Amino acid, fatty acid, and mineral profiles of materials recovered from rainbow trout (Oncorhynchus mykiss) processing by-products using isoelectric solubilization/precipitation

ABSTRACT:  Protein, lipid, and insolubles (bones, skin, scales, fins, insoluble protein, and more) were recovered from rainbow trout processing by-products by means of isoelectric solubilization/precipitation at basic pH and acidic pH. Isoelectric solubilization/precipitation of the trout processing by-products resulted in the recovery of protein that was higher ( P < 0.05) in essential amino acids (EAAs), non-EAAs, and total EAA/total AA ratio when compared to the processing by-products. Basic pH treatments yielded a higher ( P < 0.05) content of EAAs than the acidic pH treatments. Nutritional quality of the recovered protein was high based on EAAs meeting the FAO/WHO/UNU recommendations for adults. The presence of omega-3 and omega-6 fatty acids (ω-3, ω-6 FAs) and the ω-3/ω-6 ratio in the recovered lipids were similar to the trout processing by-products, indicating that the pH treatments had no effect on these FAs. Ca and P contents of the processing by-products exceeded the recommended dietary allowances (RDA), but Fe and Mg did not. Basic pH treatments yielded protein with the lowest ( P < 0.05) amount of minerals and the highest ( P < 0.05) amount of Ca, P, and Mg in the insolubles when compared to acidic pH. The isoelectric solubilization/precipitation of the processing by-products effectively removed minerals from the recovered protein without removal of the bones, skin, scales, fins, and so on, prior to processing. The results indicated that isoelectric solubilization/precipitation, particularly at basic pH, permitted recovery of high-quality protein and lipids from fish processing by-products for human food uses; also, the recovered insolubles may be used in animal feeds as a source of minerals.     

酸碱法分离斑节对虾蛋白的营养特性研究

本研究分别以斑节对虾全虾和虾肉为原料,采用酸碱法(Isoelectric solubilization/precipitation)提取蛋白,探讨了极端酸碱pH溶解-沉淀条件对分离蛋白的提取得率、基本营养成分及营养品质的影响。结果表明:在料液比1:9(g/mL)、pH 2.0、pH 3.0以及pH 11.0、pH 12.0条件下溶解,pH 5.5条件下沉淀,全虾的蛋白提取得率在75.67%~82.72%,虾肉的蛋白提取得率在68.33%~80.5%,且均在pH 2.0和12.0时有最大蛋白提取率。斑节对虾分离蛋白中干基粗蛋白含量在82%以上,灰分含量在1.3%左右,且酸性溶解条件提取的分离蛋白中粗蛋白和灰分含量显著(p0.05)高于碱性溶解条件。对虾分离蛋白中必需氨基酸量、半必需氨基酸量、总氨基酸量和风味鲜度均高于原料对照,但虾味氨基酸量低于对照;所得分离蛋白的必需氨基酸配比符合FAO/WHO/UNU的理想模式。对虾分离蛋白中K、Mg、Cu、Zn和Mn五种元素的含量均显著(p0.05)低于原料虾和虾肉,碱性溶解条件下分离蛋白中矿质元素含量低于酸性溶解条件(p0.05)。酸碱法制备斑节对虾分离蛋白具有蛋白得率高、营养品质佳的特点,可用于生产优良的食品和饲料。     

冻藏过程中南极磷虾蛋白理化特性和品质的变化

为了解冻藏南极磷虾理化性质和品质变化,本文测定了全虾和虾肉中不同蛋白组分含量变化,并采用二维电泳分析全虾样品的等电点和分子量分布,以水分含量、持水率、pH、硫代巴比妥酸反应物(TBARS)值为指标,进一步分析了蛋白品质的变化。结果表明:随冻藏时间的增加,南极磷虾全虾和虾肉盐溶性蛋白显著下降(p<0.05),碱溶性蛋白和非蛋白氮(NPN)显著上升(p<0.05)。二维电泳(2-DE)结果表明,盐溶性蛋白的蛋白点大多集中于pH4~6区域,水溶性和碱溶性蛋白在pH8~9也有分布;盐溶性蛋白的损失主要发生在肌球蛋白重链(210 kDa)和轻链(17~23 kDa)分子上;水溶性和碱溶性蛋白中蛋白点少量丢失。长期冻藏过程中,全虾和虾肉的含水量和持水率显著下降(p<0.05);全虾的pH和TBARS值明显升高(p<0.05),虾肉的pH和TBARS总体趋势略微上升(p>0.05)。各指标相关性分析表明,冻藏过程中虾品质指标的变化趋势具有一定的一致性。因此,随冻藏时间的增加,虾蛋白凝胶性质减弱,品质下降。     

南极冰鱼与南极磷虾营养成分分析及比较

本文采用国标方法分析了南极冰鱼的营养成分,并与南极磷虾营养成分进行了比较,期望为南极冰鱼的开发利用提供依据。南极冰鱼肌肉中的蛋白质和灰分含量与南极磷虾差异显著(p0.05),脂质和碳水化合物含量与南极磷虾差异不显著。南极冰鱼肌肉与南极磷虾均含有17种氨基酸,必需氨基酸指数分别为44.24和34.03,必需氨基酸的构成比例符合FAD/WHO的标准;鲜味氨基酸占总氨基酸的比例分别为35.86%和40.51%。南极冰鱼中饱和脂肪酸(33.37%)和单不饱和脂肪酸(41.22%)含量分别高于南极磷虾(32.60%和29.75%),南极磷虾多不饱和脂肪酸(25.12%)含量低于南极磷虾(45.38%)。南极冰鱼肌肉中的矿物质(Ca、Fe、Zn、Cu等)含量低于南极磷虾。因此,南极冰鱼具有较高的营养价值和良好的开发应用前景。     

Characterization of lipids and antioxidant capacity of novel nutraceutical egg products developed with omega‐3‐rich oils

BACKGROUND: Cardiovascular disease has had an unquestioned status of the number one cause of death in the US since 1921. Omega‐3 polyunsaturated fatty acids (ω‐3 PUFAs) have cardio‐protective benefits. However, egg is typically a poor source of ω‐3 PUFAs and, in general, the American diet is low in these cardio‐protective fatty acids. Novel, nutritionally enhanced egg products were developed by substituting yolk with ω‐3 PUFA‐rich flaxseed, menhaden, algae, or krill oil. Experimental egg products matched composition of hen egg (whole egg). The experimental egg products, mixed whole egg, and a liquid egg product (Egg Beaters^?) were microwave‐cooked and compared. RESULTS: Although fat, protein, and moisture contents of experimental egg products matched (P > 0.05) mixed whole egg, experimental egg products had more (P < 0.05) ω‐3 PUFAs, lower (P < 0.05) ω‐6/ω‐3 ratio, and depending on oil added, a higher (P < 0.05) unsaturated/saturated fatty acids ratio compared to mixed whole egg. Triglycerides were the main lipid class in all experimental egg products except those developed with krill oil, which had even more phospholipids than mixed whole egg. Analysis of thiobarbituric acid reactive substances showed that lipid oxidation of experimental egg products was lower (P < 0.05) or similar (P > 0.05) to mixed whole egg, except for experimental egg products with krill oil. However, peroxide value showed that all egg samples had minimal oxidation. Experimental egg products developed with menhaden or flaxseed oil had the highest (P < 0.05) concentration of the antioxidant, ethyoxquin compared to all other egg samples. However, experimental egg products with krill oil likely contained a natural antioxidant, astaxanthin. CONCLUSION: This study demonstrated an alternative approach to developing novel, nutraceutical egg products. Instead of dietary modification of chicken feed, yolk substitution with ω‐3 PUFAs oils resulted in enhancement of ω‐3 PUFAs beyond levels possible to achieve by modifying chicken feed. Copyright © 2011 Society of Chemical Industry     

南极磷虾冷藏过程中的品质变化

以pH 值、出肉率、可溶性蛋白质含量为指标,结合感官评价,探讨了南极磷虾0℃和3℃贮藏过程中的品质变化,运用SDS- 聚丙烯酰胺凝胶电泳(SDS-PAGE)分析南极磷虾的蛋白质相对分子质量变化。实验结果显示,南极磷虾24h 贮藏后,pH 值都逐渐升高,分别达到8.21 ± 0.01 和8.28 ± 0.02;出肉率从(61.92 ± 2.50)% 分别减少到(22.65 ± 6.81)% 和(13.64 ± 2.72)%;可溶性蛋白质含量都逐渐降低,分别降为(19.0 ± 0.50)mg/10g 湿质量和(25.5 ± 2.00)mg/10g 湿质量。SDS- 聚丙烯酰胺凝胶电泳出现5 条蛋白质条带,1h 时0℃和3℃的蛋白质分子质量分别为49.5、32、29、26、13.2kD,且29kD 的蛋白质条带被分解的最快。感官评分最高值和最低值分别为9.5 ± 0.05、9.4 ± 0.12 和1.3 ± 0.10、1.0 ± 0.08。表明在0℃和3℃条件下贮藏的南极磷虾自溶迅速,品质下降很快,因此冷藏条件下的南极磷虾开始进行加工的时间应该在10h 之内。     

南极磷虾及其产品中砷含量分析及安全性评价

南极磷虾作为一种重要的海洋生物资源,其相关产品的食用安全性受到广泛关注,特别是由于南极磷虾油中总砷含量较高,使其在保健品和膳食补充剂等方面的应用受到限制。本研究采用氢化物发生-原子荧光光谱法和液相色谱-原子荧光光谱法分别对南极磷虾及其产品中总砷、无机砷含量进行检测,同时基于检测数据和南极磷虾产品的膳食消费量,采用点评估方法对南极磷虾产品中砷膳食暴露量及食用安全性进行初步研究。结果显示：南极磷虾整虾和磷虾肉中总砷含量均低于0.50 mg/kg,南极磷虾粉、南极磷虾油及其胶囊产品中总砷含量相对较高,但是南极磷虾产品中无机砷含量一般低于0.050 mg/kg;点评估结果表明,摄食南极磷虾油等产品对无机砷膳食暴露量的贡献率极低,长期食用磷虾油不会增加总膳食无机砷的摄入量。因此,南极磷虾及其产品可以作为安全、优质的食品、饲料或保健品原料予以广泛应用。     

Functional properties of proteins recovered from silver carp (Hypophthalmichthys molitrix) by isoelectric solubilization/precipitation

Isoelectric solubilization/precipitation at acidic and basic pH ranges was applied to whole gutted silver carp (Hypophthalmichthys molitrix) in order to recover muscle proteins. Thermal denaturation (T_onset, T_max, and ΔH), viscoelasticity (G′), and texture properties (shear stress) of proteins recovered from carp as affected by functional additives (beef plasma protein, potato starch, exogenous transglutaminase, polyphosphate, and titanium dioxide) were determined and compared to Alaska pollock surimi. Proteins recovered from carp showed typical endothermic transitions only when functional additives were used. Similar to endothermic transitions, viscoelasticity in carp proteins increased only when the additives were used. Typical endothermic peaks and viscoelasticity increase were recorded for Alaska pollock surimi. Carp protein-based gels with functional additives had lower (P < 0.05) shear stress than their surimi counterparts, but greater (P < 0.05) or similar (P > 0.05) when compared to surimi gels without functional additives. In addition, generally higher shear stress was measured for carp protein-based gels developed from basic pH treatments than the acidic counterparts. The present study indicates that proteins can be recovered from whole gutted carp using isoelectric solubilization/precipitation. However, if the recovered proteins are used for subsequent development of restructured food products, functional additives should be used.     

Nutritional composition of novel nutraceutical egg products developed with omega-3-rich oils

The ω-3 fatty acids (ω-3 FAs)-fortified eggs are typically developed through alteration of hen feed. The present study aimed at creating ω-3 FAs-fortified egg products via processing. Novel, nutritionally-enhanced egg products were developed by substituting cholesterol-containing yolk with ω-3 FAs-rich flaxseed, menhaden, algae, or krill oil. Experimental egg products (egg whites, ω-3 oils, and annatto), whole egg, and liquid egg product (Egg Beaters™) were microwave-cooked, analyzed, and compared. Protein, fat, and moisture contents of experimental egg products matched (P > 0.05) whole egg. Cholesterol was the highest (P < 0.05) in whole egg (1.35 g/100 g, dry weight basis); while it ranged 0.01-0.24 g/100 g (dry weight basis) in experimental egg products. On a per egg basis, one whole egg contained 216 mg; while experimental egg products ranged 1-38 mg. The total ω-3 FAs content was the lowest (P < 0.05) in whole egg (5.9% of total FAs) and the highest (P < 0.05) in experimental egg products developed with krill oil (46.5%), followed by flax (43.1%), algae (DHASCO-42.5% and DHAS-39.5%), and menhaden oil (27.6%). The essential amino acid (EAA) content of experimental egg products was similar (P > 0.05) to whole egg except methionine, phenylalanine, and valine were generally greater in experimental egg products. Experimental egg products also had similar (P > 0.05) content of non-EAA to whole egg except alanine and glutamic acid were higher (P < 0.05); while arginine and cysteine were generally lower and higher in experimental egg products, respectively. However, total EAA, total non-EAA, and the ratio of total EAA to total AA were similar (P > 0.05) between experimental egg products and whole egg. Whole egg contained more (P < 0.05) Ca, P, and Fe, but less Mg than experimental egg products.     

南极磷虾不同部位氟形态及其分布特征

利用连续化学-超声波浸提法,对南极磷虾全虾、虾头、虾壳、虾肉中总氟含量以及氟的存在形态进行研究分析。结果表明：总氟含量依次为虾壳＞虾头＞全虾＞虾肉。不同部位不同形态氟含量以残余态最高,其次为可交换态,氧化态氟和有机态氟含量相对较低,水溶态氟含量极少。由此可见,南极磷虾中氟的形态大部分以残余态和可交换态存在。相关性分析表明：水溶态氟与可交换态氟呈显著正相关（r=0.495**）,氧化态氟与残余态氟呈显著负相关（r=－0.254*）,有机态氟与残余态氟呈显著正相关（r=0.312*）。水溶态氟与南极磷虾pH值和水分含量均呈显著正相关（r=0.737**,r=0.292*）,有机态氟与蛋白质含量呈显著正相关（r=0.324*）,残余态氟与蛋白质含量呈显著负相关（r=－0.366*）。本研究可为南极磷虾不同组织中氟的不同存在形态提供科学依据,也为南极磷虾脱氟研究提供理论基础。     

A Comparative Study between Acid-and Alkali-aided Processing and Surimi Processing for the Recovery of Proteins from Channel Catfish Muscle

ABSTRACT: Channel catfish muscle was subjected to 2 novel protein extraction and precipitation techniques using acid (pH 2.5) or alkaline (pH 11) pH and compared with surimi processing (3 wash cycles). Solubility of catfish proteins was found to be highest at pH 2.5 and 11, and at these pH levels, viscosity was found to be low enough to cause separation of proteins from insoluble materials via centrifugation. Both the acid-aided and alkali-aided processes led to higher recoveries ( P < 0.05) of protein and larger reduction ( P < 0.05) in lipids compared with surimi processing. The protein recovery could be increased even more with a modified version of the acid-aided and alkali-aided processes. There was no hydrolytic breakdown detected during low and high pH. The acid-aided process recovered more protein types than the alkali-aided process during isolelectric precipitation (pH 5.5), which indicated that it led to more protein denaturation and thus more aggregation at pH 5.5. The alkali-aided process had more soluble proteins (including heme proteins) at isoelectric precipitation than the acid-aided process, and the soluble proteins were of the same type as the soluble proteins for non-pH-treated catfish muscle at pH 5.5. This suggested the alkali-aided process led to less denaturation than the acid-aided process. Both acid-aided and alkali-aided processes recovered proteins of higher ( P < 0.05) whiteness scores than surimi. The alkali-aided process recovered proteins of higher whiteness ( P < 0.05) than the acid-aided process. The acid-aided process led to higher yellowness ( P < 0.05) than the other 2 processes. All processes led to minimal levels of lipid oxidation as assessed by secondary oxidation products.     

不同水分含量对南极磷虾烤虾质构和色泽的影响

以质构和色泽为指标,并结合感官评定,对水分含量分别为22％、25％、28％和31％的四种南极磷虾烤虾品质进行研究。实验结果表明,水分含量对南极磷虾烤虾质构有一定影响,水分含量22％的南极磷虾烤虾的硬度、胶粘性、咀嚼性和剪切力与其他水分含量的南极磷虾烤虾呈显著性差异（P〈0．05）,水分含量25％和28％的南极磷虾烤虾的内聚性和弹性相对较高,品质较好;通过测定四种烤虾的RG雅,发现四种样品的色泽均属于粉色系,对外观的影响不是很大,随着烤虾水分含量下降,制品的色泽越容易接受。水分含量28％的南极磷虾烤虾的感官评分最高,为8．99±0．05,通过对不同水分含量的南极磷虾烤虾的质构和色泽分析,结合感官评定,认为南极磷虾烤虾的水分含量为28％时品质最佳。     

南极磷虾副产物酶解蛋白胨工艺优化及实际应用

本试验以南极磷虾副产物为原料,采用单因素和正交试验确定最佳的水解工艺,测定南极磷虾蛋白胨中的游离氨基酸,确定接种微生物的最适浓度以及培养效果的比较。结果表明,制备南极磷虾蛋白胨的最佳水解工艺条件为:温度60 ℃,pH5.0,加入碱性蛋白酶水解1.5 h后,再加入风味蛋白酶继续水解3.5 h,总加酶量1%,复合酶比1:1,该条件下水解率为28.38%。南极磷虾蛋白胨富含17种游离氨基酸,总游离氨基酸含量为(2968.83±35.1) mg/100 g。以南极磷虾蛋白胨溶液为培养基培养大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、蜡状芽孢杆菌的最适浓度分别为3.5、5.0、4.0、4.5 g/L。测得4种微生物在牛肉膏蛋白胨中的OD₆₀₀仅比在南极磷虾蛋白胨中大8%左右,说明南极磷虾蛋白胨可以替代牛肉膏蛋白胨作为微生物培养基的成分。     

优选南极磷虾蛋白肽抗氧化活性组分

目的制备南极磷虾抗氧化肽,优选出抗氧化活性最好的南极磷虾肽成分。方法采用脱脂、酶解、超滤等手段制备南极磷虾抗氧化肽;以DPPH自由基清除率、ABTS自由基清除率、抗氧化能力指数3个抗氧化指标和超氧化物歧化酶(superoxide dismutase, SOD)、过氧化氢酶(catalase, CAT)活力2个酶活力指标为评价指标,优选出抗氧化活性最好的南极磷虾肽组分;基于G-25凝胶层析技术对抗氧化活性最好的南极磷虾肽组分进行分离纯化,进一步基于电子顺磁共振(electron paramagnetic resonance,EPR)方法测定洗脱后各峰的DPPH自由基清除率,得到抗氧化活性最好的南极磷虾抗氧化肽组分。结果通过抗氧化指标测定,截留分子量3～10 KDa的肽的DPPH自由基清除率最高,为(30.10±1.10)%,截留分子量3 KDa的南极磷虾肽的ABTS清除能力和抗氧化指数较好,则IC50值为(0.74±0.08) mg/mL、氧化自由基吸收能力(oxygen radical absorbance capacity, ORAC)值为6.39±0.21;通过酶活力指标测定,截留分子量3 KDa的肽的SOD活力和CAT活力最好,分别为(45.7±0.13)U/mg和(17.1±0.19)U/mg蛋白质。对截留分子量3KDa和3～10KDa的南极磷虾肽进行G-25分离纯化后,测定各组分的DPPH自由基清除率,可知截留分子量3～10KDa的F2-2峰清除率最好,为(51.55±1.54)%。结论基于EPR方法优选出分子量为3～10 KDa的南极磷虾肽的F2-2组分的DPPH自由基清除率最高。     

捕捞月份对南极磷虾营养成分的影响

为了研究南极磷虾营养成分随月份的变化,以2016年3~8月份在南极48.1区捕捞的南极磷虾为材料,测定其水分、蛋白质、脂肪和灰分等基本营养成分含量,利用氨基酸分析仪测定其氨基酸种类和含量,并对其进行评分,利用气相色谱仪测定其脂肪酸含量,系统地分析评价了南极磷虾的营养价值,为南极磷虾的加工与利用提供参考。结果表明:南极磷虾蛋白质含量范围为13.07%~15.15%,脂肪含量范围为1.13%~4.36%,两者随着月份有相同的变化趋势,并在4月份达到最高。氨基酸分析结果表明,其总氨基酸含量(T)范围为99.83~151.33 mg/g,必需氨基酸含量(E)范围为41.63~64.66 mg/g,六个月份中E/T和E/N值(N表示非必需氨基酸总量)均高于FAO/WHO提出的理想蛋白质条件,但4~6月份T和E值为最高。各月份南极磷虾必需氨基酸指数(EAAI)均接近1,比例均衡,其中缬氨酸为限制性氨基酸。南极磷虾中共检出29种脂肪酸,不饱和脂肪酸有19种,占脂肪酸总量的60%以上,以C16:1、C18:1n9c、EPA和DHA为主,饱和脂肪酸总量(SFA)从3~8月份呈逐渐增加的趋势,增幅为2.34%;ω-3/ω-6值在2.96~4.37,比例合适。综合分析,4~6月份的南极磷虾营养价值更高,可选择此阶段对南极磷虾进行捕捞。     

Extraction and characterisation of lipids from Antarctic krill (Euphausia superba)

There is significant commercial interest in oil extraction from krill because it is rich in omega-3 polyunsaturated fatty acids (n-3 PUFA) such as eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic (DHA, 22:6n3) acids. The objectives were to determine oil extraction efficiency using different solvent systems and the composition of extracted oil and spent krill following extraction. Extraction efficiency was the highest (P < 0.05) for one-step extraction using freeze-dried krill with 1:12 or 1:30 krill:solvent ratio (w:v) compared to Folch, Soxhlet, and conventional two-step extraction. Extracted oils contained predominantly phospholipids (20–33%), polar non-phospholipids (64–77%), and minor triglycerides (1–3%). Triglycerides contained much less (P < 0.05) total n-3 (4.0%), DHA (1.1%), and EPA (2.3%), but more (P < 0.05) saturated FA (38.7%) than phospholipids (total n-3-47.4%, DHA-18.0%, EPA-28.2%, saturated FA-23.5%). Antioxidant capacity of krill oil extracted by one-step extraction (9.4–14.2 μmol Trolox Equivalents/ml oil) was generally similar to antioxidant capacity of krill oil extracted by ethanol (22.9), but greater (P < 0.05) than antioxidant capacity of krill oil extracted by acetone (1.2) and Folch method (1.5). The spent krill following oil extraction contained protein (72.9–75.8%, dry basis). Based on the extraction efficiency and composition of the extracted oil, the one-step extraction using 1:12 krill:solvent ratio is recommended.     

Antarctic Krill (Euphausia superba) Oil: A Comprehensive Review of Chemical Composition,Extraction Technologies,Health Benefits,and Current Applications

Antarctic krill (Euphausia superba) oil has been receiving increasing attention due to its nutritional and functional potentials. However, its application as a novel food ingredient has not yet been fully explored. This review summarizes the chemical composition, extraction technologies, potential health benefits, and current applications of krill oil, with the aim of providing suggestions for its exploitation. Krill oil is a unique lipid consisting of diverse lipid classes and is characterized by a high concentration (39.29% to 80.69%) of phospholipids (PLs) associated with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It also contains considerable amounts of bioactive minor components such as astaxanthin, sterols, tocopherols, vitamin A, flavonoids, and minerals. The current technologies used in krill oil production are solvent extraction, nonsolvent extraction, super/subcritical fluid extraction, and enzyme‐assisted pretreatment extraction, which all greatly influence the yield and quality of the end‐product. In addition, krill oil has been documented to have various health benefits, including anti‐inflammatory effects, cardiovascular disease (CVD) prevention, women's health, neuroprotection, and anticancer activities. Although krill oil products used for dietary supplements have been commercially available, few studies have attempted to explore the underlying molecular mechanisms to elucidate how exactly the krill oil exerts different biological activities. Further studies should focus on this to improve the development of krill oil products for human consumption.     

南极磷虾海鲜酱油的品质评价

以Alcalase酶水解南极磷虾制得的酶解液为原料,经降氟,调配,灭菌,包装后制成南极磷虾酱油。该酱油总氮含量为(20.93±0.23)mg/L,氨基酸态氮含量为(12.32±0.27)mg/L,含量均高于GB18186-2000中特级酱油的标准。可溶性无盐固形物含量较高,为22.09%±0.52%。氯化钠、总酸、铅和砷含量分别为15.27%±0.26%、(0.61±0.05)g/100mL、(0.92±0.42)mg/L和(0.38±0.01)mg/L,均低于GB2717-2003酱油卫生标准中的限量。该酱油中硒含量为(1.31±0.04)mg/L,牛磺酸含量为139.30mg/100mL,赋予了酱油新的功能活性。南极磷虾酱油在贮藏过程中无微生物风险,经QDA定量描述感官评价分析知其风味鲜美,鲜咸适口。该酱油氨基酸种类全面,必需氨基酸和鲜味氨基酸含量高,氨基酸的支/芳值也较高,其符合FAO/WHO推荐的理想蛋白质模式。因此,南极磷虾海鲜酱油是一种营养价值高、风味优良且具有特殊功能活性的海鲜调味品。     

Recovery and Properties of Muscle Proteins Extracted from Tilapia (Oreochromis niloticus) Light Muscle by pH Shift Processing

ABSTRACT: Functional proteins can be extracted from fish muscle using acid- or alkali-aided solubilization and recovered with isoelectric precipitation. It was of interest to evaluate acid- and alkali-aided solubilization/precipitation on muscle material from the warm-water fish tilapia. Higher levels of proteins were extracted with high compared with low pH ( P < 0.05) because of higher protein solubility at high pH. Protein extraction was not influenced by the specific low or high pH tested or homogenization time. Similar protein types were extracted for the low and high pH solubilization, while proteolysis was observed at low pH. Viscosity was significantly higher at pH 2.3 to 2.9 compared with pH 10.8 to 11.4 ( P < 0.05) and varied greatly at low pH indicating a more unstable system. Two different low (pH 2.5 and 2.9) and high (pH 11 and 11.2) solubilization pH values were selected and protein recovery investigated in the pH range 5.1 to 5.7. The alkali-extracted proteins had more solubility at pH 5.1 to 5.7 ( P < 0.05) and thus less protein ( P < 0.05) was precipitated compared with the acid-aided process. More protein was recovered as pH increased from 5.1 to 5.7 ( P < 0.05). More protein types were found in the supernatant after precipitation for the alkali-aided treatment, and soluble proteins were similar to those of untreated tilapia muscle homogenate. Viscosities of the acid- and alkali-extracted proteins at pH 5.1 to 5.7 were significantly higher than the viscosity of native proteins at that pH ( P < 0.05). While this study demonstrated significant differences in protein extractability and precipitation of the 2 processes, no statistical difference ( P > 0.05) was found for overall protein recovery (61% to 68% for alkali-aided process and 56% to 61% for acid-aided process) of the 2 processes.     

南极磷虾贮藏过程中氟赋存形态转化与其品质变化的相关性分析

本文以TVB-N（挥发性盐基氮）和TBARS（硫代巴比妥酸反应物）作为品质指标,模拟食品的贮藏条件,分析南极磷虾中氟的赋存形态转化与其品质变化的相关性。实验结果表明,新鲜解冻后的南极磷虾分别暴露在常温（20℃）10 h、冷藏（4℃）28 h后,其TVB-N值分别由9.85 mg/100 g增加到31.96 mg/100 g和30.19 mg/100 g,超过海虾中规定的限量要求（30 mg/100 g）;冷冻（-20、-40、-80℃）6个月后,其TVB-N均未超过30 mg/100 g。TBARS值在常温（20℃）8 h、冷藏（4℃）20 h后,均超过1 mg MDA/kg,之后进一步氧化其值下降;冷冻（-20、-40、-80℃）6个月后,TBARS值均未出现下降的趋势。在冷冻（-20、-40、-80℃）6个月、冷藏（4℃）28 h和常温（20℃）12 h下南极磷虾中的总氟含量几乎不发生变化;游离态氟在不同贮藏条件下含量均增高,且存明显差异性（p<0.05）;相关性分析结果表明,游离氟含量变化与TVB-N和TBARS的变化呈明显的正相关,说明南极磷虾的品质变化对氟的形态转化有较大的影响。