超临界CO2萃取南美白对虾虾青素的工艺优化

为提高虾青素萃取物得率和虾青素纯度,采用超临界CO2萃取南美白对虾虾头废弃物中的虾青素,皂化后用高效液相色谱对虾青素含量进行测定。单因素试验确定萃取参数对虾青素萃取物得率和虾青素纯度的影响,然后进一步运用响应面法对萃取工艺参数进行优化。结果表明：超临界CO2萃取工艺参数对虾青素萃取物得率影响不显著（P＞0.05）,但对虾青素纯度影响显著（P＜0.05）;物料粒径40目,质量含水率9%时,响应面理论优化最佳萃取参数为萃取压力403.95 Pa,萃取温度39.95℃,CO2流量1.16 L/min,虾青素纯度为796.3 mg/g。结合实际应用,验证试验在萃取压力400 Pa,萃取温度40℃,流量1.2 L/min时,虾青素纯度为789.61 mg/g。研究结果可为虾青素的提取和纯化提供参考。     

涂膜及气调保鲜对南美白对虾品质的影响

为了改善南美白对虾黑变快、货架期短的情况,制备含黑变抑制组分（M）和1%壳聚糖（Chitosan）的复合保鲜剂,用其涂膜保鲜南美白对虾,采用高阻隔复合包装袋（K-PET/PE）,采用40%CO2/30%O2/30%N2（Ⅰ）和85%CO2/ 5%O2/10%N2（Ⅱ）2种气调包装,(4±1)℃冷藏,通过菌落总数、挥发性盐基氮、pH值、多酚氧化酶的活性和感官评定等指标评价不同保鲜工艺对南美白对虾的黑变抑制和防腐保鲜效果。通过正交试验获得的黑变抑制组分（M）最优组合为：0.01%4-己基间苯二酚+1.5%柠檬酸+1.0%抗坏血酸;组合（Chitosan+Ⅰ）、（Chitosan+M+Ⅰ）、（Chitosan+Ⅱ）、（Chitosan+M+Ⅱ）分别在第6天、第8天、第12天和第14天开始出现显著黑变;相比对照组,所有处理组在整个贮藏期内的菌落总数、挥发性盐基氮、pH值、多酚氧化酶的活性的增长速度均有所下降,组合（Chitosan+M+Ⅱ）保鲜效果最佳,使(4±1)℃条件下的货架期延长2倍多。涂膜保鲜剂结合气调包装(MAP)的处理方式是南美白对虾保鲜的有效手段,具有应用推广价值。     

南美白对虾脱壳工艺比较及其对虾仁品质的影响

为了确定较优的南美白对虾脱壳工艺,该文比较了不同脱壳工艺下南美白对虾脱壳的效果、虾仁品质及能耗。通过对脱壳时间、虾仁得率和虾仁完整性等方面的综合评价表明速冻和超高压脱壳均具有突出的优势,差异不显著(P>0.05),进一步综合脱壳对品质的影响及能耗分析发现,速冻和超高压脱壳可降低品质的破坏程度,但速冻脱壳对虾仁的色泽破坏显著(P<0.05),色差ΔE值达到6.4;另外,超高压脱壳的能耗较低,仅为速冻脱壳的1/3。综合以上结果,确定超高压脱壳工艺更适合于工业生产,且各参数中200MPa、3min脱壳后虾仁完整性最高,外观色泽好,而300MPa、1min的脱壳效率较高且咀嚼性好。研究结果为超高压技术应用于南美白对虾的脱壳提供了参考。     

气浮机对高位池养虾水质的调控效果

为了探索气浮机在对虾高位池系统中的调控效果,该文利用2口高位池对射流式气浮机对养虾水质和养殖生物的影响进行了研究,试验结果表明:气浮机在对虾养殖试验中取得了显著的调控效果,试验组虾池40 d平均氨氮浓度(0.052±0.012)g/m3比对照组虾池(0.14±0.025)g/m3显著降低了0.088 g/m3、40 d平均亚硝氮浓度(0.0004±0.0001)g/m3比对照组虾池(0.004±0.001)g/m3显著下降了0.0036 g/m3、40 d平均溶解氧质量浓度(7.5465±0.3222)g/m3比对照组虾池(6.5398±0.2843)g/m3显著升高了1.007 g/m3,试验组虾池40 d平均弧菌总数(3553±1873)cfu/mL显著低于对照组(4907±1858)cfu/mL,试验组虾池40 d平均荧光菌(3±1.86)cfu/ml,显著低于对照组(9±2.14)cfu/mL,试验组虾池在60 d时凡纳滨对虾体质量(5.97±0.67)g大于对照组(5.53±0.61)g,差异显著。     

微酸性电解水对虾仁的杀菌效果及其动力学

为探明微酸性电解水(slightly acidic electrolyzed water,SAEW)对南美白对虾(Litopenaeus vannamei)虾仁表面杀菌效果及其动力学规律,选取料液比1:4、1:10、1:20,将虾仁分别浸洗杀菌2、5、10 min,对杀菌过程中虾仁表面及SAEW残存液中总菌落数,与有效氯质量浓度(available chlorine concentration,ACC)的变化进行测定,建立ACC衰减与微生物减灭的动力学模型,并通过颜色、硬度、pH值,及水分横向弛豫行为分析,探讨SAEW杀菌处理对虾仁品质的影响。结果表明SAEW对虾仁表面大肠杆菌有较强杀菌效果,并随处理时间的延长、作用量的增大,SAEW的杀菌效力不断增强,处理5 min时,随着料液比的增加,虾仁表面菌落数从最初的6.6 l(CFU/mL),依次降到5.0、4.7、4.4 lg(CFU/mL),料液比为1:20时,静置浸洗10 min后,虾仁表面菌落数由最初的6.6 lg(CFU/mL)降至3.9 lg(CFU/mL);同时SAEW浸洗液中残存菌落数也随处理时间的延长、作用量的增大,而不断减少,在处理2、5和10 min时,SAEW中的残存菌落数分别为4.18、3.47、2.78 lg(CFU/mL),处理时间为5 min时,随料液比的增加,SAEW中的残存菌落数分别为3.47、2.78、2.65 lg(CFU/mL);同时SAEW中ACC的消耗随处理时间的延长、而不断变大,杀菌处理5、10 min时,ACC质量浓度从初始的20.53 mg/L分别降至7.79、10.97 mg/L。动力学分析表明:SAEW在杀灭虾仁表面大肠杆菌的过程中,ACC的衰减可以用一级动力学模型描述,拟合后决定系数R2均大于0.9,而微生物的减灭遵循更为复杂的动力学模型;此外经过SAEW杀菌处理的虾仁,其颜色、pH值、硬度、以及水分的横向弛豫行为,与未处理样品相比,基本没有显著性变化。相关结果能为SAEW在水产品加工过程中的应用提供技术指导,同时也有助于SAEW杀菌技术理论的完善。     

2-羟基-4-甲氧基苯甲醛和2-羟基-4-甲氧基苯甲酸对菜粉蝶多酚氧化酶的抑制作用

测定了2羟-基-4-甲氧基苯甲醛和2羟-基-4-甲氧基苯甲酸两种效应物对菜粉蝶多酚氧化酶(po lypheno lox idase,简称PPO,EC.1.14.18.1)催化L-多巴(L-DOPA)氧化活力的抑制作用。结果表明,这两种效应物对该酶的活性均有明显的抑制作用,抑制中浓度(IC50)分别为2.71和5.66 mm o l/L,抑制常数分别为2.82和3.35 mm o l/L;2羟-基-4-甲氧基苯甲醛对该酶的抑制作用显著高于2羟-基-4-甲氧基苯甲酸的;这两种抑制剂对酶的抑制作用机理完全不同,2羟-基-4-甲氧基苯甲醛对酶的作用表现为混合型抑制,而2羟-基-4-甲氧基苯甲酸对酶的作用表现为竞争性抑制。研究结果为设计以该酶为靶标的杀虫剂提供理论依据。     

高密度CO2处理虾肌球蛋白形成凝胶的临界浓度与凝胶强度

为了探讨高密度CO_2(dense phase carbon dioxide,DPCD)诱导蛋白质形成凝胶的机制,以凡纳滨对虾肌球蛋白为研究对象,研究了DPCD处理压强、温度和时间对虾肌球蛋白形成凝胶的临界浓度和对虾肉糜凝胶强度的影响。研究结果表明:DPCD处理压强和温度对虾肌球蛋白溶液形成凝胶的临界浓度有显著影响,处理时间对肌球蛋白溶液形成凝胶的临界浓度无显著影响,但增加处理时间,可以形成更加紧实的凝胶。在40℃和5~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为14 mg/mL,在50℃和5、10 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为12 mg/mL,在50℃和15~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为11 mg/mL,在60℃和5~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为10 mg/mL。DPCD处理压强和温度对虾肉糜的凝胶强度也具有显著影响(P0.05),且随着压强增加和温度升高,虾肉糜凝胶强度呈增加趋势(P0.05);在50℃和25 MPa下处理虾肉糜20 min,形成的凝胶强度较好,达到了(14.28±0.57)N·mm。DPCD处理温度越高,虾肌球蛋白形成凝胶的临界浓度就越低,而虾肉糜形成凝胶的强度越高;DPCD处理压强越高,虽然对虾肌球蛋白形成凝胶的临界浓度影响较小,但能使虾肌球蛋白和虾肉糜形成凝胶的强度增加。从分析中还可以推断,DPCD低压(5~10 MPa)诱导虾肉糜形成凝胶主要是热效应的作用,DPCD较高压强(10 MPa)诱导虾肉糜形成凝胶是热和CO_2分子效应的共同作用。研究结果为进一步阐明DPCD诱导蛋白质形成凝胶的机制提供了基础数据。     

超高压联合高密度CO2处理钝化对虾多酚氧化酶

为了弥补超高压(UHP,ultra high pressure)钝化凡纳滨对虾多酚氧化酶(PPO,polyphenol oxidase)效果差的缺点,同时利用高密度CO_2钝化凡纳滨对虾PPO的优势,初步研究UHP+CO_2处理对凡纳滨对虾PPO的钝化效果,以探讨UHP+CO_2联合处理用于开发虾类新产品的可行性。研究结果表明:UHP+CO_2联合处理比单独CO_2处理和UHP处理更能有效地钝化PPO;100 MPa UHP+CO_2联合处理30 min,PPO相对酶活降至18.92%±1.52%;200 MPa UHP+CO_2联合处理10 min,PPO相对酶活降至10.91%±1.08%;300 MPa UHP+CO_2联合处理10 min,PPO被钝化95%;400 MPa UHP+CO联合处理5 min,PPO被钝化97%;500 MPa UHP+CO联合处理10 min,PPO100%被钝化;与单独UHP处理相比,UHP+CO_2联合缩短了处理时间,提高了钝化PPO的效果;PPO经UHP+CO_2联合处理后在4℃贮藏6 d后活性未见恢复,说明PPO在处理过程中发生了不可逆的变性失活。研究结果为虾类的贮藏和加工以及开发新产品提供基础数据和技术参考。     

柿叶提取物对马铃薯多酚氧化酶的抑制作用

多酚氧化酶（PPO）是生物体内黑色素合成的关键酶。研究了甜柿叶乙醇提取物、涩柿叶乙醇提取物、甜柿叶水提取物、涩柿叶水提取物对马铃薯多酚氧化酶活性的抑制作用。结果表明,上述4种柿叶提取物对马铃薯多酚氧化酶具有明显的抑制作用,使该酶活力下降50％所需的浓度（IG50）分别为0．21、0．26、0．37、0．45mg／mL。乙醇提取物较水提取物的作用效果更强,甜柿叶提取物的抑制作用比涩柿叶提取物的强,4种柿叶提取物对酶的抑制作用均为非竞争性可逆抑制,其抑制常数（KI=KIS）分别为0．18、0．23、0．34、0．45mg／mL。     

Effect of ultrahigh hydrostatic pressure on the activity and structure of mushroom (Agaricus bisporus) polyphenoloxidase

High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.     

涌浪机在对虾养殖中的增氧作用

溶解氧是对虾正常代谢和生长中所必需的,为了探索对虾养殖增氧方式的新途径,该文进行了涌浪机在高位池凡纳滨对虾高密度养殖条件下增氧情况的研究,并进行了不同天气状况下与水车增氧机增氧效果的对比。试验表明:涌浪机在晴好天气下增氧能力远超同功率水车增氧机。在试验养殖密度约为10000kg/hm2时,0.75kW涌浪机在晴好天气白天时与同功率水车增氧机相比,使池中溶解氧质量浓度平均提高1.24mg/L,但在阴雨天和夜间涌浪机的增氧效果较差,增氧能力与同功率水车增氧机相近。因此,涌浪机在实际应用中需与其他增氧模式相结合使用,将会取得较好的增氧效果。     

Inhibitory effect of hot-water extract from dried fruit of Crataegus pinnatifida on low-density lipoprotein (LDL) oxidation in cell and cell-free systems

The dried fruit of Crataegus pinnatifida, a local soft drink material and medical herb, was found to possess potential against oxidative stress. In the preliminary study, the antioxidant potential of a hot-water extract obtained from the dried fruit of C. pinnatifida (CF-H) was evaluated in terms of its capacity of quenching 1,1-diphenyl-2-picrylhydrazyl free radicals (EC(50) = 0.118 mg/mL). After content analysis, it was found that CF-H is mainly composed of polyphenols including flavonoids (6.9%), procyanidins (2.2%), (+)-catechin (0.5%), and (-)-epicatechin (0.2%). The antioxidative bioactivity of CF-H had been assess previously using the models of CuSO(4) as cell-free system and sodium nitroprusside (SNP) plus macrophage RAW 264.7 cells as cell system to induce human low-density lipoprotein oxidation. CF-H was found to inhibit relative electrophoretic mobility and thiobarbituric acid reactive substances at the concentration of 0.5-1.0 mg/mL in the cell-free system and at 0.01-0.10 mg/mL in the cell system. Furthermore, it was found that CF-H decreased the SNP-induced cell lipid peroxidation and reduced glutathione depletion.     

Inhibitory effect of a glycoprotein isolated from golden oyster mushroom ( Pleurotus citrinopileatus ) on the lipopolysaccharide-induced inflammatory reaction in RAW 264.7 macrophage

Mushrooms have become an important source of natural antitumor, antiviral, antibacterial, immunomodulatory, and anti-inflammatory agents. Golden oyster mushroom, Pleurotus citrinopileatus , is a common mushroom in oriental countries for human consumption. The present study investigated the anti-inflammatory reaction of the bioactive nonlectin glycoprotein (PCP-3A) isolated from the fresh fruiting body of this mushroom. Western blot analysis on LPS-induced iNOS, COX-2, and NF-κB expressions in RAW 264.7 cells as affected by PCP3-A was performed to elucidate the mechanism of NO and PGE2 reduction. The results showed that PCP-3A failed to affect RAW 264.7 viability at a concentration up to 6.25 μg/mL, but inhibited LPS (1 μg/mL)-induced expression, and that PCP-3A inhibited the production of NO and PGE2 in LPS-activated macrophages via the down-regulation of certain pro-inflammatory mediators, including iNOS and NF-κB.     

超高压处理对南美白对虾在冷藏过程中贮藏特性的影响

该文以不同的超高压条件(200,400,600,700MPa)对南美白对虾进行处理,通过考察与比较不同压力处理组冷藏过程中感官、微生物以及各化学指标的变化情况,揭示超高压技术对南美白对虾冷藏特性的影响。结果表明:超高压处理可以有效地杀灭南美白对虾中绝大多数微生物,抑制贮藏过程中挥发性盐基氮的积累,延缓pH值的变化,从而延长南美白对虾的货架期,且处理压力越高延长效果越显著;超高压处理会给鲜虾带来不同程度上的煮熟虾的风味;400MPa和600MPa处理使虾在冷藏过程的黑变提前,而700MPa处理可以完全抑制南美白对虾黑变现象的发生;超高压能够改变腺苷三磷酸(ATP)及其代谢产物的代谢情况,但不影响腺苷酸(AMP)的代谢途径。因此超高压处理可以改善南美白对虾在冷藏过程中的品质,对南美白对虾冷藏具有潜在的应用价值。     

Inhibitory effect(s) of polymeric black tea polyphenol fractions on the formation of [(3)H]-B(a)P-derived DNA adducts

Five polymeric black tea polyphenol fractions (PBP-1-5) were isolated from a popular brand of black tea. The effect of these PBPs and epigallocatechin gallate (EGCG), a major green tea polyphenol, was studied on the formation of [(3)H]-B(a)P-derived DNA adducts in vitro, employing rat liver microsomes. PBP-1-3 inhibited microsome-catalyzed [(3)H]-B(a)P-derived DNA adduct formation in vitro in a dose-dependent manner. This inhibition was further enhanced on preincubation of microsomes with each of the PBPs. PBP-4 was not effective per se and required preincubation with microsomes to exhibit its inhibitory effect, whereas PBP-5 remained ineffective with or without preincubation with microsomes. Further investigations revealed that the observed decrease in [(3)H]-B(a)P-DNA adduct formation was due to inhibition of isozymes of CYP450s by PBPs. Overall, results suggest that polymeric black tea polyphenol fractions retain one of the chemopreventive effects exhibited by the monomeric green tea polyphenol EGCG in vitro.     

Purification and characterization of collagenolytic proteases from the hepatopancreas of northern shrimp (Pandalus eous)

Three gelatinolytic proteases (A1, A2, and B) were purified using a synthetic substrate, DNP-Pro-Gln-Gly-Ile-Ala-Gly-Gln-d-Arg, from the hepatopancreas of Northern shrimp (Pandalus eous) by several chromatographic steps involving hydroxyapatite column chromatography, gel filtration on Superdex75, and ion-exchange chromatography on a MonoQ column. Collagenolytic proteases A2 and B, but not protease A1, were demonstrated to digest native porcine type I collagen at 25 degrees C and pH 7.5. Further characterizations of these two collagenolytic proteases showed that the pH optimum of enzyme A2 against DNP-peptide was found to be 11, whereas that of enzyme B was 8.5. The optimum temperature ranged between 40 and 45 degrees C for both enzymes, although enzyme B appeared to be thermally more stable than enzyme A2 at pH 7.5. Both enzymes were strongly inhibited by PMSF and antipain, which suggests that they belong to collagenolytic serine proteases.