Solid-phase micro-extraction (SPME-GC) and sensors as rapid methods for monitoring lipid oxidation in nuts

Dry foods with high fat content are susceptible to lipid oxidation, which involves a quality deterioration of the product, since this process is responsible for the generation of off-flavours. Hexanal is considered to be a good shelf-life indicator of such oxidation products. In addition, due to its high volatility, hexanal can be easily determined by fast headspace analytical techniques. For this reason an electronic nose comprising ten metal oxide semiconductors (MOS) and a solid-phase microextraction (SPME) coupled with gas chromatography and flame ionization detector (GC-FID) method were compared in order to determine hexanal formed in hazelnuts during storage under different conditions (room temperature, 40°C, ultraviolet light, with and without oxygen scavenger). The results obtained by the two methods showed a good correlation, confirming the possibility of using a multi-sensor system as a screening tool for the monitoring of shelf-life and oxidation state of nuts.     

Post-harvest technologies applied to edible flowers: A review

This review intends to summarize the current knowledge on the post-harvest technologies applied to edible flowers, to help producers to increase their market share and to inform consumers on the technologies that are available to maintain edible flowers’ quality and safety. Emerging post-harvest technologies as High Hydrostatic Pressure (HHP) or irradiation have given good results. Freeze- or vacuum-drying has shown to be highly effective in the preservation of flowers’ bioactive compounds in comparison with classical drying approaches. While osmotic dehydration is already in use, the application of edible coatings and films can be a healthier alternative, without increasing solute contents.     

生鲜食品联合干燥节能保质技术的研究进展

生鲜食品联合干燥是指根据物料的特性将2种或2种以上的干燥方式组合应用,达到优势互补与节能保质目的的一种复合干燥（脱水）技术。介绍了国内外联合干燥研究的进展情况以及不同物料采用联合干燥技术的优点和目前尚存在的问题,认为开发集各种干燥方式优点于一体的多功能干燥器是未来的一种发展趋势。     

润滑油贮存寿命的预测

对30^#机械油与4106^#和4109^#航空润滑油进行了加速老化试验;在此基础上,运用阿累尼鸟斯方程和性能变化的时温关系式,采用线性回归方法推导出30^#机械油粘度变化的老化动力学方程,以粘度增加率20％为使用极限值,预测它在25℃条件下的贮存年限为12a。该方法可用于其它润滑油的贮存及使用寿命的预测。     

Storage of common mushroom under controlled atmospheres

The effect of controlled atmosphere (CA) on the shelf-life of the common mushroom ( Agaricus bisporus ) was assessed using six parameters correlated with its commerical qualities. Low CO₂ concentrations (up to 2.5%) reduced brown discolouration compared to the control in air. Higher CO₂ concentrations enhanced both internal and external browning. Low O₂ concentrations reduced growth of micro-organisms, including pseudomonads. Respiration rate, when the mushrooms are placed again in normal air, is proportional to CO₂ concentration during storage suggesting that CO₂ exhibits a phytotoxic effect on mushrooms. A lower mannitol content was noted in mushrooms stored under CA than those stored in air (control). Mushrooms stored in a 5% CO₂ atmosphere for 7 days did not break their veil but their texture was very soft and spongy. Texture losses decreased when CO₂ concentrations increased.     

负载山梨酸的壳聚糖微囊-EVOH抗菌薄膜对黑鱼鱼肉保鲜的影响

分别以质量分数3%山梨酸(sorbic acid,S)、3%壳聚糖(chitosan,CS)、3%山梨酸-壳聚糖微囊粉末(sorbic acid-chitosan microcapsules,S-MP)为抗菌物质,以乙烯-聚乙烯醇共聚物(ethylene-vinyl alcohol,EVOH)为基材树脂,通过共混造粒、挤出吹塑等工艺,制备山梨酸-EVOH(S-EVOH)、壳聚糖-EVOH(CSEVOH)、山梨酸-壳聚糖微囊-EVOH(S-MP-EVOH)3种抗菌薄膜,并以对苯二甲酸乙二醇酯(polyethylene terephthalate,PET)薄膜为外层薄膜进行复合,制备出S-EVOH/PET、CS-EVOH/PET、S-MP-EVOH/PET复合薄膜以及纯EVOH/PET,在(4±1)℃对黑鱼鱼块进行冷藏保鲜,通过菌落总数、挥发性盐基氮含量、硫代巴比妥酸值、pH值、汁液流失率、K值和感官评定对抗菌薄膜的保鲜效果进行评价。结果表明,若以菌落总数小于6?(lg(CFU/g))为可食用的标准,在(4±1)℃贮藏环境下,相对于EVOH/PET薄膜,CS-EVOH/PET薄膜能有效延长黑鱼货架期2 d,S-EVOH/PET、S-MP-EVOH/PET两种复合薄膜均能有效延长黑鱼货架期4 d。     

生鲜鸡肉货架期预测模型的建立与评价

为了建立生鲜鸡肉货架期的动力学模型,将自然污染的生鲜鸡肉经PS/PE托盘包装后,置于0、5、10、15、20、25℃贮藏,分别测定不同贮藏时间的假单胞菌数量,同时对5℃贮藏的生鲜鸡肉进行品质分析,确定腐败限控量。结果表明:假单胞菌用来预测生鲜鸡肉时的腐败限控量为5.39(lg(CFU/g)),Gompertz函数能很好的描述假单胞菌在不同温度下的生长动态,建立6种温度条件下假单胞菌在生鲜鸡肉中的生长模型。采用Belehradek方程描述温度对最大比生长速率和延滞时间的影响,呈现良好线性关系,模型残差值的绝对值均小于0.07,表明该模型描述的温度与比生长速率和延滞时间是可信的。在此基础上,建立了生鲜鸡肉贮藏过程中货架期的预测模型。     

New package system for fresh berries

This paper presents the design criterion and evaluation of a new package system designed to ship fresh strawberries and raspberries. the study describes the evaluation of the new package systems for pre-cooling after field picking. in addition data is presented describing damage to berries in the form of bruising and cutting owing to vibration in shipment. the paper compares this new concept to the traditional polyethylene injection moulded baskets used in the usa for the past 30 years.     

Quality of rainbow trout chilled-stored after post-catch holding

The shelf-life of headed and gutted rainbow trout (Salmo gairdneri) was evaluated over period of storage at 0°C. There were three groups of samples: (i) fish held at 10°C for 6h and iced, (ii) fish held at 20°C for 6h and iced and (iii) fish held at 30°C for 6h and iced. Quality was assessed over the period of iced storage by measurements of total volatile bases (TVB), hypoxanthine, thiobarbituric acid, pH, water holding capacity (WHC) and tissue compressibility (TC). The results indicated that holding at various time/temperature periods before icing influences quality over the period of iced storage. Deterioration in quality was most pronounced when the fish had been held at high ambient temperatures of 30°C. Hypoxanthine values appeared to give an accurate indication of quality of freshwater fish. There was a linear increase in hypoxanthine values over the period of iced storage for all samples. However, for trout held at 30°C for 6 h before icing the values appeared to be highest. The coefficients of linear regression for fish iced immediately on receipt were lowest per day. It is suggested that hypoxanthine values may be used as chemical indicators of quality of freshwater trout.     

Detection of expired vacuum-packed smoked salmon based on PLS-DA method using hyperspectral images

Consumers want fresh food with a long shelf-life, which in 2010, resulted in an important increase in packaged and processed food. This is especially important for fishery products due to their highly perishable nature. One problem is that it is not possible to measure freshness in packaged food only using the visible spectrum. Moreover, the detection of freshness is a complex problem as fish has different tissues with different biodegradation processes. Therefore, it would be especially interesting to have a non-destructive method to evaluate the shelf-life of packed processed fish. This paper proposes a method for detecting expired packaged salmon. Firstly, this method uses hyperspectral imaging spectroscopy (HIS) using visible and SW-NIR wavelengths. Secondly, a classification of different salmon tissues is carried out by image segmentation. Finally, classifications of expired or non expired salmon are performed with the PLS-DA statistical multivariate method due to the large amount of captured data. In a similar way, spectral data and the physicochemical, biochemical and microbiological properties of salmon are correlated using partial least squares (PLSs). The result obtained has a classification success rate of 82.7% in cross-validation from real commercial samples of salmon. Therefore, this is a promising technique for the non-destructive detection of expired packaged smoked salmon.