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。     

Antioxidant and modified atmosphere packaging prevention of discoloration in pork bones during retail display

The objective of this study was to evaluate the ability of antioxidants to prevent discoloration in pork rib bones. Pork rib bones were removed from carcasses, frozen (−20 °C, 24 h), split lengthwise, exposed to antioxidant solutions (ascorbic acid, citric acid, propyl gallate or ascorbic/EDTA mix), packaged (modified atmosphere [80% O₂ and 20% CO₂] or air), then displayed in a retail case at 4 °C for 8 days. Dark pigment formation was visually evaluated during the display period. Instrumental color was determined at the end of the 8-day display period. Visual bone discoloration increased over time for all treatments. After 2 days of display, samples treated with propyl gallate were visually redder, less discolored and less green/black than samples treated with other antioxidants. After 8 days of display, propyl gallate-treated samples had higher a* and b* values, as well as chroma (intensity). However, this difference was no longer large enough to be visually detected.     

某灯具LED灯珠封装胶体失效分析

针对某发光二极管（LED）灯具在老化过程中,灯珠封装胶体的变色甚至脱落问题,开展失效分析。通过LED灯珠切片分析、X射线透视、红外光谱分析、红外热像分析、有限元分析等技术手段,并设计相关验证试验分析灯珠封装胶体失效的原因。结果表明,灯珠封装胶体靠近芯片和灯珠外表面变色严重;灯珠内部结构一致,均串联连接;失效和正常灯珠封装胶体均为有机硅树脂材料,灯具整体散热性能对灯珠失效没有影响;有限元分析和模拟验证表明封装有机硅树脂材料的失效是LED芯片热量和腔体内积聚热量双重作用的结果;建议将灯具支撑柱进行开孔或直接制成网状结构,以让反射罩和支撑柱之间阻隔散热的静止空气流动起来,然后再根据实际情况进行优化。     

Packaging for freshness and the prevention of discoloration of fish fillets

Fillets of various kinds of fish are currently packed in thin films (e.g. polyvinyl chloride) for sale at supermarkets; however, these fillets are not necessarily fresh or of good quality. Packed fillets must be certified for safety, freshness and quality, because sensory judgement is difficult. In order to understand how the freshness and colour of red fish meat can be retained, the methods of packaging were examined. It was known that for freshness the packed fillets must be kept at a low temperature, but discoloration of red meat could not be prevented by this alone. However, discoloration of red-meat fish, such as yellowtail and oceanic bonito, can be prevented by packing with nitrogen gas (N₂).     

Effects of gold plating on the resistance to high temperature discoloration of the cavity for ceramic packages

The effects of thickness and types of gold plating on the resistance to high temperature discoloration of gold plating on cavity surface of ceramic package were investigated. It was found that the thicker gold plating, the less discoloration degree for ceramic packages. Non-cyanide gold plating performed better resistance to high-temperature aging than cyanide gold plating. The relationship between the gold plating thickness and the amount of diffused Ni to the gold plating of ceramic packages with Au/Ni and Au/Ni-Co platings after heating at 420℃ for 15 min was also studied. When the gold plating thickness reach 2.0 μm and 1.6 μm for Au/Ni and Au/Ni-Co plating systems, respectively, no discoloration was observed on the gold plating surface of cavity, and the corresponding diffused Ni amounts (mass fraction) are 1.0% and 0.4%, while the diffused Co to the gold plating is 0.04%.     

紫铜管氧化变色的防治

对紫铜管氧化变色的机理、产生的原因与防治措施进行了分析和探讨。