冰温贮藏对鲢、草、鲤鱼糜制品品质的影响

为了明确冰温对淡水鱼糜制品品质的影响,以鲢鱼、草鱼、鲤鱼鱼糜制品为研究对象,通过测定三者在冰温贮藏后鱼糜饼的蒸煮损失率、L*值、持水性、质构特性、硫代巴比妥酸反应物（thiobarbituric acid reactivesubstances,TBARS）值等指标,分析冰温贮藏过程中其品质的变化。结果表明：随冰温贮藏时间的延长,鲢鱼鱼糜制品的蒸煮损失率先降低后升高,草鱼和鲤鱼鱼糜制品呈降低趋势;3 种鱼糜制品的持水性均随冰温贮藏时间的延长而降低;鲢鱼鱼糜制品的L*值和剪切力均随冰温贮藏时间的延长而降低,草鱼和鲤鱼鱼糜制品的L*值、剪切力值随冰温贮藏时间的延长呈波动的变化;3 种鱼的硬度、弹性、黏聚性、咀嚼度随贮藏时间的延长而呈降低。3 种鱼糜制品的剪切力值差异显著（P＜0.05）,鲢鱼鱼糜制品的硬度、弹性、黏聚性以及咀嚼度显著低于草鱼和鲤鱼鱼糜制品（P＜0.05）。3 种鱼鱼糜制品的TBARS值均随冰温贮藏时间的延长而升高。鲢鱼、草鱼和鲤鱼鱼糜制品在冰温（－1.5±0.03）℃条件下最佳的贮藏期为3 周。     

Inhibition of frozen storage‐induced oxidation and structural changes in myofibril of common carp (Cyprinus carpio) surimi by cryoprotectant and hydrolysed whey protein addition

The objective of the present study was to evaluate the efficacy of combined cryoprotectants (sucrose + sorbitol) and whey protein isolate (WPI) hydrolysates to inhibit protein oxidation and quality loss in common carp (Cyprinus carpio) surimi during frozen storage at ?25 °C. With increasing storage time, the carbonyl content of myofibrillar proteins increased from 4.02 nmolmg^‐1 protein (0 day) to 7.25, 6.31, 5.26 and 4.83 nmol mg^?1 protein (180 days; P < 0.05) for the control and samples with cryoprotectants, with cryoprotectants + WPI hydrolysates and with cryoprotectants + propyl gallate, respectively; protein surface hydrophobicity and turbidity increased in a similar trend, while sulfhydryl content, Ca‐ATPase activity, protein solubility and protein thermal stability decreased (P < 0.05). These results suggest that treatments with combined cryoprotectants and antioxidative WPI hydrolysates offer an effective approach to reducing the extent of protein oxidation in common carp surimi, thereby limiting protein structural changes known to impair texture of surimi products.     

Optimal blending of differently refined fish proteins based on their functional properties

Two different mixtures (Alaska pollock surimi with grass carp fish protein isolate (FPI) and grass carp surimi with grass carp FPI) were investigated for their compatibility and functionalities. As the proportion of FPI increased, it was observed surface hydrophobicity and surface reactive sulfhydryl (SRSH) content increased significantly, indicating the degree of fish protein unfolding prior to gelation was much higher than surimi alone. Comparable results were shown as measured by storage modulus (G′) in oscillatory dynamic rheology, demonstrating the gelling temperature was reduced when the proportion of FPI increased. Effects of mixing surimi and FPI on gel functionality (hardness, cohesiveness, and whiteness) exhibited a linear pattern when the proportion of surimi was larger than or equal to that of FPI. However, there were no linear relationships when the proportion of FPI exceeded that of surimi.

Practical applications

Commercial surimi has been successfully used in the Western world over 30 years. Unlike surimi which is a refined fish myofibrillar protein composite, fish protein isolate (FPI) is a refined composite of myofibrillar protein and sarcoplasmic protein. The former is made by avoiding any chemical/physical denaturation, while the latter can be made by inducing chemical denaturation and renaturation with pH shift. Even though FPI is not currently available in a commercial scale, it has a great potential to replace all or a part of surimi for the manufacture of fish protein gel products. This study reveals how to optimally mixed these two differently refined fish proteins based on their functional properties. The results suggested that blending surimi and FPI may be feasible only when the proportion of FPI does not exceed 50%.     

Compositions and antioxidant properties of protein hydrolysates from the skins of four carp species

Compositions and antioxidant properties of protein hydrolysates prepared from four carp skins: black carp, grass carp, silver carp and bighead carp, using pepsin, with a degree of hydrolysis (DH) of 6–15%, were investigated. The yield of freeze‐dried hydrolysates was in the range of 54–62 g/100 g (dry skin). The content of protein and ash in four freeze‐dried hydrolysates was 72–81% and 8–17%, respectively. All hydrolysates contained high amount of hydrophobic amino acid residues (389–480 residues/1000 residues). Meanwhile, their antioxidant properties were evaluated by in vitro assays. The results revealed that all hydrolysates possessed potent antioxidant activities and showed dose dependency as the activity increased with sample concentration, capable of scavenging 72–88% of DPPH and 61–69% of hydroxyl radicals, respectively, at the highest tested concentration. The hydrolysates exhibited high reducing power and β‐carotene–linoleic acid oxidation inhibition. Among the four hydrolysates, the hydrolysate derived from bighead carp skin was superior to others in terms of yield, DH and antioxidant activities.     

Grass carp peptides hydrolysed by the combination of Alcalase and Neutrase: Angiotensin‐I converting enzyme (ACE) inhibitory activity,antioxidant activities and physicochemical profiles

In this study, grass carp peptides were prepared by enzymatic hydrolysis of grass carp protein using the combination of Alcalase and Neutrase, and angiotensin‐I converting enzyme (ACE) inhibitory activity in vitro, antihypertensive activity in vivo, antioxidant activities, and physicochemical properties of peptides achieved from grass carp protein were characterised after ultrafiltration and desalted processes using mixed ion exchange resins. The purified peptides exhibited strong ACE inhibitory activity (IC₅₀ = 105 μg mL^?1), antihypertensive activity with the maximal drop for systolic blood pressure (SBP) of 43 mmHg at a dosage of 100 mg per kg body weight in spontaneously hypertensive rat (SHR), and antioxidant activities indicated by thiobarbituric acid‐reactive substance values in a liposome‐oxidising system, radical‐scavenging activity and chelation of metal ions (Fe²⁺). The molecular weight of peptides was <1000 Da. Compared to grass carp protein, the peptides separated from enzymatic hydrolysates possessed similar amino acid compositions, but contained higher concentrations of essential amino acids. Moreover, the peptides exhibited excellent solubility at a wide range of pH values from 2 to 10, and lower apparent viscosity than the protein. The peptides separated from enzymatic hydrolysates might be used as a promising ingredient in antihypertensive functional foods and nutraceuticals.     

Physicochemical stability of antilisterial proteins from P. polymyxa Kp10 as potential food biopreservative

Listeria monocytogenes has continuously become a significant threat to consumers worldwide. The use of chemical-derived preservatives that are commonly associated with safety and nutritional issues has prompted the use of natural-based preservatives as a better alternative. Many bacterial strains including Paenibacillus polymyxa Kp10 have been reported to produce various antimicrobial proteins and compounds that are considered more natural. However, their stability in various physicochemical conditions should be examined before being applied in various types of food. In this study, the stability of four previously identified antilisterial proteins in P. polymyxa Kp10 upon exposure to several physicochemical conditions was examined. More than 80% residual antilisterial activity is conserved upon heat and proteinase K treatment. But, sensitivity to 24 h trypsin digestion has been observed. P1 and P2 proteins (histone-like DNA binding proteins HU) were sensitive to alkaline pH (pH 10-12) as compared with other proteins. More than 70% and 97% residual antilisterial activity were recovered after incubation in raw beef homogenates and simulated meat gravy model, respectively. However, the antilisterial activity of most proteins was highly compromised in chicken and salmon meat homogenates, and UHT cow milk. Inoculation of these proteins into Listeria-contaminated simulated meat gravy showed that all proteins exerted a bactericidal action against L. monocytogenes. P1 and P2 shared almost similar antilisterial activity rates, while P4 was the most potent antilisterial protein. The findings in this study could provide important preliminary data for future applications of these proteins as preservative in food products especially beef-based meat products.     

Gel‐forming ability of surimi from grass carp (Ctenopharyngodon idellus): influence of heat treatment and soy protein isolate

The effects of setting conditions and soy protein isolate (SPI) on textural properties of surimi produced from grass carp were investigated. Effects of setting temperature, setting time and protein concentration on the breaking force and distance were evaluated and compared utilizing response surface methodology. Models for breaking force and breaking distance of grass carp surimi were established. Protein concentration was the major factor affecting the gel strength of grass carp surimi. Breaking force and distance of grass carp surimi gels decreased with increase of protein ratio from SPI at 30 °C and 40 °C for 60 min setting and heating at 85 °C for 30 min, but the breaking force obtained for addition of 100 g kg^?1 SPI protein to grass carp surimi was higher than that for surimi alone at 60 °C for 60 min incubation and heating at 85 °C for 30 min. Copyright © 2005 Society of Chemical Industry     

Influence of the extent of enzymatic hydrolysis on the functional properties of protein hydrolysate from grass carp (Ctenopharyngodon idella) skin

Protein hydrolysates from grass carp skin were obtained by enzymatic hydrolysis using Alcalase^®. Hydrolysis was performed using the pH-stat method. The hydrolysis reaction was terminated by heating the mixture to 95 °C for 15 min. At 5.02%, 10.4%, and 14.9% degree of hydrolysis (DH), the hydrolysates were analyzed for functional properties. The protein hydrolysates had desirable essential amino acid profiles. Results demonstrated that the hydrolysates had better oil holding and emulsifying capacity at low DH. The water holding capacity increased with increased levels of hydrolysis. Enzymatic modification was responsible for the changes in protein functionality. These results suggest that grass carp fish skin hydrolysates could find potential use as functional food ingredients as emulsifiers and binder agents.     

牦牛血红蛋白活性肽酶法制备工艺的优化及脱色技术研究

为开发具有保健功能的新型高附加值生物制品,本实验采用胰蛋白酶、木瓜蛋白酶及AS1.398中性蛋白酶3种食品级内切蛋白酶对牦牛血红蛋白进行酶解,以水解度及三氯乙酸可溶性氮为评价指标,采用酶解-活性炭法对水解液进行脱色,筛选出AS1.398中性蛋白酶为最佳水解用酶。通过正交实验对其酶解工艺进行优化后,得出AS1.398中性蛋白酶最佳水解条件为:底物浓度5%,加酶量8000U/g,温度55℃,初始pH7.5,酶解时间5h。在此条件下水解产物为淡黄色,并具有较高的低分子量生物活性肽含量。     

乳清分离蛋白水解物对冷藏鱼糜的保鲜作用

通过测定不同贮藏时间内(0 d、1 d、3 d、5 d、7 d、9 d)草鱼鱼糜的羰基含量、硫代巴比妥酸反应物(thiobarbituric acid-reactive substances,TBARS)、细菌总数、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值、三甲胺(trimethylamine,TMA)值、K值等指标的变化,并分析各指标之间的相关性,研究冷藏(4℃)条件下乳清分离蛋白(WPI)水解物对草鱼鱼糜的抗氧化及保鲜效果。实验分为5组,第1组为对照组,第2~4组中分别加入2%、4%和6%的水解物,第5组中加入0.02%的BHA。结果表明:随着WPI水解物添加量的增加,鱼糜的蛋白和脂肪氧化抑制显著(p0.05),保鲜效果明显改善,其中6%WPI水解物处理组效果最明显,在贮藏9 d内,与对照组相比,羰基含量、TBARS值、TVB-N值和K值分别降低了1.54 nmo L/mg蛋白、0.21 mg/kg、5.84×10~(-2) mg/g和11.7%,此时鱼糜仍处于二级鲜度。各指标间存在显著正相关(p0.05)。因此,WPI水解物可以起到很好的抗氧化和保鲜作用,未来可以考虑把乳清蛋白水解物作为天然保鲜剂用于鱼糜制品生产中。     

Effect of enzyme type and hydrolysis conditions on the in vitro angiotensin I‐converting enzyme inhibitory activity and ash content of hydrolysed whey protein isolate

Removal of salts from protein hydrolysate mixture on large scale is very difficult and relatively inefficient. Selecting practical proteinase system and hydrolysis conditions for the production of whey protein isolate (WPI) enzymatic hydrolysates with high angiotensin I‐converting enzyme (ACE) inhibitory activity and low ash content is very useful. The effect of alcalase, neutrase, trypsin and their combined system, i.e. alcalase‐neutrase and trypsin‐neutrase, under two different hydrolysis conditions, i.e. pH‐controlled and pH‐spontaneous drop, on the formation of ACE‐inhibitory peptides and the characteristics of WPI hydrolysate was investigated. Results showed that the ACE‐inhibitory activity of WPI hydrolysate obtained with alcalase was significantly higher than that of its trypsin or neutrase hydrolysate obtained at the same hydrolysis time by both pH‐controlled and pH‐spontaneous drop method (P < 0.05). The WPI hydrolysate obtained after 3 h incubation with alcalase plus 2 h with neutrase under pH‐spontaneous drop condition possessed the highest ACE‐inhibitory activity of 54.30% and the lowest ash content of 2.95%. This is practical as a functional ingredient in the food industry because of its high ACE‐inhibitory capability, commercial availability in large supply of alcalase and neutrase and no needing for additional desalting process.     

Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella)

The cryoprotective effect of konjac glucomannan (KGM) on myofibrillar protein from grass carp (Ctenopharyngodon idella) during frozen storage at −18 °C and the influence of five levels of KGM (0%, 0.5%, 1%, 1.5%, and 2%) on texture properties, water-holding capacity, and whiteness of grass carp surimi gels were investigated. KGM as a novel cryoprotectant could significantly mitigate the decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, and total sulphydryl and active sulphydryl contents of myofibrillar protein during frozen storage. KGM at the level of 1% showed the same good cryoprotective effect as a conventional cryoprotectant (10% sucrose–sorbitol, 1:1, w/w). As the levels of KGM increased, breaking force and deformation of grass carp surimi gels increased significantly. Water-holding properties of the surimi gels are improved with the increasing addition of KGM, but the whiteness decreased and the colour became darker. The optimum addition level of KGM was suggested to be 1%.     

Effects of Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Scales on Rancidity Stability and Gel Properties of Fish Products

This study aimed to evaluate the effectiveness of hydrolysates, which were obtained from the scales of silver carp (Hypophthalmichthys molitrix) by papain, flavourzyme, and Alcalase 2.4 L, as natural antioxidants in silver carp mince and surimi gels during storage at 4 °C. The hydrolysates that possess greater in vitro antioxidant activities (DPPH radical-scavenging activity, Fe²⁺-chelating activity, and reducing power), including hydrolysates catalyzed by papain at 10 min (HP), flavourzyme at 5 min (HF), and Alcalase 2.4 L at 5 min (HA), were chosen as additives. Color, cooking loss, conjugated dienes (CDs), thiobarbituric acid reactive substances (TBARS), fatty acids, and sensory scores of mince were measured on days 0, 2, 4, 6, and 8 during 4 °C storage; additionally, whiteness, breaking force, deformation, gel strength, and sensory score of surimi gels were measured on days 1, 3, 5, 7, 9, and 11 during 4 °C storage. The results indicate that HA was conducive to lowering the cooking loss of mince and that HF significantly (P?<?0.05) reduced the CDs value of mince. For surimi gels, HF improved whiteness, deformation, and gel strength. Hence, HF could serve as a natural antioxidant during early oxidation and improve gel formation of silver carp products.     

Proteolysis characteristics of sarcoplasmic, myofibrillar, and stromal proteins separated from grass carp and antioxidant properties of their hydrolysates

Proteolysis of grass carp sarcoplasmic, myofibrillar, and stromal proteins by 5 commercial proteases were studied. Sarcoplasmic and myofibrillar protein could be well hydrolyzed by Alcalase 2.4 L to reach high protein recoveries (PR) (71.86±2.46 and 80.77±3.05%, respectively), while the maximum PR for stromal protein was only 42.83±2.84%. However, stromal hydrolysates, containing mostly 6–10 kDa fraction, exhibited higher ·OH scavenging activities due to its high content of antioxidant-assisting amino acids. Alcalase 2.4 L and pancreatin 6.0, which produced hydrolysates with relative high degree of hydrolysis (DH), were used for further hydrolysis of whole grass carp protein with the assistance of response surface methodology (RSM). The results showed that serine proteases (Alcalase 2.4 L and pancreatin 6.0) could produce sarcoplasmic, myofibrillar, or stromal hydrolysates with relatively high PR, DH, and strong ·OH scavenging activity, which may be used to prepare antioxidant hydrolysates from grass carp.     

微波调理食品——牛乳鱼糜面条的研制

以鲢鱼、奶粉、土豆淀粉为主要原料,制作牛乳鱼面,研究牛乳鱼面的去腥工艺及配方。并对鲢鱼肉去腥进行研究。通过正交试验、感官评价,得出去腥效果的最佳组合为茶多酚浓度0.5%、浸泡时间20 min、浸泡温度20℃。牛乳鱼面的最佳配方为每百克鲢鱼肉添加鱼汤120 mL、土豆淀粉50 g、食盐3 g、奶粉10 g、海藻酸钠0.4 g。研制出营养丰富、色泽乳白、口味鲜香,富有弹性的新型鱼肉面条。面条经过调味、冷冻后,直接用微波加热即可食用。     

不同蛋白酶水解高温花生粕和低温花生粕及其水解产物抗氧化活性的对比研究

由于高温花生粕中的花生蛋白在高温压榨过程中高度变性,因此在食品工业中蛋白利用率较低。本研究通过对比高温花生粕和低温花生粕经过不同商业蛋白酶(Alcalase 2.4 L,Neutrase,Papain,Protamex及Flavorzyme 500 MG)水解后水解产物特性的蛋白回收率、水解度、分子量分布及抗氧化活性,确定高温花生粕是否适合采用生物酶解的方式利用其中的蛋白质并筛选合适的蛋白酶。结果表明,高温花生粕经不同蛋白酶水解后,其蛋白质利用率均在60.61~67.86%,与低温花生粕相当;水解度及分子量分布方面,高温花生粕Flavorzyme水解产物的DH最高,高达44.92%,且含有较多的3 ku小分子肽及游离氨基酸;此外,高温花生粕不同酶水解产物的DPPH自由基清除活性均高于低温花生粕,这可能是由于高温花生粕水解产物中含有较多具有供电子的小分子肽、游离氨基酸以及高温压榨过程中生成的美拉德反应产物。     

Evaluation of free radical‐scavenging activities of sweet potato protein and its hydrolysates as affected by single and combination of enzyme systems

To evaluate the free radical‐scavenging activities of sweet potato protein (SPP) and its hydrolysates, single enzymes alone (alcalase, neutrase, protamex) or in combination with flavourzyme were employed. Compared with SPP, free radical‐scavenging activities of the resulting hydrolysates were all significantly increased (P < 0.05). Alcalase (ALC) hydrolysates exhibited the highest superoxide, hydroxyl and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activities (P < 0.05), which was 18.71 ± 0.22, 27.13 ± 0.24 and 90.10 ± 0.15% respectively. Compared with SPP hydrolysates by single enzymes, the hydrolysates obtained by combination of enzyme systems exhibited higher degree of hydrolysis, but lower free radicals scavenging activities. In addition, the content of several antioxidant amino acid residues, such as His, Met, Tyr and Phe, in ALC hydrolysates was much higher compared with SPP and other hydrolysates using amino acids composition assay. The results suggested that peptides with free radical‐scavenging activity could be released from entire SPP chain via moderate enzymatic hydrolysis.     

Antilisterial Activity of Hops Beta Acids in Broth with or Without Other Antimicrobials

ABSTRACT: Hops beta acids (HBA) are parts of hops flowers used to preserve wort and provide flavor in beer, and are reported as having antimicrobial properties. This study evaluated the antilisterial activity of HBA alone or in combination with other known antimicrobials in a culture broth medium. Listeria monocytogenes (10‐strain mixture) was inoculated (2.6 to 2.8 log CFU/mL) into tryptic soy broth supplemented with 0.6% yeast extract (TSBYE) without (control) or with HBA (0.5 to 5.0 μg/mL), potassium lactate (1.0%), sodium diacetate (0.25%), or acetic acid (0.1%), alone or in combination with HBA (0.5 to 3.0 μg/mL). Survival/growth of the pathogen during storage at 4 °C (35 d), 10 °C (20 d), or 25 °C (2 d) was periodically monitored by spiral plating onto tryptic soy agar plus 0.6% yeast extract. As expected, TSBYE without antimicrobials (control) supported rapid pathogen growth with growth rates of 0.40, 2.88, and 9.58 log CFU/mL/d at 4, 10, and 25 °C, respectively; corresponding Y_end values exceeded 9.0 log CFU/mL at 35, 20, and 2 d storage. HBA used alone (1.0 to 5.0 μg/mL) inhibited growth of L. monocytogenes at all 3 temperatures, with inhibition being more pronounced at higher concentrations and at the lower storage temperature (4 °C). The antilisterial activity of HBA (0.5 to 3.0 μg/mL) was enhanced when combined with sodium diacetate, acetic acid, or potassium lactate, achieving complete inhibition at 4 °C when 3.0 μg/mL HBA were used in combination with each of the above antimicrobials. Overall, HBA exhibited promising antilisterial activity in a broth medium and further studies are needed to investigate its potential antilisterial effects in food products.     

Characterization of cottage cheese using Weissella cibaria D30: Physicochemical,antioxidant, and antilisterial properties

This study aimed to evaluate the potential of Weissella cibaria D30 as an adjunct culture in cottage cheese, including an assessment of antioxidant, antilisterial, and compositional parameters. Cottage cheese samples were manufactured using a commercial starter culture and probiotic strains Lactobacillus rhamnosus GG (GG) or W. cibaria D30 (W) and without probiotic (control). Samples were stored at 4 ± 1°C for 28 d. Bacterial cell counts (log cfu/g) of control, GG, and W samples were counted at 0, 7, 14, 21, and 28 d. Counts of W. cibaria D30 in the W samples remained at 6.85 log cfu/g after 28 d. Total solids, fat, protein, ash, and pH were measured and no significant differences were observed in compositional parameters or pH after 28 d of storage in all cheeses except those inoculated to Listeria monocytogenes. To measure the antilisterial effect, Listeria monocytogenes was inoculated into the cottage cheese samples and bacterial cell counts were obtained at 0, 6, 12, 24, 48, 72, 96, 120, and 144 h. Listeria monocytogenes counts were less than the analytical limit of detection (<10 cfu/g) in the inoculated GG and W samples, whereas the counts of L. monocytogenes in the inoculated control sample remained at 3.0 log cfu/g after 144 h. We used the DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical scavenging activity assays to assess antioxidant activity: GG and W samples exhibited significant increases in antioxidant activity compared with the control sample. These results indicate that W. cibaria D30 has potential as an adjunct culture in the dairy industry.     

Effect of enzymatic hydrolysis of proteins on growth of Bifidobacterium bifidus in milk

The effect of enzymatic hydrolysis of proteins in milk using neutrase on the growth of the probiotic strain Bifidobacterium bifidus was evaluated by estimation of microbial growth, acidity, viscosity and flavour production. A significant increase in the growth of B bifidus was observed in neutrase‐hydrolysed milk. The setting time of bifidus‐cultured milk was advanced by about 12 h at 5% degree of hydrolysis. Enzymatic hydrolysis of proteins prior to cultivation also significantly increased the viscosity of the product. An approximately 60% increase in viscosity of the product was observed in neutrase‐hydrolysed milk. Production of steam‐volatile monocarbonyls as an indication of development of flavour was also higher in neutrase‐hydrolysed milk. The concentration of steam‐volatile monocarbonyls was 2.47 µmol per 100 ml in neutrase‐hydrolysed milk but only 1.84 µmol per 100 ml in control milk at the setting point of the curd. © 2002 Society of Chemical Industry