Food corruption and spoilage caused by food-borne pathogens and microorganisms is a serious problem. As a result, the demand for antibacterial drugs in food packaging is growing. In this review, biodegradable and non-biodegradable materials for food packaging are discussed based on their properties. Most importantly, antibacterial agents are essential to inhibit the growth of bacteria in food. To keep food fresh and prolong the shelf life, different kinds of antibacterial agents were used. The composition and application of natural antibacterial agents and synthetic antibacterial agents are discussed. Compared with natural antibacterial agents, synthetic antibacterial agents have the advantages of low cost and high activity, but their toxicity is usually higher than that of natural antibacterial agents. Finally, future development of antimicrobial food packaging is proposed. It is an urgent problem for researchers to design and synthesize antibacterial drugs with high efficiency and low toxicity.

BACKGROUND Maize is frequently subjected to simultaneous water (drought or waterlogging) and heat (HS) stresses during grain formation in southern China. This work examined the effect of high temperature combined with drought (HD) or waterlogging (HW) during grain formation on the starch physicochemical properties of two waxy maize hybrids, namely Suyunnuo5 (SYN5) and Yunuo7 (YN7). RESULTS Heat stress enlarged the starch granule size, and water stresses aggravated this effect. Heat stress reduced the ratio of small molecular weight fractions for both hybrids, and HD aggravated this reduction only in SYN5. Relative crystallinity in SYN5 was increased by stresses but in YN7 it was unaffected by HD, reduced by HS, and increased by HW. Fourier‐transform infrared (FTIR) spectrometry results showed that the 1045/1022 cm−1 ratio in SYN5 was not influenced by HW but was increased by other stresses, and that in YN7 it was increased by all stresses, with the highest value induced by HW. Peak viscosity was decreased, whereas gelatinization temperatures and retrogradation percentage were increased by all of these stresses. These effects were exacerbated by combined heat and water stresses. The maximum decomposition rate was severely increased by HW. CONCLUSION Drought or waterlogging at grain formation stage aggravated the detrimental effects of HS on the starch physicochemical properties of waxy maize. © 2020 Society of Chemical Industry

Heat stress increased the pasting viscosities and retrogradation percentage of starch by causing change in granule size, amylopectin chain length distribution and crystallinity, and the effects observed were more severe with earlier introduction of heat stress after pollination. © 2017 Society of Chemical Industry.

Core Ideas Heat stress decreased the translocation of dry matter from vegetative organs after pollination. Heat stress during grain filling accelerated leaf senescence of waxy maize. This study provides leaf senescence and dry matter translocation data for waxy maize production. Waxy maize (Zea mays L. sinensis Kulesh) is frequently exposed to high temperatures (higher than 35.0°C) during grain filling in southern China. This pot trial was conducted to study the effect of heat stress during grain filling on grain yield, dry matter (DM) accumulation and translocation, and leaf senescence of plants. Post‐pollination plants of Suyunuo 5 and Yunuo 7 (waxy maize varieties) were planted under high temperature (35.0°C) and ambient temperature conditions (daytime temperatures during grain filling were 29.0 and 28.2°C in 2014 and 2015, respectively).The decrease rate of grain yields for Suyunuo 5 and Yunuo 7 were 31.3 and 21.9% due to the reduced grain number and weight, respectively, indicating that Suyunuo 5 was more sensitive to heat stress. Heat stress decreased dry matter accumulation after pollination (DMA) . The photosynthate of vegetative organ post‐pollination translocated to grain decreased by 36.1 and 55.9% for Yunuo 7 and Suyunuo 5, respectively. However, the translocation amount and rate of assimilates pre‐pollination increased, with greater increase observed in Suyunuo 5. The malondialdehyde (MDA) content was increased by heat stress 25 and 20 d after pollination in Yunuo 7 and Suyunuo 5, respectively. Leaf chlorophyll (Chl), carotenoid (Car), and soluble protein contents were decreased, and the activities of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], and peroxidase [POD]) were suppressed by heat stress in both varieties. The findings suggested that reduced DMA and accelerated leaf senescence under heat stress post‐pollination result in the grain yield loss.

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