水分活度对干制虾仁产品的货架寿命和质构的影响

采用真空微波脱水的方法将虾仁干制成不同水分活度(Aw)的样品,测定样品在20℃时的水分吸附等温线,并通过保藏试验分析比较Aw对常温保藏后虾体内的细菌菌落总数以及对虾体的弹性、硬度等质构参数的影响。结果表明,当Aw控制在0.86~0.9(水分含量约25%(W/W))时,常温保藏的虾仁干制产品在口感及微生物指标等方面可取得平衡。     

水分活度降低剂在半干鱿鱼制品加工中的应用

水分活度(Aw)与食品品质及贮藏性有着密切的关系,降低半干鱿鱼制品的Aw有利于保持其品质并延长保质期。为寻求有效降低鱿鱼制品水分活度的方法,采用Box-Behnken试验设计和响应面分析法,研究了丙三醇、海藻糖和柠檬酸等3种水分活度降低剂对半干鱿鱼制品水分活度的影响。结果表明:丙三醇、海藻糖、柠檬酸均能有效降低半干鱿鱼制品的水分活度,最佳组合为:丙三醇1.80%,海藻糖4.00%,柠檬酸0.40%,此时鱿鱼制品的水分活度为0.872。     

水产品的腌制加工

鱼的腐败,主要是鱼体内的水分为细菌和酶提供了作用的条件。腌制就是向鱼体渗入食盐或食盐水,使水分渗出,盐分增加,直至鱼体细胞内的盐浓度与体外盐浓度相当,这个过程叫做盐渍。它可在一定程度上抑制细菌的繁殖和酶的作用。腌制方法有干渍法、水渍法和混合渍法三种。沿海地区普遍采用干渍法。干渍法操作简便,     

干贝水分、盐分适宜含量的研究

运用水分活度概念．试验分析了干贝水分、盐分含量与贮藏性关系。能保证干贝质量及良好贮藏性的适宜水分含量为１６～１８％；盐分含量为４～５％。     

带鱼腌制加工过程理化指标、微生物和生物胺的动态变化及相关性

为探明鱼类腌制过程生物胺形成机理,本文研究了带鱼(Trichiurus haumela)在腌制加工过程盐度、水分含量、水分活度(Aw)、pH、蛋白质水解指数(P.I.) 非蛋白氮(NPN) 、游离氨基酸、微生物和生物胺的动态变化及相互关系,结果表明：pH在腌制阶段增加但在干燥阶段下降;盐度、P.I和微生物(菌落总数、乳酸菌、葡萄球菌和微球菌)在整个加工过程持续上升,水分含量和Aw则持续下降。整个加工过程,发生了明显的蛋白质降解反应,NPN 和游离氨基酸在干燥阶段含量显著上升;总生物胺含量增加了2.26倍(p＜0.05),其中尸胺含量显著增加了157倍,其次是组胺。带鱼腌制过程,游离氨基酸与生物胺显著正相关(p＜0.05),作为生物胺前体物质对生物胺的形成影响较大,微生物则起到了促进和抑制生物胺的作用,生物胺的形成还受pH、盐度、Aw等因素的共同影响,是一个极其复杂的过程。     

真鲷水分脱湿等温曲线和热力学性质的研究

研究了真鲷水分脱湿(解吸附)等温曲线的动力学特性、不冻结水和冻结点之间的关系以及热力学性质.研究采用水蒸汽压法和差示扫描量热法测定了真鲷各个处理条件下的水分活度、熔融热和冰点.实验通过GAB(Guggenheim-Anderson-de Boer)模型和BET(Brunauer-Emmett-Teller)模型对真鲷的水分解吸附等温曲线进行了拟合,确定了各参数间的拟合方程.实验发现,真鲷的水分解吸附等温曲线为Ⅱ型(S形),GAB模型和BET模型均具有较好的拟合度,R2分别为0.991 5(GAB模型,aw: 0.13～0.98)和0.982 5(BET模型,aw＜0.90 ).由拟合方程计算得真鲷的单分子层饱和水分含量分别为0.082 0 g/g 干基(GAB模型)和0.078 1 g/g 干基(BET模型).实验发现,真鲷中可冻结水含量与熔融热存在线性关系(R2 = 0.999 6),并计算得当熔融热(ΔH f)为0时,真鲷的不可冻结水水分含量为0.291 2 g/g干基.     

腌制方式对卵形鲳鲹理化指标及其挥发性风味成分的影响

为了探究干腌、湿腌、超声波辅助腌制对卵形鲳鲹的理化特性及挥发性风味成分的影响,实验对腌制加工后鱼肉的基本营养成分、盐含量、pH、硫代巴比妥酸(TBA)值、脂肪酸组成及挥发性风味成分等指标进行测定分析。结果显示,在腌制加工后,卵形鲳鲹粗蛋白和粗脂肪含量升高、而水分含量下降,其中干腌、湿腌、超声波辅助腌制鱼肉中水分含量分别为53.71%±0.97%、61.45%±0.72%和59.29%±1.41%。与卵形鲳鲹原料相比,干腌、超声波辅助腌制、湿腌鱼肉中盐含量增加,依次为(3.29±0.15)、(2.64±0.02)和(2.15±0.11) g/100 g,而在腌制加工后鱼肉的pH值下降。在腌制加工后,卵形鲳鲹的脂质发生氧化反应,TBA值增加,干腌、湿腌、超声波辅助腌制鱼肉的TBA值分别为(0.80±0.07)、(0.55±0.09)和(0.73±0.08) mg MDA/kg,饱和脂肪酸和单不饱和脂肪酸含量增加,而多不饱和脂肪酸含量减少。冻藏保鲜、干腌、湿腌、超声波辅助腌制鱼肉中分别检测出54、56、62和57种挥发性风味物质,主要为醛类、醇类和酮类,对风味形成有重要贡献作用。研究表明,卵形鲳鲹经3种不同腌制方式加工后,干腌鱼肉水分含量最低,而盐含量和TBA值最高;超声波辅助腌制鱼肉的挥发性风味物质中醛类、醇类相对含量最高,而pH值最低。本研究可为腌制加工及生产工艺优化提供理论参考。     

软烤扇贝加工过程的细菌学研究

对软烤扇贝加工过程中物料的细菌特性和有关理化特性进行了研究,并对细菌菌群进行了定性和定量分析。结果表明,实验室加工中,水分含量和水分活度(Aw)的降低都主要发生在调味腌制、焙干过程,最终产品水分含量为42%左右,Aw为0.902±0.003。工厂加工在焙干、烤制过程水分含量和Aw的降低较多,成品水分含量为42%左右,Aw为0.910±0.007,控制良好。实验室加工pH下降主要发生在调味腌制过程,产品pH为5.83左右,工厂产品pH没有明显下降,最终pH为6.70左右,不符合标准要求。实验室加工原料菌落总数是(4.47±1.59)×102cfu/g,在调味摆盘和包装过程分别上升到(1.35±0.83)×103cfu/g、(7.30±0.53)×102cfu/g,在焙干、烤制过程分别下降到(5.43±0.67)×102cfu/g、(2.90±0.75)×102cfu/g,二次杀菌冷却后产品菌落总数均小于300 cfu/g。工厂加工原料菌落总数为(9.08±0.20)×103cfu/g,焙干过程上升至(4.69±0.10)×105cfu/g,烤制过程下降到(1.12±0.40)×104cfu/g,包装过程上升至(2.58±0.20)×106cfu/g。二次杀菌冷却后3个产品中,有1个产品细菌总数为340 cfu/g,不符合企业标准要求。实验室烤制冷却后样品的主要菌群为芽孢杆菌,但仍含有小比例的葡萄球菌。二次杀菌冷却后,样品中仅残存芽孢杆菌,无球菌。工厂二次杀菌冷却后样品中主要菌群为芽孢杆菌,但仍含有相当数量的球菌,比例接近1/3,表明其生产过程不良,产品质量安全存在一定的问题。     

鱼皮明胶蛋白膜的制备及其热稳定性

利用鲨鱼皮明胶制备蛋白可食膜,测定了成膜液蛋白浓度、甘油含量对明胶蛋白膜理化性质的影响,以及环境湿度对膜热稳定性的影响.结果发现,利用鲨鱼皮明胶可以制备成无色透明的蛋白可食膜,成膜液蛋白浓度对明胶蛋白膜的断裂延伸率(EAB)、水蒸气透过率(WVP)以及透明度值有一定的影响,对拉伸强度(TS)没有发生显著影响,但甘油含量从10％增加到70％时蛋白膜的TS逐渐降低.利用DSC对膜的热稳定性进行分析,结果表明当水分活度(Aw) ＜0.33时,明胶蛋白膜在常温下可以处于玻璃态,机械性质能够保持稳定.然而,当Aw超过0.44后,膜的玻璃化转变温度(Tg)起始点低于25℃,膜的EAB上升,TS出现显著下降.当Aw达到0.92时,膜甚至开始溶解变成溶胶.因此,利用鲨鱼皮制备的明胶蛋白膜只适合在Aw小于0.44的干燥环境中应用.     

黄海中南部水域鳀鱼脂肪含量的季节变化

根据 2 0 0 2年 6月～ 2 0 0 3年 5月黄海中南部水域鱼 (Engraulisjaponicus)的调查资料 ,分析其脂肪含量与叉长、性别以及水分含量的关系。产卵前期 (5月)、产卵盛期 (6月 )和越冬期 (1月 )脂肪含量同叉长呈显著正相关 (P <0 .0 1 ) ,而在产卵中后期 (7～ 1 0月 )无显著相关性。在 5～ 1 0月雌性脂肪含量比雄性高 ,其中 5月差异最大。不同季节、不同性别的脂肪和水分含量呈显著负相关(P <0 .0 1 )。脂肪和水分含量变化幅度很大 ,分别为 0 .54 %～42 .97%、36.31 %～ 85 .45%。产卵前期平均脂肪含量最高 ,产卵盛期和越冬期较高 ,产卵中后期最低     

The Effects of Light Salting on Physicochemical Characteristics of Frozen Cod (Gadus morhua) Fillets

Abstract

The effects of light salting by brine injection and brine immersion on physicochemical and textural properties of cod fillets were evaluated. Light salting significantly increased yield and water holding capacity. Adding brine injection to the process can be used to shorten the process time needed to obtain the desired salt content and increase yield. The effects on chemical composition were most significant in salt content, but water and protein content were also affected. Water content decreased from the tail to head direction of the fillets, both in unsalted and light salted fillets. Changes in protein content were in opposite proportion to changes in water content. This could be seen in the fresh fish and also after freezing, both in unsalted and light salted fillets. Texture of the fish was not significantly affected by salting and freezing.     

Optimizing Salting and Smoking of Catfish (Bagre marinus) Using Response Surface Methodology

ABSTRACT

Response surface methodology was used to assess the effects of brine concentration (0.1127–0.2473 g NaCl/g), salting time (49–271 min), smoking temperature (53.2–86.8°C), and smoking time (216–384 min) on moisture content, salt content, yield, taste preference, and texture preference of smoked catfish slices. Optimal process conditions were determined through the graphical method and desirability function approach. The desirability function showed that the optimal conditions for salting and smoking of catfish were: smoking temperature, 70°C; smoking time, 300 min; salting time, varying from 193.39 to 194.68 min; and brine concentration varying from 0.1791 to 0.1797 g NaCl/g. Under optimal conditions, moisture content, salt content, yield, taste preference, and texture preference of smoked catfish were 0.53 g water/g, 0.064 g NaCl/g, 58%, 3.7, and 3.7, respectively.     

饲料中脂肪的含量对青鱼鱼种生长的影响

本文报导了利用青鱼鱼种在饲料中的蛋白质,醣、维生素和无机盐等保持适宜含量的条件下,研究不同含量脂肪对青鱼鱼种生长影响的试验结果。试验所用的脂肪为马面鲀鱼油。试验结果表明,青鱼鱼种饲料中适宜的脂肪含量为3-8％,最佳含量为6.5％。两批实验的结果基本一致。饲料中的脂肪含量对鱼体肌肉和肝脏生化组成有一定的影响。     

Response to “Psychophysics and the Sensory Assessment of Fish”

Fillets from Pacific cod (Gadus macrocephalus) were salted with and without polyphosphates (PP) by means of a short three-step salting process. The changes in phosphate and water content during different steps of production were determined by comparing fillets with and without addition of PP. While fillet samples after salt injection and wet-salting contained different water content, from 80.1% to 74.6% depending on processing step and PP addition or not, after dry-salting there was no significant difference in water content between fillets with (58.1%) or without PP (58.9%). Dry-salted fillets with PP addition showed a phosphate content of 6.1 mg P₂O₅/g. In the following rehydration process (48 h), the total phosphate content dropped down to 2.9 mg P₂O₅/g, which was lower than the natural total phosphate content of 4.4 mg P₂O₅/g in the raw material.     

Elucidating Comminution Steps to Enhance the Value of Surimi from Tropical Fish

Biochemical and rheological properties of surimi were examined based on: (a) salting time (from 18 to 3 min) while maintaining 21 min for total chopping time; and (b) total chopping time (from 6 to 21 min) while salting during the final 3 min. Extending salting time, which was defined as time of salt contact with proteins during chopping, significantly increased breaking force and penetration distance, while chopping time extension with fixed salting time did not. Salt soluble proteins decreased when salting time decreased; however, this trend performed contrarily against chopping time. A relationship between gel texture and salt soluble proteins was not found. Oxidation of sulfhydryl groups could occur during the chopping process when chopping without salt was extended. Surface hydrophobicity, indicating a certain degree of protein unfolding, was affected differently by chopping versus salting time. Dynamic rheology demonstrated that total chopping time affected denaturation of the myosin tail region more than salting time.     

Water quality affects SDH activity, protein content and RNA:DNA ratios in fish (Catla catla, Labeo rohita and Oreochromis mossambicus) raised in ponds of a sewage-fed fish farm

The spatial and seasonal variability of the respiratory enzyme succinate dehydrogenase and the protein content were examined in different tissues of fish cultured in three ponds along the effluent gradient of a sewage-fed fish farm. Indian major carp Catla catla (150-230 g) and Labeo rohita (60-190 g) cultured in both the middle and last points of the sewage effluent (stocking pond 1) and (stocking pond 4) and Oreochromis mossambicus (50-160 g), a naturally growing fish of the inlet (facultative pond) and the out let of the sewage effluent (stocking pond 4) were procured every month during the period of January-December, 2005 and were subjected to determination of succinate dehydrogenase activity, total protein, DNA and RNA contents from gill, liver and muscle tissue respectively. The SDH activity of all three test fishes (Catla catla, Labeo rohita and Oreochromis mossambicus) was reduced significantly (ANOVA; P < 0.05) when cultured in SP-4 compared to SP-1 in the case of Catla catla and Labeo rohita and in facultative pond in the case of Oreochromis mossambicus.Conspicuous differences in the SDH activity of fish between the last and first stocking pond or the facultative pond were clearly due to the result of the differences in water quality. There was a direct relationship between SDH activity in gill tissue of any of the fish investigated and ammonia-N concentration of water or water pH. This shows that the respiratory activity of these fishes was strongly affected by the ammonia and pH of water. In other words, this suggests that as the distance from the point source increases, there was a substantial improvement of water quality in the ponds located along the sewage effluent gradient. Evidently, there is a progressive pattern of growth, survival and physiological health of fish and abundance of favorable diversity of food organisms with rich biodiversity.     

城郊养鱼高产湖塘理化特点及生物相的分析

本文报导 1973年武汉市郊两个渔业高产湖塘的理化、生物环境特点,并分析了各类环境因素间的关系。在养殖季节中,湖水溶氧量通常在7毫克/升以上,总氮平均为2.63毫克/升,总磷平均为0.38毫克/升;浮游植物平均为2,199×10~4-3,080×10~4个/升,主要为硅藻,甲藻和绿藻等小型种类;浮游动物平均为39,200-74,318个/升,以原生动物和轮虫为主。文中提出了各类环境因素间相互关系的方程式,定量地描述了饵料生物丰度和氮、磷的关系。     

Setting the Global Context in Discovery and Transformation of Seafood Products

ABSTRACT

The effects of sun drying at ambient temperature in the range of 24°C to 32°C; artificial drying at 35°C, 45°C, or 55°C; or artificial drying at 45°C after treatment with 10% brine, 20% brine, saturated (36%) brine, or dry salt at 28°C for 16 hours on the physical characteristics of the final dried Bombay duck (Harpodon neherius) were studied. Unsalted sundried fish was found unacceptable. Dry salting was more efficient in reducing the moisture level in fish than brining, but was found unsuitable by the panelists due the appearance of a powdered salt crust as the fish dries up. Bombay duck treated with 20% sodium chloride solution, artificially dried at 45°C, and kept in sealed polyethylene pouches was judged superior after sensory evaluation compared to unsalted sundried Bombay duck or unsalted artificial dried Bombay duck at 35°C, 45°C, and 55°C, or artificial dried samples at 45°C after treatment with 10% brine, saturated (36%) brine or dry salt, and kept in sealed polyethylene pouches, respectively, during storage.     

The effect of dietary sodium chloride on some osmoregulatory parameters of the teleost, Oreochromis niloticus, after transfer from freshwater to seawater

The aim of this work was to determine the effects of supplemental dietary sodium chloride on salt water acclimation of tilapia Oreochromis niloticus. Fish were fed a basal diet supplemented with NaCl (8%) during three weeks in fresh water (FW) and then transferred to salt water (SW) at 15 and 20. Changes in plasma osmolality, chloride ion concentration (Cl^–), plasma level of cortisol and gill Na⁺, K⁺-ATPase activity were measured at 6, 12, 24, 48, 72 and 168 h after transfer to 15SW, while the higher strength SW group (20) was only monitored up to 24 h. Morphological changes in the gill mitochondria-rich (MR) cells were examined in relation to environmental salinity. The changes associated with dietary NaCl were sporadic and of small magnitude. The plasma osmolality and Cl^– increased immediately after transfer up to 12–24 h, but fish fed dietary salt (S) showed lower values than the control group (C). The S group showed higher plasma levels of cortisol than the control, which maintained its initial levels during the experiment. Gill Na⁺, K⁺-ATPase activity of the S group began to increase in the first hours after transfer, reaching maximum at 12 h and returned to basal level at 24 h, while the control group maintained basal levels. The differences between gill Na⁺, K⁺-ATPase activity of S and C fish were significant (p < 0.05) at 12 h. Transmission electron microscopy (TEM) revealed that MR cells in SW show more mitochondria and a more developed tubular system arising from the basolateral membrane. The MR cells of both groups frequently formed a multicellular complex in SW, consisting of a main MR and one or more accessory cells. Such complexes are rarely observed in FW. Some MR cells of fish fed supplemented dietary salt displayed convex apical membrane in FW.