鲜切果蔬酶促褐变关键酶的研究进展

新鲜果蔬经过切割处理后,产生的机械伤害会刺激诱导表面组织发生酶促褐变反应,而使鲜切产品的感官品质下降、货架期显著缩短。鲜切果蔬的外观色泽变化主要是由酶促褐变引起的,起主要作用的关键酶有:多酚氧化酶(PPO),过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、脂氧合酶(LOX)、抗坏血酸过氧化物酶(APX)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)等。本文就近几年有关鲜切果蔬酶促褐变发生中一些关键酶的作用机理进行了综述,为鲜切果蔬酶促褐变的控制和质量保持提供理论参考。      

鲜切果蔬酶促褐变发生机理的研究

为了进一步揭示鲜切果蔬酶促褐变发生过程及其机理,采用鲜切茄子和鲜切甘薯为实验材料,研究了与酶促褐变发生密切相关的酶活性变化及伤害胁迫生理。结果表明:两种果蔬经鲜切处理后诱发了酶促褐变的快速发生,鲜切甘薯的酶促褐变反应滞后于鲜切茄子。在贮藏期间两种果蔬的过氧化物酶(POD)活性和丙二醛(MDA)含量逐渐上升,总酚含量与苯丙氨酸解氨酶(PAL)活性变化一致,均先升后降。鲜切甘薯多酚氧化酶(PPO)活性逐渐上升,但鲜切茄子的PPO却呈下降趋势。结果还表明:鲜切果蔬不仅在切割表面发生酶促褐变反应,在远离切割部位也诱发了生理生化反应,这可能是由于切割伤害胁迫产生的刺激信号转导而引致组织的整体协同伤害防御反应的结果。     

鲜切果蔬酶促褐变机理及控制研究进展

介绍酶促褐变的机理及与褐变相关的酶,并从物理、化学等方面介绍了一些新近发展的酶促褐变抑制方法.     

几种常见果蔬抗氧化活性与多酚和维生素C的关系

目的:探索几种常见果蔬的抗氧化活性与多酚、维生素C的相关关系。方法:运用二苯代苦味酰基自由基法（DPPH法）、硫代巴比妥酸反应物法（ABTS法）、血浆高铁还原能力分析能力（FRAP法）、羟自由基和超氧阴离子自由基5种抗氧化方法评价10种常见果蔬的抗氧化活性,并采用Folin-Ciocalteu法和2,4-二硝基苯肼法分别测定了果蔬中多酚和VC的含量,并对多酚、VC的含量与抗氧化活性进行相关性分析。结果:DPPH、ABTS、FRAP、超氧阴离子、羟自由基抗氧化活性最强的依次为豆角、豆角、橘子、香蕉、橘子,最弱的依次为西瓜、西瓜、西瓜、胡萝卜、卷心菜。DPPH、ABTS和FRAP测定果蔬粗提液抗氧化活性与多酚的含量的相关性强于VC。结论:多酚的含量对果蔬抗氧化活性的影响强于V_C。      

黑果枸杞与5种果蔬中花色苷组成及体外抗氧化活性比较

目的:评价黑果枸杞等6种不同花色苷来源的植物材料的花色苷组成含量及体外抗氧化活性,为花色苷的利用和具有较强抗氧化活性植物资源的筛选提供参考。方法:取黑果枸杞等6种不同花色苷来源的植物材料,采用分光光度法、HPLC-MS法分析测定黑果枸杞花色苷含量及主要组成,用DPPH、ABTS和FRAP法分析其体外抗氧化活性。结果:黑果枸杞等6种不同花色苷来源的植物材料总花色苷含量的变化幅度为0.21².26mg/g鲜果。其中黑果总花色苷含量最高,花色苷含量分别是葡萄、树莓、紫甘蓝、蓝莓和紫薯的10.72、4.91、1.91、1.75、4.45倍。黑果枸杞花色苷的主要组分为矮牵牛素衍生物,有别于其他所测果蔬材料,其抗氧化活性也最高。结论:较之5种花色苷含量较高的天然果蔬材料,黑果枸杞中花色苷主要组分与之差异很大,总花色苷含量和抗氧化活性总体都较高,是较好的开发功能性食品的资源。      

Recent developments in high-quality drying of vegetables,fruits, and aquatic products

Fresh foods like vegetables, fruits, and aquatic products have high water activity and they are highly heat-sensitive and easily degradable. Dehydration is one of the most common methods used to improve food shelf-life. However, drying methods used for food dehydration must not only be efficient and economic but also yield high-quality products based on flavor, nutrients, color, rehydration, uniformity, appearance, and texture. This paper reviews some new drying technologies developed for dehydration of vegetables, fruits, and aquatic products. These include: infrared drying, microwave drying, radio frequency drying, electrohydrodynamic drying, etc., as well as hybrid drying methods combining two or more different drying techniques. A comprehensive review of recent developments in high-quality drying of vegetables, fruits and aquatic products is presented and recommendations are made for future research.     

果蔬中农药残留降解方法研究进展

随着食品安全问题日益受到重视,果蔬中的农药残留已成为世界各国的研究热点。目前国内外有关果蔬中农药残留降解方法的研究报道很多,本文全面综述了果蔬中农药残留降解的方法和技术,主要从物理、化学和生物降解3个方面阐述。其中物理方法主要包括洗涤、加工和储藏等;化学方法主要是指采用化学试剂、臭氧和光照等方法;而生物方法是利用生物酶破坏农药的结构或者利用基因工程将生物体内能降解农药的酶基因转移到载体基因中,从而降解农药。并对新降解技术如油茶素内酯降解法等进行了展望,以期为进一步研究提供参考和借鉴。     

即食鲜切蔬果货架期保存环境对微生物指标的影响

目的 即食鲜切蔬果行业目前没有统一的行业规范,其中一个重要的原因是没有相对应的检测指标。蔬果本身就相比其它食品更难以保存,易产生食品安全问题,即食鲜切蔬果的这一特点就更为明显,所以需要展开相关研究为制定行业规范提供依据。通过开展保存环境的温度与湿度的协同研究,以获得适宜的保存条件,并确定经济安全的保存期限。方法 选取市面常见即食鲜切蔬果样品(黄瓜、梨、生菜、西红柿、火龙果)五种,经洗净、切制、分装等操作,且未经特殊消毒处理,检测微生物指标(检验菌落总数和致病菌)初始值后,在温度2℃、4℃、6℃与相对湿度50%、70%下保存,每隔24小时(至生产后4天)取样检测,并绘制微生物生长曲线。结果 对比实验中采取温度条件,保存在2℃环境下,微生物污染程度较低;对比实验中采取湿度条件,保存在相对湿度70%环境下,保存效果更好。结论 温度2℃与湿度70%以上是即食鲜切蔬果的适宜保存条件,存放一天的货架期是较为经济安全的保存期限。     

采前和采后贮藏对果蔬中抗氧化物质影响的研究进展

自由基是人体正常代谢的产物, 但自由基过量会引发一系列的疾病。越来越多的研究表明, 食用果蔬有助于预防由过量自由基引起的多种疾病, 这主要源于果蔬中富含的各种抗氧化物质。本文主要从采前和采后贮藏保鲜两个阶段对果蔬组织中的抗氧化物质(重点包括总酚、总黄酮、抗坏血酸、花青素)以及抗氧化能力的影响因素及其影响效果进行了较为全面的综述。     

Phytonutrients affecting hydrophilic and lipophilic antioxidant activities in fruits,vegetables and legumes

The antioxidant activities of fruits (n = 21), vegetables (n = 67) and legumes (n = 7) commonly consumed in Korea were determined by both the lipophilic antioxidant performance assay (LAP) and the hydrophilic oxygen radical absorbance capacity assay (ORAC). The LAP assay used the lipophilic radical initiator MeO‐AMVN [2,2′‐azobis(4‐methoxy‐2,4‐dimethylvaleronitrile)] and the lipophilic probe BODIPY 581/591 [4,4‐difluoro‐5‐(4‐phenyl‐1,3‐butadienyl)‐4‐bora‐3a, 4a‐diaza‐s‐indacene‐3‐undecanoic acid]. The ORAC assay used the hydrophilic radical initiator AAPH [2,2′‐azobis(2‐amidinopropane) dihydrochloride] and the hydrophilic probe fluorescein. In addition, the lipid‐soluble phytonutrients, carotenoids and tocopherols were determined by a reverse‐phase HPLC system using a C30 column with a UV detector. The water‐soluble phytonutrient, ascorbic acid, was analyzed using an HPLC system with an electrochemical detector. Total phenols were determined by UV spectrophotometry. Tocopherols (r = 0.774, p < 0.0001) and carotenoids (r = 0.569, p < 0.0001) were significantly correlated with LAP in total samples (n = 95). ORAC was significantly correlated with total phenols (r = 0.893, p < 0.0001), but not with ascorbic acid (r = 0.009, p = 0.929) in total samples (n = 95). These data indicate that carotenoids and tocopherols and total phenols are the major contributors to the lipophilic and hydrophilic antioxidant capacities, respectively. Therefore, the contribution of both the hydrophilic and lipophilic components of fruits and vegetables should be considered when determining the actual ‘total’ antioxidant activity of fruits and vegetables. Copyright © 2007 Society of Chemical Industry     

Recent advances in the improvement of freezing time and physicochemical quality of frozen fruits and vegetables by ultrasound application

Freezing is widely used for the preservation of fruits and vegetables (FVs). Whereas, the conventional freezing method presents low process efficiency in frozen FVs. Ultrasound application is used as a supplementary technology to improve the freezing process of FVs. This reviewed paper shows the cavitation effect of ultrasound and the effect of ultrasound application on freezing time and the physicochemical quality of frozen FVs. The cavitation effect of ultrasound in the freezing process was described in detail. Compared with conventional freezing, ultrasound application in freezing of FVs can shorten the freezing time, and improve physicochemical quality including drip loss, colour, firmness, chemical compositions (ascorbic acid, total phenolic and anthocyanin), as well as microstructure. Therefore, the results of these studies illustrated that ultrasound is a potential technology to enhance freezing efficiency and retain the quality of FVs during freezing.     

Recent developments in high efficient freeze-drying of fruits and vegetables assisted by microwave: A review

Microwave heating has been applied in the drying of high-value solids as it affords a number of advantages, including shorter drying time and better product quality. Freeze-drying at cryogenic temperature and extremely low pressure provides the advantage of high product quality, but at very high capital and operating costs due partly to very long drying time. Freeze-drying coupled with a microwave heat source speeds up the drying rate and yields good quality products provided the operating unit is designed and operated to achieve the potential for an absence of hot spot developments. This review is a survey of recent developments in the modeling and experimental results on microwave-assisted freeze-drying (MFD) over the past decade. Owing to the high costs involved, so far all applications are limited to small-scale operations for the drying of high-value foods such as fruits and vegetables. In order to promote industrial-scale applications for a broader range of products further research and development efforts are needed to offset the current limitations of the process. The needs and opportunities for future research and developments are outlined.     

Recent advances in modified atmosphere packaging and edible coatings to maintain quality of fresh-cut fruits and vegetables

Processing of fruits and vegetables generates physiological stresses in the still living cut tissue, leading to quality deterioration and shorter shelf life as compared with fresh intact produces. Several strategies can be implemented with the aim to reduce the rate of deterioration of fresh-cut commodities. Such strategies include low temperature maintenance from harvest to retail and the application of physical and chemical treatments such as modified atmosphere packaging (MAP) with low O₂ and high CO₂ levels and antioxidant dips. Other technologies such as edible coatings with natural additives, new generation of coatings using nanotechnological solutions such as nanoparticles, nanoencapsulation, and multilayered systems, and nonconventional atmospheres such as the use of pressurized inert/noble gases and high levels of O₂ have gained a lot of interest as a possibility to extend the shelf life of minimally processed fruits and vegetables. However, the high perishability of these products challenges in many cases their marketability by not achieving sufficient shelf life to survive the distribution system, requiring the combination of treatments to assure safety and quality. This review reports the recent advances in the use of MAP, edible coatings, and the combined effect of both technologies to extend the shelf life of fresh-cut fruits and vegetables.     

Analysis of furanocoumarins in vegetables (Apiaceae) and citrus fruits (Rutaceae)

Several alternative approaches applicable for the analysis of furanocoumarins, toxic components occurring in some fruits and vegetables representing both Apiaceae and Rutaceae families, were tested in our study. Limits of detection (LODs) for angelicin, psoralen, bergapten, xanthotoxin, trioxsalen, isopimpinellin, sphondin, pimpinellin and isobergapten obtained by GC/MS (SIM) were in the range 0.01–0.08 µg g^?1. Slightly higher LODs (0.02–0.20 µg g^?1) were achieved by LC/MS–MS. The latter is the only alternative for analysis of bergamottin (LOD = 0.01 µg g^?1) in citrus fruits because this furanocoumarin is unstable under GC conditions. Regardless of the determination step used, the repeatability of the measurements (expressed as RSD) did not exceed 10%. As shown in our study the levels of furanocoumarins in celery, celeriac, parsnip, carrot, lemon and other foods obtained at a retail market varied over a wide range; the highest contents were determined in parsnip, while the levels of these toxins in carrots and citrus pulps were relatively low. Copyright © 2007 Society of Chemical Industry     

Recent advances in pressure modification-based preservation technologies applied to fresh fruits and vegetables

Fresh fruits and vegetables are important parts of the human diet. The consumer demand for fruits and vegetables is increasing due to their rich nutritional value, appealing taste, and healthy perception. However, due to their highly perishable nature, appropriate preservation technologies must be developed to meet the consumer’s demand for healthy, additive-free, microbiologically safe, and high quality fresh fruits and vegetables. The preservation technologies based on modification or control of pressure alters the normal atmospheric pressure of the preservation environment. The materials to be preserved are subjected to either very high or low pressure to extend their shelf life. The mechanism, advantages, and limitations of pressure modification-based preservation methods such as high hydrostatic pressure, hyperbaric treatment, vacuum cooling, hypobaric storage, and vacuum packaging focusing on their applicability to fresh fruits and vegetables have been reviewed. This review suggests that these technologies have potential to extend the shelf life and achieve a better preservation of the quality of fresh fruits and vegetables.     

4种常见果蔬保鲜运输超声波加湿的生命周期模拟研究

通过生命周期评估显示:与传统供应链相比,超声波加湿可将部分水果和蔬菜的环境影响(包括气候变化影响)降低23%,当加湿器应用于果蔬供应链,且总固有损失>24%时,加湿器的加入能使损失减少20%以上,说明超声波加湿技术能使果蔬供应链管理更具可持续性。     

胶体金免疫层析法同时检测果蔬中克百威、水胺硫磷、百菌清及虫酰肼的应用研究

目的 研究胶体金免疫层析法同时检测果蔬中克百威、水胺硫磷、百菌清及虫酰肼残留量的适用性。方法 考察胶体金免疫层析法同时检测克百威、水胺硫磷、百菌清及虫酰肼在不同基质中的灵敏度, 并将该方法与参比方法进行比较, 验证其假阴性率和假阳性率。结果 克百威检出限为0.02 mg/kg, 水胺硫磷为 0.05 mg/kg、百菌清为3 mg/kg、虫酰肼为0.2 mg/kg, 基本满足国家标准对果蔬中这些农药的限量要求。对韭菜、大白菜进行加标实验, 均未出现假阳性及假阴性, 与参比方法无显著差异; 除丙硫克百威、丁硫克百威与克百威有交叉反应外, 水胺硫磷、百菌清及虫酰肼与非对应农药均无交叉反应。结论 该方法操作快速、准确、灵敏、简便, 适用于果蔬中克百威、水胺硫磷、百菌清及虫酰肼的同时检测。     

Phytochemicals and antioxidant activity of fruits and leaves of paprika (Capsicum Annuum L., var. special) cultivated in Korea

The phytochemical composition of carotenoids, tocopherols, free sugars, organic acids, L-ascorbic acid, capsaicinoids, and flavonoids in green and red paprika (GP and RP), and paprika leaves (PL) cultivated in Korea were analyzed. The ethanolic extracts of GP, RP, and PL were obtained with 80% ethanol, and their antioxidative activities were determined by measuring their ABTS and DPPH radical scavenging activities. RP showed the highest contents of capsanthin (58.33 ± 3.91 mg/100 g dry weight) and L-ascorbic acid (1987.25 ± 19.64 mg/100 g dry weight), and main compounds of PL were lutein, chlorophyll, and γ-tocopherol (96.91 ± 14.58, 2136.71 ± 21.11, and 723.49 ± 54.10 mg/100 g dry weight, respectively). RP showed the strongest antioxidant activity (IC(50) = 55.23 ± 6.77 μg/mL in a 2, 2'-azino-di-[3-ethylbenzthiazoline sulphonate] assay and 150.40 ± 8.07 μg/mL in a 2, 2-diphenyl-2-picrylhydrazyl assay), and the antioxidant activity of PL was higher than β-carotene but lower than RP. The results indicate that the amounts of capsanthin and L-ascorbic acid in RP correlate well with antioxidant activity. PL, which has various phytochemicals such as lutein, chlorophyll, and γ-tocopherol, might be used in nutraceuticals and pharmaceuticals for improving human health.     

Antioxidative enzyme activity and internal browning of 1‐methylcyclopropene‐treated European pear fruits (cv. ‘Shahmiveh’ and ‘Sebri’)

The effects of 1‐methylcyclopropene (1‐MCP) on antioxidative enzyme and internal browning (IB) incidence of two European pear cultivars ‘Shahmiveh’ and ‘Sebri’ stored at 0.5 °C were investigated. Ethylene production of ‘Sebri’ was delayed by 1‐MCP but suppressed in ‘Shahmiveh’. IB increased in both cultivars, with a higher level of the incidence in ‘Shahmiveh’, and was reduced by 1‐MCP. Activities of catalase (CAT) and peroxidase, but not superoxide dismutase (SOD), decreased in untreated fruit during the first 40 days. 1‐MCP had little effect on SOD activity or on total phenolics. Polyphenoloxidase activity did not increase over time in 1‐MCP‐treated fruit of the IB sensitive ‘Shahmiveh’, and the effect was inconsistent for ‘Sebri’. Ascorbic acid (AA) levels in 1‐MCP‐treated fruit of both cultivars declined at a lower rate compared with untreated fruit during storage, but the reduction in AA levels was faster in ‘Shahmiveh’ compared with ‘Sebri’. Also, the effects of 1‐MCP on antioxidative systems may be related to IB development.     

Effect of cell wall-disruption processes on wall disruption,antioxidant activity and nutrients in tea pollen

Tea pollen is rich in nutritional and bioactive compounds; however, the pollen wall limits their release. In this study, we explored the effects of freeze–thaw processing (FT), a combination of enzymatic hydrolysis and ultrasonication (EHUS) and superfine grinding (SG) on the wall disruption, antioxidant activity, sensory qualities and nutrients in tea pollen. SG-treated pollen had the highest broken-wall ratio (100%), followed by EHUS (79.14%), while FT-treated pollen displayed the lowest ratio (59.86%). Release of nutrient compounds, including polyphenols, flavonoids, carbohydrates, total free amino acids, proteins and theanine, increased after treatment with the three wall-disruption methods compared with untreated samples. Moreover, levels of epigallocatechin gallate (EGCG), epigallocatechin (EGC), catechin gallate (CG) and gallocatechin gallate (GCG) were higher following EHUS or SG than in untreated or FT-treated tea pollen. EGCG was the most potent catechin involved in antioxidant activity of tea pollen, making major contributions to the significant improvement of antioxidant activity in SG- and EHUS-treated groups. Additionally, the overall sensory qualities of tea were lower after treatment with the three wall-disruption methods compared with untreated samples. In summary, SG and EHUS treatment had greater effects on cell wall disruption, nutrient release and antioxidant activity in tea pollen.