值下降,其中33.33%(14/42)下降显著(P<0.05),且全部为粳米;71.43%(30/42)样品的直链淀粉质量分数升高,其中14.29%(6/42)升高显著(P<0.05),表明大部分样品的食味品质下降,尤其体现在粳米上。在外观品质方面,储藏3个月后,大米的垩白粒率(质量分数)、垩白度(投影面积百分率)、黄粒米率(质量分数)和白度均升高,而整精米率(质量分数)和Ym有所下降。此外,储藏期间未发现储粮害虫危害,但在水分高于14.4%的大米中存在霉菌孢子生长,但未达到危害程度,霉菌污染加快了食味值、整精米率(质量分数)的下降率和黄粒米率(质量分数)的升高率,对大米的食味和外观品质均有一定的影响。研究结果为企业市售大米包装规格和消费者合理食用时间等方面提供参考。

Rice is one of the staple foods of the Chinese people.There is little research on how the quality of the vacuum-packed rice purchased by residents is changed during the period after they are unpacked and consumed.In this paper,42 samples of vacuum-packed rice were randomly collected from large chain supermarkets in several grain storage ecological areas in China.It was found that most of the commercial rice packages were 5 kg,and the shelf life was mainly 12 months.The average moisture content of japonica rice was 14.4%,and the highest was 15.6%,while that of indica rice was slightly lower,with an average of 13.5%.After unpacking,42 samples of vacuum-packed rice were stored at 25℃and 65%RH.The results indicated that in terms of eating quality,after 3 months of storage,the eating value of 59.52%samples decreased,of which 33.33%decreased significantly(P<0.05),and all of them were japonica rice.The starch mass fraction of 71.43%samples increased,and 14.29%of them increased significantly(P<0.05).In terms of appearance quality,after storage for 3 months,the chalky grain rate(mass fraction),chalkiness(projected area percentage),yellow grain rice rate(mass fraction)and whiteness of rice all increased,while the whole polished rice rate(mass fraction)and Ym index decreased.In addition,no stored grain pest damage was found during storage,but mold spores grew in rice with a moisture content higher than 14.4%,but it did not reach the extent of damage.Mold pollution accelerated the decrease rate of taste value and polished rice rate(mass fraction),and the increase rate of yellow-grained rice rate(mass fraction),which had a certain impact on the taste and appearance quality of rice.Based on the research results of this paper,suggestions were made for enterprises in terms of packaging specifications of commercially available rice and consumers reasonable consumption time.