Zein-based anti-browning cling wraps for fresh-cut apple slices

The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials.     

Effect of Calcium Lactate, 4-Hexyl Resorcinol and Vacuum Packing on Physico-chemical, Sensory and Microbiological Qualities of Minimally Processed Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D₆ Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.     

迭香精油活性贴对鲜切猪肉保鲜效果的研究

目的 为了提高迷迭香精油(REO)的稳定性,开发出一种安全、便捷的实用型活性包装。方法 以迷迭香精油为活性成分,采用三步法(乳化、包埋、多层复合)制备出精油缓释活性贴,并验证其对鲜切猪肉的保鲜效果。结果 在4 ℃下,不同比例的迷迭香精油活性贴均可在一定程度上抑制鲜切猪肉的腐败变质,最佳处理效果的体积比为4∶6,贮藏至第6天时,猪肉的pH值、挥发性盐基氮(TVB–N)含量、硫代巴比妥酸(TBARS)值较空白对照(CK)分别降低了0.7 mg/g、0.073 1 mg/g、0.63 mg/kg;延缓了猪肉色度、汁液流失率、菌落总数(TVC)、感官品质的变化,可延长鲜切猪肉货架期2 d左右。结论 制备的缓释型活性贴具有稳定性好、操作简单易行的优势。作为绿色、可生物降解的包装材料,在食品保鲜领域具有潜在的应用价值。     

超高氧高阻隔膜气调包装对鲜切胡萝卜品质的影响

高氧气调包装是近年来研究较多的气调包装方式之一.研究了在不同储藏温度（4,15,25℃）下,高阻隔膜超高氧气调包装的鲜切胡萝卜品质变化规律（对照空气包装）.结果表明,超高氧气调包装显著增加了鲜切胡萝卜的失重率、呼吸强度,同时加速了维生素C、总胡萝卜素含量的损失,但能提高多酚类物质含量.总之,高阻隔膜超氧气调包装不能有效地维持鲜切胡萝卜的品质.     

Efficacy of thyme oil-alginate-based coating in reducing foodborne pathogens on fresh-cut apples

In this study, the inhibition of an alginate-based edible coating (EC) containing thyme oil (0.05%, 0.35% and 0.65%) was evaluated against Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus and Escherichia coli O157:H7 inoculated onto fresh-cut apples. To investigate the antibacterial mechanism of thyme oil, the constituent compounds of that were analysed by gas chromatography-mass spectrometry (GC-MS), and the cellular damage of pathogens was observed by scanning electron microscopy (SEM). Results showed that alginate-based EC containing thyme oil effectively inhibited the growth of pathogens on fresh-cut apples. GC-MS analysis revealed thymol (47.23%) as the major compounds in thyme oil. SEM showed that the cell membrane of foodborne pathogens was damaged by thyme oil, causing their inactivation. Treatment with alginate-based EC containing 0.05% thyme oil preserved the sensory characteristics of fresh-cut apples. Therefore, using alginate-based EC with thyme oil may represent a potential approach to preserve and enhance the safety of fresh-cut apples.     

Growth of Escherichia coli,Salmonella enterica and Listeria spp., and their inactivation using ultraviolet energy and electrolyzed water,on ‘Rocha’ fresh-cut pears

The present study aimed at evaluating the growth of Escherichia coli, Salmonella enterica, and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on ‘Rocha’ pear. Fresh-cut pieces were inoculated and incubated at 4–20 °C for 8 days. Inoculated pears were treated with UV-C (2.5–10 kJ/m²), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1–6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 °C reaching populations of 8.1–8.6 log cfu/g, in 24 h. At 8 °C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 °C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/g, while the best UV-C dose (7.5 kJ/m²) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears.     

壳聚糖-柠檬烯涂膜对鲜切哈密瓜贮藏品质的影响

目的 探究壳聚糖-柠檬烯涂膜对鲜切哈密瓜贮藏品质的影响。方法 以无菌蒸馏水和2%壳聚糖涂膜处理鲜切哈密瓜作为对照组,用2%壳聚糖复配0.1%柠檬烯涂膜处理鲜切哈密瓜作为实验组,在贮藏第0、1、3、5、7 d对鲜切哈密瓜的感官、硬度、呼吸强度、可溶性固形物含量、色差、维生素C含量、多酚氧化酶(polyphenol oxidase, PPO)活性、过氧化物酶(peroxidase, POD)活性、过氧化氢酶(catalase, CAT)活性、超氧化物歧化酶(superoxide dismutase, SOD)活性及菌落总数进行测定。结果 2%壳聚糖复配0.1%柠檬烯涂膜显著(P<0.05)减缓了鲜切哈密瓜果肉软化,可溶性固形物和维生素C含量的下降及色差值L^*、a^*、b^*的改变;抑制了鲜切哈密瓜的呼吸强度、PPO和POD活性,增强了SOD和CAT活性,并抑制了菌落的生长,有利于鲜切哈密瓜感官品质的维持。结论 2%壳聚糖复配0.1%柠檬烯涂膜处理鲜切哈密瓜可以降低鲜切哈密瓜贮藏期间的营养物质损耗,减缓果肉的衰老变质,较好地...     

臭氧对鲜切青花菜品质的影响

研究了臭氧水浸泡对鲜切青花菜品质的影响。用10mg /L的臭氧水将鲜切青花菜浸泡5 min和15 min后置入0℃冷库贮藏。在贮藏期间发现臭氧抑制了青花菜的黄化,延缓了青花菜中叶绿素的降解,抑制了类胡萝卜素的合成;同时增加了失重率,降低了叶绿素荧光比值Fm/Fv,但对Vc、蛋白质和总酸并没有影响。