Carbon Monoxide in Modified Atmosphere Packaging Affects Color, Shelf Life, and Microorganisms of Beef Steaks and Ground Beef

ABSTRACT— Color and microbiology of steaks and ground beef stored in 0.4% CO, 30% CO2, and 69.6% N2 (but removed from the modified atmosphere before display) were compared with product displayed immediately after packaging in polyvinyl chloride film (only atmospheric oxygen). Storage of ground beef, loineye, inside round, and tenderloin steaks for up to 35 d in 0.4% CO resulted in typical initial bloomed color. Compared with product exposed to only oxygen, storage of ground beef and loineye steaks in 0.4% CO decreased color stability, whereas color life increased for tenderloin and inside semimembranosus muscles. No steaks having acceptable color had spoilage levels of microbes (≥log 7). Thus, carboxymyoglobin formed from 0.4% CO did not mask microbial spoilage.     

甲基锡及其复合热稳定剂在PVDC中的应用

用变色法测定了甲基锡、甲基锡/环氧大豆油和甲基锡/硬脂酸钙3种热稳定剂对PVDC的热稳定作用.结果表明:3种热稳定剂对PVDC的热稳定作用是甲基锡/硬脂酸钙＞甲基锡/环氧大豆油＞甲基锡,甲基锡/环氧大豆油复合热稳定剂的最佳组成为(1:1)～(2:1),甲基锡/硬脂酸钙复合热稳定剂的最佳组成为1:3.     

电气设备镀银面变色机制分析与处理

实际应用中发现镀银后的铜排出现严重变色问题,影响电气设备的可靠运行.对制造过程发现的问题进行深入分析,指出其形成原因是与镀银工艺、储存防护不当和项目管理密切相关,最后提供了具体处理方案.     

锦氨纤维高温模压色变问题的改善

探讨了采用尼龙抗热色变整理剂NK 001改善锦氨白坯布及染色布高温热压模色变问题的应用工艺及效果。结果表明,浸轧20~40 g/L尼龙抗热色变整理剂NK 001后,锦氨白坯布的ASTM白度下降率由原先的43.32%降低至20%左右;配合菲诺酸性B LV系列染料,可将压模前后总色差值控制在1.0,最大力份差在7%以内,可满足浅色系的匀染性和压模热变色需求。此外,浸轧NK 001不会影响染色样的耐水洗色牢度。     

淀粉热变色性质的研究

研究了淀粉在直接加热、与水组合后加热时的色泽变化。淀粉的热变色温度范围为190~210℃,水浸胀后,淀粉的热变色温度范围下降。     

Post-harvest kernel discoloration and fungi activity in long-grain hybrid,pureline and medium-grain rice cultivars as influenced by storage environment and antifungal treatment

Milled rice grade is diminished as the quantity of discolored kernels increases. This study evaluated the magnitude of kernel discoloration and relationship to fungal growth for long-grain hybrid (XL 753), long-grain pureline (Roy J.) and medium-grain (Titan) rice, exposed to storage moisture contents (MCs) of 16 and 21%, wet basis, temperatures of 20, 30, 40 °C, and durations up to 16 weeks. Impact of postharvest treatments with the antifungal agents, natamycin and sodium chloride, on rice discoloration and fungal growth was compared with untreated (control) samples. Subsamples were taken every four weeks to determine total fungal counts, discoloration, and water activity. Rice stored at 40 °C had six-to eleven-times more discoloration than at 20 °C. Increased storage duration significantly increased discoloration. Discoloration was not different between MC levels. Discoloration was significantly lower by sodium chloride treatment, while natamycin was not effective compared to control. Rice samples treated with sodium chloride also had significantly less water activity (mean a_w = 0.73) compared to samples treated with natamycin (mean = 0.84) and control samples (mean = 0.83). Hybrid rice had significantly less discoloration compared to pureline and medium-grain. Fungal counts were similar across all cultivars. Increasing temperature and duration decreased fungal count. An inverse relation between fungi and discoloration suggests microbe activities did not explain discoloration. The findings provide important information to growers and processors on conditions necessary to maintain rice quality.     

四甲基哌啶醇生产过程中异常问题的处理

2,2,6,6-四甲基-4-哌啶醇有时久置易变色,本文通过GC-MS联用技术分析了变色问题产生的根本原因,是由于未完全还原的哌啶酮氧化所致,并以硼氢化钠为还原剂,通过二次还原的方法处理变色哌啶醇,效果较好。     

水性木器封闭底漆的配方探讨

为了解决水性木器色漆涂膜快速变色的问题,使用水性封闭底漆是一种简单有效的方法。测试了封闭底漆中不同水性成膜物、助溶剂、底材润湿剂对封闭性能的影响,探讨了水性木器涂料变色的原因。     

平衡营养盐变色原因分析及预防改进措施

对于近期营销环节频繁出现平衡营养盐变色的质量问题,通过大量的试验工作,找到了平衡营养盐变色的原因和影响因素。针对变色的原因提出了相应的预防措施和改进方法。     

甲基红褪色光度法测定自来水中的二氧化氯

探讨以二氧化氯(ClO2)氧化甲基红(MR)褪色光度法测定自来水中ClO2的新方法。在c(MR):c(ClO2)=6.4:1、pH4.0～4.5、温度25℃、反应时间40min条件下,以λmax=518nm测定ΔA518。结果其线性方程为ΔA518=-1.7845c(ClO2)+1.5228(r=0.992),表观摩尔吸光系数ε=1.2×105L/(mol.cm),适用测定范围为0.0004～0.80mg/L,DL为0.0036mg/L;ClO2氧化MR褪色反应具有一级反应的特点,在25℃的动力学方程为ln[c∞/(c∞-c)]=-0.000689t+2.263669、Ea为87.3kJ/mol、t1/2为16.8min。本法经自来水和消毒剂中ClO2含量的测定结果表明,相对标准偏差为2.43%～3.83%,加标回收率为98.2%～103.2%。经F检验和t检验,本法与对氨基-N,N-二乙基苯胺(DPD)光度法不存在显著差异(P=0.05),测定结果符合分析的要求。