Angiotensin-I-converting enzyme inhibitory activity and bitterness of enzymatically-produced hydrolysates of shrimp (Pandalopsis dispar) processing byproducts investigated by Taguchi design

The importance of water-to-substrate ratio, protease type, percent enzyme and incubation time on hydrolysates produced from shrimp processing byproducts was investigated using Taguchi’s L₁₆ (4⁵) experimental design. Protease type significantly (p < 0.05) influenced soluble yield, degree of hydrolysis (DH), angiotensin-I-converting enzyme (ACE) inhibitory activity and bitterness of hydrolysates, while percent enzyme only affected the DH. Hydrolysates produced by Alcalase and Protamex possessed strong ACE inhibitory activity (IC₅₀ = 100–200 μg/ml and 70 μg/ml, respectively), accompanied by high yield, high DH and strong bitterness. Furthermore, ACE inhibition was positively correlated (r² = 0.87) with bitterness of the hydrolysates. Fractionation by size-exclusion chromatography revealed that the bitter substances, which also showed strong ACE inhibition, were <3 kDa in size and contained many hydrophobic residues, including Tyr, Phe, Leu, Ile, Val and Lys. Despite the bitterness, these hydrolysates may have potential health benefits, arising from their potent ACE inhibitory activity.     

不同初始pH对枯草芽孢杆菌发酵虾副产物的影响

目的 探讨初始发酵pH对枯草芽孢杆菌发酵虾副产物的组胺含量和发酵液抗氧化活性调节作用。方法 中华管鞭虾加工副产物灭菌后接种枯草芽孢杆菌,在37℃下进行发酵,添加适量葡萄糖,调节初始发酵pH 7.0～10.0,测定发酵1～7 d时组胺含量、pH、肽浓度和氨基酸态氮(amino acid nitrogen, AA-N)含量动态变化和发酵液的抗氧化活性,分析各指标间相关性。结果 添加5%葡萄糖液可显著抑制组胺生成,初始发酵pH影响发酵液组胺和AA-N含量,其中初始发酵pH10.0发酵6d时组胺的含量低至(17.54±2.64)mg/100mL,而AA-N含量则提高到(0.81±0.02) g/100 mL。而且,初始发酵pH 10.0的发酵液具有很强的清除1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl, DPPH)自由基、总抗氧化能力及清除羟基自由基能力。Pearson相关分析得出发酵液的组胺含量与肽浓度呈极显著正相关(P<0.01),与AA-N含量、羟自由基清除能力和总抗氧化能力呈显著负相关(P<0.01或P<0.05)。结论 ...     

虾副产物制备的钙肽结合物理化性质研究

研究由虾加工副产物经过胰蛋白酶水解得到的多肽与氯化钙反应制备的钙肽结合物的理化性质。钙肽结合物中肽含量75.03 g/100g,钙含量11.56 g/100g,水分含量6.02 g/100g。温度对钙肽结合物的溶解度影响较小,在酸性或碱性条件下钙肽结合物溶解性很好,不溶于常见的有机溶剂。钙肽结合物的紫外、红外光谱均表明钙与肽之间形成了新的化学键。     

Bioactive peptides from collagen hydrolysates from squid (Dosidicus gigas) by-products fractionated by ultrafiltration

The bioactive properties of peptide fractions obtained from the hydrolysis of squid (Dosidicus gigas) by-products collagen, using Protease type XIV and ultrafiltration (UFI), were studied. The basic objective was to improve the bioactivity of squid hydrolysates via the application of UFI. Peptide fractions obtained after UFI had higher antioxidant and antimutagenic activities, but the antiproliferative activity did not improve after UFI. Peptides <5 kDa (Fraction F3) showed higher antioxidant and antimutagenic activities, as well as lower antioxidant and antiproliferative activities than both, peptides >10 kDa (F1) and those within the range of >5 to <10 kDa (F2). Band at lower field observed in FT-IR spectra and proton-peaks observed at higher ¹H-NMR fields, both associated to aromatic amino acids, as well as to other antioxidant amino acids such as hydroxyproline, glycine, arginine and lysine, may explain F3 bioactivity. Ultrafiltration can, therefore, be used to improve some bioactivities of squid collagen hydrolysates.     

Angiotensin I-converting enzyme (ACE) inhibitory activities of sardinelle (Sardinella aurita) by-products protein hydrolysates obtained by treatment with microbial and visceral fish serine proteases

The angiotensin I-converting enzyme (ACE) inhibitory activities of protein hydrolysates prepared from heads and viscera of sardinelle (Sardinella aurita) by treatment with various proteases were investigated. Protein hydrolysates were obtained by treatment with Alcalase^®, chymotrypsin, crude enzyme preparations from Bacillus licheniformis NH1 and Aspergillus clavatus ES1, and crude enzyme extract from sardine (Sardina pilchardus) viscera. All hydrolysates exhibited inhibitory activity towards ACE. The alkaline protease extract from the viscera of sardine produced hydrolysate with the highest ACE inhibitory activity (63.2 ± 1.5% at 2 mg/ml). Further, the degrees of hydrolysis and the inhibitory activities of ACE increased with increasing proteolysis time. The protein hydrolysate generated with alkaline proteases from the viscera of sardine was then fractionated by size exclusion chromatography on a Sephadex G-25 into eight major fractions (P₁–P₈). Biological functions of all fractions were assayed, and P₄ was found to display a high ACE inhibitory activity. The IC₅₀ values for ACE inhibitory activities of sardinelle by-products protein hydrolysates and fraction P₄ were 1.2 ± 0.09 and 0.81 ± 0.013 mg/ml, respectively. Further, P₄ showed resistance to in vitro digestion by gastrointestinal proteases. The amino acid analysis by GC/MS showed that P₄ was rich in phenylalanine, arginine, glycine, leucine, methionine, histidine and tyrosine. The added-value of sardinelle by-products may be improved by enzymatic treatment with visceral serine proteases from sardine.     

Valorisation of protein hydrolysates from animal by-products: perspectives on bitter taste and debittering methods: a review

Conversion of animal by-products to high value-added food ingredients is one of the top trends in the slaughter industry. Enzymatic hydrolysis of animal by-products can generate protein hydrolysates, which provides an opportunity for effective utilisation. However, bitterness of protein hydrolysate is a major undesirable aspect for various applications. In this review, the current knowledge on protein hydrolysates from animal by-products is briefly reviewed. The structural features of bitter peptides and bitter taste receptors are summarised. Moreover, the potential approaches for debittering protein hydrolysates are highlighted, including exopeptidase treatment, Maillard reaction, plastein reaction and encapsulation. In addition, the current debittering strategies and challenges are also discussed. This article presents some opportunities to utilise protein hydrolysates from animal by-products and their debittering methods.     

Characterisation and partial purification of proteolytic enzymes from sardine by-products to obtain concentrated hydrolysates

A procedure to recover proteases and lipases from the by-products of Monterey sardine (Sardinops sagax caerulea) has been developed, comprising 2 steps: a centrifugation at low temperature to eliminate more than 90% of the initial fat content, and an acetone precipitation step. After this treatment, enzymatic activity increased by 33.8% for lipase, 15.5% for trypsin, 14.8% for chymotrypsin, 93.4% for aminopeptidase, and 19.7% for pepsin. The extents of hydrolysis of fish by-product proteins by endogenous enzyme by-product extract, viscera concentrate extract, and commercial Alcalase® were 62%, 85%, and 28%, respectively. The two extract preparations from sardine by-product (viscera and by-product concentrate extracts) produced 3-fold greater hydrolysis than with the commercial enzyme. The recovery of enzyme concentrates from sardine waste has both ecological and economical advantages for the fish industry.     

虾加工副产品中虾油提取工艺研究

通过比较碱性蛋白酶、中性蛋白酶、风味蛋白酶、复合蛋白酶和胰蛋白酶对虾加工副产品的酶解,确定风味蛋白酶作为最佳水解酶,并确定其起始pH值为6．5,考察了酶添加量、料液比、酶解时间和温度对虾油提取率的影响,确定最优工艺：酶添加量1．0g／100g,料液比1g：8mL,酶解时间2．5h,酶解温度50℃。     

活性炭静态吸附草鱼蛋白水解物中氨基酸特性的研究

研究了6种活性炭对草鱼蛋白水解物中氨基酸的吸附情况。发现AK-220型活性炭的静态吸附量最大,且吸附可使酶解液颜色和风味有良好改善;AK-220对芳香氨基酸（AAA）的吸附能力明显优于其对支链氨基酸（BCAA）的吸附程度,同时还可吸附一定数量的肽分子。     

Microbiological and fermentation characteristics of togwa,a Tanzanian fermented food

Selected microbiological and metabolic characteristics of sorghum, maize, millet and maize-sorghum togwa were investigated during natural fermentation for 24 h. The process was predominated by lactic acid bacteria (LAB) and yeasts. The mesophiles, lactic acid bacteria, and yeasts increased and the Enterobacteriaceae decreased to undetectable levels within 24 h. The isolated microorganisms were tentatively identified as Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus cellobiosus, Pediococcus pentosaceus, Weissella confusa, Issatchenkia orientalis, Saccharomyces cerevisiae, Candida pelliculosa and Candida tropicalis. The pH decreased from 5.24-5.52 to 3.10-3.34. Maltose increased initially and then decreased, fructose decreased and glucose levels increased during the first 12 h of fermentation. The organic acids detected during fermentation included DL-lactic, succinic, formic, pyruvic, citric, pyroglutamic and uric acid. Lactate was the predominant acid and increased significantly with time. The volatile organic compounds (VOC) detected included acetaldehyde, 2-methyl-propanal, 2-methyl-butanal, 3-methyl-butanal, ethanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, diacetyl and acetoin. Ethanol was the predominant VOC and it increased significantly with time.     

虾蛋白粉的制备及其分析

以虾加工下脚料为原料,利用酶法提取蛋白质,研究喷雾干燥的工艺,并对所得到的产品进行了理化分析。结果表明：采用离心喷雾干燥的条件为进风温度180℃,出风温度80℃,生产粗蛋白粉、可溶性蛋白粉的物料进料浓度分别为30％、50％;粗蛋白粉和可溶性蛋白粉中蛋白质、脂肪、灰分、水分含量分别为60．7％,15．0％,12．0％,4．9％及82．3％,0．5％,2．4％,6．3％;虾蛋白粉中必需氨基酸含量较高,占氨基酸总量的41．29％,牛磺酸含量0．280％。     

Seasonal amino acid profiles and mineral contents of green tiger shrimp (Penaeus semisulcatus De Haan, 1844) and speckled shrimp (Metapenaeus monoceros Fabricus, 1789) from the Eastern Mediterranean

The amino acid and mineral contents of green tiger shrimp (Penaeus semisulcatus) and speckled shrimp (Metapenaeus monoceros) from the North Eastern Mediterranean were determined for each season of the year. For both species, the highest protein values were recorded during the summer (p < 0.05). The most abundant amino acids were, in decreasing order, glutamic acid, aspartic acid, arginine, lysine, leucine, glycine and alanine. The ratio of essential to nonessential amino acids (mean value) for green tiger shrimp and speckled shrimp were 0.60 and 0.59, respectively. Mineral contents of the two species varied with season (p < 0.05), except for the Ca content in green tiger shrimp.     

Rhizopus oryzae LS1利用丢糟水解液发酵生产乳酸

研究了一株诱变米根霉Rhizopus oryzae LS-1利用丢糟水解液发酵生产乳酸的可行性。首先考察R.oryzae LS-1利用葡萄糖和木糖的糖代谢差异特性,并通过正交实验优化丢糟水解液发酵生产乳酸的工艺参数。结果表明,R.oryzae LS-1能代谢利用葡萄糖和木糖,且二者存在协同互补作用,有利于乳酸生成和糖酸转化,可用于木质纤维原料的乳酸生产。丢糟水解液发酵生产乳酸的实验表明,氯化铵是R.oryzae LS-1适宜的氮源。在接种量为3.0%、p H为6.5、发酵时间为96h、Ca CO3添加量为80g/L的条件下,乳酸生成浓度为13.27g/L,糖利用率为79.61%。说明诱变菌株R.oryzae LS-1具备发酵丢糟水解液制备乳酸的潜力。      

Amino acid,structure and antioxidant properties of Haematococcus pluvialis protein hydrolysates produced by different proteases

The impact of different protease hydrolysis on the amino acid, structure and antioxidant properties of H. pluvialis protein (HP) was investigated. Results showed that the hydrolysate obtained by Alcalase exhibited the highest degree of hydrolysis (20.59%) and peptide yield (92.64%). The essential amino acid, hydrophobic, sulphur and aromatic amino acid contents of enzyme hydrolysates were significantly higher than HP (P < 0.05). FTIR spectra showed that the β-sheet proportion of HP hydrolysates were higher compared with HP, the proportion of random coil structure was lower. The α-helix content of the hydrolysate obtained by Alcalase was the highest, while the turn proportion was the lowest. The Trypsin derived hydrolysate presented the best DPPH and ABTS scavenging ability, and ferric reducing antioxidant power than other HPHs. These results suggested that HP hydrolysates have a great potential as natural functional ingredients in food manufacture.     

Physicochemical and rheological properties of interacted protein hydrolysates derived from tuna processing by-products with sodium alginate

The physicochemical properties of tuna protein hydrolysates were enhanced by interaction with sodium alginate. The increase in emulsifying capacity and stability was from 50 to 150 m² g⁻¹ and from 36 to 49 min, respectively. The increase in foaming capacity and stability was from 100% to 140% and from 65% to 70%, respectively. The reason for the increased physicochemical properties was the reduced zeta potential level of tuna protein hydrolysates after interaction with sodium alginate. The change in internal structure of tuna protein hydrolysates after interaction with sodium alginate was determined by SEM and FTIR. The SEM results showed that a net cross-linking structure was formed from a sheet structure after the tuna protein hydrolysates interacted with sodium alginate. FTIR demonstrated that parts of the β-sheet of tuna protein hydrolysates were changed into an irregular coiled structure or α-helix after interaction with sodium alginate. In order to understand the interacted complex better, the rheological properties of interacted tuna protein hydrolysates with sodium alginate were further determined. In this study, the one-step was developed, easy-to-operate and cost-effective process that can further add value to tuna protein hydrolysates derived from tuna processing by-products.     

Antioxidant activity of protein hydrolysates derived from threadfin bream surimi byproducts

Antioxidant activities of protein hydrolysates from threadfin bream surimi wastes, including frame, bone and skin (FBS) and refiner discharge (RD), were investigated. FBS and RD were rich in Lys, Glu, Gly, Pro, Asp, Leu, His, Tyr and Phe. FBS was hydrolysed to a greater extent than RD regardless of proteinases tested (Virgibacillus sp. SK33 proteinase, Alcalase, pepsin and trypsin). Pepsin-hydrolysed FBS, at a 5% degree of hydrolysis (DH), showed the highest antioxidant activity based on 2,2′-azinobis (3-ethyl-benzothiazoline-6-sulphonate) (ABTS) radical (0.455 ± 0.054 mg Trolox equivalents/mg leucine equivalents), ferric reducing antioxidant power (FRAP) (0.221 ± 0.005 mM Trolox equivalents) and inhibition of β-carotene bleaching assays. FBS hydrolysates showed higher antioxidant activity based on chemical assays than their RD counterparts. However, FBS and RD hydrolysates protected HepG2 cells against tert-butyl hydroperoxide-induced oxidative damage to a similar extent. Therefore, FBS and RD hydrolysates have a potential as antioxidative neutraceutical ingredients.     

Sweet potato protein hydrolysates: antioxidant activity and protective effects on oxidative DNA damage

In this study, sweet potato protein (SPP) hydrolysates were prepared by six enzymes (alcalase, proleather FG‐F, AS1.398, neutrase, papain and pepsin). The antioxidant activities and protective effect against oxidative DNA damage of SPP hydrolysates were investigated. Alcalase hydrolysates exhibited the highest hydroxyl radical‐scavenging activity (IC₅₀ 1.74 mg mL^?1) and Fe²⁺‐chelating ability (IC₅₀ 1.54 mg mL^?1) (P < 0.05). Compared with other five hydrolysates, the hydrolysates obtained by alcalase had the most abundant <3‐kDa fractions. In addition, below 3‐kDa fractions of alcalase hydrolysates showed the highest antioxidant activities and protective effects against DNA damage through both scavenging hydroxyl radicals and chelating Fe²⁺, which was probably because of the increase in several antioxidant amino acids, such as His, Met, Cys, Tyr and Phe, as well as the hydrophobic amino acids. The results suggested that enzymatic hydrolysis could be used as an effective technique to produce high value‐added peptides products from SPP.     

牡蛎肉酶解液的抗氧化工艺研究

采用胰蛋白酶酶解牡蛎肉蛋白,以酶解液清除DPPH自由基的效果为分析指标,采用单因素和正交试验,分析酶解的固液比、加酶量、时间、温度对酶解效果的影响,研究酶解的最佳工艺参数。结果显示,牡蛎肉酶解的最优水平组合为固液比1:3、加酶量0.25%、酶解时间2h、酶解温度45℃,牡蛎肉酶解液抗氧化性最强。     

Chemical composition and antioxidative activity of Thai traditional fermented shrimp and krill products

Chemical composition and antioxidative activities of some Thai traditional fermented shrimp and krill products including Jaloo, Koong-Som and Kapi were studied. All products did not contain myosin heavy chain or actin, but contained a large amount of small peptides. Kapi had the highest protein content, whereas carbohydrate content varied with products. Water-soluble fraction from all products possessed DPPH and ABTS radical-scavenging activity, as well as ferric reducing antioxidant power (FRAP) in a concentration-dependent manner. At the same concentration tested, the water-soluble fraction from Kapi exhibited the highest antioxidative activity. Soluble fraction of all products showed high stability over a wide pH range (2–11) and was stable after heating at 40–100 °C for 15–60 min. Fractions from all products heated at 100 °C had increases in FRAP, suggesting the enhancement of antioxidant activity. Therefore, fermented shrimp and krill products could be used as a potential source of nutrients and natural antioxidants.