渗透压脱水前处理对芒果冻藏中品质变化的影响

本文研究了渗透脱水前处理对芒果冷冻时间和品质的影响,渗透脱水条件是:分别采用不同浓度(30%、40%、50%(m/m))的混合溶液(蔗糖、葡萄糖、果糖质量比为3.6:1:3)作为渗透液、温度30℃,时间2 h;冻藏条件为-18℃,为期6个月。实验结果表明,与直接冷冻相比,渗透脱水联合冷冻能够缩短6.3~13.8%的芒果冷冻时间。并且,在经过6个月的冻藏后,渗透脱水联合冷冻使得芒果的总色差降低了12.5~36.8%,硬度提高了35.8~65.5%,汁液流失率减少了11.3~44.5%,维生素C含量提高了21.2~134.8%。结果显示,较高浓度的渗透脱水前处理能够较好地保持冻藏芒果的品质,而40%的渗透液浓度是芒果冷冻保藏的最优条件。同时,芒果阴面(较硬)比阳面(较软)更适合于冷冻保藏。随着冻藏时间延长,渗透脱水前处理的冻藏芒果比直接冷冻的芒果品质下降缓慢。本文表明渗透脱水联合冷冻能够提高芒果的冷冻速率和品质。     

Instrumental Textural Properties of Mesir Paste Kept at Different Temperatures

Traditional mesir paste bar samples were kept at different temperatures (4 ± 1°C, 20 ± 1°C, or 30 ± 1°C) and their textural properties were determined by conducting instrumental texture profile analysis. Total sugar content of mesir was 85 g/100 g sample, whereas the inverted sugar amount was 79 g/100 g. Saccharose content of mesir was 10 g/100 g. It was determined that temperature significantly affected the textural attributes of mesir paste samples (P < 0.05). Hardness of mesir paste kept in a refrigerator was 2241 N, whereas it was 273 N and 8.24 N for the samples kept at ambient temperature and 30 ± 1°C, respectively.     

Food Phenolics,Pros and Cons: A Review

Phenolic compounds like simple phenols, flavonoids, and phenolic acids are commonly in foods of plant origin. Several studies, including animal and epidemiological investigations, have demonstrated that phenolic compounds in foods possess positive attributes such as anticarcinogenesis, antioxidant potential, antiviral activity, antimicrobial activity, and antimutagenic activity. However, other studies have shown that the same phenolics have negative attributes such as carcinogenic activity and antinutritional activity, as well as imparting negative attributes to foods. This review summarizes the information about food phenolics and presents the most current knowledge with respect to its role in human health, food attributes, and toxicity among others.     

Beef quality of young Angus × Nellore cattle supplemented with rumen-protected lipids during rearing and fatting periods

This work evaluated the beef quality parameters of 108 bulls randomly administered to three treatments during rearing in pastures and two treatments during fatting in feedlots, including mineral and rumen-protected lipids. Meat and fat color, cooking yield, shear force, sensorial traits and chemical and fatty acid compositions were evaluated. Generally, the beef quality parameters were not affected by the rumen protected lipids; however, supplementation with rumen-protected lipids during the rearing period yielded darker beef and brighter fat and increased beef tenderness in meat aged for 28 days compared to the meat from animals that received only mineral supplementation. In addition, the percent of meat polyunsaturated fatty acids was negatively affected by the inclusion of protected lipids, yielding 5.58 and 3.72% in animals fed with and without rumen-protected lipids, respectively, during the fatting period.     

香菇脆热泵—瞬时压差膨化干燥工艺优化

目的:针对真空油炸香菇脆片含油率高,长期食用存在健康隐患问题,开发优质非油炸香菇(整果)脆。方法:利用瞬时压差膨化(instant controlled pressure drop, DIC)技术,通过均匀设计,探究热泵预干燥含水率、膨化温度、真空干燥温度对香菇脆膨化度、复水比、总色差、硬度和脆度的影响,通过加权综合评分法构建多项式回归模型,优化求解并进行实验验证。结果:香菇脆DIC最优工艺参数为预干燥含水率35.63%,膨化温度100℃,真空干燥温度64.17℃,此条件下的香菇脆膨化度为69.34%,色差为20.68,硬度为108.16 N,脆度为75.79。结论:均匀设计结合响应面可优化香菇脆DIC工艺,得到高品质非油炸香菇脆。     

基于混合属性的产品优化聚类算法

针对分类研究中采用单一类型数据造成的结果失真, 提出了综合考虑产品属性和销售时间序列的两阶段优化聚类算法。分别采用基于属性的相似性排序及时间序列的分层优化聚类实现产品单独聚类, 然后基于初始聚类结果及参数化的动态相对权重提出考虑噪声数据处理的分层聚类方法实现产品综合优化分类。企业实例应用研究表明综合聚类模型及两阶段算法在聚类精度及时间复杂度上具有明显的优势, 相对权重的动态参数化设置有效解决了不同产品间个性化特征的差异表示。通用数据集的仿真进一步验证了算法在解决混合属性产品聚类问题时的优越性及广泛适用性。     

Consumer preferences and willingness to pay for value-added chicken product attributes

A growing demand for convenient and ready-to-eat products has increased poultry processors' interest in developing consumer-oriented value-added chicken products. In this study, a conjoint analysis survey of 276 chicken consumers in Edmonton was conducted during the summer of 2009 to assess the importance of the chicken part, production method, processing method, storage method, the presence of added flavor, and cooking method on consumer preferences for different value-added chicken product attributes. Estimates of consumer willingness to pay (WTP) premium prices for different combinations of value-added chicken attributes were also determined. Participants'"ideal" chicken product was a refrigerated product made with free-range chicken breast, produced with no additives or preservatives and no added flavor, which could be oven heated or pan heated. Half of all participants on average were willing to pay 30% more for a value-added chicken product over the price of a conventional product. Overall, young consumers, individuals who shop at Farmers' Markets and those who prefer free-range or organic products were more likely to pay a premium for value-added chicken products. As expected, consumers' WTP was affected negatively by product price. Combined knowledge of consumer product attribute preferences and consumer WTP for value-added chicken products can help the poultry industry design innovative value-added chicken products. Practical Application: An optimum combination of product attributes desired by consumers for the development of a new value-added chicken product, as well as the WTP for this product, have been identified in this study. This information is relevant to the poultry industry to enhance consumer satisfaction of future value-added chicken products and provide the tools for future profit growth.     

Essential oils as biopreservatives: different methods for the technological application in lettuce leaves

Investigations were carried out to assess the efficiency of 3 essential oils, clove, tea tree, and rosemary, as natural preservatives during the postharvest of lettuce leaves. The effect of different concentration (1 and 0.5 MIC) of plant essential oils applied in 3 forms (spray, immersion, and capsules) was studied on lettuce leaves. The evolution of different microbial populations was evaluated during refrigerated storage. The application forms of the biopreservatives were shown to be an important factor in determining the effectiveness of the essential oils. Clove and tea tree essential oils at 1 MIC and applied embedded in lactose capsules presented a significant inhibition on mesophilic, psicrotrophic, and coliforms populations, while rosemary in none of the 3 technological applications forms exerted inhibitory effect on all microbial populations evaluated. Essential oils (at 0.5 MIC) applied by spray, immersion, and embedded in lactose capsules exerted lower inhibitory effects, with respect to 1 MIC, on the different microbial populations present on lettuce leaves. At the end of the storage (7 d), lettuce samples treated with tea tree, clove, and rosemary (at 1 and 0.5 MIC) by spray were the only organoleptically acceptable. It is concluded that clove and tea tree essential oils can control different microbial population present in lettuce. Practical Application: The exploration of naturally occurring antimicrobials in food preservation receives increasing attention due to consumer awareness of natural food products. Biopreservatives are useful in extending the shelf life of foods, reducing or eliminating pathogenic bacteria and increasing overall quality of food products. The effectiveness of essential oil application in foods is the result of factor associations such as applications forms, concentration applied, the way of action, storage temperatures. The application methods (spray, immersion, and embedded in lactose capsules) and the concentration of essential oils have been shown to be important factors in determining the effectiveness of these biopreservatives. The oil concentrations required to produce a certain level of inhibition in actual foods could be questionable due to the organoleptic impact. However, these novel natural preservatives in combination with other factors in obstacle technologies are an alternative to control the pathogen growth minimizing undesirable changes in organoleptic characteristics.     

Physicochemical and sensory characteristics of soya protein isolate hydrolysates with added substrate‐like amino acids

Soya protein isolate (SPI) with or without added substrate‐like amino acid was subject to enzymatic hydrolysis catalysed by commercial proteases (Alcalase 2.4 L, flavourzyme and pancreatin). Addition of a small amount of amino acids (amino acid: SPI = 1: 2500, mol g^?1) during hydrolysis would cause a significantly (P < 0.05) reduced protein recovery, increased degree of hydrolysis, and altered amino acid composition and antioxidant activities of SPI hydrolysates. The SPI hydrolysates prepared with added Asp, Arg or Lys exhibited a higher antioxidant activity than the control. The bitterness of SPI hydrolysates was largely reduced upon addition of Met, Asp or Glu during hydrolysis, whilst the umami taste and mouthfeel‐liking were remarkably increased. Therefore, adding amino acid during hydrolysis is a feasible and beneficial approach to improve both the functional and sensory properties of SPI hydrolysate.