Retardation of Listeria Monocytogenes Growth in Mozzarella Cheese Using Antimicrobial Sachets Containing Rosemary Oil and Thyme Oil

An antimicrobial sachet containing microcellular foam starch (MFS) with embedded rosemary oil and thyme oil was developed to reduce bacterial growth in shredded mozzarella cheese. The efficacy of the volatiles of oils at various concentrations in reducing Listeria monocytogenes as well as the release of the oils from the MFS have been also determined in this study. The cheese, inoculated with a cocktail of 5 strains of L. monocytogenes (approximately 3 log CFU/g), was packaged in a Nylon/EVOH/PE bag. A paper sachet containing MFS embedded with rosemary oil and thyme oil, separately or together, was inserted into the bag. Rosemary and thyme oil volatiles released from the sachet restricted the growth of L. monocytogenes, resulting in a 2.5 log CFU/g reduction on day 9 at 10 °C. The volatile oils also showed inhibitory effects on the growth of lactic acid bacteria (LAB) and total aerobic bacteria (TAB). After 15 d at 10 °C, the numbers of LAB and TAB in the samples containing the sachet with both oils experienced a 1.2 and 1.4 log CFU/g reduction, respectively, compared to untreated samples. Nonetheless, the sachet treatment produced a distinct odor, unfavorably received by the panelists. The results suggest the potential for application of the sachet system for the reduction of growth of L. monocytogenes, LAB, and TAB in food products.     

Antimicrobial Polylactic Acid Packaging Films against Listeria and Salmonella in Culture Medium and on Ready-to-Eat Meat

The contamination of Listeria monocytogenes and Salmonella spp. in ready-to-eat (RTE) meat products has been a concern for the meat industry. In this study, edible chitosan-acid solutions incorporating lauric arginate ester (LAE), sodium lactate (NaL), and sorbic acid (SA) alone or in combinations were developed and coated on polylactic acid (PLA) packaging films. Antimicrobial effects of coated PLA films on the growth of Listeria innocua, L. monocytogenes, and Salmonella Typhimurium in a culture medium (tryptic soy broth, TSB) and on the surface of meat samples were investigated. Antimicrobial PLA films containing 1.94 mg/cm² of chitosan and 1.94 μg/cm² of LAE were the most effective against both Listeria and Salmonella in TSB and reduced them to undetectable level (<0.69 log CFU/ml). The same PLA films with LAE significantly (p?L. innocua, L. monocytogenes, and S. Typhimurium on RTE meat during 3 and 5 weeks’ storage at 10 °C, achieving 2–3 log reduction of Listeria and 1–1.5 log reduction of Salmonella as compared with controls. PLA films coated with 1.94 mg/cm² of chitosan, 0.78 mg/cm² of NaL, and 0.12 mg/cm² of SA significantly reduced the growth of L. innocua but were less effective against Salmonella. The combination of NaL (0.78 mg/cm²) and SA (0.12 mg/cm²) with LAE (1.94 μg/cm²) did not generate additional or synergetic antimicrobial effect against Listeria or Salmonella on the meat surface. L. innocua had a similar sensitivity to the film treatments as L. monocytogenes, suggesting that L. innocua may be used as a surrogate of L. monocytogenes for further scaleup and validation studies. The film treatments were more effective against the microorganisms in TSB culture medium than in RTE meat, which suggests that in vivo studies are a necessary step to develop antimicrobial packaging for applications in foods.     

地下储油对提升浓香花生油风味稳定性及综合品质的作用

浓香花生油储存期间的风味稳定性是评价其保质保鲜储存效果的重要指标。实验将浓香花生油分别储存于室外地上油罐和地下室油罐,储期18个月,期间自动检测和记录储油温度,定期取油样,采用顶空固相微萃取-气相色谱-质谱联用仪(SPME-GC-MS)及气相-嗅闻仪(GC-O)对油样中挥发性风味成分进行检测和风味嗅闻评价,并对酸价和过氧化值及维生素E和甾醇含量进行检测,分析比较地下储存和地上储存对浓香花生油风味稳定性及综合品质影响的差异。结果表明：初始浓香花生油中共分离鉴定出9类64种挥发性风味成分,其中吡嗪类和醛类是含量最高也是对浓香花生油特征风味有重要影响的挥发性风味成分,经18个月储存,地下储油和地上储油中吡嗪类物质质量分数从初始的36.42%分别降低至29.08%、16.33%,醛类物质中苯乙醛质量分数从9.23%分别减少至1.29%、0.83%,而作为表征油脂氧化程度的己醛含量分别升高至初始值的2.10、6.40倍,地下储油能明显提高浓香花生油中正面属性挥发性风味成分的保留率、减少负面属性挥发性风味成分的生成,同时维生素E和甾醇损失率分别降低13.12%和9.06%,储油保质期延长8个月。与...     

高温熟制杀菌对小龙虾品质及贮藏特性的影响

以小龙虾为研究对象,采用熟制杀菌一步到位的工艺对小龙虾进行加工。通过测定不同熟制杀菌条件下小龙虾的色差、pH值、质构及感官评分变化,分析不同熟制杀菌条件对小龙虾品质的影响,确定较佳熟制杀菌工艺。结果表明：杀菌温度和杀菌时间对小龙虾产品品质有显著影响（P＜0.05）,且杀菌温度越高、时间越长,影响越大;110 ℃、10 min杀菌工艺下小龙虾的弹性、硬度、咀嚼性显著优于其他组（P＜0.05）,黄度值显著低于其他组（P＜0.05）,且感官评分最高。因此,110 ℃、10 min杀菌工艺下的小龙虾品质最好,该工艺是最优熟制杀菌工艺。同时在该工艺条件下,即食小龙虾产品4 ℃贮藏条件下的货架期为35 d。     

聚乳酸薄膜对西兰花的保鲜效果分析

用聚乳酸（polylactic acid,PLA）薄膜包装西兰花,以聚乙烯（polyethylene,PE）薄膜包装和无膜包装为对照组,在（20±3）℃条件下对西兰花的相关指标进行定期测定,研究PLA薄膜对西兰花的保鲜效果。结果表明：在PLA薄膜、PE薄膜和无膜包装贮藏过程中,西兰花的VC、叶绿素含量均呈下降趋势,且前者含量明显高于后两者,而相对电导率、过氧化物酶活性均呈上升趋势,前者明显低于后两者。可见,PLA薄膜包装处理对常温条件下的西兰花有明显的保鲜效果,能有效地延长西兰花的常温货架期。     

交变电场对储藏中毛油氧化及酚酸的影响

为探索交变电场处理对食用毛油氧化的影响规律以及潜在的内在因素,采用交变电场处理大豆和菜籽毛油,研究其储藏期间的主要酚酸含量变化及其与氧化特征的关系。结果表明,与对照相比,交变电场处理可显著抑制油脂POV升高,减缓氧化;在储藏期间电场处理 大豆和菜籽毛油的主要酚酸总量显著降低了20.1%和25.2%;大豆毛油中对羟基苯甲酸、丁香酸、香草醛和芥子酸显著降低了18.4%、6.5%、46.8%和21.4%,菜籽毛油分别降低了56.0%、42.5%、3.0%和23.6%。对照组大豆和菜籽毛油POV与各酚酸组分含量具有不同程度的正相关,而电场处理几乎相反,尤其是大豆毛油POV与芥子酸和香草醛含量呈显著负相关,菜籽毛油POV与芥子酸含量呈极显著负相关。交变电场处理促进了毛油中酚酸的消耗,延缓了油脂的氧化。本结果可为进一步研究电场对油脂氧化的影响机理和控制奠定理论基础。     

大豆分离蛋白对调理重组牛肉品质特性的影响

为探讨大豆分离蛋白添加量对调理重组牛肉制品品质特性的影响,以碎牛肉为实验原料,经过调理和重组工艺,研究不同大豆分离蛋白添加量对产品的各项品质特性的影响。结果表明:随着大豆分离蛋白添加量的增加,调理重组牛肉制品的解冻损失显著降低(P0.05),出品率显著提高(P0.05),产品的质构特性得到显著改善(P0.05),黏结强度显著增强(P0.05),但是产品的色泽变暗(P0.05)。另外,低场核磁检测发现,增加大豆分离蛋白的添加量,T_(2b)和T_(21)的弛豫时间均逐渐变短,而T_(22)的弛豫时间逐渐延长,说明产品的保水性逐渐增强。对产品进行感官评价表明,大豆分离蛋白添加量为2.0%时,产品品质最好。综合考虑产品品质和感官质量,确定在调理重组牛肉制品中大豆分离蛋白的最佳添加量为2.0%。     

1-MCP 结合PE 包装处理对带壳茭白贮藏品质的影响

为探究低温贮藏条件下1-甲基环丙烯（1-methylcyclopropene,1-MCP）结合聚乙烯（polyethylene,PE）保鲜袋包装处理对带壳茭白采后贮藏品质和木质化进程的影响,以新鲜带壳茭白为原料,将其分别用0.07 mm PE 袋、0.14 mm PE 袋、0.07 mm 纳米复合PE 袋、1-MCP 结合0.07 mm PE 袋、1-MCP 结合0.14 mm PE 袋包装。各处理组于（1±1）℃条件下贮藏,定期检测分析各组原料的理化指标。结果表明：1-MCP 结合不同厚度的PE 袋处理均能有效减缓茭白硬度和L* 值的降低,维持果实中总糖和还原糖的含量,并且通过抑制丙二醛含量的升高和过氧化物酶活性的增加,减缓茭白中纤维素和木质素的合成和积累。其中1-MCP 结合0.14 mm PE 袋对带壳茭白的保鲜效果最好,能够有效延缓茭白的采后衰老,延长贮藏期并改善其贮藏品质。     

低密度聚乙烯袋厚度对杏鲍菇减压贮藏品质的影响

为了探寻杏鲍菇减压贮藏适宜的包装材料厚度,以杏鲍菇为试材,分别采用0.03、0.05、0.07 mm低密度聚乙烯袋（low density polyethylene,LDPE）抽真空减压至0.06 MPa包装后,置于4 ℃冷藏30 d,探究不同厚度包装材料对减压贮藏条件下杏鲍菇的生理生化指标及品质的变化规律。结果表明:到贮藏结束时,与0.03、0.05 mm处理组相比,0.07 mm低密度聚乙烯袋组的杏鲍菇水分含量最高,为80.42%,其能有效减少杏鲍菇失水,抑制呼吸速率,缓减过氧化氢酶（catalase,CAT）和超氧化物歧化酶（superoxide dismutase,SOD）活性下降,抑制丙二醛（malondialdehyde,MDA）含量及多酚氧化酶（polyphenol oxidase,PPO）活性的上升,对杏鲍菇的硬度、内聚性、弹性、咀嚼性等质构特性及色泽品质影响越小。因此,0.07 mm厚的低密度聚乙烯袋为杏鲍菇减压贮藏的适宜包装材料厚度,其能有效延缓杏鲍菇的后熟衰老,延长杏鲍菇的保鲜期。     

乳酸和聚乳酸的最新进展

综述了不同的产酸菌发酵生产乳酸、乳酸的提取与检测以及聚乳酸的生产等方面的最新进展     

Preliminary Studies on Composition,Quality and Oxidative Stability of Commercial Avocado Oil Produced in Chile

Avocado oil is a relatively new oil in the market and is highly appreciated by the consumers because of its fine aroma, pleasant taste and health benefits. A study on the characterization of commercial avocado oils produced in Chile was conducted in order to discuss their quality parameters. The study was applied to two marketed avocado oils. The main analytical parameters evaluated to the oils were： fatty acid composition, total chlorophylls, total carotenoids, tocopherols, acid value, peroxide value, total phenolic compounds, polar compounds, oil stability, UV absorption and 3.5-stigmastadiene content. The fatty acid compositions of the studied oils were according with oil composition of pulp pure of avocado fruit. The analysis of tocopherols by high performance liquid chromatography （HPLC） revealed significant differences between the avocado oils studied. Total phenolic compounds, oil stability, UV Absorption characteristics, peroxide value, acid value, tocopherols content, total chlorophylls, total carotenoids and polar compounds were also significantly different between the commercial studied oils. All the above results show a different quality between both commercial avocado oils, showing that the sample C has worse values for the parameters of quality as those required by legislation in many countries. Also, 3.5-stigmastadiene content shows high concentration for one of the commercial avocado oil evaluated which demonstrates the presence of refined oil or that the oil has been submitted to high temperatures. On the other hand it is remarkable that despite the fact that there are many differences in quality parameters, both oils are labeled and marketed as extra virgin quality oils, demonstrating the need to regulate the classification of appreciated oils by the consumers.     

1-甲基环丙烯结合草酸处理对锦绣海棠贮藏品质的影响

为探究1-甲基环丙烯（1-methylcyclopropene,1-MCP）、草酸及二者协同作用对锦绣海棠贮藏品质的影响,该试验经过 1-MCP（1 μL/L）处理、草酸（10 mmol/L）处理和草酸协同 1-MCP 处理,在（4±1）℃、湿度（75±5）%环境下贮藏,测定果实贮藏期间的失重率、硬度、呼吸强度、可溶性固形物、维生素C、总酚、抗氧化相关酶活性指标。结果表明,复合处理相较于单一处理能够降低果实的失重率、丙二醛含量,对其硬度、可溶性固形物、维生素C和总酚含量的下降有减缓效果,并且对呼吸强度、多酚氧化酶和过氧化物酶活性有抑制作用,可提高锦绣海棠的贮藏品质。     

百里香精油对羊奶脱膻效果的评价及机理研究

研究百里香精油对羊奶膻味的脱除效果及作用机理。采用水蒸气蒸馏法制备百里香精油;利用气相色谱-质谱联用技术对百里香精油的挥发性风味成分进行测定;通过感官评价分析百里香精油对羊奶膻味的脱除效果;根据羊奶中致膻性脂肪成分的分析,探讨了百里香精油对羊奶脱膻作用的机理。结果表明,百里香精油中鉴定出18种挥发性成分,百里香酚(14.40%)和龙脑(28.24%)为其主要的风味成分;百里香精油的添加可有效脱除羊奶的膻味,最优添加量为0.025mL/L;百里香精油通过降低羊奶中显著致膻的癸酸、辛酸和己酸的含量而脱除羊奶的膻味。     

鼠尾草酸/LDPE活性膜对新鲜鸡肉丸品质特性的影响

本文使用鼠尾草酸/LDPE活性膜对新鲜鸡肉丸进行真空包装,于4℃、20℃、37℃下贮藏,对不同时期贮藏的鸡肉丸进行感官评分,并测定酸价、质构及硫代巴比妥酸值(TBARS)的变化,并与空白LDPE膜包装的鸡肉丸进行对比,以研究不同温度下CA/LDPE膜包装膜对鸡肉丸品质的影响。结果显示,鼠尾草酸/LDPE活性膜包装的鸡肉丸各项指标(感官评分、酸价、质构和TBARS)均优于空白LDPE膜包装的鸡肉丸,且温度越高,两种包装膜之间的差异越明显:37℃第10 d时,CA/LDPE膜包装的鸡肉丸口感味道感官评分为1.22±0.26,比LDPE膜高22%;酸价为20.53±0.43 mg/(g鸡肉丸),比LDPE膜低28.5%;硬度、凝聚力、咀嚼性分别为43.30、0.21和42.87,比LDPE膜高95.4%、53.2%和81.9%;TBARS值为0.698 mg/kg,比LDPE膜低47.2%。研究表明,添加鼠尾草酸的LDPE膜能够有效改善鸡肉丸的贮藏品质特性。     

不同储存方式对榛子油品质的影响

采用真空、充氮气、添加抗氧化剂3种方式处理榛子油,通过高温强制氧化缩短榛子油试验观察期,以色泽、气味、过氧化值、酸值、羰基值为判断榛子油品质的指标,试验储存榛子油的方法。试验结果表明,经过60℃20 d的强制氧化后,空白、真空、充氮气、充氮气+0.01%TBHQ、0.02%TBHQ 5种方式处理的榛子油样品的色泽均加深,添加0.02%TBHQ样品的气味未变,其他均有哈败气味;随着强制氧化时间的延长,空白、真空、充氮气的榛子油样品的过氧化值、酸值、羰基值均显著升高,充氮气+0.01%TBHQ、0.02%TBHQ处理的榛子油样品的过氧化值、酸值、羰基值升高缓慢,过氧化值升高的幅度最小;添加0.02%TBHQ可以有效地延长榛子油保质期,并保持其感官品质。     

食盐对调理重组牛肉制品品质及水分分布特性的影响

为探讨不同食盐添加量(0%、0.5%、1.0%、1.5%、2.0%和2.5%)对调理重组牛肉制品品质特性的影响,以碎牛肉为实验原料,经过调理和重组工艺,研究不同食盐添加量对产品的质构特性、黏结强度、色差、水分活度、弛豫时间以及肌肉微观结构的变化。结果表明,随着食盐添加量的增加,调理重组牛肉制品的水分活度显著降低,黏结强度显著增强,产品的质构特性得到显著改善(P0.05),但是色泽变暗。另外,低场核磁共振分析发现,增加食盐的添加量,不易流动水含量逐渐增多,自由水含量逐渐减少,产品的保水性逐渐增强。扫描电子显微镜结果显示,增加食盐的添加量可以使肉块黏结处的三维网络结构越来越致密,提高了产品的保水性和黏结强度。对产品进行感官评价表明,当食盐添加量为1.5%时,产品品质最好,咸味适中。综合考虑产品品质和感官品质,确定在调理重组牛肉制品中食盐的最佳添加量为1.5%。     

聚乳酸棉混纺纱混纺比对成纱性能的影响

研究混纺比对聚乳酸棉混纺纱成纱性能的影响。分析了聚乳酸纤维含量分别为20%、35%、50%、65%、80%的聚乳酸/棉混纺纱的条干CV值、强伸性能、毛羽值与混纺比之间的关系。并采用Borda数法对混纺纱的成纱性能优劣进行判断。试验结果表明,混纺纱的条干CV值、断裂强力、断裂伸长率、毛羽值均与混纺比有较强的相关关系,在一定的条件下,聚乳酸/棉混纺比为50/50时,其成纱质量较好。     

颗粒酒花在贮藏过程中的变化研究

研究了颗粒酒花在贮藏期间 ,酒花贮藏指数、α -酸和 β -酸的变化情况。并对酒花氧化的机理进行初步探讨     

不同贮藏条件下菜籽油品质变化的研究

本文采用不同贮藏容器(玻璃油壶、塑料油壶PET)、不同贮藏方式(油壶密封、油壶开盖)来研究菜籽油(无抗氧化剂、添加TBHQ)在食用过程中酸价和过氧化值的变化规律。结果表明：菜籽油在不同的贮藏容器中和不同的贮藏方式下的酸价和过氧化值均随着贮藏时间的延长呈现上升的趋势,而过氧化值的上升速度远大于酸价。密封条件下,玻璃油壶中菜籽油的酸价和过氧化值在6周之内均合格,塑料油壶则是5周;开盖条件下,所测指标均比密封时提前1周超过国家标准;添加TBHQ可以使菜籽油的酸价和过氧化值晚2周超过国家标准。当家庭购买充氮包装的食用菜籽油进行分装时,分装贮藏容器应选择玻璃油壶,用完之后立即密封,并且在6周之内食用完毕。