Effect of Environmental Salinity on the Free Amino Acid Composition and Concentration in Penaeid Shrimp

White shrimp, Penaeus vannamei, kept in laboratory aquaria at a salinity of 35 parts per thousand (ppt) were subjected to increased and decreased salinity changes by either 5, 15 or 25 ppt. Shrimp were periodically removed from the aquaria and analyzed for total free amino acid nitrogen and also specific free amino acid composition. Decreasing salinities resulted in corresponding decreases in free amino acid concentration; minimum values were reached after 24 - 48 hr. Increasing salinities were likewise shown to result in corresponding increases in the tissue free amino acid concentration with maximum values being reachedin 24 hr. Glycine, proline, arginine, serine/threonine, and alanine were the most significant contributors, comprising from 93 - 96% of the total free amino acid pool.     

超高压处理对中华管鞭虾虾肉风味的影响

为研究超高压处理对虾仁风味的影响,将中华管鞭虾分别在100、200、300 MPa条件下常温保压3、5 min处理,通过测定虾肉三磷酸腺苷关联化合物、游离氨基酸含量,计算鲜度指标K值及味精当量,并利用电子鼻和顶空固相微萃取-气相色谱-质谱(headspace-solid phase microextraction-gas chromatography-mass spectrometry,HSSPME-GC-MS)联用分析虾肉挥发性气味成分,确定超高压处理前后虾肉风味物质的变化。结果表明,超高压处理后虾肉腺苷酸含量有所上升,保压5 min组鲜味氨基酸含量明显高于对照组,结合氨基酸与呈味核苷酸的鲜味协同效应,得到200 MPa-3 min组和200 MPa-5 min组具有较高的味精当量,分别为13.04、13.81 g MSG/100 g。电子鼻结果显示,300 MPa组虾肉的嗅感有显著变化,100 MPa与200 MPa组虾肉的嗅感变化不显著;GC-MS结果显示对照组和超高压处理组虾肉的关键嗅感成分均为1-辛烯-3-醇、2-壬酮、芳樟醇。综合虾肉挥发性与非挥发性的变化,选择200 MPa保压5 min处理的中华管鞭虾能得到风味较好的虾仁。     

食盐浓度对虾油风味成分形成的影响研究

本文以虾头虾壳酿制虾油,研究了酿制过程中食盐浓度对风味成分形成的影响,数据显示:20%食盐浓度下酿制的虾油其游离氨基酸含量为16.8450 mg/g,挥发性成分中醛类占2.77%、吡嗪类占28.47%;而30%食盐浓度下上述各物质含量分别为14.4886mg/g、0.67%、7.33%。但TVBN值则是20%食盐浓度的虾油显著高于25%和30%食盐浓度的虾油,且前者有较明显的臭味,虾油的总体风味较差。以上结果表明;食盐浓度对虾油风味物质的形成有显著影响,虽然较低的食盐浓度有利于产生较多的游离氨基酸以及醛类、吡嗪类物质,但过低的食盐浓度不能完全抑制腐败作用。综合考虑,食盐浓度25%较为合适。     

Growth and toxin production by Clostridium botulinum in fish (Mugil cephalus) and shrimp (Penaeus indicus) tissue homogenates stored under vacuum

Toxin production by Clostridium botulinum types A–E in mullet and shrimp tissue homogenates stored between 4 and 30°C under vacuum for 6 weeks was evaluated. Mullet and shrimp tissue homogenates were inoculated with C. botulinum spores, then packaged under vacuum and held at 4, 10, 15 and 30°C. At 30 and 15°C storage, growth and toxin production by types A–E resulted in both mullet and shrimp tissue homogenates. Only type E toxin was observed in the homogenates held at 4 and 10°C. The storage temperature and the growth substrate markedly influenced the toxin titres.     

通电加热过程中凡纳滨对虾虾肉糜的游离氨基酸和核苷酸含量变化研究

为研究通电加热过程中不同加热温度(40、55、65、75、85和95℃)对凡纳滨对虾虾肉糜中主要非挥发性滋味成分的影响,采用氨基酸自动分析仪和高效液相色谱仪分别检测了虾肉糜中的游离氨基酸和核苷酸及其关联产物含量,并采用味道强度值(TAV)确定其中主要的呈味物质及贡献程度,最后通过味精当量(EUC)分析鲜味氨基酸和呈味核苷酸之间的协同作用,并对其鲜味进行评价。结果表明,与鲜虾相比,通电热处理的虾肉糜中游离氨基酸总量均有不同程度的减少。随着温度的升高,鲜味氨基酸、甜味氨基酸和苦味氨基酸的含量均呈现先减少后增加的趋势,且在65℃达到最小值(鲜味氨基酸、甜味氨基酸和苦味氨基酸的总TAV值分别为0.86、4.40、4.46)。通电加热并不影响ATP的降解途径只是会改变核苷酸及其关联产物的相对含量,尤其是促进Ado的产生。甘氨酸、精氨酸、谷氨酸、AMP和IMP在不同加热温度下其TAV几乎都大于1,是虾肉糜滋味的主要贡献者。味精当量以谷氨酸钠质量计,40℃最能促进虾肉糜鲜味的产生(EUC值为5.54 g MSG/100 g),在85℃处虾肉糜风味损失最小(EUC值为4.02 g MSG/100 g)。     

弱酸性电解水冰衣和气调包装对凡纳滨对虾(Litopenaeus vannamei)虾仁品质的影响

为研究弱酸性电解水(WAEW)冰衣和气调包装(MAP)对水产品的杀菌保鲜效果,以凡纳滨对虾为研究对象,对其保藏过程中质构特性、颜色、挥发性风味、微生物活性、挥发性盐基总氮(TVBN)、三甲胺总量(TMA)和硫代巴比妥酸反应物(TBARS)值的变化进行了研究。结果表明,经过40% CO₂＋10% O₂+50% N₂或30% CO₂+20% O₂+50% N₂气调包装和弱酸性电解水冰衣处理能够显著抑制虾仁中需氧菌和金黄色葡萄球菌的生长(p<0.05);采用弱酸性电解水冰衣和气调包装后,冻虾中的TVBN、TMA、TBARS的值相对较低,同时,联合处理对虾仁样品L*和a*值的降低表现出了显著的抑制作用,说明采用弱酸性电解水冰衣和气调包装联合处理能有效地保持虾仁的品质,对冷冻期间虾仁颜色的稳定性具有积极作用。但是WAEW冰衣产生的挥发性氯和二氧化氯使得其对生虾仁的挥发性风味具有不良影响,而对煮熟的样品没有显著影响。因此,弱酸性电解水冰衣结合气调包装作为一种新型的杀菌保藏技术,可以有效的保持水产品的品质和风味提高产品的商业价值。     

低值虾发酵制备传统虾酱风味的综合分析与比较

为研究虾酱的工艺、营养及风味特色,探讨中国传统发酵调味料的产业化。以低值虾为原料,模拟传统虾酱工艺,在恒温40 ℃条件下自然发酵42 d。然后与市售产品（S1、S2）相对照,检测了产品发酵过程中的游离氨基酸、固相微萃取-气相色谱-质谱挥发性风味成分及变化,同时以感官品评结合电子鼻对风味特点进行综合分析与比较。结果表明,游离氨基酸总量从发酵开始到结束由2 590 mg/100 mL增加到7 826 mg/100 mL;鉴定了3 种虾酱中的主要挥发性风味成分：自制虾酱53 种、S1 62 种、S2 62 种。发酵过程中醛类和吡嗪类化合物相对含量分别由0.62%、1.73%增加到了10.92%、8.48%,胺类和醇类相对含量则分别由77.4%、12.3%降低到了13.35%、6.75%,增加及下降均较显著（P＜0.05）;电子鼻检测发现自制虾酱与S2相似度最高,这与感官品评的结果一致。感官评价结合氨基酸分析、固相微萃取-气相色谱-质谱和电子鼻技术,综合评价了传统水产发酵调味品虾酱的风味。     

Use of Electrolyzed Oxidizing Water for Quality Improvement of Frozen Shrimp

The bactericidal effect of electrolyzed oxidizing (EO) water was evaluated on Escherichia coli O157:H7‐inoculated and Salmonella‐inoculated shrimp. The shrimp were inoculated on day 0 and stored frozen at ‐20°C. Bacterial enumeration was done on days 0, 24, 49, and 119 of frozen storage. Acidic EO water at 40 ppm free available chlorine was as effective as aqueous chlorine of the same concentration and was significantly more effective (P < 0.05) than tap water in reducing pathogen load on the inoculated shrimp. Further reduction of pathogen numbers was observed after each frozen storage period. Prewashing with alkaline EO water did not enhance the bactericidal activity of the acidic EO water on the shrimp. The washed acidic EO water of the inoculated shrimp had a nondetectable bacterial population compared with treated aqueous chlorine, alkaline EO water, and tap water. Non‐inoculated shrimp subjected to similar treatments were served cooked or uncooked to a minimum of 10 experienced panelists for sensory evaluation on days 0, 24, 49, and 119 of frozen storage. The cooked shrimp were evaluated for the presence of off‐odor, juiciness, tenderness, shrimpy flavor, aftertaste, and overall acceptability; whereas the raw shrimp were evaluated for color, firmness, presence of off‐odors, melanosis, and overall acceptability. Raw shrimp thawed from each frozen storage period were stored at refrigeration temperature (4 °C) for 3 d to observe for melanosis. No difference of sensory attributes was detected among the various treatment groups. Therefore, acidic EO water can be used as an effective disinfectant to replace aqueous chlorine for thawing shrimp blocks.     

高压蒸汽灭菌时间对冷吃兔风味物质的影响

该文探究了高压蒸汽灭菌时间(15、20、25、30、35 min)对风味物质理化指标、滋味物质及风味物质的影响.结果表明,高压蒸汽灭菌的时间对冷吃兔的水分、蛋白质、脂质、pH及氯化物无明显影响.咸味的呈味效果显著,灭菌20 min时氯化物的滋味活性值(TAV)与未灭菌最为相似.总游离氨基酸含量在15～20 min明显降...     

以虾头虾壳为原料酿制虾油的影响因素研究

文章以虾头虾壳为原料酿制虾油,采用感官评定、氨态氮( AAN)、三氯乙酸可溶性氮(TCA-N)、挥发性盐基氮(TVBN)等指标,研究温度、食盐浓度、酿制过程中pH值控制对虾油酿制的影响.研究结果表明:温度和食盐浓度太高和太低均不利于提高虾油的酿制速度和品质,偏碱性的酿制环境比偏酸性的酿制环境有利于提高虾油的酿制速度和品质,其中20％食盐浓度,酿制过程中控制pH8.0,酿制温度45℃有利于虾油酿制.     

Response surface methodology for autolysis parameters optimization of shrimp head and amino acids released during autolysis

Protein hydrolysates were prepared from the head waste of Penaens vannamei, a China seawater major shrimp by autolysis method. Autolysis conditions (viz., temperature, pH and substrate concentration) for preparing protein hydrolysates from the head waste proteins were optimized by response surface methodology (RSM) using a central composite design. Model equation was proposed with regard to the effect of temperature, pH and substrate concentration. Substrate concentration at 23% (w/v), pH at 7.85 and temperature at 50 °C were found to be the optimal conditions to obtain a higher degree of hydrolysis close to 45%. The autolysis reaction was nearly finished in the initial 3 h. The amino acid compositions of the autolysis hydrolysates prepared using the optimized conditions in different time revealed that the hydrolysates can be used as a functional food ingredient or flavor enhancer. Endogenous enzymes in the shrimp heads had a strong autolysis capacity (AC) for releasing threonine, serine, valine, isoleucine, tyrosine, histidine and tryptophan. Endogenous enzymes had a relatively lower AC for releasing cystine and glycine.     

Encapsulation of protein hydrolysates by spray drying: feasibility of using buffalo whey proteins

This work aimed to produce and encapsulate protein hydrolysates of buffalo origin using spray drying with gum arabic and maltodextrin as encapsulating agents. The following core ratios were applied: encapsulating agent in the ratios of 1:10 and 1:15, with 50% gum arabic and 50% maltodextrin (50:50), and 70% gum arabic and 30% maltodextrin (70:30). The encapsulated particles were between 2.0 and 20.0 μm. The encapsulation efficiency of the samples was above 95% at the initial time. After 45 days of storage, encapsulation efficiency decreased to values below 60%. The 70:30 samples showed a significant decrease (P < 0.05) in hygroscopicity, moisture and water activity compared with free hydrolysates. The encapsulation process increased the values of oil retention, emulsifying activity and solubility of whey protein hydrolysates for all proportions evaluated, both at the initial time and after 45 days of storage. The branched-chain amino acid concentration was higher in samples encapsulated at the 1:10 ratio. The spray drying encapsulation of buffalo protein hydrolysates with suitable encapsulating agents improves the techno-functional characteristics of these hydrolysates, hence expanding their use in different food matrices and enabling the use of buffalo cheese whey.     

加热方式对凡纳滨对虾滋味成分的影响

以凡纳滨对虾为原料,通过仪器分析法对微波加热与水煮处理的对虾的游离氨基酸、呈味核苷酸、有机酸、甜菜碱和无机离子这些主要滋味成分进行了分析。结果表明:凡纳滨对虾经微波加热与水煮处理后,游离氨基酸总量均有减少,分别下降了15.81%,20.19%;呈味核苷酸总量也均有减少,分别降低了25.07%,25.89%,其中含量最高的腺苷酸(AMP)有所提高,分别增加了4.01%,5.95%;乳酸含量大幅降低,分别减少了53.64%,77.24%;甜菜碱的含量也有明显的差异,分别减少了7.26%,8.83%;呈味无机离子含量差异明显,且微波虾的要高于水煮虾。通过研究分析发现,微波虾中除AMP含量略低于水煮虾外,游离氨基酸、有机酸、甜菜碱和无机离子的含量均高于水煮虾,表明微波虾的滋味优于水煮虾。     

Nutritional quality of red shrimp,Aristeus antennatus (Risso), pink shrimp,Parapenaeus longirostris (Lucas), and Norway lobster,Nephrops norvegicus (Linnaeus)

The proximate composition, amino acid and fatty acid profiles, lipid classes and cholesterol and glycogen contents were determined in the edible part of red shrimp, Aristeus antennatus (Risso), pink shrimp, Parapenaeus longirostris (Lucas), and Norway lobster, Nephrops norvegicus (Linnaeus), in two distinct periods of the year. The proximate composition did not vary significantly between species or between periods of sampling. Significant differences in glycogen content were obtained between winter and summer; the lowest values were attained in winter (1.2, 1.1 and 1.0% wet weight for red shrimp, pink shrimp and Norway lobster respectively). With the exception of Norway lobster, an opposite trend was obtained for cholesterol content, ie lower values in summer (60.8 and 57.8 mg per 100 g wet weight for red shrimp and pink shrimp respectively). The major essential amino acids (EAA) were arginine, lysine and leucine and the limiting amino acid was methionine in all three crustacean species. The most important non‐essential amino acids (NEAA) were glutamic acid, aspartic acid, proline and glycine. In respect to lipid classes, phospholipids and free cholesterol predominated. The major fatty acids were 16:0, 18:1n‐9, 20:5n‐3 and 22:6n‐3. The polyunsaturated fraction was dominant (42.1–48.4%), followed by the monounsaturated (26.3–34.6%) and saturated (22.9–27.4%) fatty acids. In conclusion, the nutritional quality of these shellfish species is similar, they are valuable protein and lipid sources for the human diet and are adequate elements of the traditional Portuguese diet. Copyright © 2003 Society of Chemical Industry     

南美白对虾虾头自溶产物主要呈味成分分析

以南美白对虾虾头为原料,制备风味良好的自溶产物。采用高效液相色谱法、原子吸收光谱等方法分析其主要的呈味物质。结果表明：游离氨基酸含量丰富,总量达9300mg/L,其中天门冬氨酸、谷氨酸、甘氨酸、丙氨酸4 种呈鲜味氨基酸的总含量达2130mg/L,占总游离氨基酸的22.9%;核苷酸及其关联化合物中,与鲜味有着密切联系的肌苷酸(IMP)含量为6.12mg/L;无机质离子Na+、K+、Cl －含量分别达663.7、182.1、417.2mg/L;甜菜碱、乳酸和琥珀酸含量分别达2400、15.27、13.32mg/L。这些成分都影响着南美白对虾虾头自溶产物的鲜味、甜味及整体的滋味。     

Effect of cooking conditions on the flavour compounds and composition of shrimp (Parapenaeus longirostris) broth

 To achieve a shrimp broth with the best flavour, the whole shrimp must be cooked at 85°C for 30 min in a 0.5% NaCl solution in proportions 1 : 2 (w : v). Quantitatively, the main components of the broth were nitrogen substances, the most abundant of these being peptides of molecular weight less than 600 Da. Levels of ATP metabolites were also determined [the more abundant compounds were inosine, guanosine 5′-monophosphate (GMP) and inosine 5′-monophosphate (IMP)], as were free sugars (glucose, fructose and ribose) and fat content. The free amino acid composition was also determined. A significant correlation (P <0.0001) between cooking temperature and different nitrogen fractions was observed. Received: 22 September 1997 / Revised version: 13 November 1997     

Non-Volatile Taste Components of Different Cultivated Mushrooms at Mycelia,Primordium, and Fruit Body Cultivation Stages

Free amino acid, flavor 5’-nucleotides, organic acid, and the values of equivalent umami concentration of cultivable mushrooms, namely Pleurotus eryngii, Agrocybe aegerita, and Lentinus edodes, were investigated at different cultivation stages, mycelia, primordium, and fruit bodies. Fruit bodies were higher than mycelia in contents of total free amino acid, flavor 5’-nucleotides, and the values of equivalent umami concentration in three cultivated mushrooms, but lower in contents of total organic acid in P. eryngii and L. edodes, respectively. Contents of total organic acid at three cultivation stages of three cultivated mushrooms ranged from 32.65 to 125.50 mg g^–1 with the primordium stage of L. edodes being the highest. Overall, the amount of the nutrition and flavor components of mushroom might be related with mushroom species, fermentation way, and cultivated time. Some compounds could be also extracted from mycelia or primordium of mushrooms other than fruit body.     

Proteolysis of Cheese Slurry Made from Pulsed Electric Field-Treated Milk

Raw milk cheeses have unique flavor and texture characteristics not obtainable in cheeses made from pasteurized milk. However, cheeses made from pasteurized milk are widespread, primarily for public health reasons. Pulsed electric field (PEF) treatment as a non-thermal pasteurization method has shown its ability to keep the flavor and natural characteristics of food samples intact, thus providing advantage over conventional heat processing. In this study, PEF treatment was performed in a continuous treatment chamber, consisting of two parallel stainless steel electrodes separated by a 50-mm-thick insulator. A 30-kV pulse generator was used to deliver bi-polar square waveform electric field to milk sample. Pulse width was 2 μs; pulse frequency was 2 Hz, and up to 120 pulses were applied. Cheese curds were made from raw milk, pasteurized milk, and PEF-treated milk, and their proteolysis processes were compared using curd slurry incubated at 30 °C for 5 days. The profiles of water-soluble peptides were measured using an reversed-phase high-performance liquid chromatography (RP-HPLC) system. The concentration of free amino acids was measured by Cd–ninhydrin method. Results indicated that PEF-treated milk has intermediate proteolysis profiles between raw milk and pasteurized milk in terms of peptide and free amino acid concentration. The results showed the potential of making high-quality cheeses by PEF treatment without sacrificing the natural characteristics of the cheeses.     

Free Amino Acids in Ham Muscle During Successive Aging Periods and Their Relation to Flavor

SUMMARY— The free amino acids and total ninhydrin positive material (NPM) in a 1% picric acid extract from dry-cured hams were measured after six different periods of aging. Correlation coefficients were calculated between amino acid values and taste panel scores. Significant (P < .051 increases were observed for NPM, serine, glutamic acid, threonine, leucine and isoleucine (not separated), valine, phenylalanine, proline, tyrosine, alanine, glycine and histidine during successive aging periods. Correlation coefficients between NPM and the organoleptic measurements of aged flavor, acidity, elasticity, crumbliness and softness were all highly significant. It k postulated that the increase in free amino acids can be attributed to action of the naturally occurring cathepsins. The free amino acids and their changes in concentration in relationship to flavor are discussed.     

食盐浓度对熟腌茭白理化性质及品质的影响

以茭白为原料,研究了不同食盐浓度腌制茭白其发酵过程中理化指标(p H、总酸、盐度、亚硝酸盐含量和氨基酸态氮)和微生物指标(细菌、乳酸菌总数)的变化,并对成品的色泽、质地、挥发性风味物质进行了分析。结果表明,3%、5%和8%食盐浓度下腌制的茭白p H分别为3.73、3.18和3.48,酸度分别为13.77、23.67和17.05 g/kg,平衡盐度分别为1.21%、2.51%和3.42%,"亚硝峰"值分别为7.86、11.6和11.79 mg/kg,氨基酸态氮含量分别为0.012、0.027和0.048 g/m L,细菌和乳酸菌数均稳定在107CFU/m L。腌制后茭白的色泽和质地都会有所改变,食盐浓度越低其失色越严重,腌制后茭白的硬度低于新鲜茭白,咀嚼性和内聚性随食盐浓度的升高而增大;三种食盐浓度腌制后茭白均检测到39种挥发性化合物,主要挥发性风味物质为乙醇、2,3-丁二醇、乙酸、乙酸乙酯和苯甲醛等。建议茭白腌制初始食盐浓度为5%。