Heat transfer during contact cooking of minced meat patties

Experimental results on heat transfer during heating of four types of minced meat patties by contact with hot plates are given. Experimental equipment, method of measurement and experimental values of heat flux from heating plate to heated product surface during 4 min contact cooking are described. Simultaneous measurements of product and heating plate temperatures as a function of time were used to determine the contact heat transfer coefficient between heating plate and product surface. The results show that the heat flux varied during the heating process. The magnitude of the heat flux as a function of time varies with the type of material heated and the heating plate temperature. The heat transfer coefficients measured were in the range 200 to 1200 W m^?2 K^?1, depending on product type, contact plate temperature, contact pressure and stage in the heat treatment.     

Development and characterisation of structurally reforming engineered flat-rice xerogel for hot water cooking

Shape transforming foods are an emerging area of interest that could be customised according to consumer needs with the desirable structure and reduced package space. The current work aims to investigate the shape transformation behaviour of a 2D xerogel developed from rice hydrogel at the concentration of 4% and 90 °C. This flat xerogel is coated with ethyl cellulose as constraint material in the form of linear equally spaced strips. Immersing the xerogels in hot water over a temperature of 70 °C, resulted in a 3D transformation of the discs in 12 s (Video  S1 ). The transformation is achieved owing to xerogel's increased swelling power (0.27–0.78) due to the anisotropic nature. This is confirmed by the SEM images of top (smooth) and bottom (rough) xerogel. In order to characterise the process of shape transformation bending analysis was done wherein a significant difference in bending angle (35.86–63.10°), height (24.73–50.26 mm), curvature (0.57–2.38 μ mm⁻¹) and end-to-end distance (118.23–15.11 mm) from 2 to 12 s. The formed 3D shape was similar to the commercial tubular (penne) pasta. This study opens up the utilisation of less concentrated rice xerogel in shape transformation for designing engineered food.     

Heat and mass transfer modeling in air drying of foods

Heat and mass transfer modeling in the air drying of solids is considered as a two stage procedure. The former aims to discover the dominant heat and mass transfer phenomena (heat versus mass, internal versus external), the latter aims to formulate empirical equations for the calculation of the corresponding heat and mass transport properties (mass diffusivity, thermal conductivity, boundary heat and mass transfer coefficients). A model discrimination procedure was proposed in the first stage, and a model building procedure was examined in the second stage. The proposed procedures were applied to a wide set of experimental data in potato drying. The resulting model takes into account moisture diffusion and convective heat and mass transfer in the air boundary layer. Moisture diffusivity is dependent on material moisture content and temperature, while heat and mass transfer coefficients can be considered as constants.     

A 2-step cooking method of searing and hot water pasteurization to maximize the safety of refrigerated, vacuum packaged, chicken breast meat

ABSTRACT:  Americans consume almost 40 kg per capita of chicken each year. Increasing consumption of chicken surpassed pork in 1982 and beef in 1992. The objectives of this study were to examine the effectiveness of a novel, 2-step cooking method of grilling, slicing, vacuum packaging, and hot water pasteurization to inhibit the growth of Listeria monocytogenes in chicken breast meat. Because this study required the use of pilot plant scale pasteurization equipment, Listeria innocua M1, a nonpathogen with slightly greater heat resistance than L. monocytogenes , was used as a surrogate. We first examined the lethal effects of grilling on a boneless skinless chicken breast to mimic cross-contaminated, surface-inoculated Listeria . Searing produced a mean reduction of 2.5 log CFU/g of Listeria and a moisture loss of only 7% (w/w). A 2nd experiment studied the lethal effect of pasteurization of the sliced seared chicken breast. L. innocua M1 inoculated between the slices mimiced contamination in deep muscle. Pasteurization in a 71 °C bath (final internal temperature of 66 °C) gave an additional 2.3 log CFU/g reduction. L. innocua M1 did not show significant regrowth during a wk of refrigerated storage. The combined 2-step cooking method of searing and pasteurization gave a combined 4.8 log reduction in LI M1. In parallel tests a non- Listeria indicator, Corynebacterium glutamicum , inoculated between sliced, seared chicken, showed a 3 log reduction after pasteurization for 10 min in a 71 °C bath compared to 2.3 log reduction of Listeria . Corynebacterium regrowth occurred much faster than did L. innocua M1.     

Heat and mass transfer in chicken breasts – effect on PhIP formation

Heterocyclic amines are mutagenic/carcinogenic compounds that are found in cooked meat and fish. These compounds are of concern in the aetiology of human cancer and therefore it is important to minimise their formation during cooking, and their intake. PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine, CAS no: 105650-23-5) is one heterocyclic amine that is found at high levels in cooked chicken. Chicken breast was cooked to a centre temperature of 72 °C using the following cooking methods: boiling, oven roasting, oven roasting in a special roasting-bag or in a clay pot, broiling, deep-frying and pan-frying. The temperature on the surface and at the centre was monitored by thermocouples during cooking, and these data, together with drip loss determined by means of weight reduction, were used to create temperature profiles and to calculate cook-values and rate of drip loss. The samples were analysed for PhIP using solid-phase extraction and HPLC. PhIP was detected in the broiled (0.07 ng/g), deep fried (0.02 ng/g) and pan-fried (0.04 30 ng/g) chicken breast. The cooking temperature and rate of drip loss had great impact on crust formation during pan-frying, and greatly affected the amount of PhIP formed. High temperature and high rate of drip loss were found to be most favourable for the formation of PhIP.     

Effect of cooking on enrofloxacin residues in chicken tissue

The aim of this study was to determine the effect of different cooking processes (microwaving, roasting, boiling, grilling and frying) on naturally incurred enrofloxacin residues in chicken muscle. Enrofloxacin and its metabolite, ciprofloxacin, were analysed using a validated LC-MS method with limits of detection (LOD) and quantification (LOQ), respectively, of 2 and 5 ng g^-1 quinolones in muscle samples. The method was shown to be linear over the range 5-500 ng g^-1. Mean intra-day relative standard deviation (RSD) at a concentration of 50 ng g^-1 (n = 6) was 6%; inter-day RSD was 12%. A recovery study demonstrated that 65-101%, of the drug and metabolite could be recovered from the tissue. The RSD with naturally incurred roasted chicken breast was 9.18% at a concentration of 11 ± 1.01 ng g^-1 (n = 6). In water, enrofloxacin remained stable for 3 h when heated at 100°C. It was concluded that residue data from raw tissue are valid for estimation of consumer exposure to this drug, as well as the ADI calculations because cooking procedures did not affect enrofloxacin residues, which remained stable during heating. However, there was an apparent decrease in quinolone concentration in tissue because some was lost by exudation into the liquid used for cooking. Conversely, for a cooking procedure with water loss, there was an apparent increase in residue concentration.     

Effect of cooking procedures on tylosin residues in chicken meatball

Most information about drug residues is related to their concentrations in raw products. The objective of this study was to assess the effects of various microwave and boiling treatments on the stability of different concentrations of tylosin in chicken meatballs. The chicken meatball samples (75 g) were prepared and fortified by 3 concentrations of tylosin (100, 200 and 300 μg kg^?1) and were cooked by boiling (100 °C for 10, 20, 30 min) and microwave procedure (power 450 W for 1, 1.5 and 2 min). The tylosin content was measured in raw and cooked samples through the use of high performance liquid chromatography. The microwave and the boiling process significantly reduced the tylosin. In both procedures, there were negative correlations between the length of cooking time and the reduction percentage of tylosin. In addition, tylosin reduction percentage in chicken meatball cooked by boiling depended on its concentration in uncooked samples. There was a relationship between tylosin reduction percentage and the increase in the internal temperature and weight loss during the cooking process. The results of this study indicate that tylosin residues in the food are decreased during the cooking process. Thus, given that a food product is cooked to be consumed, the surveillance of data obtained from tylosin measurement in the raw tissues samples could not be considered as consumers’ exposure to tylosin via dietary intake.     

煮制条件对卤鸡肉品质的影响

通过研究90℃和95℃两个温度条件下不同煮制时间对卤鸡肉品质的影响,以期获得卤鸡肉的适宜煮制条件。结果显示,卤煮温度和卤煮时间均显著影响卤鸡腿的品质(p<0.05)。同温下煮制10~120min,卤鸡腿的出品率、汤pH均大体呈现下降趋势,亮度L*、黄度b*、羰基值逐渐增加,红度a*值无明显变化,卤鸡腿pH、嫩度先增后降;煮制相同时间,两温度的出品率除20min外90℃始终高于95℃,亮度L*在30min之前90℃显著低于95℃(p<0.05),40min开始变化不再显著(p>0.05),黄度b*和红度a*无显著差异,剪切力除60min和90min外90℃均高于95℃,pH从60min开始90℃高于95℃,羰基含量在60min之后95℃开始明显高于90℃;60min是两温度在卤煮过程中品质差异显著的时间拐点。      

室外高温环境下通风服装的传热模型与实验研究

为提高夏季室外高温日晒环境下作业人员的热舒适性,对人体、服装与环境之间传热过程进行分析,以此作为针对性降温方式的理论基础建立了通风服装在室外高温日晒环境下的传热模型,并采用真人实验的方法验证了该传热模型;分析了送风后衣下空间空气参数及人体主观反映的改变.结果表明:采用该模型计算得到的人体得热量与失热量误差仅为9.1％,...     

烹饪方式对鸡肉挥发性香气及质构特征的影响

分别以炒、炖、焖3种方法对鸡肉进行烹饪,比较烹饪方式对鸡肉挥发性香气、形态的影响。结果表明:烹饪后鸡肉的感官品质特性发生了显著变化,鲜肉挥发性成分中醛类物质显著高于醇类和烷烃类,烹饪后鸡肉中挥发性成分主要是醛类和烷烃类物质,醛类和醇类物质含量显著降低,降低程度大小顺序均为:炒焖炖;而烷烃类物质含量显著增加,增加程度大小顺序均为:炒焖炖,并且检测出几个新的高分子物质;烹饪后鸡肉的硬度、弹性、内聚性和咀嚼性均大幅度升高,3种烹饪方式中,炒能显著降低鸡肉硬度和咀嚼性,且弹性和内聚性较高;而焖具有增加鸡肉的硬度和咀嚼性,且降低弹性和内聚性的趋势。     

Influence of cooking conditions on cooking loss and tenderness of raw and marinated chicken breast meat

The influence of different cooking treatments on tenderness and cooking loss, as main quality characteristics of chicken breast meat, was investigated. Industrial skinless chicken breast meat samples were designated as raw and marinated and cooked in the oven by hot air and hot air-steam mixture at 130, 150 and 170 °C, for 4, 8 and 12 min. Cooking losses were evaluated by weight changes before and after cooking, and tenderness changes were determined on cooked samples by measuring shear force using instrumental texture analysis. Results showed that marination, followed by air-steam cooking is the best combination to obtain the most tender chicken breast slices. The time and temperature of cooking showed similar effects on cooking loss and tenderness: short cooking time (4 min) and temperatures of 130–150 °C resulted in lower cooking losses and best meat tenderness, in both not marinated and marinated meat. Statistically significant correlations between tenderness and cooking loss indicated that the cooking loss correlated better with cooking time than with cooking temperature. An opposite phenomenon was observed for meat tenderness.     

药膳鸡汤的选方及制作工艺

本研究首先以鸡汤感官评定结果及鸡汤中粗蛋白含量、氨基酸含量作为评价指标,确定最佳药膳鸡汤的基础配方;继而在此配方下进行L9（3^4）正交试验,分别以鸡龄、切块大小、烹煮时间、放盐先后作为试验影响因素,通过对鸡汤的感官评定,鸡汤的粗蛋白、氨基酸的测定及Ca含量的分析,确定烹制药膳鸡汤最佳的鸡龄选择及煮制工艺：选择250日龄母鸡,以配方3作为药膳鸡汤的基础方,加入食用盐,煮沸后转小火烹制2h。     

Stability at cooking temperatures of model chicken breast muscle emulsions

Emulsion stability (ES) was measured on timed emulsification (TE) samples made with natural actomyosin (NAM) and exhaustively washed (EW) muscle, heated to 75°C, before using the Omni-mixer or after centrifugation. All emulsions cooked after centrifugation were found to be stable. The emulsions made with NAM showed a large decrease in ES when heated above 40°C prior to using the Omni-mixer. However, aqueous protein disappearance did not decrease significantly after TE until NAM was heated to between 60°C and 75°C. On the other hand, emulsions made with EW muscle heated prior to using the Omni-mixer showed a large decrease in both ES and aqueous protein disappearance after TE between 60°C and 75°C.     

Lipid oxidation in chicken as affected by cooking and frozen storage

Oxidative rancidity in fresh, frozen and cooked chicken breast and leg meat was evaluated by measuring malondialdehyde (MDA) in fat from meat with an improved 2-thiobarbituric acid (TBA) assay with antioxidant protection, and by measuring the relative fluorescent products of organic and aqueous layers from Folch extracted meat. Fresh samples were frozen for 3 and 6 months at ?18 °C and cooked in convection and microwave ovens. Frozen storage for 3 and 6 months either before cooking or after convection and microwave cooking substantially increased MDA concentrations in fat from meat, whereas cooking was more effective in generating fluorescent products. There were no significant differences in free MDA concentrations or TBA numbers in chicken meat between convection and microwave cooking methods. The certain secondary fluorescent products were significantly higher in meat cooked by convection oven. The initial levels of either MDA or fluorescent products in meat are of primary importance in determining the final MDA and fluorescence levels after processing.     

煮制对鸡肉及汤汁中游离氨基酸的影响

本文采用柱前衍生-反相高效液相色谱法（RP-HPLC）对95℃条件下不同煮制时间,不同部位的鸡肉及鸡汤中游离氨基酸（FAA）含量进行测定,研究煮制时间对鸡肉及鸡汤游离氨基酸含量的影响规律。结果表明:95℃煮制不同时间,蛋白质发生不同程度的降解。因FAA形成量与降解量的比率及溶于汤中量的差异,鸡肉表层的FAA含量先升高后降低,在40min时达到最大值;鸡肉中心的FAA含量呈现升高趋势,在120min时达到最大值。鸡汤中的FAA含量因肉样中FAA溶于其中而随煮制延长呈显著升高趋势,煮制120min时的含量约是10min的5倍。因此加热120min内,随煮制时间延长鸡汤会更加鲜美可口,且营养价值高。      

卤煮时间对酱卤鸡腿品质的影响

本实验旨在研究在95℃条件下,不同卤煮时间对酱卤鸡腿品质的影响。以黄羽肉鸡琵琶腿为研究对象,在煮制0、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4.0 h后,对样品出品率、水分含量及迁移变化、色差值、p H以及质构指标进行测定。结果表明:随着卤煮时间的延长,出品率及T23峰面积逐渐降低;亮度L*值逐渐下降,红度a*值和黄度b*值逐渐增加;p H波动下降;而硬度则呈现出先增加后下降的趋势。经研究,在卤煮1.5 h时,鸡腿出品率为71.2%;色泽均匀,表面呈黄褐色,内部呈浅棕色;p H为6.43,呈弱酸性,易于人体消化吸收;硬度、咀嚼性及弹性符合产品应有的口感。综合以上研究,鸡腿经95℃卤煮1.5 h后得到的酱卤鸡腿口感和品质最佳。