半干咸鱼水分活度的研究

研究了影响半干咸鱼水分活度的因素,采用添加品质改良剂和控制终产品的含盐量等方法,探讨其对半干咸鱼水分活度的影响状况。结果表明,半干咸鱼制品的水分活度主要取决于终产品的含盐量,随着含盐量增加,水分活度显著下降;丙二醇、丙三醇、磷酸二氢钠与磷酸氢二钠等品质改良剂的适量添加,也可明显降低半干咸鱼的水分活度。      

半干咸鱼水分活度的研究

研究了影响半干咸鱼水分活度的因素,采用添加品质改良剂和控制终产品的含盐量等方法,探讨其对半干咸鱼水分活度的影响状况。结果表明,半干咸鱼制品的水分活度主要取决于终产品的含盐量,随着含盐量增加,水分活度显著下降;丙二醇、丙三醇、磷酸二氢钠与磷酸氢二钠等品质改良剂的适量添加,也可明显降低半干咸鱼的水分活度。     

红笛鲷肌肉中三种性腺激素残留的分析

采用放射免疫分析法测定了养殖红笛鲷与野生红笛鲷肌肉中雌二醇、孕酮、睾酮三种性腺激素残留量。结果表明,在养殖红笛鲷与野生红笛鲷肌肉中均检出三种激素,养殖红笛鲷肌肉中三种性腺激素的残留量分别是野生红笛鲷的5.39、2.43、4.40倍;野生红笛鲷中的激素残留量较低,但仍能被检出,可能与环境激素有关。实验结果提示,放射免疫分析法可作为水产品中激素残留量的有效检测手段。     

红笛鲷肌肉中三种性腺激素残留的分析

采用放射免疫分析法测定了养殖红笛鲷与野生红笛鲷肌肉中雌二醇、孕酮、睾酮三种性腺激素残留量。结果表明,在养殖红笛鲷与野生红笛鲷肌肉中均检出三种激素,养殖红笛鲷肌肉中三种性腺激素的残留量分别是野生红笛鲷的5.39、2.43、4.40倍;野生红笛鲷中的激素残留量较低,但仍能被检出,可能与环境激素有关。实验结果提示,放射免疫分析法可作为水产品中激素残留量的有效检测手段。      

三种甾体激素在湛江海域的紫红笛鲷体内的残留调查

本文采用放射免疫分析法测定了湛江海域养殖紫红笛鲷与野生紫红笛鲷肌肉中雌二醇、孕酮、睾酮三种甾体激素的残留量。结果表明，在养殖紫红笛鲷与野生紫红笛鲷肌肉中均检出三种激素，养殖紫红笛鲷肌肉中三种甾体激素的残留量分别是野生紫红笛鲷的4．50、1．57、5．00倍；野生紫红笛鲷中的甾体激素残留量较低，但仍能被检出，可能与环境激素有关。实验研究提示，放射免疫分析法可作为水产品中激素残留量的有效检测手段。     

半干鸭血干加工工艺及食用品质的研究

研究半干鸭血干的加工工艺和食用品质。将鸭血用3种不同方式进行卤制,通过感官评定选出最佳卤制方式,后通过热风干燥、微波干燥及微波真空干燥对卤制过的鸭血进行干制,控制水分含量在38%左右,比较后得出最理想的半干鸭血干。对半干鸭血干和鸭血豆腐进行质构、色泽、感官及硫代巴比妥酸(thiobarbituric acid,TBA)值的对比,结果显示:与鸭血豆腐相比,半干鸭血干具有较好的棕红色色泽,硬度适中、弹性良好、有嚼劲儿,贮藏时间较长,便于携带和食用。因此,半干鸭血干的研发为更好的开发鸭血产品提供了一条新思路。     

基于低场核磁共振技术检测秋刀鱼腌干制过程 水分状态变化

目的探讨腌干处理对秋刀鱼水分状态的影响,为秋刀鱼的高值化加工提供参考。方法秋刀鱼进行"三去"(去头、去尾、去内脏)处理,采用10%食盐溶液(料液比1:2)进行腌制,选取腌制2 h的样品进行40℃热风干燥,检测样品的水分含量、盐含量以及水分活度,利用低场核磁共振技术(low-field nuclear magnetic resonance,LF-NMR)测定腌干过程样品的水分存在状态。结果秋刀鱼样品腌干过程中均存在结合水、不易流动水和自由水3种状态水分。腌制10 h过程中样品的水分活度未低于0.90的细菌生长临界值。结合水比例呈现先增大后减小的变化趋势,自由水比例相对降低,不易流动水比例增大,表明腌制处理使得部分结合水与自由水转化为不易流动水。随干制时间的延长,样品的水分含量和水分活度均显著降低(P0.05),结合水变化较小,不易流动水比例呈降低趋势,表明干制处理一方面使得秋刀鱼组织内不易流动水流失,另一方面使其部分转移成其他相态的水。同时,核磁共振成像灰度图和伪彩图深色区域面积逐渐增大,表明干制过程伴随油脂的溢出。结论腌制和干制处理降低了秋刀鱼鱼肉的水分活度,同时改变了水分存在状态。核磁共振成像灰度图和伪彩图表明干制处理改变了秋刀鱼样品的油水平衡。     

怎样制作水咸鱼

水咸鱼是指粤厨利用复制咸鱼水．对小型鱼类原料进行加工制作后的半成品。制作水咸鱼的目的是．延长鱼的保存期；其制作方法是，食品加工里的腌制和干制的方法．故水咸鱼属于腌腊制品。     

肉制品施工技术经验交流(之五)——干制品

肉的干制品根据原料的性质和食用需要,有的接进行干制,有的须经加盐稍予腌制后干制,一般都在肉品干制之前进行调味、烧煮等处理。经过干制的肉品,具有风味独特,体积小,重量轻,不易腐败,便于贮藏和运输等特点。肉品干制的基本原理就是脱水,使水分蒸发。     

厨房里的知识问答

问：干咸鱼晾在家里的通风处会让家里的空气有异味,有什么更好的方法保存千咸鱼吗？ 答：为了避免发出异味,可以用密封的袋子将干咸鱼包好后放在冰箱里储存。如果干咸鱼比较大,可以切成小块再装袋。如果没有冰箱,也可以用罐子装盛,但在咸鱼上面要撒些花椒、生姜、丁香等,密封好罐口放在阴凉、通风、干燥的地方。也可以把剥开的大蒜瓣铺在罐子里的最下层,再把咸鱼放进去,将盖封紧,这样干咸鱼也能保存很长时间不会变质。值得注意的是,贮存干咸鱼一定要防潮,因为干咸鱼受潮后会使含水量增加,容易使微生物生长繁殖,导致干咸鱼发霉变质。     

半干咸鱼不同脱盐方式的研究

分别研究了清水浸泡、添加脱盐剂、扎孔、振荡、真空反渗透等不同脱盐方式对半干咸鱼含盐量的影响,以鱼块含盐量及浸泡液的电导率、可溶性蛋白质含量、色差为监测指标,进行比较。结果表明,使鱼块含盐量降至质量分数3%的不同脱盐方式的脱盐时间:真空反渗透<振荡处理<扎孔处理<清水浸泡;添加质量分数1.5%海藻糖能最大限度地保持产品品质;综合脱盐速率和营养物质的损失,振荡处理是脱盐的有效手段之一;真空反渗透是一种快速脱盐的有效方式。     

Effect of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid diesters and glycidol fatty acid esters in fish,meats and acylglycerols during heating

The effects of the presence of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid esters (3-MCPDEs) and glycidol fatty acid esters (GEs) in saltwater fish, meats and acylglycerols (diacylglycerol and triacylglycerol) during heating were investigated in this study. Five saltwater fish species (salmon, saury, yellowtail, mackerel and Spanish mackerel) were grilled with a fish griller. 3-MCPDEs and GEs were detected in all of the grilled fish samples. The total amount of GEs was higher than 3-MCPDEs. Beef and pork patties with or without sodium chloride (1.5%) were cooked using gaseous fuel. The formation of 3-MCPDEs was significantly increased by the addition of sodium chloride to the meat patties, whereas the concentration of GEs in the cooked meat patties was not changed by the content of sodium chloride. Hexadecane solutions of diacylglycerol or triacylglycerol containing FeCl₃ were heated at 240°C. The formation of 3-MCPDEs was greatly increased by adding FeCl₃ to the solutions of triacylglycerol. The amounts of 3-MCPDEs decreased with the extension of the heating time. From these results, it is suggested that 3-MCPDEs and GEs are formed in saltwater fish and meats by cooking, and that the formation of 3-MCPDEs was affected by chloride in foodstuffs.     

浙江省部分水产品中硼含量调查

目的检测浙江省部分水产品中硼的含量。方法在浙江省11个地市的超市和农贸市场采集部分水产品,按照GB/T 21918—2008《食品中硼酸的测定》的第二法测定样品的硼含量。结果共采集样品296份,硼检出率为66.2%(196/296),硼含量中位数、P25、P75和最大值分别为0.19、0.025、0.47和26.8 mg/kg。海水水产品硼检出率和硼含量高于淡水水产品。海水中甲壳类、鱼类、软体类硼检出率和硼含量差异无统计学意义(P0.05);淡水中甲壳类、鱼类硼检出率和硼含量差异无统计学意义(P0.05);淡水虾和淡水蟹硼检出率和硼含量差异无统计学意义(P0.05)。结论本研究淡水水产品均为活水产品,海水水产品均为冰鲜水产品,前者测得的硼含量可以认为是本底含量,而后者因不能确定是否人为添加了硼,故测得值尚不能认为是本底含量。因此,对于两种生活环境中水产品硼含量的比较尚不能确定不同生活环境(海水或淡水)会影响硼在生物体内的富集。本研究中淡水水产品硼含量的测定可为硼限量标准的制定提供一定的参考。     

Changes in fatty acid composition in muscle and adipose tissue of farmed rainbow trout (Oncorhynchus mykiss) in relation to ration and age

To evaluate the importance of age and feed ration level (RL) on the composition of tissue fatty acid (FA) in rainbow trout (Oncorhynchus mykiss), fish were fed rations ranging from appreciable underfeeding to gross overfeeding in a longitudinal experiment lasting from start of feeding to onset of sexual maturation 2.4 years later. In order to study the effects of compensatory growth and reduced feed availability, fish were moved from high to low ration and vice versa. Changes of individual FA of total lipid (TL), triacylglycerols (TAG) and total phospholipids (PL) were studied in white and red muscle, as well as in three major adipose tissues. The effect of saltwater transfer on FA composition was also examined. A strong interdependence was found between the relative proportion of PL and TAG with changes in TL content. This was most prominent in white muscle. In parallel with this change in relative lipid class composition, a major effect was seen on FA in the TL fraction. The most marked effect of RL was an inverse relationship between 22:6 n-3 of the PUFA n-3 series and 16:1 and 18:1 of the MUFA series. This was seen in all tissues studied. It is suggested that the most important factor governing FA composition in muscle, pending changes in feed intake, is the TL content, affecting the relative level of PL and TAG. In adipose tissue, consisting mainly of TAG, more subtle changes were observed. The FA compositions of PL and TAG were not affected to any major extent by RL, except at extreme reductions. Significant changes in FA of PL and TAG were observed as an effect of saltwater transfer.     

Bromophenol Distribution in Salmon and Selected Seafoods of Fresh- and Saltwater Origin

Analysis of saltwater Pacific salmon (Onchorynchus sp.) showed that sufficient concentrations of bromophenols were present in saltwater salmon to provide sea-, brine-, or iodine- like flavor notes, but the compounds were virtually absent in spawning run ocean and prime condition Great Lakes freshwater salmon. Octanol/water partition coefficients revealed that bromophenols would be readily absorbed by fish from the diet. Analysis of marine fish, crustaceans, and molluscs also revealed notable concentrations of bromophenols in all samples. Only sporadic, low concentrations of bromophenols were found in freshwater fish. The data support the hypothesis that simple bromophenols are widely distributed in marine species via the food chain.     

半干鲐鱼片冷风干燥工艺优化及货架期预测

实验以鲐鱼为原料,分析了冷风干燥工艺参数对半干鲐鱼片品质和风味的影响,通过U^*₉(9⁴)均匀设计实验,以不同的干燥工艺因素(温度、相对湿度、风速)为自变量,测定半干鲐鱼片的挥发性盐基氮值(TVB-N值)、菌落总数(TVC)与硫代巴比妥酸值(TBA值),进行感官评价,并建立干燥条件下的回归模型,对其结果进行综合分析,确定冷风干燥工艺的最优参数组合,并结合一级动力学模型与Arrhenius方程,研究其货架期预测模型。结果表明:温度、风速对TVB-N值有显著影响(p<0.05),温度对TBA有显著作用(p<0.05)。半干鲐鱼片冷风干燥工艺的最优条件为温度15℃,风速2.4 m/s,相对湿度25%。在此条件下验证得到实测值与预测值的一致性较好,TVB-N、TBA值误差分别为0.71%、1.16%。半干鲐鱼片干燥时间为21 h,TVB-N值为25.33 mg/100 g,TVC为5.93×10³ CFU/g,TBA值为1.11 mg/kg,感官评分为94.38分,鲜度好,风味佳。在-5~10℃范围内,建立的TVB-N值、TVC、TBA值与贮藏时间的动力学模型有较高拟合度,选用TVB-N、TBA值作为评判指标,可以准确预测半干鲐鱼片的货架期,本研究结果可为半干鲐鱼片的工业化生产提供理论依据。     

膨化鱼片的热风-微波干燥工艺研究

研究草鱼鱼片的干燥工艺,探讨了热风预脱水鱼片的含水量以及降温、升温和恒温三种预脱水热风干燥模式,微波间歇加热工艺对鱼片品质的影响,并对不同干燥条件下的产品进行了感官、质构和膨化效果分析。结果表明,热风预脱水鱼片含水量控制在35%～50%,选择降温热风干燥模式,微波功率设定中高火档(418±2.5W),加热60s,间歇30s的干燥工艺条件是最佳的。     

Prevalence and survival of Listeria monocytogenes in Danish aquatic and fish-processing environments

Listeria monocytogenes contamination of ready-to-eat food products such as cold-smoked fish is often caused by pathogen subtypes persisting in food-processing environments. The purpose of the present study was to determine whether these L. monocytogenes subtypes can be found in the outside environment, i.e., outside food processing plants, and whether they survive better in the aquatic environment than do other strains. A total of 400 samples were collected from the outside environment, fish slaughterhouses, fish farms, and a smokehouse. L. monocytogenes was not detected in a freshwater stream, but prevalence increased with the degree of human activity: 2% in seawater fish farms, 10% in freshwater fish farms, 16% in fish slaughterhouses, and 68% in a fish smokehouse. The fish farms and slaughterhouses processed Danish rainbow trout, whereas the smokehouse was used for farm-raised Norwegian salmon. No variation with season was observed. Inside the processing plants, the pattern of randomly amplified polymorphic DNA (RAPD) types was homogeneous, but greater diversity existed among isolates from the outside environments. The RAPD type dominating the inside of the fish smokehouse was found only sporadically in outside environments. To examine survival in different environments, L. monocytogenes or Listeria innocua strains were inoculated into freshwater and saltwater microcosms. Pathogen counts decreased over time in Instant Ocean and remained constant in phosphate-buffered saline. In contrast, counts decreased rapidly in natural seawater and fresh water. The count reduction was much slower when the natural waters were autoclaved or filtered (0.2-microm pore size), indicating that the pathogen reduction in natural waters was attributable to a biological mechanism, e.g., protozoan grazing. A low prevalence of L. monocytogenes was found in the outside environment, and the bacteria did not survive well in natural environments. Therefore, L. monocytogenes in the outer environment associated with Danish fish processing is probably of minor importance to the environment inside a fish production plant.     

Associations of diet with body burden of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs): observations on pregnant women from central Taiwan.

The aim of this study was to examine the relationship between placental polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F) and polychlorinated biphenyls (PCBs) toxic equivalent (TEQ) levels and the consumption of various food types in pregnant women from central Taiwan. Placental PCDD/Fs and PCB congener TEQ levels were evaluated in 109 pregnant women and dietary information was obtained by questionnaire. TEQ levels of PCDD/Fs and PCBs were positively associated with age and annual family incomes (p < 0.05). PCDD/F TEQs were significantly associated with freshwater fish and dairy product consumption after adjustment for age and body mass index (BMI) (p < 0.05). For PCB TEQs, significant associations were detected for saltwater fish consumption (p < 0.05). In summary, positive correlations were found between freshwater fish and dairy product intake and PCDD/F levels, and a marginal correlation between saltwater fish intake and the body burden of PCBs in pregnant women from central Taiwan. Risk assessment of PCDD/Fs and PCB in fishery products is warranted in a future study to quantify the benefits of fish consumption during the perinatal period.     

Fish flavor

This article reviews features of flavor in three groups of fishes and summarizes them as follows: (1) fresh saltwater fish are nearly odorless because they contain a small quantity of volatiles; (2) freshwater fish give off pyrrolidine and earthy‐odor compounds, which are responsible for their maturity and surrounding water pollution, and (3) euryhaline fish exhibit a variety of unsaturated carbonyls and alcohols derived from enzymatic and nonenzymatic oxidation of polyunsaturated fatty acids (PAs). These features are discussed, as are the effects of different enzymatic activities on PA oxidation and the effects of pH on mechanisms of formation of the volatiles. The monotonous volatile constitution of saltwater fish is likely caused by an unknown antioxidation system restraining the fish from oxidizing. The variety of constitution of euryhaline fish, especially that of anadromous fish under spawning conditions, could result from the loss of that system. The thermal environments of heated foods are also reviewed. The basic environment of fish, which allows the formation of the flavor compounds, is discussed to confirm the volatiles found in unheated fish.