强酸性电生功能水提高鲜切莲藕品质的研究

以鲜切莲藕为试材,研究了强酸性电生功能水对鲜切莲藕表面微生物的杀灭作用及抑制酶促褐变效果,探究了强酸性电生功能水的有效氯浓度、贮藏时间、贮藏温度对其抑制褐变效果的影响,进一步考察几种不同清洗方式处理的莲藕切片在贮藏期间的色差值变化。结果表明:贮藏温度为4℃条件下,与对照组比,不同处理液均能显著(p<0.05)抑制鲜切莲藕的酶促褐变,其中p H3.0、有效氯浓度(ACC)40 ppm的强酸性电生功能水浸泡处理15 min,能最好保持鲜切莲藕的色泽品质,最大程度地抑制褐变反应。贮藏两周后,对照组褐变度(L*值)下降了45.0%以上,色泽变暗,而经强酸性电生功能水处理的莲藕其褐变度值保持最高,下降了约30.0%,且表面微生物数量减少最多,减少了42.9%,很好的保护了鲜切莲藕的色泽,提高产品品质。      

Slicing increases antioxidant capacity of fresh‐cut lotus root (Nelumbo nucifera G.) slices by accumulating total phenols

Slicing is an abiotic stress during fresh‐cut lotus root slices (FLS) preparation. To evaluate the potential ability of slicing to induce antioxidant capacity (AC) in FLS, fresh lotus roots were sliced into 0.4 cm thick slices and stored at 7 °C for 7 days using intact root segments as control. Results showed slicing induced 68.3% higher phenylalanine ammonia‐lyase (PAL) activity and parallel 130.5% more total phenol (TP) accumulation after 7 days storage compared to control. AC values in FLS assayed by FRAP and ABTS^●+ were 41.5% and 93.8% more than those in control samples at the end of storage, respectively. Such increases in AC values were mainly attributed to TP accumulation as a positive correlation existed between AC and TP. However, slicing significantly accelerated FLS browning by increasing the polyphenol oxidase (PPO) activity during storage. Nevertheless, FLS was still marketable with the maximum browning index of 1.9 after 7 days storage.     

4种不同切割方式对鲜切莲藕品质和抗氧化性的影响

目的 分析比较4种不同切割方法处理莲藕在贮藏期间品质和抗氧化性的变化,筛选出最优的切割莲藕方式,为鲜切莲藕加工和贮藏提供理论基础。方法 以鄂莲5号莲藕为原料,采用去皮、切片、切丝以及切碎4种不同切割方式进行处理,分析菌落总数、色泽、呼吸强度、抗坏血酸、酚类物质、活性氧以及抗氧化酶等在贮藏期间的变化。结果 对比4种切割方式,去皮处理有效抑制菌落总数和失重率的增加,延缓鲜切莲藕褐变,更好维持莲藕的色泽。同时鲜切处理能够增强苯丙氨酸解氨酶和多酚氧化酶活性,诱导酚类物质含量积累,且随着切割损伤的越强而降低。去皮处理能够显著提高鲜切莲藕的总酚含量,其含量从140.46mg/kg增加到191.03mg/kg,增加率为36%,同时提高了1,1-二苯基-2-三硝基苯肼清除率和超氧化物歧化酶活性,提高率分别为84.01%和15.4%。结论 与切片、切丝和切碎处理相比,去皮处理能够显著抑制鲜切莲藕的褐变,同时诱导酚类物质含量增加,增强1,1-二苯基-2-三硝基苯肼清除率和超氧化物歧化酶活性,从而提高鲜切莲藕的抗氧化能力。     

高浓度二氧化碳气调包装通过调节酚代谢抑制鲜切莲藕的酶促褐变

鲜切莲藕褐变的主要原因是酶促褐变,高浓度CO_2气调包装(Modified-atmosphere packaging,MAP)可以有效延缓鲜切果蔬褐变,而苯丙氨酸解氨酶(L-phenylalanine ammonia-lyase,PAL)、多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)的编码基因是引起果蔬褐变的主要基因。然而,高浓度CO_2 MAP对鲜切莲藕片PAL、PPO、POD酶及其编码基因表达的影响却鲜有报道。本文分析了100%CO_2MAP对鲜切莲藕贮藏过程中褐变度、总酚含量、PAL、PPO和POD酶活性及其编码基因表达的影响。结果表明:100%CO_2 MAP对延缓鲜切莲藕褐变有较好效果,且100%CO_2 MAP贮藏期间鲜切莲藕PAL、PPO和POD酶活性随褐变程度的增加而同步变化。此外,Nn PAL1,Nn PPOA和Nn POD2/3的表达变化与PAL,PPO和POD酶活性的变化及褐变相一致,说明高浓度CO_2 MAP可能通过下调Nn PAL1,Nn PPOA和Nn POD2/3的表达来延缓鲜切莲藕褐变。     

柠檬酸亚锡二钠对鲜切莲藕护色作用的研究

柠檬酸亚锡二钠(DSC)是一种新型护色剂。将DSC用于鲜切莲藕预处理阶段,抑制莲藕多酚氧化酶活力及褐变,探讨影响DSC对鲜切莲藕片护色作用的因素,并与其他常用护色剂的护色效果进行对比。结果表明:DSC对鲜切藕产品低温保藏期间的褐变和多酚氧化酶活力都有很好的抑制作用,在pH 3～6条件下用0.05%～0.2%DSC浸泡液处理15min后,鲜切藕产品可保持较低的褐变度和多酚氧化酶活力,同时在4℃、20d内DSC的护色效果稳定;与其他常用护色剂比较,在0.1%的等量护色剂浓度下,DSC护色效果优于柠檬酸、抗坏血酸、异抗坏血酸钠,与亚硫酸氢钠效果相当。     

短波紫外线处理对鲜切莲藕酶促褐变的影响

以'粉红藕'为试材,研究了短波紫外线处理对鲜切莲藕4℃冷藏过程中褐变效果的影响。主要分析了不同照射剂量(1.0、3.0和5.0 kJ/m²)下鲜切莲藕色泽、失水率、硬度、没食子酸含量、儿茶酚含量、多酚氧化酶(PPO)和超氧化物歧化酶(SOD)活性等对生理生化指标的影响。结果表明,5.0 kJ/m²剂量UV-C处理的鲜切莲藕褐变指数在贮藏第12 d时低于30,显著低于对照和其他处理组(P<0.05),5.0 kJ/m²剂量UV-C处理可通过抑制褐变底物儿茶酚、没食子酸与PPO反应来延缓鲜切莲藕的酶促褐变,并通过延缓硬度的下降,提高鲜切莲藕的贮藏品质。综合保鲜效果得出,12 d的贮藏期内,5.0 kJ/m²剂量UV-C处理抑制鲜切莲藕的褐变效果最佳。     

高压静电场（HVEF）联合冰温处理对莲藕贮藏品质变化的影响

以新鲜莲藕为试材,研究了高压静电场联合冰温技术对莲藕贮藏期间褐变和贮藏品质的影响。结果表明,高压静电场处理联合冰温贮藏对莲藕贮藏期间的褐变有抑制作用,贮藏28 d后褐变度仅为7(A410×10),腐烂指数为15%,均明显低于对照。同时产品保持较高的硬度和可溶性固形物含量,贮藏28 d后硬度约保持为3 kgf/cm2,可溶性固形物约为4%。并且贮藏28 d后,呼吸强度为50 mg/kg.h,乙醇含量为18 nmol/g,细菌总数为5 CFU/g,均明显低于对照,说明该处理可以有效地抑制呼吸强度和乙醇的积累,控制微生物数量的增加,减少腐烂发生。     

Fogging with antibrowning agents as an alternative to conventional immersion treatments to extend shelf life of mushrooms

Mushroom (Agaricus bisporus) is a highly perishable product and can be easily damaged when immersion in antibrowning solutions is performed; therefore, fogging application represents a less aggressive technique. The objective of this work was to evaluate the effect of different antibrowning agents (ascorbic acid, sodium metabisulphite and L-cysteine) applied by two methodologies (immersion and fogging) on the quality of mushrooms during storage at 5 °C. Weight losses, microstructural organisation, colour and texture changes were evaluated as quality indicators. Polyphenol oxidase activity, phenolic content and antioxidant activity were also evaluated. Fogging achieved browning inhibition without major changes in firmness, while immersion treatments inhibited browning but significant changes in firmness were found. Browning inhibition achieved by fogging showed similar results when compared to the conventional immersion treatments. Fogging has the advantage of being less aggressive than immersion while requiring a significantly smaller amount of antibrowning solution than traditional immersion.     

精准温度处理对鲜切莲藕褐变、生理和品质的影响

为了明确精准温度处理对防褐变剂处理后鲜切莲藕褐变、生理和品质的调控作用,采用防褐变剂（质量分数1.0%无水柠檬酸+0.1%抗坏血酸钙+0.2% L-天门冬氨酸）处理鲜切莲藕,在相温（?0.5±0.1）℃、冰温（?0.5±0.3）℃和冷藏（4±1）℃的条件下贮藏,研究不同精准温度对鲜切莲藕表观色泽、褐变底物与相关酶活性、生理指标和营养品质的影响。结果表明,贮藏6 d时,精准温度（相温、冰温）处理可以延缓L*的降低、a*和褐变度的增加,抑制总酚的下降和褐变相关酶多酚氧化酶和过氧化物酶活性,其中相温贮藏维持鲜切莲藕原有色泽最佳。在贮藏过程中,精准温度（相温、冰温）处理能够抑制鲜切莲藕呼吸强度、乙烯生成速率、相对电导率和丙二醛含量上升,同时延缓鲜切莲藕还原糖的升高和V_C含量的下降。通过SPSS综合评分显示,相温组综合得分最高,主成分分析显示,相温组与多酚氧化酶、相对电导率、褐变度、丙二醛、a*的相关性较低。因此,相温贮藏更好地延缓鲜切莲藕贮藏期间褐变的发生并维持其品质。     

Evaluation of Alternative Preservation Treatments (Water Heat Treatment,Ultrasounds, Thermosonication and UV-C Radiation) to Improve Safety and Quality of Whole Tomato

Previously optimised postharvest treatments were compared to conventional chlorinated water treatment in terms of their effects on the overall quality of tomato (‘Zinac’) during storage at 10 °C. The treatments in question were water heat treatment (WHT?=?40 °C, 30 min), ultrasounds (US?=?45 kHz, 80 %, 30 min), thermosonication (TS?=?40 °C, 30 min, 45 kHz, 80 %) and ultraviolet irradiation (UV-C: 0.97 kJ m^?2). The quality factors evaluated were colour, texture, sensorial analysis, mass loss, antioxidant capacity, total phenolic content, peroxidase and pectin methylesterase enzymatic activities, and microbial load reduction. The results demonstrate that all treatments tested preserve tomato quality to some extent during storage at 10 °C. WHT, TS and UV-C proved to be more efficient on minimising colour and texture changes with the additional advantage of microbial load reduction, leading to a shelf life extension when compared to control trials. However, at the end of storage, with exception of WHT samples, the antioxidant activity and phenolic content of treated samples was lower than for control samples. Moreover, sensorial results were well correlated with instrumental colour experimental data. This study presents alternative postharvest technologies that improve tomato (Zinac) quality during shelf life period and minimise the negative impact of conventional chlorinated water on human safety, health and environment.     

Suppression of internal browning and maintenance of antioxidants in beeswax plus salicylic acid coated pear fruit during different storage conditions

Postharvest application of edible waxes blended with antioxidants is an effective strategy to regulate postharvest quality and antioxidant losses in fruits. Effect of beeswax coatings (BW 1.0% and 2.0%) alone or enriched with salicylic acid (SA) on antioxidant properties of pear fruit was studied during 67 days of cold storage and 20 days of supermarket storage conditions respectively. Results showed that under both the storage conditions fruits coated with BW + SA maintained higher total phenolic content (TPC), antioxidant activity and ascorbic acid content (AsA) as compared to the control. Furthermore, combined coatings significantly reduced polyphenol oxidase (PPO) activities and inhibited internal browning (IB) in pears throughout cold and supermarket storage. Overall, the BW 2.0% + SA 2.0 mM exhibited the most competitive effect in terms of preserving the antioxidant properties and preventing internal browning in pears during storage.     

热处理结合γ-氨基丁酸对鲜切苹果生理特性和品质的影响

为提高鲜切苹果贮藏期的品质,本文以富士苹果为材料,研究了45 ℃水整果浸泡(2 min)、果实鲜切后γ-氨基丁酸(GABA)处理(1.5%,10 min)及热处理结合GABA对贮藏期间苹果切片品质的影响。结果表明:4 ℃贮藏8 d时,对照组苹果切片感官品质下降迅速,可溶性固形物和可滴定酸含量降低,L*值降低,BI值升高,褐变明显发生,多酚氧化酶(PPO)和过氧化物酶(POD)活性升高,DPPH自由基清除率下降,贮藏后期MDA大量积累。与对照相比,热处理、GABA处理及热处理结合GABA均获得较高的感官评分,抑制了果肉可溶性固形物和可滴定酸含量的下降,保持较高的L*值,减轻褐变的发生,提高了总酚含量,抑制了多酚氧化酶(PPO)和过氧化物酶(POD)活性上升,减少了抗氧化物质的损失,保持较高的DPPH清除率,并减轻了MDA积累,其中,以热处理结合GABA效果最好。     

气体结合高静压对干锅藕片贮藏期品质及微生物的影响

研究气体结合高静压(high hydrostatic pressure,HHP)处理对干锅藕片的货架期及贮藏品质的影响。测定充气包装后经高静压处理的干锅藕片在贮藏过程中微生物菌落总数、质构、色差、油脂过氧化值的变化及感官评价。结果表明:充CO_2结合高静压(CO_2-HHP)处理的干锅藕片贮藏期较充N_2、充CO_2、真空包装结合高静压(vacuum-HHP)处理、充N_2结合高静压(N_2-HHP)处理长,且第一循环硬度保持在14 000 g左右,b*值变化在2以内CO_2-HHP处理的干锅藕片在贮藏期内感官评价始终较好。这为低酸性食品的保藏提供了新的思路与方法。     

Physicochemical and Sensorial Properties of Grapefruit Jams as Affected by Processing

Jam is an effective and tasty way of preserving fruit. Jam processing procedures as well as storage conditions and duration are important factors for jam quality. Traditional jam processing involves the application of severe thermal treatments that imply undesirable changes in the product quality characteristics such as colour, texture, flavour and nutritional and functional value. In this work, osmotic dehydration (OD) and/or microwave energy (MW) was proven as adequate to obtain jam with the typical characteristics of water content, degree Brix, pH and water activity of jam obtained by conventional thermal heating. The sensory evaluation carried out to compare the product showed that samples submitted to more intense heating treatments (conventional or MW) had significantly higher scores in colour saturation, brightness, grapefruit taste and extensibility than OD or OD+MW ones. As deduced from the obtained results, OD treatment prevents grapefruit colour changes, and mild MW heating contributes to increase the consistency and decrease the extensibility of the obtained jam. In this way, OD+MW jam was preferred by assessors mainly due to its higher consistency. The sample obtained by this procedure was stable during storage.     

壳聚糖/竹叶抗氧化物复合处理对鲜切生姜保鲜效果的影响

目的：为研究壳聚糖（chitosan,CTS）/竹叶抗氧化物（antioxidant of bamboo leaves,AOB）复合处理对鲜切生姜保鲜效果的影响。方法：将鲜切生姜分别采用蒸馏水、0.3% AOB、1.5% CTS以及0.3% AOB＋1.5% CTS浸泡处理 5 min,取出沥干分装于市购的聚乙烯保鲜袋中,置于（14±1.0）℃恒温库中贮藏,每5 d测定各项生理生化指标。结果：与对照组相比较,3 种不同处理均能对鲜切生姜起到不同程度的保鲜效果;均能抑制鲜切生姜的褐变;减缓VC含量的下降,抑制营养物质的损失;减少丙二醛的积累;抑制微生物生长;维持良好的硬度、弹性、咀嚼性,抑制生姜质构品质的下降。同时,CTS与AOB复合处理能够有效抑制鲜切生姜细胞内含物的破坏及质壁分离现象的发生。结论：在研究的3 种不同处理方式中0.3% AOB＋1.5% CTS处理效果最为明显,其次是1.5% CTS处理组,0.3% AOB处理组的保鲜效果不显著。     

Combined effect of microwave and ultrasonication treatments on the quality and stability of sugarcane juice during cold storage

The main objective of this study was to investigate the combined effect of microwave (MW) treatment (2450 MHz for 120 s), ultrasonication (US) (24 KHz, 20 °C for 20 min) and combined treatment (MW-US) on the quality and stability of sugarcane juice (SCJ) during 21 days of storage at 4 °C. The effect of the treatments and storage time on physicochemical, bioactive compounds (total phenolic, flavonoids and ascorbic acid content) and microbial analysis of SCJ. No significant (P < 0.05) changes were observed in °Brix, while there was an increase in pH and a decrease in titratable acidity in all treatments. Compared to US and MW, MW-US treatments was more effective in preserving colour attributes, total phenolic and flavonoids contents, ascorbic acid and antioxidant capacities of the SCJ during storage. The results regarding the microbial count indicate that more microbial safety and longer shelf life was achieved by MW-US. MW-US treatment is an effective technology for improving the safety and shelf life of SCJ by minimising quality changes, retaining bioactive compounds and reducing microbial growth during storage.     

超声强化方式对热泵干燥莲藕品质特性的影响

目的：探明适宜的莲藕超声强化干燥方式,提高莲藕加工品质。方法：将超声（US）、直触超声（CU）、超声渗透脱水（USOD）3种超声处理方式与热泵干燥（HPD）进行串并联处理,研究US、CU和USOD对莲藕HPD过程中干燥特性、外观色泽、微观结构、质构、营养成分及抗氧化特性等指标的作用规律,并采用变异系数法对不同超声强化方式干燥的莲藕品质进行综合评价。结果：US、CU和USOD均能提升莲藕的HPD干燥速度;USOD-HPD所得到莲藕的亮度（L^*）、多糖含量和羟自由基清除率最好,分别为77.98、51.68 mg/g和45.94%;US-HPD处理可较好地保留莲藕中的黄酮和维生素C含量;HPD莲藕的多酚含量和DPPH自由基清除率最高;变异系数法综合评价结果表明USOD-HPD的综合评分最高（0.422）。结论：USOD-HPD可以有效提升莲藕的干燥品质。     

两种不同质地的莲藕碱溶性果胶组分热降解规律及流变学差异

选择两种不同质地的莲藕作为材料，研究其碱溶性果胶（sodium carbonate-soluble pectin fraction，NSF）的热降解差异及其与流变的关系。对碳酸钠提取的NSF进行不同温度处理，通过一级结构和纳米微观结构观察和分析发现，沔城藕（粉藕）的NSF热降解程度大于芦林湖藕（脆藕）；芦林湖藕NSF链呈星型状（长支链）而沔城藕NSF链大多呈短直链，两者经加热后均出现链长变短、链高降低、分支度减小的现象；流变学结果表明两种NSF的黏稠度经热处理后均明显降低，沔城藕的NSF假塑性略有增加而芦林湖藕NSF假塑性减小。结合结构分析与流变学结果分析得到果胶链的长度、高度与黏稠度呈正相关；分支度和不同长度的链长所占百分比（分子质量分布）是导致其假塑性不同的重要原因。因此，NSF的结构与流变学特性密切相关，同时也说明NSF的热降解差异与两种藕质地差异存在关联。本研究为NSF的热降解与果蔬质构（加工、成熟度）之间的关系提供了一定理论依据。     

Effects of chitosan-based coating and modified atmosphere packaging (MAP) on browning and shelf life of fresh-cut lotus root (Nelumbo nucifera Gaerth)

The present study investigated the effect of chitosan coating containing antibrowning agents and modified atmosphere packaging (MAP) on the browning and shelf life of fresh-cut lotus root stored at 4 °C for 10 days. The atmosphere in the packages was evaluated for O₂ and CO₂ concentrations. The browning on the surface of lotus root slices was prevented by chitosan-based coating and MAP treatment. L* values of coated + MAP and control samples were 68.8 and 48.9 after 8 days storage, respectively. For a^? and b^? values, samples of coated + MAP treatment had the slowest increasing trends among all the treatments. At the end of storage, the coated + MAP samples exhibited the lowest polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content. Its highest overall visual quality (OVQ) scores (> 7) demonstrated that chitosan-based coating + MAP treatment could provide a better inhibitory effect on the browning and extend the shelf life of fresh-cut lotus root.Industrial relevance: Fresh-cut vegetables have drawn the attention of industry as a novel lightly processed product. Both edible coating and MAP treatment cause changes in atmosphere composition and respiration rate of lotus root slices. This combined treatment could be used to control the browning and improve the storage life of this fresh-cut vegetable. This information could be useful for the development of novel application to edible coating and MAP design for lightly processed lotus root.     

Total phenolics,antioxidant properties and quality of fresh-cut onions (Allium cepa L.) treated with mild-heat

This study investigated the effect of mild-heat on fresh-cut onion slices by treating in hot water (50, 60, 70 °C) for 1 min. Total phenolics (TP), antioxidant properties, colour, and weight loss of slices were evaluated during 4 °C storage at 7-day intervals (21 days total). The 60 °C heat treatment resulted in a significant increase in TP, from 44.92 to 52.32 mg GAE/100 g. Except for 50 and 70 °C treatments, TP in control and 60 °C treated fresh-cut onions decreased during storage. The antioxidant properties of fresh-cut onions were 1.31, 0.99, and 62.49 μM TE/g using ABTS, DPPH, and ORAC assays, respectively. The mild-heat treatments did not affect ABTS and DPPH antioxidant activities and the colour of fresh-cut onions. The storage time had mixed effect on the antioxidant properties (ABTS decreased; DPPH and ORAC remained fairly stable). The 50 °C samples exhibited the lowest weight loss during 21-day storage.