Effect of Processing Under Ultraviolet Light on the Shelf Life of Fresh-Cut Cantaloupe Melon

ABSTRACT: The effect of processing cantaloupe melon under ultraviolet-C (UV-C) radiation on storage properties of the cut fruit at 10 °C was compared with post-cut UV-C fruit treatment and the untreated control. Cutting fruit under UV-C light induced a hypersensitive defense response that resulted in increased accumulation of ascorbate peroxidase relative to the other 2 treatments. Fruit processed under UV-C radiation had the lowest esterase activity throughout the storage period. Lipase activity was higher in post-cut treated fruit than fruit processed under UV-C light and the control fruit. Lipase activity, however, decreased rapidly in fruit processed under UV-C and was undetectable after 7 d of storage. Human sensory aroma evaluation indicates reduced rancidity, and instrumental texture measurements suggested improved firmness retention in fruit cut under UV-C radiation. The treatment also reduced respiration during cut fruit storage. UV-C was effective in reducing yeast, mold, and Pseudomonas spp populations in both treatments. Fresh-cut pieces from whole melon cut under UV light had lower populations of aerobic mesophilic and lactic acid bacteria relative to the control and post-cut treated pieces. Results indicate that while post-cut application of UV improved shelf life of cut cantaloupe melon, cutting fruit under UV-C radiation further improves product quality.     

Edible Active Coatings Based on Pectin,Pullulan, and Chitosan Increase Quality and Shelf Life of Strawberries (Fragaria ananassa)

Edible active coatings (EACs) based on pectin, pullulan, and chitosan incorporated with sodium benzoate and potassium sorbate were employed to improve the quality and shelf life of strawberries. Fruits were washed, disinfected, coated by dipping, packed, and stored at 4 °C for 15 d. Application of EACs reduced (P < 0.05) weight loss and fruit softening and delayed alteration of color (redness) and total soluble solids content. In contrast, pH and titratable acidity were not affected (P > 0.05) throughout storage, and ascorbic acid content was maintained in pectin‐EAC coated strawberries. Microbiological analyses showed that application of EACs reduced (P < 0.05) microbial growth (total aerobic counts, molds, and yeasts) on strawberries. Chitosan‐EAC coated strawberries presented the best results in microbial growth assays. Sensory quality (color, flavor, texture, and acceptance) improved and decay rate decreased (P < 0.05) in pectin‐EAC, pullulan‐EAC, and chitosan‐EAC coated strawberries. In conclusion, EACs based on polysaccharides improved the physicochemical, microbiological, and sensory characteristics, increasing the shelf life of strawberries from 6 (control) to 15 d (coated fruits).     

Effect of an Edible Nanomultilayer Coating by Electrostatic Self-Assembly on the Shelf Life of Fresh-Cut Mangoes

This work aims at evaluating the effect of an alginate-chitosan nanomultilayer coating, obtained by electrostatic layer-by-layer self-assembling, in the quality and shelf life of fresh-cut mangoes. Coated and uncoated fresh-cut mangoes were stored under refrigeration (8 °C) for 14 days. The changes in mass loss, titratable acidity, pH, ascorbic acid content, total soluble solids, malondialdehyde content, browning rate, and microbial count were evaluated during storage. At the end of the storage period, lower values of mass loss, pH, malondialdehyde content, browning rate, soluble solids, microorganisms’ proliferation, and higher titratable acidity were observed in the coated mangoes. The nanomultilayer coating did not improve the retention of vitamin C during storage of fresh-cut mangoes. Results suggest that chitosan-alginate nanomultilayer edible coating extends the shelf life of fresh-cut mangoes up to 8 days.     

茶多酚/海藻酸钠膜对鲜切猕猴桃品质的影响

为了延长鲜切猕猴桃的货架期和保持其新鲜品质,本试验研究了不同浓度茶多酚/海藻酸钠涂膜处理对(4±0.5)℃贮藏鲜切猕猴桃的可溶性固形物、色泽、总叶绿素、抗坏血酸、总酚和细菌总数的影响。试验分为对照组(Control),海藻酸钠处理组(T0),1.0%茶多酚/海藻酸钠组(T1),1.5%茶多酚/海藻酸钠组(T2)和2.0%茶多酚/海藻酸钠组(T3)。结果显示,在(4±0.5)℃贮藏12d,T0处理可减缓可溶性固形物含量和总叶绿素含量降低的速度,对鲜切猕猴桃的L*值和a*值无显著影响。T1、T2和T3处理可显著抑制抗坏血酸含量和总酚含量的下降,并显著降低鲜切猕猴桃表面的细菌总数(TPC),使TPC在贮藏12 d时保持在106 CFU/g以内。然而,T2和T3处理显著降低了猕猴桃片的L*值和a*值。研究结果表明,当膜液中茶多酚的质量分数为1.0%时,可较好的保证鲜切猕猴桃的品质。     

切分方式对鲜切哈密瓜品质和活性成分含量的影响

本实验将哈密瓜切分成梯形、方块和片状,置于10 ℃贮藏72 h,研究不同切分方式对鲜切哈密瓜贮藏期间品质及总酚和γ-氨基丁酸（γ-aminobutyric acid,GABA）含量的影响。结果表明：鲜切处理促进了哈密瓜L值、a值、b值、硬度、可溶性固形物质量分数和抗坏血酸含量的下降及菌落总数和透明率的上升,且损伤程度越大,其变化幅度越大。同时,鲜切处理可显著诱导苯丙氨酸解氨酶（L-phenylalanine ammonialyase,PAL）及谷氨酸脱羧酶（glutamate decarboxylase,GAD）活力、总酚及GABA含量和1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力的上升（P＜0.05）,以切分损伤强度最大的切片处理组PAL、GAD活力及DPPH自由基清除能力最高,酚类物质和GABA积累最多。综上,切分处理虽可加速鲜切哈密瓜品质的下降,但同时可促进酚类和GABA等生物活性成分的积累,提高其抗氧化活性。     

光照处理对鲜切薄皮甜瓜货架期品质的影响

评价光照处理对鲜切薄皮甜瓜货架期品质的影响。研究以绿宝甜瓜为原料,将鲜切薄皮甜瓜在5 ℃冷藏柜中光照处理5天,将白色光照处理设定为对照组,比较红色、蓝色、绿色光照处理和避光处理对鲜切甜瓜失重率、可溶性固形物含量、可滴定酸含量、丙二醛含量、果肉硬度、褐变度、颜色和风味的影响。结果显示,蓝色光照处理的光源光谱位于442 nm的主波长轨迹上,光源纯度接近100%,强度为(128±17.10) Lux。与对照组样品相比,蓝光光照处理降低鲜切甜瓜褐变程度10.70%,降低产品的失重率3.76%,减少果肉细胞的破裂,提高产品硬度60.60%;并且蓝光光照处理延缓鲜切甜瓜风味劣变。因此,在销售陈列过程中利用蓝光光照处理不仅维持鲜切甜瓜原有质地、颜色等外观特征,还减缓风味的劣变现象,所以蓝光光照处理有利于延长鲜切薄皮甜瓜的货架期。     

不同处理对西州蜜瓜货架期品质变化的影响

为研究不同处理对西州蜜瓜货架期品质的影响,以西州蜜17 号哈密瓜为试材,分别采用1.5% CaCl2 处理,于保鲜库（1.0～2.0 ℃）中贮藏;近冰温处理,于（-2.0～-1.0 ℃）的冰温库中贮藏;果实干化后近冰温结合1.5% CaCl2 处理,于冰温库（-2.0～-1.0 ℃）中贮藏。通过测定其在货架期间的商品率、呼吸强度、原果胶含量以及过氧化物酶（peroxidase,POD）、过氧化氢酶（catalase,CAT）活性等指标,分析各处理西州蜜瓜在贮藏过程中品质的变化规律。结果显示,近冰温及近冰温结合CaCl2 处理均能提高西州蜜瓜的商品率,有效抑制果实的呼吸强度、保持果实的硬度、延缓原果胶含量的下降,推迟果实呼吸高峰的出现,提高了POD 和CAT 的活性。综上,近冰温结合CaCl2 处理抑制了西州蜜瓜的软化,最大限度地保持了果实的新鲜品质,可作为西州蜜瓜规模化贮运保鲜的实用技术。     

Viscoelastic Behavior of Melon Tissue as Influenced by Blanching and Osmotic Dehydration

ABSTRACT: Viscoelastic properties of melon tissue exposed to steam blanching and osmotic dehydration (atmospheric or under vacuum) in glucose aqueous solutions were analyzed in a dynamic rheometer using oscillatory shear and creep tests. The storage modulus (G') greatly exceeded the viscous modulus (G') for raw and treated melon tissues, but the elastic component was partially lost because of processing. Blanching caused less than a 1 -fold decrease in G', whereas osmotic dehydration resulted in approximately a 3-fold decrease in G'relative to the untreated melon. Both moduli showed a weak dependence on frequency, with greater slope of the G'frequency lines for treated samples. A mechanical model, consisting of a spring in series with 2 Voigt elements and a dashpot element, properly predicted the creep compliance response for all melon samples. In general, overall compliance significantly increased by the treatments. The instantaneous elastic compliance and the viscoelastic compliances were the most sensitive viscoelastic parameters for distinguishing the differences in cell wall structure among osmotically dehydrated sample at atmospheric pressure and the tissues exposed to the other osmotic treatments. In contrast, G'modulus did not show an ability to evidence these structural differences because there were no significant differences in the G'values of osmotically dehydrated tissues at atmospheric pressure or in vacuum, with or without calcium addition.     

渗透脱水对真空油炸辣椒脆片品质的影响

为研究渗透脱水预处理对辣椒脆片品质的影响,以湖南大红椒为原料,将辣椒渗透处理后真空油炸,研究渗透时间、料液比、渗透液含盐率等因素对辣椒脆片感官品质、色泽、含油率和脆度的影响。结果表明,辣椒脆片最佳工艺条件为渗透液含盐率6%、料液比1∶12（g/g）、渗透时间10 h、真空油炸温度90 ℃、油炸时间20 min、脱油时间10 min。由此方法加工得到的辣椒脆片色泽均匀,表面完整,咸甜适中,口感清爽而不油腻,其含油率、脆度及感官评分分别为6.67%、1 119.40 g、85.60。     

真空腌制条件对猪肉食盐渗透规律及品质变化的影响

以猪肉为原材料,探讨了不同真空度以及真空腌制时间对其在真空腌制过程中的食盐渗透规律及品质变化的影响。实验数据表明：随着真空度及腌制时间的增大,食盐内渗量以指数方式增长,猪肉水分含量不断减小,并在6 h左右分别达到渗透平衡;猪肉在腌制过程中一直保持增重且增重率随腌制时间的延长而极显著增大;猪肉食盐渗透速率显著减小,食盐渗透速率常数随真空度的增大而先增后减,并在0.08 MPa下达到最大值0.977。在品质变化方面,真空度对猪肉的pH值没有显著影响,盐溶液中可溶性蛋白含量随真空度的增大先增后减且在0.08 MPa下达到最大值;在真空腌制过程中,猪肉的L*值和b*值不断增大,a*值不断减小,嫩度显著提高;硬度、弹性和咀嚼性不断增大,恢复性逐渐减小,粘聚性先减小后增大。     

可食性壳聚糖复合涂膜对干豆腐货架期的影响

壳聚糖是一种理想的防腐涂层材料,主要探索可食性壳聚糖复合涂膜的最适配方,以及可食性壳聚糖复合涂膜延长干豆腐货架期的效果。采用可食性壳聚糖涂膜剂对干豆腐进行保鲜处理,通过单因素试验和正交试验对干豆腐涂膜进行配方和工艺的优化。在常温下以干豆腐样品的感官评价、菌落总数为衡量指标,确定干豆腐涂膜的保鲜效果。通过正交试验设计和验证试验确定干豆腐最佳涂膜保鲜配方和工艺:壳聚糖添加量为1.6%、柠檬酸添加量为1.5%、乳酸链球菌素(Nisin)添加量为0.04%、氯化钙添加量为0.8%、甘油添加量为1.0%,在80℃下涂膜2 min,并对涂膜处理后的干豆腐进行保鲜密封包装。在常温条件下,普通包装保质期达到4 d。     

淀粉-壳聚糖可食性复合薄膜保鲜布林的研究

本文主要研究了不同种类的淀粉与壳聚糖复合所形成的被膜对于布林的保鲜效果。分别用木薯淀粉,土豆淀粉,玉米淀粉与壳聚糖制成不同涂膜液对布林进行涂膜处理,在常温(15～25℃)下储藏。涂膜的布林在贮藏期间,其水分损失,硬度,可溶性固形物,总酸度的变化均小于对照组, 并且可延长保质期3～7d。就不同的淀粉成分而言,对于布林的保鲜作用,土豆淀粉-壳聚糖复合薄膜的保鲜作用最佳,玉米淀粉-壳聚糖复合薄膜的作用优于木薯淀粉-壳聚糖复合薄膜。     

Osmotic Dehydration of Fruit: Influence of Osmotic Agents on Drying Behavior and Product Quality

Different osmotic solutions, with or without low quantities of added NaCl, were tested to evaluate their effects on the characteristics of the osmosed apples (chosen in our experiences as a fruit “model”). Water loss and water activity of final product were affected not only by the a_w of the osmotic agent but also by the gain of solids in the sample. At the same time of treatment, solid gain depended on chemical composition of the syrups and the shape of the samples. Addition of small quantities of NaCl to osmotic solutions increased the driving force of the drying process.     

Suitability of Aloe Vera and Gum Tragacanth as Edible Coatings for Extending the Shelf Life of Button Mushroom

Button mushroom have a short postharvest shelf life compared to most vegetables, due to a very high metabolic activity and high water content. This makes them prone to microbial spoilage and to exhibit enzymatic browning. In this research, the effects of aloe vera, gum tragacanth, and combination of both as edible coatings on the shelf life and postharvest losses of mushrooms were studied. Physical characteristics, general appearance (color and texture), weight loss, and carbohydrate percentage were evaluated during storage. Mushrooms were stored at 4, 10, and 15 °C for 13 days and physicochemical characteristics were analyzed after 2, 4, 6, 8, 10, and 13 days of storage. During cold storage, the uncoated mushrooms showed rapid weight loss, color changes, and accelerated softening while mushrooms treated with aloe vera gel, gum tragacanth, and the combination of both significantly delayed these phenomena. Among different coatings, the combination of aloe vera and gum tragacanth was more effective.     

Effects of Vacuum Impregnation with Calcium Lactate and Pectin Methylesterase on Quality Attributes and Chelate-Soluble Pectin Morphology of Fresh-Cut Papayas

Vacuum impregnation was used to improve the quality attributes of fresh-cut papayas. Vacuum pressure of 5 kPa was applied for 5 min, then calcium lactate (1%, w/w) and pectin methylesterase (PME) (15 U/ml), alone and in combinations (calcium lactate plus PME), were vacuum impregnated into fresh-cut papaya cubes. Papaya cubes were stored at 4 °C, and the quality of fresh-cut papaya was studied at intervals for 8 days. The hardness and chewiness levels of fresh-cut papayas that were treated with calcium lactate and PME were 8.02 and 7.83 times of untreated fresh-cut papayas at day 8, respectively. After vacuum impregnation, colour of fresh-cut papayas changed significantly (P < 0.05) and an overall weight loss was observed as well. Chelate-soluble pectin (CSP) was extracted and its content correlated well with texture properties of fresh-cut papayas. Qualitative and quantitative analyses of CSP were conducted using atomic force microscopy. The proportion of chain widths greater than 45 nm had increased 35.0% in fresh-cut papayas vacuum impregnated with calcium lactate and PME at the end of storage. The results indicate that a combination of calcium ions and PME was able to maximally preserve the quality attributes of fresh-cut papayas and extend the shelf life.     

不同预冷方式对西兰花货架期品质的影响

本文研究了不同预冷方式对西兰花货架期品质的影响。将三组西兰花分别做如下三种预冷处理:冷库预冷(对照)、冰预冷、冷水预冷。西兰花中心品温度降至(1±1) ℃后,将西兰花从箱中取出后将西兰花放入温度为(20±1) ℃的库中贮藏。取降至(1±1) ℃的西兰花作为初值,之后每24 h取一次样,用于各种指标的测定。测定结果表明:与冷库预冷比较,冰预冷和冷水预冷处理可以有效抑制西兰花黄化,保持西兰花的色泽和良好的感官品质;提高了西兰花V_C含量、叶绿素和硫代葡萄糖苷含量,贮藏至4 d,冰预冷和冷水预冷处理西兰花的V_C含量要比CK处理分别高出15.6%和39.2%,叶绿素含量分别是CK组的1.87倍和2.44倍,硫代葡萄糖苷的含量仍能达到0.71 mg/g;抑制了西兰花电导率和丙二醛(MDA)含量的上升;提高了西兰花抗坏血酸过氧化物酶(APX)、超氧化物岐化酶(CAT)和过氧化物酶(POD)的活性,其中冷水预冷的西兰花POD活性变化最为显著,保持在一个很高的水平,清除了西兰花体内的H₂O₂和过氧化物、促进了抗氧化系统中的物质,增强了西兰花的抗氧化能力。冰预冷和冷水预冷处理可提高西兰花感官品质,延缓西兰花衰老,延长货架期2~3 d。     

可食用膜保鲜阳山水蜜桃的初步研究

采用多糖（ＣＭＣ－Ｎａ）、蛋白质（ＳＰＩ）以及脂（硬脂酸）所形成的可食用膜，通过Ｌ_９（３~４）正交试验进行桃果实保鲜研究。极差分析表明：桃果实在贮藏期间的失重率主要受ＳＰＩ与ＣＭＣ－Ｎａ含量的控制，而ＣＭＣ－Ｎａ的含量是影响烂果率的主要因素。     

渗透脱水膜包装对南美白对虾干制品品质的影响

以感官评价、硫代巴比妥酸值(TBARS)、总挥发性盐基氮含量(TVB-N)、复水率和质构等为指标研究渗透脱水膜包装(ODS)脱水过程中南美白对虾的品质变化,并与热风干燥法(HAD)比较。结果表明:随脱水时间的延长,ODS处理的对虾水分含量先下降后趋于稳定,HAD处理的对虾则持续下降。当水分含量由74.15%降至约46.55%时,ODS和HAD所需时间分别约为128.5和5.4 h。ODS的虾干硬度适中,保持了鲜虾原有的色泽和固有气味。对虾脱水过程中TVB-N含量与TBARS值逐渐增加,脱水结束时,ODS与HAD处理的对虾TVB-N含量分别为37.80和63.71 mg/100 g,TBARS值分别为0.28和0.35 mg/kg。ODS处理的虾干复水率为90.64%显著高于HAD的72.14%(p<0.05);虾干复水后,ODS组的硬度、弹性和咀嚼性分别为3217.24 N、0.24 mm和273.80 mJ,显著低于热风干燥组的4928.97 N、0.32 mm和605.29 mJ(p<0.05),其质构特性均较接近鲜虾。ODS虽然脱水时间较长,但可在冷藏过程中完成脱水,减缓虾干的蛋白质分解与脂肪氧化程度、提高复水性能和质构特性,可为对虾及其他高值水产品的干制提供一种新方法。