鲟鱼肉冷藏期间腥味及品质变化

为探明鲟鱼肉冷藏过程腥味形成规律及其影响因素,文中研究分析了鲟鱼背部、腹部和尾部肌肉组织品质指标和鱼腥味变化情况。结果表明:冷藏前期3个部位的鱼肉挥发性盐基氮(TVB-N)值增加缓慢,5 d后TVB-N呈现快速增长,表明鱼肉开始出现微生物腐败迹象。表征脂肪氧化程度的硫代巴比妥酸值(TBARS)冷藏前期增幅缓慢,第3天后增幅加速,脂肪氧化速度加快;冷藏期间脂肪氧化酶(LOX)活性呈先升高后降低的趋势;冷藏2 d后鱼体主要不饱和脂肪酸下降幅度加快,挥发性物质总量增加明显。对鱼肉冷藏期间挥发性物质风味特征进行分类分析表明,鱼肉冷藏过程中以鱼腥味、青草味及脂肪氧化气味变化为主,其中以鱼腥味变化最为突出。将贮藏过程中鱼肉品质指标与鱼腥味变化规律进行分析发现,鱼腥味等异味的产生主要是由脂肪氧化所致,后期微生物腐败对鲟鱼肉风味变化起协同作用。     

Effect of chitosan and chitooligosaccharide on vitamin C and polyphenols contents in cherries and strawberries during refrigerated storage

The objective of this research was to investigate the effect of treatment with chitosan and chitooligosaccharide on vitamin C and polyphenols contents in cherries and strawberries during refrigerated storage. Chitosans and chitooligosaccharides, as well as vitamin C and polyphenols are associated with reduced risk of cardiovascular diseases and cancer. Synthesis of vitamin C in strawberries and loss of vitamin C in cherries were observed during refrigerated storage. The treatment with chitosan and chitooligosaccharides inhibits vitamin C synthesis in strawberries and promotes vitamin C synthesis in cherries. Lower values of anthocyanin content for strawberries and higher values of anthocyanin content for cherries treated with chitosan and chitooligosaccharide compared with anthocyanin content in control strawberries and cherries were found after 7 days storage at 4 °C. Total phenols content in strawberries decreased and in cherries increased after storage 7 days at 4 °C and more pronounced changes observed for samples treated with high molecular weight chitosan. The correlation between moisture content in treated and non-treated strawberries and contents of vitamin C, anthocyanin and total phenols was shown. No correlation between moisture content and content of vitamin C, anthocyanins and total phenols was found for cherries.     

New packaging strategies to preserve fresh-cut artichoke quality during refrigerated storage

The influence of both post-harvest treatments and film permeability on the quality loss kinetic of minimally processed artichokes is assessed in this study. In particular, fresh-cut artichoke heads were subjected to dipping in citric acid/calcium chloride water solution, and coating with citric acid loaded sodium alginate, respectively. Three different packaging materials were used: a polyester-based biodegradable film, an aluminum-based multilayer film, and a commercially available oriented polypropylene film. Artichokes quality loss kinetic during storage was determined by monitoring produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms. Results suggest that among the selected treatments, coating shows the best performance in terms of artichokes shelf life. As far as the packaging material is concerned, the biodegradable film tested in this work seems to be the most suitable packaging to preserve the quality of the coated fresh-cut produce.Industrial relevance: Fresh-cut vegetables market has grown rapidly in recent years as a result of changes in consumer attitudes. There is a real need to find methods for preservation of minimally processed food products that can gain widespread acceptance by the industry. This paper suggests effective packaging solutions to delay the quality decay kinetic of fresh-cut artichokes. Moreover, the present study proposes a new “green packaging system” that could emphasize the relevance of the obtained results due to the increased attention to the environmental impact.     

Improvement in the quality of ground chevon during refrigerated storage by tocopherol acetate preblending

A study was conducted on -tocopherol acetate (TA) preblending at 0, 6, 8, 10, 12 and 14 ppm levels with ground chevon (GC) obtained from adult male Beetal×Black Bengal goat carcasses, to identify the optimum level of TA required for improving the quality of the meat during refrigerated storage. It was observed that the GC samples preblended with 10 ppm TA had significantly (P<0.05) higher WHC%, colour score, odour score and lower metmyoglobin (MMb) per cent, TBARS number, peroxide value, free fatty acids per cent and psychrotrophic plate count as compared to other TA levels. All the quality parameters studied showed a highly significant (P<0.01) correlation (r-value) between each other. A strong relationship was observed between TBARS number and MMb% during refrigerated storage. A regression equation (Y=0.2800+0.0055X, where Y=TBARS number, X=MMb%) was established. It was concluded that 10 ppm TA was the optimum level for preblending with ground chevon, which extends the shelf life of the meat up to 7 days as compared to 3 days in the control samples during refrigerated storage.     

Effects of pomegranate sauce on quality of marinated anchovy during refrigerated storage

Effects of pomegranate sauce on the quality of marinated anchovy during storage at 4 °C were investigated. Anchovy were marinated with 30 g/L acetic acid and 150 g/L salt, put into glass jars, filled with either sunflower oil or pomegranate sauce and stored at 4 °C. Total volatile basic nitrogen (TVB-N) and trimethylamine (TMA-N) values increased during the storage. Higher values for free fatty acid (FFA), conjugated diens (k-dien) and para-anisidine (p-Av) were found in samples with sunflower oil than those with pomegranate sauce. Samples in pomegranate sauce showed better oxidative stability. Higher taste and flavour and lower appearance scores were found for samples in pomegranate sauce than those samples in sunflower oil. It was found that pomegranate sauce was as least effective as the traditional sunflower oil to keep quality. Pomegranate sauce also produced desirable taste and flavour but the coloration should be studied in further studies.     

壳聚糖复合涂膜对冷藏虾蛄保鲜效果的影响

以虾蛄为研究对象,选用壳聚糖、维生素C、玉米淀粉为复合涂膜材料,以壳聚糖单一涂膜和空白作为对照,以感官、菌落总数(TVC)、pH值、挥发性盐基氮含量(TVB-N)、硫代巴比妥酸值(TBA)等为指标,研究复合涂膜对冷藏虾蛄品质的影响。结果表明:壳聚糖—维生素C—玉米淀粉复合涂膜有效延缓了虾蛄样品的菌落总数、pH值、TVB-N值、TBA值的上升,且效果优于空白组和壳聚糖单一涂膜组;与空白组相比,壳聚糖—维生素C—玉米淀粉复合涂膜可延长冷藏虾蛄货架期2～3d。     

超高压处理对冷藏鲈鱼品质的影响

研究了不同超高压条件(0、100、200、300 MPa,保压处理10 min)对鲈鱼冷藏过程中感官、p H值、白度、质构特性和持水性的影响。结果表明:鱼肉的感官评分、硬度、弹性和咀嚼度随贮藏时间的延长逐渐降低,白度逐渐升高,p H值先下降后上升,而持水性先上升后下降。超高压处理可显著提高鱼肉的硬度和咀嚼度(P0.01),同时提高了鱼肉的p H值和持水能力,增加了白度,200 MPa处理组的细菌总数低于对照组和其他2个处理组。此外,300 MPa的超高压处理对鲈鱼鱼肉品质的影响最大。综合感官和理化测定结果可知,超高压在改善鲈鱼肉质方面具有潜在的应用前景。     

迷迭香与葡萄籽复合保鲜剂对白鲢鱼丸的保鲜效果

该研究以白鲢鱼丸为研究对象,通过测定微生物(菌落总数)、感官特性(质构、凝胶强度、水分分布和白度)、理化(挥发性盐基氮值、pH值)等指标,研究了由迷迭香及葡萄籽提取物组成的复合生物保鲜剂对冷藏条件下白鲢鱼丸品质的影响。结果表明,经复合生物保鲜剂处理过的鱼丸在冷藏期间菌落总数、TVB-N值和pH值等指标均优于对照组;质构及凝胶强度结果显示复合保鲜剂可以较好地维持鱼丸的硬度,对弹性影响不大,能够保持鱼丸良好的质构特性,并可有效提高鱼丸凝胶强度;低场核磁共振检测结果显示,复合保鲜剂可有效控制鱼丸水分分布,减少自由水的生成;由于迷迭香和葡萄籽提取物本身具有一定颜色,处理组鱼丸的白度跟对照组相比略有降低,但是颜色变化不显著(P0.05)。其中,复合生物保鲜剂的添加量为0.1 g/kg迷迭香提取物和0.3 g/kg葡萄籽提取物时,各指标反映出对白鲢鱼丸的保鲜效果最优,具有良好的抑菌及抗氧化的效果,可有效延缓鱼丸劣变,延长货架期。     

蓝莓叶多酚复合保鲜剂对冷藏南美白对虾品质的影响

南美白对虾营养丰富,但冷藏期间容易腐败变质,为保持对虾品质和延长货架期,采用质量分数0.4%蓝莓叶多酚和1%壳聚糖的复配液对南美白对虾进行浸泡处理,以未处理的对虾作为对照,分别测定感官指标、微生物指标和理化指标(质构、硫代巴比妥酸值、挥发性盐基氮值、p H值等),用以评价蓝莓叶多酚复合保鲜剂对冷藏南美白对虾的保鲜效果。结果表明:4℃冷藏条件下,蓝莓叶多酚复合生物保鲜剂能有效控制冷藏南美白对虾的感官品质,抑制微生物生长,减缓脂肪氧化,延长对虾的货架期,较对照组南美白对虾货架期延长3~4 d。     

Effects of light-emitting diode illumination on the quality of fresh-cut cherry tomatoes during refrigerated storage

The effects of light-emitting diode (LED) illumination on the quality of fresh-cut cherry tomatoes were investigated. Tomatoes were exposed continuously to red, green, blue and white LED light for 7 days and control samples stored in darkness. Results showed that blue light treatment significantly led to more total soluble solids, lycopene concentration and individual phenolic compounds (chlorogenic acid, caffeic acid, rutin) after 7 days of storage. On day-5, green and blue light-treated tomatoes showed relatively higher firmness than samples treated by other lights and the control. At the early stage of storage, blue light could preserve the fresh flavour of tomatoes compared to other treatments. Overall, the blue light was most effective in the quality preservation of fresh-cut cherry tomatoes and could be used as a novel strategy in the preservation of fresh-cut fruits and vegetables during shelf life.     

植物乳杆菌发酵枣汁在冷藏期间的营养品质变化研究

以陕北木枣、新疆和田枣为原料,经植物乳杆菌（Lactobacillus plantarum）发酵制备发酵枣汁,分析两种发酵枣汁在冷藏过程（4 ℃、28 d）中的理化特性、酚类化合物、抗氧化活性以及风味特征变化。结果表明,在冷藏过程中发酵枣汁的活菌数逐渐减少,但28 d后发酵枣汁中活菌数仍高于6.0 lg（CFU/mL）。冷藏过程中发酵枣汁总糖和还原糖含量有所降低,可滴定酸含量有所升高。冷藏28 d后的发酵枣汁总酚含量高于冷藏前的发酵枣汁,冷藏过程较好地保持了发酵枣汁的1,1-二苯基-2-三硝基苯肼（DPPH）自由基清除活性和铁离子还原能力。经过冷藏后的枣汁中风味物质含量相较于冷藏前的发酵枣汁有所降低,但始终高于未发酵枣汁,植物乳杆菌发酵赋予枣汁丰富的花香和果香。     

Texture changes in fresh cut celery during refrigerated storage

The effect of refrigerated storage temperature (0 or 10 °C) on variations in texture and lignin content of minimally processed celery was assessed. In addition, the evolution of soluble phenols was studied, as well as changes in other quality parameters, namely weight loss, surface colour and contents of chlorophyll and free sugars. To this end, celery cuts were packaged on PVC film‐covered polystyrene trays. The maximum shear force required to cut the strips transversally followed a similar tendency during storage at both temperatures tested. Increases in lignin content were observed which could be related to corresponding texture increases during the first few days in cold storage. There was no evidence that lignification occurred by a cicatrix‐forming process in the wounds caused during cutting. Copyright © 2003 Society of Chemical Industry     

Kinetic modelling of the degradation of quality of osmo-dehydrofrozen tomatoes during storage

Tomato slices were submitted to osmotic pretreatment in a high DE maltodextrin syrup and were subsequently frozen. The objective was to evaluate the quality stabilisation of the osmo-dehydrofrozen samples during their frozen storage over a wide temperature range from −5 to −20 °C. Colour change, total lycopene content and vitamin C (l-ascorbic acid) loss were kinetically studied, and their temperature dependence was modelled by the Arrhenius equation. Dehydrofrozen samples exhibited significantly improved stability, with the rates of colour change, total lycopene and l-ascorbic acid loss being reduced by up to 64% for osmotically pretreated tomatoes, compared to the untreated samples.     

Antioxidant responses in minimally processed celery during refrigerated storage

This work studies the effect of storage temperature (0, 4 and 10 °C) and time on the antioxidant capacity of cut celery packaged in polystyrene trays sealed with PVC film. Samples were taken at 0, 7, 14, 21 and 28 days of storage to determine total phenols, chlorogenic acid and ascorbic acid. The browning potential and antioxidant capacity of the product were also evaluated. The antioxidant power presented similar behaviour for the three temperatures tested, decreasing after the first 7 days and then increasing up to day 14. Such increase coincided with an elevation of the ascorbic acid content, which was stronger for higher temperatures. As a general conclusion, minimally processed celery retained its initial antioxidant capacity for a period of 21 days at 0 °C, showing the lowest levels of browning potential at this temperature.     

Hot air treatment delays senescence and maintains quality of fresh-cut broccoli florets during refrigerated storage

A postharvest treatment with hot air (48 °C during 3 h) was applied to fresh-cut broccoli to investigate its effect on quality and senescence during storage at 0 °C. The treatment delayed yellowing as evidenced by lower decrease of Hue values during storage. After 21 days of storage, treated broccoli had chlorophyll content approximately 40% higher than controls. The treatment did not affect either weight loss or respiratory activity but induced lower electrolyte leakage, indicating that treated samples conserved higher tissue integrity. Heating reduced phenolic content and antioxidant capacity during the first two weeks, but the samples recovered after 3 weeks reaching values similar to controls. Finally, after 3 weeks of storage, treated samples had higher levels of total sugars, and total and soluble proteins. The results suggest that a short postharvest heat treatment may reduce senescence, tissue damage and contribute to maintain a better quality of the product during storage at 0 °C.     

Viability of microencapsulated bifidobacteria in set yogurt during refrigerated storage

Bifidobacteria are probiotic organisms that improve the microbial balance in the human gut. They can be incorporated as live cultures in fermented dairy foods, including yogurt, for transmission to humans. Because bifidobacteria are sensitive to high acidity, their viability in yogurt is limited. The objective of the present study was to investigate the effect of microencapsulation on the viability of bifidobacteria in yogurt during refrigerated storage for 30 d. Live bifidobacterial cells were encapsulated in kappa-carrageenan. Cell enumeration, determination of titratable acidity and pH, quantitation of lactic and acetic acids, and sensory evaluation (consumer test) were carried out on the yogurt samples. Microbiological results showed a decline of 78 and 70.5% in the population of Bifidobacterium longum B6 and B. longum ATCC 15708, respectively, for the treatments containing nonencapsulated cells. No difference in bifidobacterial population was observed in the encapsulated treatments. The acetic acid content in the yogurt with nonencapsulated bifidobacteria was higher than that in the plain yogurt (control) and encapsulated treatments. The increase in lactic acid content during storage was not different among the various treatments for B. longum B6, but was greater for nonencapsulated than encapsulated B. longum 15708 and the control. Consumers judged the nonencapsulated treatment as the most sour, which was likely due to the higher acetic acid content. Consumers preferred the control and nonencapsulated treatments over the encapsulated treatment. Microencapsulation appears to increase the viability of bifidobacteria in yogurt. This technique can be used to transmit bifidobacteria via fermented products provided that sensory characteristics of the product are improved or maintained.     

Effect of natural antioxidants and vacuum packaging on the quality of buffalo meat nuggets during refrigerated storage

Buffalo meat nuggets (BMN) were incorporated with 500 ppm sodium ascorbate, 10 ppm -tocopherol acetate and 0.5% sodium tripolyphosphate while processing. There were three experimental groups of BMN, namely control aerobic packaged (CAP), treated aerobic packaged (TAP) and treated vacuum packaged (TVP), refrigerated and stored at 4 °C. It was observed that the treated samples (TAP and TVP) had significantly (p < 0.05) higher pH, W-B shear force, moisture and protein contents, sensory attributes and lower free fatty acids content in comparison to CAP samples. Vacuum packed nuggets (TVP) had significantly (p < 0.05) lower free fatty acid content, higher lactobacilli and total anaerobe counts and markedly higher scores for flavour and overall palatability, even at the 25th day of storage. Product quality reduced as storage time increased. Use of natural antioxidants and vacuum packaging extended the shelf life of BMN from 10 to 30 days under refrigerated storage.