动态温湿度条件下糙米主要储藏品质指标变化

Changes in Main Storage Quality Indices of Brown Rice under Dynamic Temperature and Humidity Conditions

目的:本实验通过研究温湿度动态变化条件下糙米储藏过程中主要生理生化指标的变化,为优化糙米安全储藏条件提供基础数据。方法:将初始水分质量分数分别为15%、17%、19%和21%的糙米,分别在低温动态组(L组)、中温动态组(M组)、高温动态组(H组)3种不同温湿度动态条件下模拟储藏240 d,观测糙米发芽率、脂肪酸值、过氧化氢酶活力等主要品质指标和低场核磁共振水分迁移规律的变化。结果:在240 d的储藏过程中,随着储藏时间的延长,发芽率、过氧化氢酶活力呈显著下降趋势,脂肪酸值呈先上升后下降的趋势,糙米品质发生劣变。初始水分质量分数高的糙米其自由水的质量分数要高于初始水分质量分数低的糙米;高温会引起水分迁移混乱,吸附水向自由水迁移,自由水质量分数升高。水分质量分数越高、温度越高,糙米就越容易发生霉变变质。储藏温度对发芽率、脂肪酸值、过氧化氢酶活力有显著影响,初始水分质量分数对发芽率、脂肪酸值有显著影响。结论:初始水分质量分数和储藏温度对糙米的品质特性影响显著。为防止糙米发生品质劣变,正常水分(质量分数15%)和偏高水分(质量分数17%、19%)的糙米安全储藏期为120 d,低温或中温可以延长正常水分糙米储藏期至180 d。

Objective:To investigate the changes in the main physiological and biochemical indexes of brown rice during storage under dynamic temperature and humidity conditions for the purpose of establishing the optimal conditions for safe storage of brown rice.Methods:Samples of brown rice with initial moisture contents of 15%,17%,19%and 21%were stored for 240 days under dynamic conditions of low(Group L),medium(Group M)and high(Group H)temperatures.The changes in germination rate,fatty acid value and catalase activity were examined and the change in moisture migration pattern was assessed by low field nuclear magnetic resonance(LF-NMR).Results:The germination rate and catalase activity decreased significantly with the increase of storage time,the fatty acid value increased first and then decreased,and the quality of brown rice was deteriorated.The higher the initial moisture content in brown rice,the higher the free water content.High temperature could cause disordered water migration,transforming bound water into free water and consequently increasing free water content.The higher the moisture content and the temperature,the more susceptible brown rice is to mildew.The storage temperature had a significant effect on germination rate,fatty acid value and catalase activity.The initial moisture content also had a significant effect on germination rate and fatty acid value.Conclusion:Both initial moisture content and storage temperature have significant effects on the quality characteristics of brown rice.To prevent the occurrence of quality deterioration,the safe storage period for brown rice with normal(15%)and high moisture content(17%and 19%)is 120 days.Low or medium temperature can extend the safe storage period for brown rice with normal water(15%)to 180 days.