纳米二氧化硅改性LDPE膜对贡柑贮藏品质的影响

为了探索纳米二氧化硅改性低密度聚乙烯薄膜(LDPE)对贡柑的保鲜效果,分别研究了未包装、常规LDPE膜包装和纳米二氧化硅改性LDPE膜包装三种贮藏方式对贡柑采后贮藏品质的影响。结果表明:两种包装材料均能改善贡柑的贮藏品质,其中纳米二氧化硅改性LDPE膜能够更好地延缓贡柑采后失重率、腐烂率的上升和硬度的下降,更好地抑制丙二醛的积累,贮藏后期保持较高的可溶性固形物和可滴定酸含量,并能较好地维持果实抗氧化性能和感官满意度。     

不同气调包装材料对红香酥梨贮藏品质的影响

为了初步筛选红香酥梨的气调包装材料,本研究选用7种常见的塑料包装材料(CPP、LDPE、HDPE、PP6、PP12、OPP、PO)作为气调贮藏包装,分别进行N2、空气、真空处理,以敞口放置作为对照,进行红香酥梨的气调保鲜实验。红香酥梨气调包装后置于室温下进行贮藏,考察贮藏期间包装袋内气体含量、失重率、感官品质的变化,并将贮藏始末果实品质指标(果实硬度等)的变化进行对照。结果表明:气调包装材料种类及厚度对红香酥梨保鲜效果差异较大,PO、LDPE、CPP材料较适合于红香酥梨的气调保鲜,N2处理效果明显优于空气和真空处理。     

不同包装材料对草莓贮藏品质和保鲜期的影响

在4℃贮藏条件下,采用不同的塑料包装材料(LDPE、HDPE和OPP膜)对草莓进行保鲜包装,测定不同贮藏时间下草莓的失重率、好果率、VC含量、果实硬度和可溶性固形物。结果表明:塑料包装膜能明显抑制草莓变质;具有较低透气率的HDPE薄膜保鲜效果最好,其次是OPP膜,再次是LDPE膜。     

香菇气调保鲜包装工艺研究

以香菇为试验材料,研究1%壳聚糖涂膜结合不同气调包装工艺低温贮藏香菇的保鲜效果。分析了不同保鲜工艺对其感官品质、失重率、Vc含量变化、细胞膜透性等生理生化指标的影响。结果表明,采用1%壳聚糖涂膜结合314μm OPP/PE微孔膜气调包装的方法,可延长货架期到19d,并能较好的保持香菇的感官品质和营养价值。     

分子筛改性LDPE活性包装膜在草莓保鲜中的应用研究

新鲜草莓易腐烂,贮藏保鲜较为困难.为了延长草莓的贮藏期,本研究采用硅铝分子筛对低密度聚乙烯(LDPE)进行改性,制备了具有高透气性的改性LDPE包装膜.以LDPE膜包装的草莓和裸放草莓为实验对照组,在(5±1)℃的低温和加乙烯吸附药包的条件下,分别研究了LDPE和改性LDPE包装膜对草莓储存期的影响.实验中分别测定了草莓果肉中可溶性固形物含量、维生素C含量以及草莓的失重率、硬度、烂果率等指标.实验结果表明:对照组中裸放和用LDPE膜包装的草莓储藏期分别为3天和7天,而分子筛改性LDPE膜加乙烯吸附剂包装能够将草莓的贮藏期延长至11天,草莓的好果率、硬度和可溶性固形物含量等均明显高于对照组.该分子筛改性LDPE膜加乙烯吸附剂的综合包装方案能够有效延长草莓的低温贮藏保鲜时间.     

纳米二氧化钛改性LDPE薄膜包装对草莓品质的影响

为了探索纳米二氧化钛改性LDPE薄膜对采后草莓的保鲜效果,研究了普通LDPE薄膜和纳米二氧化钛改性LDPE薄膜两种不同包装对4 ℃下草莓贮藏品质的影响。研究发现,与对照组相比,纳米二氧化钛改性LDPE薄膜可抑制草莓贮藏过程中腐烂指数和失重率的上升,延缓可滴定酸含量和硬度的下降,减少乙烯释放量,保持果实贮藏后期较高的抗坏血酸和总酚含量以及较高的抗氧化能力。至贮藏第14 d,纳米二氧化钛改性LDPE薄膜包装中草莓的腐烂指数和乙烯释放量分别比对照组低60.72%和40.32%,可滴定酸含量和硬度分别比对照组高9.02%和24.31%,抗坏血酸和总酚含量分别比对照组高29.22%和10.73%。研究结果表明,纳米二氧化钛改性LDPE薄膜有利于保持草莓的贮藏品质,其作为草莓保鲜包装具有潜在的应用前景。     

纳米二氧化钛改性 LDPE 薄膜包装对草莓品质的影响

为了探索纳米二氧化钛改性LDPE薄膜对采后草莓的保鲜效果,研究了普通LDPE薄膜和纳米二氧化钛改性LDPE薄膜两种不同包装对4 ℃下草莓贮藏品质的影响。研究发现,与对照组相比,纳米二氧化钛改性LDPE薄膜可抑制草莓贮藏过程中腐烂指数和失重率的上升,延缓可滴定酸含量和硬度的下降,减少乙烯释放量,保持果实贮藏后期较高的抗坏血酸和总酚含量以及较高的抗氧化能力。至贮藏第14 d,纳米二氧化钛改性LDPE薄膜包装中草莓的腐烂指数和乙烯释放量分别比对照组低60.72%和40.32%,可滴定酸含量和硬度分别比对照组高9.02%和24.31%,抗坏血酸和总酚含量分别比对照组高29.22%和10.73%。研究结果表明,纳米二氧化钛改性LDPE薄膜有利于保持草莓的贮藏品质,其作为草莓保鲜包装具有潜在的应用前景。     

不同厚度LDPE膜对平菇保鲜效果的影响

为比较不同厚度的低密度聚乙烯(LDPE)膜对平菇保鲜效果的影响,分别以0.015mm、0.030mm和0.045 mm 3种不同厚度的LDPE膜为包装材料,在模拟超市冷鲜货架温湿度条件(温度约14±1℃,贮藏环境相对湿度约85%)下,探讨了不同厚度LDPE膜对平菇保鲜效果的影响。结果表明:与0.015mm膜和0.030mm膜相比,0.045 mm LDPE膜虽能显著提高平菇的失重率,保持包装内的较高的CO2体积分数和较低O2的体积分数(P0.05);但在贮藏的第4天后,0.045mm LDPE膜对抑制平菇呼吸强度、维持细胞膜透性,提高平菇感官分值的效果显著低于0.030mm LDPE膜(P0.05)。3种不同厚度的保鲜膜以0.030mm LDPE膜对平菇的保鲜效果最佳。     

鼠尾草酸/LDPE活性膜对新鲜鸡肉丸品质特性的影响

本文使用鼠尾草酸/LDPE活性膜对新鲜鸡肉丸进行真空包装,于4℃、20℃、37℃下贮藏,对不同时期贮藏的鸡肉丸进行感官评分,并测定酸价、质构及硫代巴比妥酸值(TBARS)的变化,并与空白LDPE膜包装的鸡肉丸进行对比,以研究不同温度下CA/LDPE膜包装膜对鸡肉丸品质的影响。结果显示,鼠尾草酸/LDPE活性膜包装的鸡肉丸各项指标(感官评分、酸价、质构和TBARS)均优于空白LDPE膜包装的鸡肉丸,且温度越高,两种包装膜之间的差异越明显:37℃第10 d时,CA/LDPE膜包装的鸡肉丸口感味道感官评分为1.22±0.26,比LDPE膜高22%;酸价为20.53±0.43 mg/(g鸡肉丸),比LDPE膜低28.5%;硬度、凝聚力、咀嚼性分别为43.30、0.21和42.87,比LDPE膜高95.4%、53.2%和81.9%;TBARS值为0.698 mg/kg,比LDPE膜低47.2%。研究表明,添加鼠尾草酸的LDPE膜能够有效改善鸡肉丸的贮藏品质特性。     

包装材料与贮藏环境对青椒的影响

为了研究包装材料与贮藏环境对青椒的影响,并寻找对青椒合适的包装材料以及贮藏环境。使用LDPE,PP,BOPP三种包装材料并分别以有孔和无孔的两种处理的包装方式分别进行常温和冷藏方式贮藏。得出青椒在有孔的PP薄膜在冷藏环境下气调包装贮藏会有很好的保鲜效果。将青椒包装并储存在合适的具有低O2和高CO2浓度的环境中,可以更好地保留蔬菜的新鲜度和降低腐烂程度。采用PP有孔薄膜的气调包装可用于存储青椒,冷藏条件下可以在20 d内保持其质地、颜色、抗坏血酸和低腐烂度,相比之下常温条件只能存储4 d左右。     

鲜香菇在不同处理方式下的甲醛含量分析研究

目的检测分析经匀浆、干燥等方式处理鲜香菇中的甲醛含量,反映处理后鲜香菇的生物活性随时间的变化情况,为香菇的储存提供数据支持。方法利用液相色谱法测定香菇甲醛含量。结果匀浆后的鲜香菇中甲醛含量随时间增长而降低,至腐烂后消失。真空包装经高燥处理的香菇中甲醛含量随时间增长呈上升趋势,而真空包装未经干燥处理的香菇,其甲醛含量呈下降趋势。结论通过连续检测鲜香菇中的甲醛含量,验证了香菇中的甲醛来源于其生理活动这一科学论断。基于此,通过检测香菇的甲醛含量判断香菇得生物活性,以观察香菇在贮藏及运输过程中的保质效果。     

Retention of α-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) in contact with foodstuffs and food-simulating liquids

Alpha-tocopherol occurs as a natural antioxidant in many foods and has also found use as a stabiliser in polymeric packaging materials. During storage of a food in contact with a plastic material, α-tocopherol may be released from the packaging material and transferred into the food. An active packaging application with the transfer of a substance, such as an antioxidant, from a packaging material to a food may help to prolong the shelf-life of the food. In this study, the retention of α-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) was investigated for contact with liquid foods with different fat contents and food simulants with different ethanol contents. The PP film exhibited excellent retention of α-tocopherol when in contact with all media, whereas some losses were observed from the LDPE film. A number of factors including fat, alcohol and organic acid contents of the various foodstuffs seemed to influence the loss of α-tocopherol from the LDPE film. © 1999 Society of Chemical Industry     

A comparative study on the effect of packaging material and storage environment on shelf life of fresh bell-pepper

The effect of packaging materials [low density polyethylene (LDPE), polypropylene (PP)] and storage environment [modified atmospheric packaging (MAP)] on shelf life enhancement of bell pepper in terms of quality attributes such as physiological weight loss, ascorbic acid, texture, surface colour and subjective quality analysis have been studied at ambient and refrigerated condition. Different packaging techniques used for the experiment were MAP with LDPE, MAP with PP, MAP in perforated LDPE films, MAP in perforated PP films, shrink packaging with bi-axially oriented PP (BOPP) film and vacuum packaging with PP film. The in-pack bell pepper created a suitable headspace environment with low O₂ and high CO₂ concentrations, which resulted in a better retention of freshness of the vegetables and its marketability. Shrink packaging with BOPP film could not yield better result under ambient storage because of high water vapor transmission rate of the film and consequently loss of turgidity of the vegetables. Among different packaging techniques and storage conditions, MAP with PP film in refrigerated condition was found to be the best followed by vacuum pack with PP film in refrigerated condition and could be used to store for 20 days for bell pepper with maintenance of texture, colour, ascorbic acid and marketability. It is also inferred that under ambient conditions, bell pepper could be stored for 4 days using ventilated LDPE and PP as MAP storage. Further studies are needed to evaluate the sensory aspects, as well as to microbiological evaluation to characterize the fresh bell pepper during storage.     

QUALITY CHANGES IN FRESH‐CUT SPINACH (SPINACIA OLERACEA) UNDER MODIFIED ATMOSPHERES WITH PERFORATIONS

ABSTRACT

Fresh‐cut spinach leaves were stored for 4 days at 15C and 75% relative humidity under modified atmosphere packaging to assess the impact of differential in‐pack gas atmospheres generated through different packaging films and variable in‐pack weight on the quality of stored produce. After 4 days of storage, retention of chlorophyll, β‐carotene and ascorbic acid was better in low‐density polyethylene (LDPE) packages than in polypropylene (PP) packages. LDPE film‐packaged samples had higher phenolic content than PP film‐packaged samples. Low in‐pack O₂ (1–2 kPa) along with the buildup of CO₂ (8–10 kPa) seems to have enhanced the retention of antioxidant components, i.e., β‐carotene and ascorbic acid, in LDPE packages. This helped in chlorophyll retention and also prevented formation of oxidation compounds of phenols that otherwise caused browning of cut surfaces. Thus, O₂ and CO₂ permeability of packaging film or in‐pack weight of produce might be such that equilibrated O₂ partial pressures remain near to 1–2 kPa so as to affect a beneficial increase in the phenolic content along with concomitant retention of chlorophyll.

PRACTICAL APPLICATIONS

Fresh‐cut spinach leaves have received an enormous demand due to their utility in various traditional Indian preparations. Shelf life and quality of fresh‐cut produce may be greatly reduced due to high rates of respiration. Traditional packaging and handling techniques reduce the shelf life and sensory quality of fresh‐cut spinach. Temperature control and atmospheric modifications help to maintain produce quality by reducing respiration rate and enhance shelf life by minimizing the adverse effects of cutting. This research focused on evaluation of respiratory behavior of fresh‐cut spinach leaves at a temperature commonly encountered during transportation and retail distribution, i.e., 15C, and the effect of different polymeric films and in‐pack weights on produce quality. The results of the study suggest that packaging of fresh‐cut spinach in polymeric film packages could maintain the sensory quality and reduce degradation of various physicochemical constituents. Utilization of the results for proper design of modified atmosphere packages for this highly perishable produce can prove to be extremely beneficial for safe storage and transportation to urban retail markets.     

Application of laminated and metalized films to prolong the shelf life of dried barberries

Barberry is a nutritional and therapeutic crop mostly dried and consumed in bulk. However, the lack of proper packaging leads to the decline of many of its valuable properties. The aim of this study was to investigate the effect of different packaging films on barberries properties during storage. 150 g of freshly dried barberries were kept for 6 months at 25 °C within different packaging materials: (i) low-density polyethylene (LDPE); two laminated layers film including LDPE and polyethylene terephthalate (PET) with a total thickness of (ii) 45 μm (LDPE/PET-45) and (iii) 60 μm (LDPE/PET-60); (iv) oriented polypropylene (OPP); (v) three laminated layers film of OPP (3OPP); (vi) three laminated layers film including LDPE, metalized PET and PET (LDPE/mPET/PET); and (vii) four laminated layers film including LDPE, PET, aluminum foil and PET (LDPE/PET/Al/PET). After six months, the least change in moisture content, the lowest loss of DPPH scavenging capacity (97.9%), the minimum overall color difference, and the least increase in acidity (39.3%) were related to barberries packaged in the LDPE/PET-45 film. This is while the lowest loss of ascorbic acid (99.8%) and anthocyanin (62.8%) contents and the minimum microbial deterioration were related to the LDPE/PET-60 film. On the other hand, the LDPE/PET/Al/PET film entailed the lowest barberry weight loss (0.67%) and the minimum increase in firmness (40.7%), while the 3OPP film providing the best preservation of phenolic compounds. In conclusion, it seems two laminated layers films composed of LDPE and PET are appropriate for the preservation of dried barberries during storage.     

香菇中甲醛含量测定的不确定度分析

依据NY/T 1283-2007《香菇中甲醛含量的测定》,对香菇中甲醛的测量不确定度进行评定。在中性条件下,将溶解于水中的甲醛随水蒸馏出,在沸水浴中,溜出液中甲醛在乙酸-乙酸铵缓冲溶液介质中,与乙酰丙酮生产稳定的黄色化合物,冷却后在412nm处测其吸光度,外标法定量。系统分析了该法测量结果的不确定度来源并对其进行评定,对各不确定度分量进行了量化,提出了该法的合成不确定度。     

Effect of a packaging material type on PAHs contents in oils and water

The aim of this study is to determine the extent of packaging material effect on the removal of polycyclic aromatic hydrocarbons (PAHs) from stored liquid media. Changes in PAHs contents were monitored in edible oils and water during their storage for 504 h. The most significant reduction in PAHs content was reported upon the use of polyethylene packagings. In the case of LDPE packagings, the Σ16PAHs content decreased to 40.07% (water) and 45.0% (rapeseed oil) of their initial level after 504 h. Most PAHs absorption occurred within the first 24 h of liquid media storage. In terms of PAHs absorption capability, the packages tested could be ordered as follows LDPE > HDPE > PET > glass. The experiment involving the re-use of LDPE, HDPE, and PET packagings earlier contaminated with PAHs demonstrated that their effective washing with detergents commonly used at household was impossible.     

挤压营养强化米的贮藏稳定性研究

研究挤压营养强化米的营养成分的贮藏稳定性。以实验室自制的挤压营养强化米为原料,研究其在不同的包装方式及不同的贮藏环境下各营养成分的变化情况。结果表明：不同的包装方式和不同的贮藏环境对挤压营养强化米的营养成分均有不同程度的影响,4℃、罐装贮藏条件是挤压营养强化米的最佳贮藏条件,在此条件下将挤压营养强化米贮藏180d,其VC和VD3的保存率可达80%以上,VB的保存率可达95%以上,酸价在1.0mg/g以下,水分含量在8%以下。     

香菇真空冷冻干燥过程中滋味物质动态变化及鲜味评价

为探究香菇真空冷冻干燥（vacuum freeze-drying,VFD）过程中滋味物质的变化规律,利用电子舌、高效液相色谱仪和氨基酸分析仪研究香菇在预冻、升华干燥和解析干燥（20、30、40 ℃和50 ℃）后的滋味变化。电子舌结果显示,不同VFD阶段的香菇能被有效区分。香菇滋味物质的检测结果表明,预冻后可溶性糖（醇）和5’-核苷酸含量均显著上升（P＜0.05）;升华干燥后可溶性糖（醇）和游离氨基酸含量均升高至整个VFD过程的最大值,分别为185.20 mg/g和44.76 mg/g;在解析干燥时,有机酸含量增加且不受解析干燥温度的影响,而可溶性糖（醇）和游离氨基酸含量均随温度变化呈现不同的下降趋势。结合等鲜浓度（equivalent umami concentration,EUC）值对鲜味变化进一步分析,结果表明香菇的鲜味强度在30、40 ℃和50 ℃解析干燥后增幅较大,其EUC值约为鲜香菇的2 倍。总体而言,香菇中大部分滋味物质在VFD过程得到很好的保留,研究结果对深入了解香菇滋味物质在该加工过程中的变化机制以及开发基于香菇滋味的调味品有重要参考价值。