Effect of integrated application of chitosan coating and modified atmosphere packaging on overall quality retention in litchi cultivars

BACKGROUND: The storage life of litchi is limited due to pericarp browning and decay. Modified atmosphere packaging (MAP) showed promising results for ensuring quality retention. However, to improve the efficiency of MAP the integrated treatment of a chitosan coating and MAP was investigated. RESULTS: The effect of chitosan (1.0 g L⁻¹) + MAP was compared with MAP (control), and was effective in preventing decay, browning and retaining the pericarp colour in the cultivar McLean's Red. Chitosan (1.0 g L⁻¹) + MAP significantly reduced polyphenol oxidase (PPO) and peroxidase (POD) activity, retained membrane integrity, anthocyanin content and prevented the decline of pericarp colour values during storage. The POD activity was greater than the PPO activity in the cultivars McLean's Red and Mauritius. The two cultivars differed in anthocyanin content and the activity of oxidation enzymes. The gas compositions within the packages were compared between chitosan at 1.0 g L⁻¹ and 20.0 g L⁻¹ concentration for both cultivars. Chitosan (20.0 g L⁻¹) + MAP lowered the respiration during storage in both cultivars compared to 1.0 g L⁻¹ + MAP. CONCLUSION: The McLean's Red cultivar is better suited for chitosan (1.0 g L⁻¹) + MAP integrated treatment than is Mauritius in retaining overall quality. Copyright © 2009 Society of Chemical Industry     

Vital Characteristics of Litchi (Litchi chinensis Sonn.) Pericarp that Define Postharvest Concepts for Thai Cultivars

To assess the fruit-specific determinants of pericarp browning, litchi pericarp was characterized in terms of appearance, the polyphenol pattern as specified by HPLC-DAD-MS ⁿ without and after thiolysis, and the activities of polyphenol oxidase (PPO) and peroxidase (POD) by exploring “Kwang Jao,” “O-Hia,” “Kim Cheng,” and “Chacapat” fruit on the respective harvest day, “Hong Huey” fruit also throughout 52 days of cold storage (5 °C, 95% relative humidity). At harvest, PPO activity was maximum for “Kim Cheng” pericarp (126 μkat/hg), whereas POD activity was striking for that of “O-Hia” (512 μkat/hg, including membrane-bound isoforms). Flavan-3-ol and proanthocyanidin patterns were consistent for all cultivars. However, cultivars with sharp-pointed and round–obtuse protuberances differed in pericarp anthocyanin and flavonol glycosylation patterns. The molar ratio of cyanidin 3-O-rutinoside to its glucoside was ≤6:1 for “Hong Huey” and “Kwang Jao,” but ≥43:1 for “Kim Cheng” and “Chacapat” pericarp. Long-term storage gave evidence of two key processes involved in pericarp browning: (1) PPO-mediated oxidation of abundant (?)-epicatechin (1.4–2.0 g/hg), resulting in dark brown pigments, and (2) microcrack-induced formation of light brown surface scurf, supposably with involvement of POD. Accordingly, an improved scheme for litchi pericarp browning was proposed. As regards recommendable postharvest concepts for each cultivar, “Chacapat” suited most for long-distance transports due to its overall low susceptibility to pericarp browning. Properties of “O-Hia” litchi, being prone to surface scurf formation, suggested preferred distribution via domestic markets. High contents of flavonols (e.g., quercetin glycosides, 166 mg/hg) and A-type-linked procyanidins (e.g., procyanidin A2, 1,092 mg/hg) qualified pericarp of “Hong Huey” litchi as raw material for polyphenol extracts exerting antioxidant properties.     

The effects of soil management systems on the chemical composition and quality of apples. II. Cox's orange pippin and red jonathan apples

The quality of fruit of Cox's Orange Pippin and Red Jonathan from different soil management treatments was tested in 1969 and again in 1970. The range of tests included soluble solids, reducing sugar and acid contents, texture measurements and taste panel assessment. The non-cultivation treatment gave the highest yields and the quality of fruit of both cultivars from all treatments was acceptable. Grass improved the quality of Cox's Orange Pippin in 1969 but not in 1970. Cultivation gave higher soluble solids levels than non-cultivation for Red Jonathan in both seasons. There was no correlation between soluble solids content and taste panel response for either cultivar. However, solids levels of fruit from the different treatments tested were close together thus making it difficult for the panel to distinguish between samples. Soluble solids levels increased in fruit of Cox's Orange Pippin during storage at 1°C in 1969 but remained constant in 1970. Levels in Red Jonathan decreased in both seasons. Fruit of Cox's Orange Pippin became softer during storage in both seasons while fruit of Red Jonathan softened only in 1969. Acid levels for fruit of both cultivars from the different soil management treatments were not significantly different in either season.     

Effect of oxalic acid on control of postharvest browning of litchi fruit

Litchi (Litchi chinensis Sonn.) fruit, cv. Huaizhi, was treated with 2 and 4 mM oxalic acid and stored at room temperature to investigate the effect of oxalic acid on pericarp browning. The results showed that the pericarp browning indices of the fruit, treated with both oxalic acid concentrations, were significantly lower than that of the control, due to increase of membrane integrity, inhibition of anthocyanin degradation, decline of oxidation, and maintanance of relatively low peroxidase activity in the fruit during storage. It appears that application of oxalic acid can effectively control the pericarp browning of litchi fruit during postharvest storage.     

Antioxidant properties of anthocyanins extracted from litchi (Litchi chinenesis Sonn.) fruit pericarp tissues in relation to their role in the pericarp browning

Anthocyanins were extracted and purified from litchi fruit pericarp and their antioxidant properties were investigated. Effects of exogenous anthocyanin treatments on pericarp browning and membrane permeability of harvested litchi fruit were also evaluated. Anthocyanins from litchi fruit pericarp strongly inhibited linoleic acid oxidation and exhibited a dose-dependent free-radical-scavenging activity against DPPH radical, superoxide anions and hydroxyl radical. The degradation of deoxyribose by hydroxyl radicals was shown to be inhibited by anthocyanins acting mainly as chelators of iron ions rather than directly scavenging hydroxyl radicals. Anthocyanins were also found to have excellent reducing power. The reducing power of anthocyanins, ascorbic acid and butylated hydroxytoluene all at 100 μg/ml were 3.70, 0.427 and 0.148, respectively, indicating that anthocyanins from litchi pericarp had a strong electron-donating capacity. Furthermore, application of anthocyanins to harvested litchi fruit significantly prevented pericarp browning and delayed the increase in membrane permeability. It was therefore suggested that anthocyanins could be beneficial in scavenging free radicals and reducing lipid peroxidation of litchi fruit pericarp.     

茶树油、丁香酚、柠檬醛在荔枝保鲜中的应用

本文研究了茶树油、丁香酚和柠檬醛的挥发性香氛对荔枝的保鲜作用,采用复配方法探究三种香料对荔枝的协同保鲜效果。结果表明:在冷藏(4±1℃)过程中,茶树油和丁香酚、柠檬醛的挥发性香氛可抑制荔枝果实腐败,延缓果皮衰老和果肉维生素C含量的降低,对保持荔枝果实的感官品质也具有积极作用;且三者复配后效果更佳,贮藏至18天,复配组荔枝的腐败率、果皮相对渗透率、维生素含量分别为对照组的56.0%、72.8%、124.8%,果皮颜色、果实滋味、果实气味和整体评价分别比对照组高2.4、3.3、2.6和3.4分。     

Antioxidant activities and contents of polyphenol oxidase substrates from pericarp tissues of litchi fruit

The experiments were performed to extract and purify substrates for polyphenol oxidase (PPO) from pericarp tissue of postharvest litchi fruit. Two purified PPO substrates were identified as (−)-epicatechin and procyanidin A2. The antioxidant properties of two PPO substrates were further evaluated in the present study. Variation in the content of the major substrate (−)-epicatechin of litchi fruit during storage at 25 °C was analysed using the HPLC-UV method. The results showed that (−)-epicatechin exhibited stronger antioxidant capability than procyanidin A2, in terms of reducing power and scavenging activities of DPPH radical, hydroxyl radical and superoxide radical. Furthermore, (−)-epicatechin content in pericarp tissue tended to decrease with increasing skin browning index of litchi fruit during storage at 25 °C. Thus, these two compounds can be used as potential antioxidants in litchi waste and the fresh pericarp tissue of litchi fruit exhibited a better utilisation value.     

Difference in volatile composition between the pericarp tissue and inner tissue of tomato (Solanum lycopersicum) fruit

Numerous studies have reported the volatile profiles in the whole fruit or pericarp tissue of tomato (Solanum lycopersicum) fruit; however, information is limited on the volatile composition in the inner tissue and its contribution to tomato aroma. For this, the pericarps and inner tissues of “Moneymaker,” “UglyRipe,” and “FL 47” fruits were separated before volatile analysis. Result showed that the volatile profiles were quite similar between the pericarp and inner tissue, suggesting the inner tissues also have a contribution to overall aroma quality. Besides the difference in volatile profile among cultivars, a higher concentration of alcohols was observed in the inner tissues of tomato fruit in comparison with that in the pericarp, which was associated with higher levels of 3‐methylbutanal, 2‐methylbutanal, 3‐methylbutanol, and 2‐methylbutanol in the inner tissue. These results also imply that different sampling methods might impact tomato aroma quality, which needs further verification via sensory penal.

Practical applications

The information on the volatile profile in the inner tissue and its contribution to tomato aroma is still rudimentary. In this study, the pericarp and inner tissue were separated from three tomato cultivars of different genetic background, and the volatile compositions were analyzed with HS‐SPME‐GC‐MS. Result showed that the volatile compositions were quite similar between the pericarp and inner tissue, suggesting that the inner tissues also have a contribution to overall aroma quality. Besides, a higher concentration of alcohols was observed in the inner tissues of tomato fruit in comparison with that in the pericarp, which was associated with higher levels of 3‐methylbutanal, 2‐methylbutanal, 3‐methylbutanol, and 2‐methylbutanol in the inner tissue. This study will provide the researchers and consumers some useful information on volatile composition in the inner tissue, its contribution to tomato aroma, and the impact of different sampling methods on the volatile profile.     

安溪油柿叶保健茶的加工工艺

本文以我国南方主栽的名优柿树品种“安溪油柿”柿叶为原料,柿叶鲜叶采摘后经挑选、萎凋、杀青、揉捻、包揉、烘干、调配、包装等加工工序,可以研制成一种色、香、味、形俱佳的新型柿叶保健茶。     

IDENTIFICATION OF PROCYANIDIN A2 AS POLYPHENOL OXIDASE SUBSTRATE IN PERICARP TISSUES OF LITCHI FRUIT

Postharvest browning of litchi fruit results in short shelf life and reduced commercial value. Experiments were conducted to separate, purify and identify polyphenol oxidase (PPO ) substrates that cause litchi fruit to brown. PPO and its substrate were extracted from the pericarp tissues of litchi fruit. The litchi PPO substrate was purified using polyamide column, silica gel column and Sephadex LH‐20 column chromatography. The browning substrate was selected by a 0.5% FeCl₃ solution and then identified using a partially purified litchi PPO. Analyses of ultraviolet spectrometry, nuclear magnetic resonance and electrospray ionization mass spectrometry indicated that the PPO substrate was procyanidin A2. The substrate can be oxidized to ο‐quinones by litchi PPO and then form brown‐colored by‐products, resulting in pericarp browning of harvested litchi fruit.     

Preliminary Aroma Comparison of Marion (Rubus spp. hyb) and Evergreen (R. laciniatus L.) Blackberries by Dynamic Headspace/OSME Technique

ABSTRACT: Marion and Evergreen blackberry aromas were analyzed with a purge-and-trap gas chromatography-olfactometry/mass-spectrometry (GC-O/MS) technique. Fifty-eight aromas were identified. Thirty were common to both cultivars, and 22 have not been previously reported in blackberry fruit. Comparison of cultivars shows the Marion blackberry contains more esters, while the Evergreen contains more alcohols. The aroma profile of blackberry is complex, as no single volatile was unanimously described as characteristically blackberry.     

Identification of (−)-epicatechin as the direct substrate for polyphenol oxidase isolated from litchi pericarp

Postharvest browning of litchi fruit results in a short life and a reduced commercial value. The experiments were conducted to separate, purify and identify the polyphenol oxidase (PPO) substrates that cause litchi fruit to brown. PPO and its substrates were, respectively, extracted from fruit pericarp tissues. The substrates for litchi PPO were separated and purified using polyamide column chromatography, silica gel column chromatography and preparative thin layer chromatography. The substrate was further identified by 0.5% FeCl₃ solution and enzymatic reaction with litchi PPO. On the basis of UV, ¹H NMR, ¹³C NMR, and ESI-MS data, the direct substrate for the PPO from litchi fruit pericarp tissues was identified to be (−)-epicatechin.     

Influence of temperature and packaging on physiological and chemical profiles of imported litchi fruit

The aim of this study was to detail the physiological and biochemical changes in non-adulterated and commercially-treated litchi fruit stored in different packaging films under different storage temperatures. Litchi fruit cv. Mauritius treated with either SO₂ and acid (commercially-treated fruit), or free from both SO₂ and acid (non-adulterated fruit), were imported from Israel and packed using two different packaging films viz. micro-perforated polypropylene or PropaFresh™ PFAM, or stored unwrapped, at 5 or 13 °C for 11 days. Both CO₂ and ethylene concentrations were lower in commercially-treated fruit and at storage of 5 °C but higher in PropaFresh™ PFAM films. Weight loss was least in commercially-treated fruit wrapped with PropaFresh™ PFAM at 5 °C. Non-adulterated fruit wrapped in PropaFresh™ PFAM had higher individual aril sugars and organic acids whilst commercially-treated fruit retained higher concentrations of anthocyanins. These results indicate that PropaFresh™ PFAM packaging at 5 °C could be used to maintain postharvest quality in both commercially-treated and non-adulterated litchi fruit.     

不同品种荔枝发酵饮料挥发性香气成分对比研究

以黑叶、禾荔、妃子笑3个广西大宗品种荔枝果肉为原料,经乳酸菌复合菌种发酵得到荔枝发酵饮料。 在此基础上,以发酵饮 料为研究对象,采用气质联用（GC-MS）法对比分析了3个品种荔枝发酵饮料的挥发性香气成分及含量。 研究结果表明,黑叶、禾荔、妃 子笑3个品种荔枝发酵饮料中共检出香气成分72、48、52种,主要以烯类和醇类为主。 黑叶、禾荔、妃子笑品种荔枝发酵饮料中含量最 高的挥发性香气物质分别为香茅醇（16.63%）、乙醇（17.62%）、顺式玫瑰醚（11.33%）。 三种荔枝发酵饮料的挥发性香气成分差异较 大,其中黑叶品种荔枝发酵饮料中致香成分最丰富,明显多于另外两种。     

魔芋葡甘聚糖可食性涂膜处理荔枝的保鲜效果

采用魔芋可食性膜处理荔枝，用PF塑料袋包装，在常温下进行保鲜试验。结果表明：经该膜保鲜后的荔枝，在贮藏过程中果皮褐变率和好果率较好的控制，基本上防止了果皮失水、腐烂变质，保持荔枝原有品质，延长了保鲜期和货架寿命。     

Quantitative analysis of flavour volatiles detects differences among closely related traditional cultivars of tomato

Volatile compounds with a major contribution to aroma have been quantitatively determined in four traditional tomato cultivars and one commercial F1 hybrid. One of the traditional cultivars was the most appreciated for flavour and overall acceptability in tests performed using a panel of 30 untrained tasters. The same cultivar showed significantly higher contents of hexanal and cis‐3‐hexenal volatile compounds, which have been previously reported to be two of the most important contributors to tomato flavour. On the basis of a small number of fruits per cultivar, significant differences among very closely related tomato cultivars can be detected for volatile aromas, thus allowing the use of the determination of volatiles as a possible tool in tomato breeding programs, making even the selection of single plants possible. Copyright © 2004 Society of Chemical Industry     

Structural changes,chemical composition and antioxidant activity of cherry tomato fruits (cv. Micro‐Tom) stored under optimal and chilling conditions

BACKGROUND: Cherry tomato fruits cv. Micro‐Tom, a model plant for tomato genetics, were analysed in order to determine the main structural and chemical changes under optimal and chilling storage conditions. The comparison of Micro‐Tom to standard tomato cultivars will give an insight into suitability of this dwarf cultivar as a model for studying the influence of low‐temperature conditions on tomato fruits. RESULTS: During chilling, fruit tissue was progressively destroyed due to the collapse of the deep layers of the pericarp. Chilling lowered the typical tomato kinetics of ripening in sugars (glucose, fructose, sucrose), organic acids (tartaric, malic, citric, ascorbic and succinic) and the antioxidants phenol and lycopene, while carotenoid synthesis seemed to be blocked. Glutathione level was elevated and the activity of ROS scavenging enzymes was altered. Essentially, Micro‐Tom fruits showed a quality evolution that was similar to that described for standard tomato cultivars. CONCLUSION: The cherry tomato cultivar Micro‐Tom could be used as a model for studying the influence of low temperature on biochemical and structural changes taking place during chilling injury conditions. Copyright © 2009 Society of Chemical Industry     

Role of endogenous and exogenous phenolics in litchi anthocyanin degradation caused by polyphenol oxidase

The degradation of anthocyanins and/or the oxidation of phenolics caused by polyphenol oxidase (PPO) results in an enzymatic browning reaction of fruits and vegetables. This work was conducted with a view to explaining the unexpected observation that litchi (Litchi chinensis Sonn.) PPO did not directly oxidise litchi anthocyanins. PPO and anthocyanin from litchi fruit pericarp were extracted and purified, respectively, and then the anthocyanin degradation by PPO in the presence of (−)-epicatechin (endogenous PPO substrate), and catechol and gallic acid (exogenous PPO substrates) were analysed comparatively. The results showed that catechol was the most effective in litchi anthocyanin degradation, followed by (−)-epicatechin and gallic acid, but no significant differences existed between catechol and (−)-epicatechin. The study suggested that litchi PPO directly oxidised (−)-epicatechin; then oxidative products of (−)-epicatechin in turn catalysed litchi anthocyanin degradation, and finally resulted in the browning reaction, which can account for pericarp browning of postharvest litchi fruit.     

不同采后处理对冷藏‘南丰蜜桔’角质层形态结构及化学组成的影响

角质层是采后果实的质量调控器,不同采后贮藏条件可以改变其形态结构及化学组成。热激（heat shock,HT）和壳聚糖（chitosan,CS）处理已被证实能有效延缓果实衰老。本文以‘南丰蜜桔’为实验对象,采用扫描电子显微镜（scanning electron microscopy,SEM）和气相色谱-质谱联用仪（gas chromatography-mass spectrometry,GC-MS）,研究不同采后保鲜方式（热激、壳聚糖、热激联合壳聚糖处理）对冷藏75 d期间‘南丰蜜桔’角质层形态结构及化学组成的影响。结果表明:‘南丰蜜桔’外蜡晶体呈不规则血小板状,热激导致外蜡重分布形成更光滑的表皮外观;外蜡和内蜡分别检出38种和50种组分,其主要成分均为烷烃、酸类、酯类、萜类,角质单体共检出7种成分,主要为酸类;十六烷酸是蜡质和角质最主要的组分。外蜡含量整体上无明显的变化规律,而内蜡呈先减后增的趋势,冷藏45 d时3种保鲜方式均能有效延缓外蜡和内蜡含量的降低,其中热激效果最为显著。冷藏期间角质单体含量持续下降,3种保鲜方式均能明显抑制其含量的降低,其中,以热激处理的效果最为明显。热激处理可通过改变外蜡晶体的结构,以及调节角质层的成分代谢来保持‘南丰蜜桔’的贮藏品质,这为其开发采后贮藏保鲜策略提供了科学依据。