Effect of hexanal on the shelf life of fresh apple slices.

In this work the effects of hexanal, as a component of packaging atmosphere, on the shelf life of and evolution of naturally occurring microbial populations in fresh apple slices during storage at 4 and 15 degrees C were evaluated. Although hexanal had no bactericidal effects, in all conditions considered, this volatile molecule significantly extended the shelf life. In fact, the presence of hexanal in the storage atmosphere (at 4 degrees C) totally inhibited mesophilic bacteria and considerably prolonged the lag phase of psychrotrophic bacteria. Also, at 15 degrees C, hexanal strongly inhibited molds, yeasts, and mesophilic and psychrotrophic bacteria. Moreover, hexanal led to a yeast selection favoring species having a reduced spoilage potential due to their prevalent respiratory activity. When added to a modified atmosphere (70% N(2) and 30% CO(2)), this molecule was also very effective in preventing browning reactions for at least 16 days at 15 degrees C. No changes in hue angle values were observed in samples packaged in modified atmosphere with hexanal, even after 16 days of storage at 4 degrees C.     

Application of hexanal,E-2-hexenal,and hexyl acetate to improve the safety of fresh-sliced apples

The aims of this work were to evaluate the effects of different concentrations of hexanal, (E)-2-hexenal, hexyl acetate, and their mixtures on the fate of pathogenic species such as Escherichia coli, Salmonella enteritidis, and Listeria monocytogenes inoculated in model systems as well as the antimicrobial activity against the target species of the chosen molecules when added to the packaging atmosphere of inoculated fresh-sliced apples. The result obtained in this work pointed out the potential use of compounds such as hexanal, (E)-2-hexenal, and hexyl acetate for both the extension of shelf life and an improvement of hygienic safety of "minimally processed foods". In fact, hexanal, (E)-2-hexenal, and hexyl acetate had a significant inhibitory effect against pathogen microorganisms frequently isolated from raw materials (E. coli, S. enteritidis, and L. monocytogenes) when inoculated in both model and real systems. In this last condition, these compounds, at the levels used (150, 150, and 20 ppm for hexanal, hexyl acetate, and (E)-2-hexenal, respectively), displayed a bactericide effect on L. monocytogenes and they exhibited significant extensions of lag phase of E. coli and S. enteritidis inoculated at levels of 10(4)-10(5) CFU/g.     

反式-2-己烯醛对猕猴桃贮藏过程扩展青霉生长的抑制作用

为研究反式-2-己烯醛对扩展青霉生长及展青霉素产生的抑制作用。选取反式-2-己烯醛和研究报道的8种具有抑菌效果的物质对5株扩展青霉进行体外抑菌试验,研究反式-2-己烯醛的抑菌效果并测定其最小抑菌浓度,然后进行猕猴桃活体试验,通过测定硬度、可溶性固形物、可滴定酸、维生素C、pH值等指标研究反式-2-己烯醛对猕猴桃品质的影响,并采用高效液相检测抑菌试验前后猕猴桃活体中展青霉素含量,最终通过扫面电子显微镜观察反式-2-己烯醛对5株扩展青霉形态的影响。结果反式-2-己烯醛与8种抑菌物质相比,反式-2-己烯醛抑菌效果最好,能够完全抑制5株扩展青霉生长且得到对5株试验菌的最小抑菌浓度(MIC,minimuminhibitoryconcentration);反式-2-己烯醛能够极显著降低扩展青霉对猕猴桃果实硬度、可滴定酸、维生素C的的影响(P0.01),并且对猕猴桃硬度、可溶性固形物、pH值和还原糖及维生素C含量等没有极显著影响(P0.01),极显著降低了染菌猕猴桃果实的腐烂率(P0.01),较好的保持了猕猴桃品质,经反式-2-己烯醛处理的染菌猕猴桃均没有展青霉素检出;扫面电子显微镜显示5株试验菌出现菌丝皱缩、折叠、干瘪,孢子生成减少现象。研究反式-2-己烯醛对扩展青霉生长及展青霉素产生均具有很好的抑制作用,可为开发具有抑菌作用可替代农药的天然产物提供理论基础。     

酶型时间温度指示器监测冷鲜猪肉贮藏货架期

为了更为便捷的指示记录食品在冷链运输过程中的品质变化情况,该文选择冷鲜猪肉的挥发性盐基氮作为其品质监控的指标,通过试验研究贮藏过程中冷鲜猪肉的品质变化动力学特性并应用本课题组研制的新型碱性脂肪酶型时间温度指示器（TTI）设计相匹配的TTI体系配方;在此基础上,分别在5种恒温模型（0、3、10、15和20℃）及4种变温模型（TP1: 3℃ 3 d,15℃ 1 d,20℃ 0.5 d,23℃ 0.5 d,10℃ 2 d,以此循环;TP2: 23℃ 0.5 d,10℃ 2.5 d,以此循环;TP3: 23℃ 0.5 d,20℃ 0.5 d,10℃ 2 d,以此循环;TP4: 23℃ 0.5 d,10℃ 2 d,3℃ 3 d,以此循环）条件下对设计的TTI以及冷鲜猪肉进行贮藏试验,评估该TTI对贮藏过程中冷鲜猪肉品质变化的指示特性。结果表明,通过分析冷鲜肉的动力学特性,得出动力学参数,进而通过活化能匹配原则可以选择出最优TTI;并且该TTI在恒温和变温条件下最终的显色带扩散值的极差分别为1.86、2.13,表明其显色变化具有良好的稳定性及其与冷鲜猪肉品质变化的高度匹配性,该TTI在恒温和变温条件下,可有效指示冷鲜猪肉在贮藏过程中基于挥发性盐基氮的品质变化历程。     

高氧对巨峰葡萄冷藏和货架期品质的影响

本文研究了高氧气调冷藏对巨峰葡萄品质、质构、贮藏性和货架寿命的影响。结果表明,与空气冷藏相比,高氧气调抑制了葡萄可溶性固形物、可滴定酸、维生素C含量和果柄耐拉力的降低,改善了葡萄的硬度、弹性、凝聚性、咀嚼性、风味和外观,减少了水分损失、腐烂、落果率和果梗褐变。与40%O₂+30%CO₂气调相比,除弹性、凝聚性、水分损失、落果和外观无显著差异外,80%O₂处理葡萄的保鲜效果更好。     

Biosynthesis of trans-2-hexenal in response to wounding in strawberry fruit

Wounded strawberry fruit produces a diverse group of volatile compounds including aldehydes, alcohols, and esters derived from the lipoxygenase (LOX) and hydroperoxide lyase (HPL) pathways. Because the wound volatiles may play an important role in plant-fungal interaction, the goal of this study was to develop a greater understanding about the biosynthesis of the major wound volatile, trans-2-hexenal (t-2-H), produced by strawberry fruit upon wounding. To that end, composition and quantity of total and free fatty acids of control and wounded strawberry fruit were analyzed. In addition, activities of the key enzymes, LOX and HPL, and production of C6 aldehydes were determined. Intact strawberry fruit did not produce detectable t-2-H which is derived from alpha-linolenic acid (18:3). However, in response to wounding by bruising, strawberry fruit emitted t-2-H and its precursor cis-3-hexenal (c-3-H). The level of total lipid 18:3 in the fruit increased 2-fold in response to wounding, whereas free 18:3 declined slightly ( approximately 30%). At 10 min following wounding, fruit exhibited a 25% increase in LOX activity, which leads to the production of 13-hydroperoxyoctadecatrienoic acid (13-HPOT) from 18:3. The activity of HPL, which catalyzes formation of cis-3-hexenal from 13-HPOT, increased 2-fold by 10 min after wounding. Thus, during a 15 min period after wounding, free 18:3 substrate availability and the activity of two key enzymes, LOX and HPL, changed in a manner consistent with increased c-3-H and t-2-H biosynthesis.     

不同冰温条件对长期贮藏牛肉品质和货架期的影响研究

该研究旨在探究标准冰温（实验室恒温条件,-2～0 ℃）和商业冰温（工厂冰温库（-4～4 ℃））对长期贮藏牛肉品质的影响,以此明确当前商业冰温条件对牛肉的保鲜效果。试验测定了贮藏期间（20周）两种冰温条件下真空包装牛肉的pH值、肉色、微生物菌落数、挥发性盐基氮（total volatile base-nitrogen,TVB-N）、脂肪氧化和感官品质等指标。结果表明：2种冰温条件下,牛肉在20周的贮藏期内均可以维持良好的肉色及感官品质。贮藏第9周时,商业冰温条件下牛肉样品的菌落总数和TVB-N值就已分别达到7.09 lg CFU/cm2和15.59 mg/100g。而标准冰温条件下的牛肉样品在贮藏期间其菌落总数始终低于7.00 lg CFU/cm2,TVB-N值在贮藏第12周时才超出限量阈值（≤15 mg/100 g）,达到16.66 mg/100 g。总体来看,标准冰温条件对真空包装牛肉的保鲜效果更佳,依据TVB-N值的限量标准,建议标准冰温和商业冰温条件下牛肉的货架期分别不超过9周和12周。     

精准温度控制对枸杞鲜果贮藏品质和香气成分的影响

为研究精准温控技术在枸杞鲜果保鲜中的应用效果,将枸杞分别装入泡沫箱（Control Check,CK）、泡沫箱+蓄冷剂（冰温）和精准温控箱+蓄冷剂（相温）中,记录箱内温度,结合贮藏期间枸杞的品质变化,通过主成分分析法对3组枸杞进行综合评价,并对不同处理香气成分进行分析。结果表明,精准温度控制后箱体内部温度更低,且温度波动保持在0.1 ℃以内,CK组、冰温组、相温组枸杞出现发霉腐烂现象的时间分别为10、20、40 d;贮藏40 d后,相温组枸杞的腐烂率为4.11%,远低于CK组的14.85%,色差低于3,亮度达34.12,可溶性固形物含量、可滴定酸含量、维生素C含量、类胡萝卜素含量分别较CK组高0.65个百分点、0.03个百分点、4.34 mg/100g、2.90 mg/g,相温组枸杞有效抑制腐烂率和失重率的增加,延缓色差的升高和亮度的降低,保持较高的可溶性固形物、可滴定酸、维生素C和类胡萝卜素含量,经主成分得分分析后得到3组枸杞的品质排序为相温组、冰温组、CK组,且精准温度控制贮藏的枸杞醛类、萜类等有利香气成分相对含量更高。因此,精准温度控制技术有利于枸杞鲜果的冷藏保鲜,其中相温贮藏效果更好。研究结果为枸杞鲜果精准温控保鲜提供参考。     

Extending storage life of fresh-cut apples using natural products and their derivatives

Prevention of browning of apples slices has been difficult to achieve because of the rapidity of the enzymatic oxidation of phenolic substrates even under reduced atmospheric pressure storage. Combinations of enzymatic inhibitors, reducing agents, and antimicrobial compounds containing calcium to extend storage life were tested to decrease the browning of Red Delicious apple slices stored at 5 and 10 degrees C under normal atmospheric conditions. Treatments were devised to prevent browning for up to 5 weeks at 5 degrees C with no apparent microbial growth using dipping solutions of compounds derived from natural products consisting of 4-hexylresorcinol, isoascorbic acid, a sulfur-containing amino acid (N-acetylcysteine), and calcium propionate. Analyses of organic acids and the major sugars revealed that the slices treated with the combinations of antibrowning compounds retained higher levels of malic acid and had no deterioration in sugar levels at 5 and 10 degrees C, indicating that higher quality was maintained during storage.     

猪肉剩余货架期快速预测电化学设备的设计与试验

针对生鲜猪肉等短货架期食品对微生物快速检测的巨大需求,该研究依据微生物呼吸作用的电子传递规律,采用原电池的工作原理,结合构建的微生物生长预测模型(4~30℃)决定系数R2为0.9954以上,试制了操作简单、方便快捷的生鲜猪肉剩余货架期的电化学预测设备,并采用Labview编程语言开发了信号采集和数据分析软件。结果表明该设备检测时间为20 min,可预测4~30℃范围内生鲜肉的剩余货架期,预测准确度为1.02~1.06,研究结果为采用电化学方法预测食品中微生物含量及其货架期提供理论参考。     

基于ISTA测试研究电商包装对莲雾货架品质的影响

莲雾果实皮薄肉脆,采后流通中极易产生机械损伤,严重影响果实货架品质。为了维持莲雾在物流运输中的货架品质,减少机械损伤,该研究基于ISTA 6-AMAZON.COM-SIOC TYPE A(ISTA 6A)测试标准模拟4种常用电商包装方式下（P1：瓦楞纸箱+单层网套、P2：瓦楞纸箱+双层网套、P3：瓦楞纸箱+发泡聚乙烯（expanded polyethylene,EPE）内衬和P4：泡沫箱+双层网套）莲雾果实的运输情况,并分析模拟测试后莲雾货架期（15℃,8 d）品质变化规律。结果表明,当外包装相同,缓冲形式不同时,双层网套（P2）组莲雾果实呼吸强度变化最为平缓,果皮亮度值为最低值32.86,果肉褐变指数（browning index,BI）与单层网套和EPE内衬相比上升了62.35%,其上升速率最慢,丙二醛含量（malondialdehyde,MDA）、过氧化物酶（peroxidase,POD）活性和多酚氧化酶（polyphenol oxidase,PPO）活性始终处于较低水平,货架品质显著好于单层网套（P1）和EPE内衬（P3）(P<0.05),原因在于单层网套的缓冲保护作用较...     

伽马辐照对冰藏大黄鱼品质和货架期的影响

为探索伽马辐照处理对冰藏鲜鱼的保鲜效果,试验分析了大黄鱼冰藏期间微生物、生化指标和感官指标的变化,探讨了低剂量辐照处理（1 kGy和2 kGy）对大黄鱼品质和货架期的影响。结果表明,辐照处理后大黄鱼的菌落总数、假单胞菌和产硫化氢细菌数量显著减少;在贮藏期间辐照处理的大黄鱼各种菌数量始终比对照组少;辐照处理可显著减缓大黄鱼挥发性盐基氮和三甲胺的增加;但会促进脂肪的氧化,2 kGy组大黄鱼在贮藏后期能闻到脂肪酸败的味道,而 1 kGy组和对照组大黄鱼始终没有闻到这种味道。辐照处理可增加大黄鱼的货架期,对照组货架期为17 d,而辐照剂量为1 kGy和2 kGy的货架期可延长至30 d和26 d。本试验为辐照商业化应用提供了技术依据。     

葡萄籽提取物对无淀粉火腿肠保质期的影响

为了探讨葡萄籽提取物对无淀粉火腿肠保质期的影响,将葡萄籽提取物配成质量分数为0.05%、0.10%、0.15%和0.20%的溶液,添加于火腿肠中,于0～4℃贮藏,测定细菌总数、pH值等的变化。结果表明：在贮藏过程中,添加葡萄籽提取物火腿肠的感官品质明显好于对照样;处理样的细菌总数、pH值、挥发性盐基氮（TVB-N值）、硫代巴比妥酸（TBA值）和黄色值（b*）明显低于对照组,亮度（L*）和红色值（a*）明显高于对照组;葡萄籽提取物的浓度越高,对细菌总数、pH值、L*的影响越明显,但对TVB-N值、TBA值、a*和b*的影响没有明显规律;从生产成本和使用效果综合考虑,建议生产中使用质量分数为0.20%的葡萄籽提取物。     

BP神经网络结合有效积温预测速冻水饺变温冷藏货架期

为了解决速冻食品在温度波动贮藏过程中的货架期预测问题,准确监测其品质变化趋势,该文以速冻水饺为研究对象,将其在-28℃～-12℃进行冷藏,测定酸价、过氧化值、饺皮水分含量、亨特白度等理化指标,并结合感官评价与有效积温理论,应用BP神经网络技术预测速冻水饺的货架期。并与动力学模型预测结果进行比较。结果表明,测试集样本的距货架期终点积温的预测值与实际测定值拟合度较好,最大误差为3.29%,模型验证最大误差为2.74%。BP模型的距货架期终点时间的最大误差为3.45%低于传统动力学模型预测的误差(5.62%)。BP神经网络预测模型为速冻食品货架期预测提供了一种新途径。     

贮藏温度和气调包装对鸡蛋保鲜效果的影响

为了延长鸡蛋保鲜期,研究在室温(25℃)和冷藏(4℃)条件下不同配比CO2、O2、N2三元混合气体包装对鸡蛋保鲜效果影响,结果表明:鸡蛋采用气体组分为50％CO2、7％～11％O2、39％～43％N2的气调包装贮藏保鲜,室温下贮藏30d仍保持AA级,而不包装室温贮藏30 d降到了B级;不包装冷藏也可延长鸡蛋保鲜期,但失重率相对较高;气调包装与冷藏结合对鸡蛋的保鲜效果不是2种处理的保鲜效果之和,与气调包装室温贮藏的保鲜效果相似.50％CO2、7％～11％O2、39％～43％N2三元气体包装、室温贮藏可实现鸡蛋就地贮藏,试验为鸡蛋贮藏保鲜提供参考.     

贮藏温度对冷破碎番茄浆品质变化的影响

为探讨冷破碎番茄浆在贮藏过程中的品质变化,以指导冷破碎番茄浆的贮藏,该文研究了其在0、25和37℃条件下贮藏150 d的品质变化,并对产品中主要指标的变化进行了动力学分析。25和37℃贮藏条件下冷破碎番茄浆中氨基酸、总糖、蔗糖、果糖、维生素C含量和颜色指标（亮度L*、红值a*和黄值b*）均显著下降,而5-羟甲基糠醛（HMF）含量、褐变度（BD）和总色差ΔE显著增加,其中总氨基酸、总糖、维生素C、HMF和BD的变化均符合一级动力学模型;而且HMF含量与BD变化呈线性关系,符合零级动力学模型。但是番茄红素和可溶性固形物含量变化不显著,而酸度随温度和时间的增加呈增加趋势。0℃贮藏条件下,除维生素C含量显著下降外,上述其他指标均无显著变化。表明高温贮藏显著降低冷破碎番茄浆的品质,而低温贮藏可有效保护冷破碎番茄浆的品质。     

外源乙烯处理对黄冠梨果皮褐变和货架期品质的影响

为了避免黄冠梨果实在低温贮藏（0 ℃左右）条件下果皮褐变的发生,该研究采用5、20和100 μL/L外源乙烯对黄冠梨进行贮前处理,以0 ℃贮藏下无外源乙烯处理作为对照组,以采后恒温至30 ℃、逐步降温至0 ℃处理作为程序降温组。通过外源乙烯处理组与对照及程序降温组的对比,探讨采后外源乙烯处理对黄冠梨果皮褐变与果实品质的影响。结果表明,不同浓度的外源乙烯处理均能完全抑制褐变的发生,且表皮无伤害,而程序降温组的发病指数为10%,对照组则高达37.6%。货架期结束时（6 d）外源乙烯处理组的果实硬度与对照组差异显著（P < 0.05）。外源乙烯各处理组果实含水率均高于对照及程序降温组（P < 0.05）,利用低场核磁共振技术检测发现对照组自由水含量最高,5和100 μL/L外源乙烯处理组自由水含量较低。与对照组和程序降温组比较,外源乙烯处理对黄冠梨果实中可溶性固形物、可滴定酸、可溶性糖和抗坏血酸等果实品质指标都能起到提高或者维持的效果,其中5 μL/L处理浓度的效果较优。研究结果表明,贮前外源乙烯处理是一种既能抑制黄冠梨果皮褐变又能保持果实货架期品质的高效、简便的技术。     

贮藏时间和温度对蓝莓花色苷微胶囊品质的影响

为了探究贮藏时间和温度对蓝莓花色苷微胶囊品质的影响,确定适宜的贮藏条件,该文研究微胶囊在?18、4和25℃下,贮藏6个月期间品质的变化。结果表明,以乳清蛋白联合多糖为壁材的微胶囊能确保贮藏期间花色苷被高效包封。贮藏期间微胶囊品质的下降可能是因分子间相互作用力减弱所致。贮藏3~4月间,微胶囊玻璃态转化温度出现大幅下降(P0.05),粉体稳定性变差。与其他贮藏温度相比,?18℃下贮藏可抑制微胶囊分子间相互作用力的减弱,使其具有更高的包埋产率(P0.05)和释放率(P0.05),保留更多的花色苷(P0.05)和其他酚类物质(P0.05)从而增强抗氧化活性(P0.05)。因此,花色苷微胶囊较适宜的贮藏时间为3个月,贮藏温度为?18℃。研究结果可为微胶囊的贮藏和应用提供理论依据。     

Effects of microwave heat, packaging, and storage temperature on fatty acid and proximate compositions in rice bran

The effect of microwave heat, packaging methods, and storage temperatures on proximate and fatty acid compositions of rice bran during 16 weeks of storage was examined. Freshly milled raw rice bran was adjusted to 21% moisture content and microwave heated for 3 min. Raw and microwave-heated brans were packed in zipper-top bags and/or vacuum-sealed bags and stored at 4-5 and/or 25 degrees C for 16 weeks. The moisture content decreased significantly from an initial 8.4 to 6.4% in microwave-heated samples regardless of packaging methods and storage temperatures. Protein, fat, linoleic, and linolenic contents did not change significantly in all raw and microwave-heated samples during 16 weeks of storage. The microwave-heated rice bran packed in zipper-top bags can be stored at 4-5 degrees C for up to 16 weeks without adverse effect on proximate and fatty acid composition quality under the conditions employed in this study.     

四种特色品种小苹果采后生理及耐贮性比较

探究四个特色小苹果品种采后生理品质及质地变化规律,为制定特色小苹果最佳贮藏货架期提供科学依据和理论参考。该研究以‘龙丰’‘金红’‘塞外红’‘乙女’4个特色小苹果为试验材料,在常温（20±1）℃条件下放置14 d,测定果实品质指标（硬度、可溶性固形物、可滴定酸、维生素C、乙醇和乙醛含量、乙烯释放量）以及穿刺参数（果肉硬度、果肉做功、破裂力、屈服力）和质地多面分析（Texture Profile Analysis）参数（脆裂性、内聚性、弹性、胶黏性、咀嚼性）等指标的动态变化,并对以上指标进行综合评分。结果表明不同品种小苹果果实的硬度、可滴定酸、维生素C含量随贮藏时间不断下降,可溶性固形物含量变化较小,其中‘龙丰’果实硬度、维生素C含量和可滴定酸含量下降均较低,常温贮藏性能优良;‘塞外红’刚采收时品质高,但在常温贮藏期间,硬度下降最大,品质下降较快,常温贮藏性能较差。‘金红’和‘乙女’硬度、维生素C含量下降也较大,且‘金红’和‘乙女’果实的乙醇、乙醛含量出现峰值,而其他小苹果的乙醇、乙醛含量均大体呈缓慢上升的趋势。不同品种小苹果果实的乙烯释放量呈现先增加后下降的趋势,均出现一个呼吸高峰,‘龙...