电子束辐照对真空包装章鱼生物胺的抑制作用研究

为分析电子束辐照处理对真空包装章鱼制品冷藏过程中生物胺形成的抑制作用,以真空包装的新鲜章鱼腕足段为研究对象,分别进行0、0.5、1.0、1.5、2.0和2.5 kGy剂量的电子束辐照处理,于4℃下冷藏63 d,每隔7 d进行感官品评和生物胺含量检测。结果表明,冷藏期间真空包装的章鱼中共检测出精胺、亚精胺、腐胺、尸胺、组胺和酪胺6种生物胺。电子束辐照处理能抑制章鱼冷藏过程中腐胺、尸胺、组胺和酪胺的生成,且抑制作用与辐照剂量成正比,其中对组胺生成的抑制效果最佳,仅在少数样品中被检出。此外,电子束辐照也抑制了章鱼中亚精胺和精胺在冷藏后期的分解。冷藏过程中的腐胺、尸胺和酪胺含量变化与样品感官品质表现出较好的一致性,高感官品质章鱼样品中的腐胺、尸胺和酪胺含量均≤10 mg·kg-1。综合电子束不同剂量辐照对章鱼感官品质和生物胺的抑制作用,1.0 kGy的电子束辐照剂量是真空包装章鱼4℃冷藏保鲜的最适前处理,其能延长高品质新鲜章鱼货架期至35 d。本研究结果为章鱼加工企业生产高品质章鱼产品提供了理论依据。     

腌干鱼贮藏过程生物胺的变化及其货架期研究

为建立以生物胺变化预测腌干鱼在贮藏过程中品质和安全食用货架期的回归方程,以多脂的腌干带鱼和低脂的腌干金线鱼为原料,研究其在常温贮藏过程中的理化指标、主要微生物和生物胺的变化及相关关系,并应用逐步回归法进行回归分析,初步建立分析腌干鱼制品的货架期预测模型。结果表明,腌干带鱼和金线鱼在贮藏过程中p H、水分含量和Aw不断下降。葡萄球菌及微球菌、乳酸菌、菌落总数在贮藏3周内呈上升趋势,从第4周开始逐渐下降,而假单胞杆菌和肠杆菌在贮藏第4周之后未检出;组胺、尸胺和腐胺为腌干鱼贮藏过程主要胺类物质,呈上升趋势。5种生物胺(组胺、尸胺、腐胺、色胺、酪胺)、总生物胺量、生物胺相关指标、理化指标、假单胞杆菌均与贮藏时间高度相关,微生物中只有假单胞杆菌与生物胺及其相关指标有相关性;生物胺与理化指标也呈高度负相关。本研究结果为腌干鱼制品货架期体系的建立提供了参考依据。     

包装方式和材料对调理脆肉鲩鱼片冷藏过程品质的影响

为延缓脆肉鲩鱼片贮藏过程中腐败变质,并延长货架期。以紫苏叶水提物浸泡腌制的新鲜脆肉鲩鱼片为原料,研究包装方式和包装材料在4℃条件下对鱼片品质的影响。结果表明:气调包装鱼片菌落总数最少、普通包装菌落总数增长最快,气调包装样品冷藏15 d菌落总数平均为5.61 log[CFU/g],未超过水产品规定的货架期终点;冷藏末期气调包装样品汁液流失率、挥发性盐基氮(total volatile base-nitrogen,TVB-N)值和硫代巴比妥酸(thiobarbituric acid,TBA)值均低于真空包装和普通包装,其中PVC材料气调包装样品汁液流失率第15天达到5.07%,TVB-N值为13.91 mg/100 mg,低于国家规定的二级鲜度,TBA值比真空包装和普通包装分别低16.40%和46.46%。气调包装样品质构降低程度比其他组慢,其中,冷藏末期硬度较另外2组分别高出26.41%和27.08%;不同包装材料样品硬度、汁液流失率、TBA值、感官分值差异显著(P0.05),其中高阻隔性NY/EVOH/PET复合材料保鲜效果最好。综合各指标变化,气调包装和高阻隔性材更有利于调理脆肉鲩鱼片冷藏过程的品质保持。研究结果为调理脆肉鲩鱼片冷藏包装应用提供理论参考。     

贮藏温度对炝蟹品质的影响

为阐明不同贮藏温度下炝蟹品质的变化和食用安全性,本试验以三疣梭子蟹为材料制作炝蟹,探讨冻藏(-18℃)和冷藏(4℃)条件下炝蟹感官品质、菌落总数(TVC)、挥发性盐基氮(TVB-N)和生物胺的变化规律,并对其生物胺与其他品质指标进行相关性分析。结果表明,贮藏温度对炝蟹感官品质TVC、TVB-N等指标的劣变具有显著的影响。-18℃冻藏和4℃冷藏条件下,炝蟹感官品质分别于第10天和第6个月超出可接受限值;随着贮藏时间的延长,4℃冷藏条件下炝蟹TVC值显著增加,但至贮藏16 d时仍小于5 lg(CFU·g^-1),TVB-N值于贮藏12 d时超出一级鲜度临界值;-18℃冻藏过程中炝蟹TVC值略有增加,但变化不显著,TVB-N值于第6个月超出一级鲜度临界值。4℃冷藏过程中炝蟹中共检测出8种生物胺,而-18℃冻藏过程中共检测出5种生物胺。此外,色胺、腐胺和酪胺是炝蟹贮藏过程中产生的主要生物胺,且与其他品质均具有显著相关性。本研究结果为炝蟹在贮藏过程中的安全性和货架期预测提供了理论依据。     

不同干燥方法对罗非鱼片品质和微观结构的影响

为了解不同干燥方法对罗非鱼片干燥后品质和微观结构的影响,采用热风干燥、真空冷冻干燥、超临界CO2干燥等3种方法对罗非鱼片进行干燥,研究其对营养成分、微生物、感官特征、复水性能、质构特征、微观结构等的影响。结果表明:与热风干燥和真空冷冻干燥相比,超临界CO2干燥的鱼片,粗蛋白含量高,脂肪含量较低;且在杀灭微生物方面有着显著的优势;但其鱼片的收缩率和复水特性稍差于真空冷冻干燥,而其感官、质构和微观结构等品质均与真空冷冻干燥的相当,而所有品质都明显优于热风干燥;结合经济性等综合考虑,罗非鱼片应用超临界CO2干燥是可行的。研究结果可为罗非鱼片干燥技术的选择提供参考。     

3种抑芽剂对马铃薯贮藏效果的影响

以马铃薯品种新大坪为试验材料,研究了氯苯胺灵粉剂、香芹酮粉利和1-萘乙酸甲酯粉剂对马铃薯贮藏效果的影响。综合其抑芽效果、失重率、呼吸强度以及品质的观测结果表明,3种抑芽剂对马铃薯的贮藏效果依次为氯苯胺灵粉剂 > 香芹酮粉剂 > 1-萘乙酸甲酯粉剂。与对照相比,3种抑芽剂处理均可将马铃薯休眠推迟70 d,使马铃薯贮藏150 d不发芽。香芹酮熏蒸粉剂剂量为0.6 mL/kg、1-萘乙酸甲酯粉剂剂量为100 mg/kg时贮藏效果最好,可取代氯苯胺灵粉剂,达到绿色安全的目的。     

CaCl2和6-BA溶液处理对枣果软化褐变及相关酶活性的影响

试验探讨了鲜枣贮藏过程中果肉软化褐变与PG活性、PPO活性的关系以及采前CaCl₂和6-BA溶液处理对采后枣果果肉软化褐变、PG活性、PPO活性的影响。结果表明，枣果采后硬度逐渐下降且与贮藏时间呈极显著负相关，PG活性在贮藏期间呈起伏变化，与枣果软化无显著相关性。 随贮藏时间延长果肉褐变指数逐渐增大，PPO活性逐渐升高，PPO活性与果肉软化褐变的发生相一致。采前用1% CaCl₂、15 mg/kg 6-BA以及1% CaCl₂+15 mg/kg 6-BA对枣果进行喷雾处理，能降低采后枣果的PG活性和PPO活性，抑制果肉硬度的下降和果肉的褐变进程。1% CaCl₂处理可使赞皇大枣贮藏末期的果肉硬度比对照增加1.2 kg/cm²；1% CaCl₂+15 mg/kg 6-BA处理可使赞皇大枣贮藏末期的果肉硬度增加1.5 kg/cm²。15 mg/kg 6-BA处理对枣果软化褐变及PG活性、PPO活性有一定影响，但效果不及CaCl₂处理。     

冰温或冷藏对牦牛肉贮藏品质及水分迁移的影响

为了从分子水平探索牦牛冷鲜肉贮藏品质特性,在冰温(-2℃)和冷藏(0℃)条件下贮藏过程中,研究牦牛肉感官品质、丙二醛含量、菌落总数和色泽的变化,利用低场核磁共振技术(low-field nuclear mag-netic resonance,LF-NMR)研究牦牛肉在贮藏过程其水分迁移规律,采用傅立叶红外光谱技术(fourier transform infrared spectroscopy,FTIR)研究牦牛肉在贮藏过程其蛋白质结构变化。结果表明:牦牛肉在冰温贮藏条件下贮藏24 d仅降为"二级鲜肉",菌落总数为5.12 lg(CFU/g),而冷藏条件下贮藏至18 d已为"二级鲜肉",菌落总数为5.25 lg(CFU/g)至24 d已腐败变质,菌落总数为6.28 lg(CFU/g)。牦牛肉样在贮藏过程色泽红度值先上升后下降,与冰温贮藏相比,冷藏条件下降速度更显著(P0.05)。牦牛肉丙二醛含量随贮藏时间延长逐渐增加,冷藏条件与冰温贮藏条件比较,丙二醛增加更快。上述数据表明冰温对牦牛肉的贮藏保鲜效果更好。同时,在上述两种贮藏条件下,牦牛肉中结合水含量变化趋势相同,两种贮藏条件下结合水含量差异不显著(P0.05),不易流动水含量在冰温条件下比冷藏条件下波动小,自由水含量在冷藏条件下比冰温条件下波动小。不同贮藏条件下牦牛肉弛豫时间对应的结合水和自由水迁移明显,且冰温条件变化幅度低于冷藏条件,说明冰温条件更利于维持水分子与其他生物大分子相互作用,间接说明冰温保鲜效果更佳。对于贮藏过程蛋白质二级结构变化,冰温条件下贮藏18 d后无规则卷曲相对平均含量,比冷藏条件下无规则卷曲相对平均含量低,且差异显著(P0.05)。综合分析表明,与冷藏条件相比,冰温条件下牦牛肉结合水、蛋白质分子结构更加稳定,对维持肉生理、生化品质更为有利,因而冰温贮藏比冷藏效果更好。研究为冷鲜肉贮藏保鲜的基础研究提供新的方法参考。     

CaCl_2和6-BA溶液处理对枣果软化褐变及相关酶活性的影响

试验探讨了鲜枣贮藏过程中果肉软化褐变与 PG活性、PPO活性的关系以及采前 Ca Cl2 和 6 - BA溶液处理对采后枣果果肉软化褐变、PG活性、PPO活性的影响。结果表明 ,枣果采后硬度逐渐下降且与贮藏时间呈极显著负相关 ,PG活性在贮藏期间呈起伏变化 ,与枣果软化无显著相关性。随贮藏时间延长果肉褐变指数逐渐增大 ,PPO活性逐渐升高 ,PPO活性与果肉软化褐变的发生相一致。采前用 1% Ca Cl2 、15 mg/kg6 - BA以及 1% Ca Cl2 +15mg/kg6 - BA对枣果进行喷雾处理 ,能降低采后枣果的 PG活性和 PPO活性 ,抑制果肉硬度的下降和果肉的褐变进程。 1% Ca Cl2 处理可使赞皇大枣贮藏末期的果肉硬度比对照增加 1.2 kg/cm2 ;1% Ca Cl2 +15 m g/kg6 - BA处理可使赞皇大枣贮藏末期的果肉硬度增加 1.5 kg/cm2 。 15 m g/kg 6 - BA处理对枣果软化褐变及 PG活性、PPO活性有一定影响 ,但效果不及 Ca Cl2 处理     

甘薯抗疮痂病多胺与吲哚乙酸代谢的研究

研究不同抗性甘薯品种受疮痂病菌侵染前后多胺和吲哚乙酸代谢变化结果表明 ,感染疮痂病菌后抗病与感病品种甘薯叶片中吲哚乙酸含量和多胺氧化酶活性降低 ,多胺总量及腐胺含量增加 ,腐胺 / (精胺 亚精胺 )比值升高 ,感病品种变化幅度高于抗病品种。疮痂病菌侵入后感病品种甘薯叶片中绿原酸含量下降 ,吲哚乙酸氧化酶和过氧化物酶活性升高 ,而抗病品种则相反。     

Multiple compound quality index for cold-smoked salmon (Salmo salar) developed by multivariate regression of biogenic amines and pH

Production of biogenic amines during chill storage of 12 lots of cold-smoked salmon was studied. These data allowed for a multiple compound quality index to be developed by multivariate regression (partial least square regression). The quality index was based on concentrations of cadaverine, histamine, putrescine, and tyramine and pH and showed good correlation with sensory assessments. Biogenic amines were indicators of spoilage rather than casual agents of spoilage off-flavors. Four different biogenic amine profiles were found at the time of spoilage in cold-smoked salmon. These were the results of differences in the spoilage microflora. Histamine was detected above regulatory limits but below toxic levels. Measurements of salt and dry matter for calculation of water phase salt could be substituted by rapid water activity measurements.     

Relation of biogenic amines' formation with microbiological and sensory attributes in Lactobacillus-inoculated vacuum-packed rainbow trout (Oncorhynchus mykiss) fillets

The biogenic amine (BA) content of vacuum-packed filleted rainbow trout (Oncorhynchus mykiss) inoculated or not with two different Lactobacillus strains, individually or in combination, was monitored during refrigerated storage for 20 days and related to respective bacteriological and sensory changes occurring during the same period. Eight amines, namely putrescine, cadaverine, tyramine, tryptamine, beta-phenylethylamine, histamine, spermine, and spermidine, were determined, whereas agmatine was not detected in any of the samples. In all cases, BA concentration was higher (P < or = 0.05) in the controls compared to all inoculated treatments, whereas the trend with regard to the bacterial populations (Enterobacteriaceae, pseudomonads, and H2S-producing bacteria) and the off-odor scores was similar. Inoculation with Lactobacillus sakei CECT 4808 showed the best preservative effect among inoculated treatments. Concentrations of putrescine and cadaverine, the main BAs formed, correlated well with both spoilage bacterial counts and off-odor scores and can be useful indicators of shelf life. Spermine and spermidine contents decreased during storage, while levels of the other determined BAs remained below 10 mg/kg even after sensory rejection.     

Determination of biogenic amines in squid and white prawn by high-performance liquid chromatography with postcolumn derivatization

A simple method was developed for the determination of biogenic amines in aquatic food products using a reverse-phase high-performance liquid chromatography with postcolumn automatic o-phthalaldehyde derivatization and fluorescence detection. The linearity, repeatability, and recovery of the method for seven amines (tyramine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine) were evaluated. This optimized method was applied to detect biogenic amines in squid and white prawn during refrigerated storage. Sensory analysis, pH value, and total volatile base nitrogen value were combined to evaluate the freshness quality of these two raw materials. Agmatine and cadaverine in squid, cadaverine, and putrescine in white prawn were the most obviously changed amines during the storage at two different temperatures, and these biogenic amines could be the effective quality indicators for the freshness of the raw aquatic materials.     

Characterization of volatile compounds in chilled cod (Gadus morhua) fillets by gas chromatography and detection of quality indicators by an electronic nose

Volatile compounds in cod fillets packed in Styrofoam boxes were analyzed during chilled storage (0.5 degrees C) by gas chromatography (GC)-mass spectrometry and GC-olfactometry to screen potential quality indicators present in concentrations high enough for detection by an electronic nose. Photobacterium phosphoreum dominated the spoilage bacteria on day 12 when the fillets were rejected by sensory analysis. Ketones, mainly 3-hydroxy-2-butanone, were detected in the highest level (33%) at sensory rejection, followed by amines (TMA) (29%), alcohols (15%), acids (4%), aldehydes (3%), and a low level of esters (<1%). The electronic nose's CO sensor showed an increasing response with storage time coinciding with the production of ethanol and 2-methyl-1-propanol that were produced early in the storage, followed by the production of 3-methyl-1-butanol, 3-methyl-butanal, 2,3-butandiol, and ethyl acetate. Lipid-derived aldehydes, like hexanal and decanal, were detected in similar levels throughout the storage time and contributed to the overall sweet odors of cod fillets in combination with other carbonyls (3-hydroxy-2-butanone, acetaldehyde, 2-butanone, 3-pentanone, and 6-methyl-5-heptene-2-one).     

Comparison of ELISA and HPLC for the determination of histamine in cheese.

A competitive direct enzyme-linked immunosorbent assay (CD-ELISA) for histamine in cheese was compared with a reversed-phase liquid chromatography (RP-HPLC) method. Cheese was homogenized with phosphate-buffered saline (PBS), centrifuged, and filtered, and the supernatant was diluted with PBS for CD-ELISA. For RP-HPLC, biogenic amines (histamine, tyramine, putrescine, and cadaverine) were derivatized with 9-fluorenylmethylchloroformate, followed by reversed-phase chromatography and fluorescence detection. Detection limits and mean recoveries (10-1000 mg/kg) were 2 mg/kg and 93% for CD-ELISA and 1 mg/kg and 99% for RP-HPLC, respectively. Analysis of 50 commercial cheeses according to both methods showed good agreement for histamine (r = 0.979; concentration range = 2-1800 mg/kg). At a threshold level of 10 mg/kg, the ELISA gave no false-negative and three false-positive results. The results show that the ELISA is suitable for the determination of histamine in cheese.     

Influence of lupin (Lupinus luteus L. cv. 4492 and Lupinus angustifolius L. var. zapaton) and fenugreek (Trigonella foenum-graecum L.) germination on microbial population and biogenic amines

Microbial population and bioactive amine profile and levels of two lupin species (Lupinus luteus L. cv. 4492 and Lupinus angustifolius L. var. zapaton) and fenugreek (Trigonella foenum-graecum L.) seeds as affected by germination were investigated. Microbial population increased considerably mainly in the first stage of germination (2 days), then small changes in bacterial numbers were observed up to 5 days to levels between 7.8 and 8.9 log colony-forming units/g. Microorganisms belonging to the Enterobacteriaceae family were dominant for the legumes tested. Ungerminated legume seeds contained putrescine, cadaverine, histamine, tyramine, spermidine, and spermine. Bioactive amine levels found in fenugreek seeds were between 3- and 4-fold higher than those found in lupin seeds. The highest total amine levels were found in fenugreek seeds [162 mg/kg of dry weight (dw)], followed by L. angustifolius var. zapaton seeds (84 mg/kg of dw) and, finally, L. luteus cv. 4492 (46 mg/kg of dw) seeds. The concentration of individual amines showed a gradual rising trend during the germination period in all tested sprouts, reaching levels >3 times higher than those found in ungerminated seeds. After 5 days of germination, the fenugreek sprouts contained the highest amount of total bioactive amines. Tyramine was the predominant amine in both lupin varieties, whereas cadaverine was the main bioactive amine detected in fenugreek. The results of this work thus indicated that microbial population and biogenic amine levels in the studied lupin and fenugreek sprouts are not a risk for healthy consumers or for individuals with restricted activity of detoxification enzymes.     

Chemical, microbiological, and AromaScan evaluation of mahi-mahi fillets under various storage conditions

The quality for mahi-mahi stored at 1.7, 7.2, and 12.8 degrees C for 0, 1, 3, and 5 days was determined using biogenic amine analysis, microbial counts, and sensory evaluation (by a sensory test panel and an AromaScan). Biogenic amines in methanol extracts from mahi-mahi samples were analyzed using capillary electrophoresis (CE) with ultraviolet detection at 210 nm and a gas chromatography (GC) method that can simultaneously determine the contents of putrescine, cadaverine, histamine, spermidine, and spermine within 20 min after pentafluoropropionic anhydride derivatization. A good correlation R2= 0.99) was found between CE and GC methods for detecting histamine in mahi-mahi. Fish quality deteriorated and correlated with increasing microbial numbers. Biogenic amines may be useful indicators for mahi-mahi quality and safety. AromaScan was able to correlate quality changes for mahi-mahi in microbiological and sensory analyses.