壳聚糖处理对纽荷尔脐橙果实采后生理及贮藏效果的影响

研究了在冷藏(7±1)℃条件下3种不同浓度(1.0%、1.5%和2.0%)的壳聚糖处理对纽荷尔脐橙果实采后生理生化及贮藏效果的影响。结果表明:壳聚糖处理能延缓脐橙果实可溶性固形物、可滴定酸、Vc的下降;抑制果实呼吸强度;减少果实水分的损失和果实腐烂;延缓果实保护性酶类SOD、CAT活性的下降,从而延长果实贮藏寿命。其中2.0%处理效果最好。     

八种水果多酚的定量分析与抗氧化活性研究

本文对比研究了8种水果的果皮、果肉、果汁及全果中维生素C与总酚含量,采用高效液相色谱法测定其多酚种类及含量,并评价其抗氧化活性。8种水果Vc含量从高到低,依次为:番石榴脐橙菠萝=木瓜青苹果=皇冠梨=金桔=芒果;总酚含量最高的水果为芒果;从8种水果中共鉴定出16种多酚类化合物,以绿原酸、儿茶素、表儿茶素、芦丁、杨梅酮和根皮苷含量较高。根据8种水果全果中多酚物质种类与含量,分为4类:(1)脐橙;(2)芒果;(3)金桔;(4)青苹果、皇冠梨、番石榴、菠萝和木瓜;DPPH自由基清除能力从强到弱,依次为芒果番石榴青苹果皇冠梨=金桔=脐橙=菠萝=木瓜;氧自由基吸收能力从强到弱,依次为脐橙番石榴皇冠梨=芒果青苹果=金桔=菠萝=木瓜。本研究可为水果精深加工及功能性食品开发提供理论指导。     

Effects of curcumin-based photodynamic method on protein degradation of oysters

Photodynamic treatment (PDT) is a novel cold-sterilisation technology, but the evaluation of the protein quality of shellfish was scarce. In this study, the effects of curcumin (CUR)-mediated PDT on delaying protein degradation of oysters during cold storage at 4 ℃ and the mechanisms were investigated. The protein-degradation indexes and related enzymes were determined every 2 days. The results showed that the content of total volatile basic nitrogen (TVB-N), polypeptide nitrogen (PeN), amino acid nitrogen (AN) and free amino acid (FAA) in photodynamic group was significantly different from the control group since the first 2 days (P < 0.05). The pH value was significantly changed by PDT at the 4th and 8th day (P < 0.05). Interestingly, the activities of serine and aspartic protease were significantly inhibited by PDT during the whole cold storage (P < 0.05). Therefore, the study indicated that PDT has a positive effect on preventing protein degradation.     

Synergistic effect between Helichrysum italicum essential oil and cold nitrogen plasma against Staphylococcus aureus biofilms on different food‐contact surfaces

Staphylococcus aureus is the most common pathogen in human, and the most diseases produced by S. aureus are associated with biofilms. Helichrysum italicum essential oil (EO), as a natural and safe spice, was employed to disperse S. aureus biofilm by cold nitrogen plasma (CNP) assist. After S. aureus biofilm formation on food container surfaces, they were exposed to CNP and then treated with Helichrysum italicumEO for biofilm dispersion. The population of S. aureus biofilm was approximately reduced by 2 logs after individual treatment of 0.5 mg mL^?1 Helichrysum italicumEO or 400 W CNP. Interestingly, the combined treatment of Helichrysum italicumEO (0.5 mg mL^?1, 40 min) and CNP (400 W, 1 min) reduced the S. aureus viable count in biofilm below 2 logs CFU per cm² after 1‐day storage. Therefore, the synergetic treatment holds great promise to improve the current treatment systems of bacterial contamination on different food‐contact surfaces.     

奉节脐橙果皮褐变生理的研究

以奉园72-1脐橙果实为材料,进行常温(15℃)、低温(5℃)贮藏、涂蜡、机械损伤等处理,测定各处理脐橙果皮褐变率、褐变指数,以及POD、PPO、PAL酶活性的变化,以探明奉节脐橙果皮褐变的影响因素,以及相关酶活性与果皮褐变的关系。结果表明：与常温贮藏的对照果相比,涂蜡、损伤处理均极显著地提高果实的果皮褐变率(p<0.01)以及褐变指数(p<0.01),而低温贮藏可降低褐变发生;说明涂蜡和机械损伤都是引发果皮褐变的主要因素之一,低温贮藏可在一定程度上减少果皮褐变的发生。损伤处理刺激了POD、PAL酶活性的上升,且酶活性的升高与果皮褐变率具有相关性;涂蜡和损伤明显促进了PPO酶活性的升高,从而加速褐变过程,而低温可有效抑制PPO酶活性;实验结果表明POD、PPO、PAL酶活性与果皮褐变间均有密切关系。     

壳聚糖处理对脐橙采后品质及抗病性的影响

研究不同质量浓度壳聚糖处理对纽荷尔脐橙采后品质及抗病性的影响。结果表明：在冷藏(8℃)条件下,壳聚糖处理抑制了脐橙果实的呼吸强度、延缓了总糖的上升和可滴定酸的下降并保持了较高的VC 含量,从而保持了较好的果实品质。同时,在贮藏后期壳聚糖处理也提高了脐橙果实超氧化物歧化酶、苯丙氨酸解氨酶、几丁质酶和β-1,3- 葡聚糖酶的活性,增强了果实的抗病性。但不同处理间存在着差异,其中以1.5g/100mL 壳聚糖效果最好,2.0g/100mL 壳聚糖次之,1.0g/100mL 壳聚糖最差。     

奉节脐橙果皮褐变的调控技术研究

以奉园72-1 脐橙为材料,研究了田间喷钙、套袋处理、延迟采收、打蜡等对果实常温贮藏期间果皮褐变率和果实品质的影响。结果表明,田间喷钙结合套袋处理可显著降低果实贮藏期间的果皮褐变率(p<0.01),钙处理还显著提高了果面的红色,改善果实商品性;而延迟采收和打蜡均极显著地增加果皮褐变率(p<0.01);说明果树缺钙、涂蜡和不适采收期都是引发脐橙果皮褐变的重要因素。     

Influence of different storage conditions on changes in the key aroma compounds of orange juice reconstituted from concentrate

Quantification of aroma compounds in an orange juice reconstituted from concentrate which had been stored at 37 °C for 4 weeks (forced storage) revealed an increase in the concentrations of, in particular, dimethyl sulphide, 2-methoxy-4-vinylphenol, α-terpineol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF) in comparison with the same orange juice before storage. On the other hand, clearly lower concentrations were found for octanal, decanal, (R)-α-pinene, linalool, and (E)-β-damascenone after storage, while the concentrations of vanillin and carvone remained nearly constant. Similar results were found for the same aroma compounds after storage of the orange juice at 20 °C for 1 year. Sensory experiments corroborated the importance of 2-methoxy-4-vinylphenol and dimethyl sulphide for the typical stale off-flavour of the stored orange juice, while the omission of e.g., α-terpineol in model mixtures could not be detected. Under both storage conditions (37 °C for 4 weeks or 20 °C for 1 year), the breakthrough odour thresholds of α-terpineol and 4-HDF were not reached, while the concentrations of dimethyl sulphide and 2-methoxy-4-vinylphenol clearly exceeded their breakthrough odour thresholds, thus confirming the crucial role of these odorants for the off-flavour of stored orange juice from concentrate. In addition, changes in the concentrations of selected orange juice odorants at various temperatures and times were investigated.     

Mandarin preservation by microwave-powered cold plasma treatment

Cold plasma treatment (CPT) was investigated as a nonthermal method for inhibiting Penicillium italicum and improving storability of mandarins (Citrus unshiu Marc.). Whole mandarin fruits or the peels were treated with cold plasma at 0.7 kPa using a microwave CPT system. The treatment variables were plasma-forming gases, plasma generation power, and treatment time. Nitrogen (N₂)-CPT at 900 W for 10 min, resulted in the highest inhibition of P. italicum (84% reduction in disease incidence), significantly increased the total phenolic content and antioxidant activity of mandarin peel after the treatment (p < 0.05), but did not significantly affect CO₂ generation, weight loss, content of soluble solids, titratable acidity, pH, ascorbic acid concentration (flesh), or surface color during storage at 4 and 25 °C. These results demonstrate the potential for CPT application as a postharvest technology for preserving mandarins, increasing the total phenolic content and antioxidant activity of mandarin peel.     

Antimicrobial Effects of Silver Nanoparticles Synthesized by Fatsia japonica Leaf Extracts for Preservation of Citrus Fruits

Due to their potent antimicrobial activity, silver nanoparticles (AgNPs) synthesized by biomass might be promising in food preservation, whereas effects of AgNPs on Penicillium italicum‐induced rot of Citrus fruits have not been investigated. In this study, a novel AgNPs biosynthesis method was developed based on Fatsia japonica leaf extracts. It was revealed that concentrations of leaf extracts, AgNO₃ and NaCl affected AgNPs yields and particle sizes obviously. Under the optimized conditions (8 mg/mL extracts, 2 mM AgNO₃ and 1 mM NaCl), AgNPs, synthesized within 80 min, showed potent preservative effect against P. italicum‐induced rot of Citrus fruits. Furthermore, inhibition test and TEM analysis indicated that as‐synthesized AgNPs caused cell deformation, cytoplasmic leakage, and thereupon cell death of P. italicum. Moreover, AgNPs had significant antibacterial activities against Escherichia coli and Staphylococcus aureus, which might be beneficial for Citrus fruits preservation. Altogether this study develops an efficient AgNPs synthesis method and a novel preservation method for Citrus fruits.     

Secondary metabolism associated with softening of shiitake mushroom (Lentinula edodes) induced by O2 depletion and CO2 accumulation

It is difficult to preserve fresh shiitake mushroom (Lentinula edodes (Berk.) sing) partly because of the rapid deterioration of texture (softening or lignification). In this study, we developed a storage model in which tissue softening was induced to analyse the relationship between changes in firmness and alterations in cell wall chemical components as well as their metabolism. The results showed that the treatment group accumulated more CO₂ and contained less O₂ because of the poorer permeability in package. The contents of glucan and chitin in the treatment group decreased from 241.3 ± 13.2 mg g^?1 and 46.3 ± 1.2 mg g^?1 to 157.3 ± 11.2 mg g^?1 and 18.0 ± 1.0 mg g^?1 (P < 0.05) with the accumulation of CO₂. The activities of major cell wall degradation‐related enzymes were enhanced in the softening model, and the expression levels of major genes that encode enzymes related to cell wall degradation were upregulated. Our results suggested that the softening of shiitake mushrooms induced by high CO₂ was associated with the degradation of polysaccharides and glycosaminoglycan and that these changes were systematically regulated by alterations in the activities and expression levels of related enzymes and genes.     

Effects of a pretreatment with nitric oxide on peach (<Emphasis Type="Italic">Prunus persica</Emphasis> L.) storage at room temperature

Peach is characterised by a rapid senescence associated with a high production of autocatalytic ethylene at the beginning of ripening, a fact which reduces markedly its postharvest shelf-life. The application of antisenescent compounds after harvesting has been assayed to solve this problem. One of the newest and more promising compounds is the free radical gas nitric oxide (NO). In this work, peaches of cv. ‘Rojo Rito’ were treated with 5 μL L⁻¹ of NO for 4 h, at 20 °C, and then stored at the same temperature for 14 days. Untreated fruits stored under the same conditions were used as control fruits in the experiment. Key physiological parameters of senescence (ethylene production and respiratory rate) and quality parameters (firmness, titrable acidity, total soluble solids and colour) were analysed. A particular emphasis was placed on the analysis of the oxidative status and the antioxidant capacity during storage and as a response to the NO treatment. The ethylene production and respiratory rate of fruits treated with NO were lower than those of control fruits. Treated fruits underwent a lesser loss of firmness during storage. The degree of disintegration of cell membranes, assessed as the percentage of electrolyte leakage, was also lower in fruits treated with NO. NO did not seem to affect lipid peroxidation or LOX activity, but it did affect PPO activity. The treatment with NO stimulated POX activity and, especially, SOD and CAT activities. It seems that total carotenoids and free ASC were not influenced by the pretreatment; however, the oxidised form of ASC, DHA, showed a slight increase. NO seemed to have a beneficial effect on the oxidation equilibrium and the antioxidant capacity of peach fruit. A delay in the initiation of the senescence of fruits treated with NO, that extended the postharvest shelf-life, was observed.     

Prosopis spp. powder: influence of chemical components in water adsorption properties

Prosopis alba and Prosopis nigra powders from pods were evaluated through chemical and mineral composition and other healthy food compounds such as polyphenols and fatty acids exhibiting antioxidant activity. P. nigra presented higher content of lipids and polyphenols leading to a higher antioxidant activity than P. alba. Although P. nigra presented lower amount (%) of fibre (20.1 vs. 23.3), the amount of total soluble sugars responsible of water retention was slightly higher (PN: 57.1, PA: 56.7). Moisture content, water activity and water absorption behaviours were different between both powders due to differences in their chemical composition. P. nigra powder presented higher amounts of polyphenols, antioxidant activity and lower initial equilibrium moisture content (a_w = 0.7), with a lower a_w at 20 °C at the same water content, suggesting that P. nigra powder would have less possibility of deterioration during storage.     

纽荷尔脐橙冷藏的最适采收期

以纽荷尔脐橙为原料,研究不同时期采摘果实耐贮性,通过分析品质、腐烂和冷害发生规律,确定冷藏脐橙最佳采收期。结果表明：贮藏结束时,脐橙糖酸比上升,而总糖、可滴定酸（titratable acid,TA）和VC含量均显著下降。在2012年10月下旬和11月上旬采摘的果实,鲜果和贮藏果有机质含量均较低,至贮藏结束,总糖、TA和VC含量均减少,且以TA含量下降最为明显。11月下旬到12月上旬采摘的果实,至贮藏结束时,TA和VC含量降低,但相比其他组的果实下降率最低。12月中旬之后采摘的果实,品质方面与11月下旬到12月上旬采摘的果实差距不大,但果实腐烂率高达9.67%。研究表明,冷藏的纽荷尔脐橙最适采摘期为11月中旬到12月上旬。     

Spray drying conditions for orange juice incorporated with lactic acid bacteria

This work aimed to develop an orange juice powder by spray drying with lactic acid bacteria (Lactobacillus plantarum 299v and Pediococcus acidilactici HA‐6111‐2), testing their survival both during drying and storage (room temperature and 4 °C). Initially, the best conditions for spray drying were chosen to allow the best survival of each LAB: (i) inlet air temperature of 120 °C and (ii) 0.5:2 ratio of the orange juice soluble solids and drying agent added (prebiotics: 10 DE maltodextrin or gum Arabic). Survival of LAB was not affected by drying process, and it was higher when cultures were stored at 4 °C. A slightly higher protection was conferred by 10 DE maltodextrin, in the case of L. plantarum and at 4 °C. Pediococcus acidilactici was more resistant during storage at 4 °C, with logarithmic reductions lower than 1 log‐unit. It was demonstrated that it is possible to produce a functional nondairy product, orange juice powder supplemented with prebiotic compounds, containing viable LAB for at least 7 months, when stored at 4 °C.     

Proteolysis of reconstituted goat whey fermented by Streptococcus thermophilus in co‐culture with commercial probiotic Lactobacillus strains

Reconstituted goat whey was fermented with the starter Streptococcus thermophilus TA‐40 in co‐culture with four probiotic adjuncts (independent treatments): Lactobacillus casei BGP93 (T1), Lactobacillus paracasei BGP1 (T2), Lb. paracasei LPC37 (T3) and Lactobacillus rhamnosus LR32 (T4). Lactobacillus populations were higher than 7 log cfu/mL after fermentation and storage. Proteolysis increased significantly (P < 0.05) during fermentation in all trials. Relative amount of low‐molecular‐weight protein fractions (<6.5 kDa) increased in goat whey trials with T1, T3 and T4 during fermentation and storage. The goat whey powder was considered a potential substrate for starter and probiotic cultures, which raised the opportunities to upgrade this by‐product into a functional food.     

Chemical composition of Ocimum basilicum L. essential oil and its efficacy as a preservative against fungal and aflatoxin contamination of dry fruits

The study presents fungal and aflatoxin contamination of some dry fruits and Ocimum basilicum essential oil (EO) as a plant‐based preservative. During mycoflora analysis, 2045 fungal isolates were recorded from dry fruits and 40% isolates of Aspergillus flavus were toxigenic in nature. The EO of O. basilicum exhibited strong fungitoxicity against toxigenic strain of A. flavus. Its minimum inhibitory concentration (MIC) was recorded at 1.0 μL ml^?1, and it completely inhibited aflatoxin B₁ production at 0.5 μL ml^?1. The oil exhibited broad fungitoxic spectrum and considerably reduced A. flavus isolates from dry fruits when used as fumigant in closed storage containers at 1.0 μL ml^?1. The chemical profile of the EO was standardised through GC–MS analysis. Based on antifungal potency, antiaflatoxigenicity and efficacy as fumigant during storage conditions, O. basilicum EO may be recommended as a botanical preservative for enhancing the shelf life of dry fruits and edible products during storage.     

赣南脐橙代谢组学研究

采用气相色谱-质谱联用技术测定赣南和其它地区的脐橙挥发性物质,对不同产地脐橙进行代谢组学研究,为赣南脐橙品质保障提供科学依据。通过GC-MS分析脐橙的挥发性成分,经数据库匹配结合相关文献鉴定物质,采用正交偏最小二乘法-判别分析(OPLS-DA)的s-plot图并结合对各组分的贡献率(VIP>1,P<0.05)筛选潜在生物标志物。结果表明,从赣南脐橙中共鉴定出66种挥发性成分,分别为萜烯类、醛类、醇类、酯类、酮类等,其中含量最高的为D-柠檬烯。根据OPLS-DA分析筛选出5个潜在生物标志物,即(1S)-(+)-3-蒈烯、4-蒈烯、壬醛、(Z)-石竹烯、桉烷-3,7(11)-二烯,其可以作为区分赣南脐橙和其它地区脐橙的潜在生物标志物。     

Effect of PrA encoding gene-<Emphasis Type="Italic">PEP4</Emphasis> deletion in industrial <Emphasis Type="Italic">S</Emphasis>. <Emphasis Type="Italic">cerevisiae</Emphasis> WZ65 on key enzymes in relation to the glycolytic pathway

S. cerevisiae proteinase A (PrA) is a member of the aspartic proteinase superfamily. The roles of PrA in S. cerevisiae physiology and cell metabolism are controversial. The objective of the current study was to elucidate the effects of the absence of PrA on key enzymes with regard to the glycolytic flux in industrial S. cerevisiae. The observed activities of hexokinase (HK), phosphofructokinase (Pfk) and pyruvate kinase (PYKi) in PrA-modified S. cerevisiae strains (SC2 and SC3) were lower than that of the wild-type strain (p < 0.01). Compared to other strains, SC3 revealed the lowest activity of three key glycolytic enzymes. Current results imply that PrA in industrial S. cerevisiae may control the glycolytic enzymes expression (HK, Pfk and PYKi) in the direct or indirect manner and thus lead to the delay of cell metabolism. The observed intracellular ATP levels between the wild-type strain and PrA-modified strains (SC1 and SC2) were significantly different (p < 0.01). The pronounced differences of key glycolytic enzymes between the wild-type and PEP4-modified strains were as well characterized by SDS–PAGE. The intracellular protein concentration in the presence of PrA is higher than those of the PrA-modified strains. As a result, the interaction mode of PrA and the glycolytic enzymes was postulated in this work. The findings herein suggest that the glycolytic flux direction and rate may be regulated by vacuolar PrA in industrial S. cerevisiae. The present data obtained provide insights into understanding the roles of PrA in industrial S. cerevisiae.