Effects of Food Storage and Handling on Blow Fly (Lucilia sericata) Eggs and Larvae

ABSTRACT: Flies can cause food-borne disease by transmitting pathogenic microorganisms into the food we eat or by being ingested themselves ("intestinal myiasis"), usually as eggs or larvae contaminating our food. Because eggs and larvae can easily contaminate our food during harvesting, handling, and preparation, this series of experiments was undertaken to define the food preparation conditions that would be necessary to kill contaminating blow fly eggs and larvae. Replicate samples of Lucilia (= Phaenicia) sericata (Meigen) eggs and larvae were exposed to increasing periods of freezing, refrigeration, baking, boiling, frying, and microwaving. Survivors were counted every 6 to 48 h thereafter, and the exposures that were lethal to 50% (LE₅₀), 90% (LE₉₀), and 99% of our samples (LE₉₉) were calculated. All of the tested food-preparation methods killed most or all of the eggs and larvae when exposed for durations typically associated with food preparation. These results indicate that the common methods of food preparation should adequately kill all L. sericata eggs and larvae that may be associated with raw meat. Freezing and extended refrigeration also killed all eggs and larvae. This supports the belief, hitherto unproven, that contamination of cooked meat products most likely occurs at or after the point of retail-consumer contact.     

采后热处理对草莓果实货架品质的影响

在预实验基础上,采用热空气46℃-1h、48℃-30min,热水浸润44℃-20min、46℃-15min对采后新鲜草莓(品种:永丰)进行热处理。处理后的草莓置(1±0.5)℃条件下冷藏1d,(20±1)℃条件下3d,对果实的呼吸作用和品质进行检测,发现处理后果实的呼吸作用明显减弱,热处理能够有效地起到防腐抑菌的作用,热水浸润处理对于根霉生长繁殖的抑制作用明显。48℃热空气处理30min和44℃热水浸润20min的果实具有较好的货架品质。     

Effects on quality attributes of commercial veal pieces under different ageing treatments

The objective of this study was to assess the effect of freezing on quality attributes of four commercial beef pieces of the ‘pistola’ under three ageing treatments: only refrigeration (T1), and refrigeration before (T2) and after (T3) freezing. Eight young calves with a low fatness score from the ‘Galician Blond’ × ‘Holstein‐Friesian’ breed cross were studied. Six steaks from each piece were allocated to treatments. Water–holding capacity (refrigeration and thawing expressible juice, and cooking losses), tenderness (shear force) and chemical composition (fat, moisture, ash and protein) were measured. Freezing produced higher total juice losses than only refrigeration; however, freezing did not improve the tenderness of beef with low fat content. Sequential order of freezing and refrigeration (T2 and T3) did not affect juice losses. The ribeye piece was the most tender veal piece and produced the lowest juice loss. Veal fat content was inversely related to juice losses and directly related to tenderness. Commercial pieces with low fat content are suggested not to be overcooked because of higher juice losses which reduce tenderness.     

Survival of Anisakis simplex in arrowtooth flounder (Atheresthes stomia) during frozen storage

Survival of naturally occurring larvae of Anisakis simplex in fresh arrowtooth flounder (Atheresthes stomia) was determined after storage for specified periods at four freezing temperatures. All larvae were killed by 96, 60, 12, and 9 h at temperatures of -15, -20, -30, and -40 degrees C, respectively. The average percentages of live larvae per fillet at the next shortest holding time were as follows: 72 h at -15 degrees C, 0 to 3%; 48 h at -20 degrees C, 11 to 30%; 9 h at -30 degrees C, 5%; and 6 h at -40 degrees C, 0 to 3%. Larval survival was directly related to fillet thickness or weight (P < or = 0.05). Larval death was directly correlated to freezing temperatures. Holding time necessary to kill larval nematodes decreased as storage temperature decreased.     

湖北风味发酵鳜鱼加工关键工艺

为了探究湖北风味发酵鳜鱼的关键工艺,分别研究了不同减菌剂、复合脱腥剂、腌制方式和发酵方式对发酵鳜鱼产品菌落总数、腥度、水分、盐分等指标及感官品质的影响。结果表明,减菌化、脱腥、腌制和发酵等四个步骤均能显著提高发酵鳜鱼的品质。其中,最优的湖北风味鳜鱼的关键工艺为,采用200 mg/L二氧化氯浸泡鱼体10 min(减菌化);采用2.5%生姜汁和2.5%食盐溶液复合脱腥处理(脱腥);采用4%腌制液浸渍后(腌制),先10 ℃发酵48 h,再25 ℃发酵24 h(发酵),所获得的发酵鳜鱼品质最佳。     

The effect of lemon juice on bonito (Sarda sarda,Bloch, 1793) preserved by sous vide packaging

This study examined the effect of lemon juice on sensory, biochemical and microbiological quality of sous vide (SV)‐packaged bonito. Bonitos were salted (0.2%) and divided into two groups. The first group (SV) was vacuum‐packaged in a gas barrier plastic pouch, pasteurised (70 °C, 10 min) and stored at 4 ± 1 °C. The second group [(lemon juice‐treated sous vide (LSV)] was treated with lemon juice, vacuum‐packaged, pasteurised and stored similarly. LSV samples had lower pH, mesophilic and psychrophilic aerobic counts than SV samples (P < 0.05), and they had better sensory quality. SV samples spoiled on the 35th day, while the LSV samples were acceptable until 49th day of storage. This result shows that treatment with lemon juice increased the acceptability and shelf life of SV packaged bonito for 2 weeks (40%). When compared to several other mild preservation procedures, addition of lemon juice to SV fish is inexpensive and uncomplicated method.     

超高压协同柠檬汁栅栏处理对软包装荔枝罐头杀菌效果及其动力学分析

目的：研究超高压协同柠檬汁栅栏处理对软包装荔枝罐头的杀菌效果,并用适宜的杀菌模型进行动力学分析。方法：以180、380、500 MPa超高压协同不同体积分数（0%、50%、100%）的柠檬汁对软包装荔枝罐头分别处理5、10、15 min,用平板计数法检测菌落总数以及霉菌、酵母菌、大肠杆菌数量,并在37 ℃保藏7 d后,对胀袋情况进行统计;采用Weibull模型,对不同处理下软包装荔枝罐头杀菌效果进行动力学分析。结果：随着压力的增加和时间的延长,杀菌效果增强,且柠檬汁协同处理比单一超高压处理更能抑制微生物生长;其中100%柠檬汁＋380 MPa处理组与500 MPa处理组对菌落总数的杀菌效果相当;霉菌、酵母菌对压力和低酸性的柠檬汁较敏感,100%柠檬汁＋380 MPa和500 MPa处理5 min即可全部被杀死;对照和超高压处理组均没有检测出大肠杆菌。在贮藏实验中,100%柠檬汁＋380 MPa和柠檬汁（0%、50%、100%）＋500 MPa加压处理15 min均无胀袋。Weibull模型拟合各处理组杀菌曲线中,决定系数R2均大于0.900,说明拟合效果较好,尺度参数b随压力和柠檬汁协同作用而增大;形状参数n随着压力的增大总体上呈现减小趋势,且在相同压力有柠檬汁协同时,n略变大。结论：柠檬汁协同超高压杀菌的栅栏效应可以在较低的超高压压力下就达到较强的杀菌效果,有利于保持软包装荔枝的品质,延长贮藏期。     

基于柠檬提取液的银纳米颗粒绿色制备工艺优化

为实现绿色制备银纳米颗粒,研究以硝酸银为原料,采用柠檬提取液为还原剂和稳定剂,在水溶剂环境中采用生物法绿色合成银纳米颗粒。研究探讨了柠檬提取液(柠檬汁、柠檬皮醇提液、柠檬皮水提液)用量,硝酸银浓度,pH调节剂,反应时间,反应温度等因素对银纳米颗粒粒径、形貌、稳定性的影响,并借助紫外-可见分光光度法(UV-Vis)、SEM对银纳米颗粒进行表征。通过工艺优化,分别确定了以柠檬汁、柠檬皮醇提液、柠檬皮水提液为原料的银纳米颗粒最佳制备工艺,所得银纳米颗粒都具有分散性能良好,颗粒均匀,粒径范围为70 nm左右,其中以柠檬皮醇提液工艺制备银纳米颗粒的形貌及稳定性最佳,即硝酸银1.0 mmol/L、柠檬皮醇提液9 mL、反应时间12 min、pH调节剂为1 mol·L-1的NaOH。该工艺采用生物法合成银纳米颗粒,绿色安全、环境友好,具有较好的实际应用价值。     

Effects of different pre-freezing blanching procedures on the physicochemical properties of Brassica rapa leaves (Turnip Greens, Grelos)

For optimal freeze storage, green vegetables should first be blanched. The present study compared four different procedures for the blanching of grelos (leaves of Brassica rapa L.): steaming for 2 min, immersion in boiling water for 2 min, immersion in boiling water containing 1% citric acid for 1 min, and immersion in boiling water containing 5% citric acid for 1 min. After blanching, the grelos were stored for up to 120 days at ?18 °C, with sampling at two‐weekly intervals for analysis of physicochemical properties (ash weight, vitamin C content, pH, acid value, moisture content and CIE_L*a*b* colour variables). In almost all respects steam blanching gave the best results: notably, vitamin C losses were markedly lower, while moisture content and colour remained closer to those of the fresh product.     

金丝枣柠檬复合果醋的发酵工艺优化

以金丝枣与柠檬为原料制备金丝枣柠檬复合果醋。通过单因素试验及正交试验确定最佳酶解工艺条件、果汁体积比及酒精、醋酸发酵工艺。结果表明,金丝枣(柠檬)最佳酶解工艺为：初始pH值pH 3.5(4.5),果胶酶添加量0.03%(0.02%),酶解温度均为45℃,酶解时间均为3 h。在此优化条件下,金丝枣、柠檬出汁率分别达93.90%、90.04%,二者最佳体积比为7∶3。酒精发酵最佳工艺条件为：初始pH值4.0,初始糖度20°Bx,SO₂含量75 mg/L,酵母菌接种量0.04%,发酵温度28℃,发酵时间6 d;醋酸发酵最佳工艺条件为：初始pH值4.5,初始酒精度6.0%vol,醋酸菌接种量0.06%,发酵温度32℃,发酵时间7 d。在此优化条件下,金丝枣柠檬复合果醋感官评分及总酸含量分别为81.2分、18.01 g/L,复合果醋品质符合NY/T 2987—2016《绿色食品果醋饮料》要求。     

Effectiveness of lemon juice in the elimination of Salmonella Typhimurium in stuffed mussels

Street foods are becoming more and more prominent in countries all over the world. There are many reports of disease due to consumption of street foods contaminated by pathogens. With the modern trend toward more natural preservatives, the use of organic acids can achieve a good microbiological safety in food. In the present study, stuffed mussels were inoculated with Salmonella Typhimurium suspension to provide initial populations of approximately 6 and 3 log CFU/g. After inoculation, samples were treated with fresh lemon juice and lemon dressing for 0, 5, and 15 min, and pathogens were enumerated by using direct plating on brilliant green agar. Treatment of stuffed mussels inoculated at high inoculum level, with lemon juice and lemon dressing for different exposure times caused reduction ranging between 0.25 and 0.56 log CFU/g and 0.5 and 0.69 log CFU/g, respectively, whereas in stuffed-mussel samples inoculated at low level, lemon juice and lemon dressing caused 0.08 to 0.25 log CFU/g and 0.22 to 0.78 log CFU/g reductions, respectively. Results of the study showed that both lemon juice and lemon dressing used as flavoring and acidifying agents for stuffed mussels caused slight decrease in Salmonella Typhimurium as an immediate inhibitor, but this effect increased by time. However, treatment of stuffed mussels with the inhibitors until 15 min is not enough to prevent Salmonella Typhimurium outbreaks related to stuffed mussels.     

Evaluation of some physical and chemical treatments for inactivating microsporidian spores isolated from fish

Microsporidia are a large diverse group of intracellular parasites now considered as fungi. They are particularly prevalent in fish and are recognized as important opportunistic parasites in humans. Although the mode of transmission of microsporidia has not been fully clarified, the consumption and manipulation of infected fish may be a risk factor for humans. Comparative analysis of rDNA sequence revealed that the microsporidians used in the present study had 99-100% identity with anglerfish microsporidians of the genus Spraguea and very low identity with microsporidians that infect humans. Microsporidian spores were exposed to different physical and chemical treatments: freezing at -20°C for 24-78 h, heating at 60°C for 5-15 min, microwaving at 700 W, 2.45 GHz for 15-60s, and treatment with ethanol at concentrations of between 1 and 70% for 15 min. The viability of the spores after each treatment was evaluated by two methods: a) haemocytometer counts, measuring the extrusion of the polar filament in control and treated spores, and b) a fluorometric method, testing the membrane integrity by propidium iodide exclusion. The results of both methods were concordant. Spores were inactivated by freezing at -20°C for more than 48 h, by heating to 60°C for 10 min and by microwaving at 750 W, for 20s. Exposure to 70% ethanol for 15 min also inactivated microsporidian spores. The results suggest that both freezing and heating are effective treatments for destroying microsporidian spores in European white anglerfish, and that 70% ethanol could be used by fish processors to disinfect their hands and the utensils used in processing fish. The fluorometric method can be used as an alternative to haemocytometer counts in disinfection studies aimed at establishing strategies for inactivating and reducing the viability and the potential infectivity of microsporidians present in fish or in the environment.     

液氮间歇式浸渍冻结对饺子冻裂率及感官品质特性的影响

为探究液氮间歇式浸渍冻结对饺子色差、质构、感官品质和微观结构的影响,本文以冻裂率为指标分别研究液氮浸入时间、间隔时间、浸入次数对饺子的影响;以低温冰箱冻结、螺旋隧道式冻结为对比,采用色差仪、质构仪、扫描电镜等分别研究液氮间歇式浸渍冻结对饺子色泽、质构、感官特性及微观结构等品质特性的影响.结果表明,当液氮单次浸入时间为2...     

Effectiveness of lemon juice, vinegar and their mixture in the elimination of Salmonella typhimurium on carrots (Daucus carota L.)

Lemon juice, vinegar and the mixture of lemon juice and vinegar (1:1) were tested for their effectiveness in reducing the counts of inoculated Salmonella typhimurium (approximately 6 and 3 log cfu/g) on carrots. Treatment of carrot samples with lemon juice vinegar alone for different exposure times (0, 15, 30 and 60 min) caused significant reductions ranging between 0.79-3.95 and 1.57-3.58 log cfu/g, respectively, while the number of pathogens was reduced to an undetectable level after 30-min treatment by combined used lemon juice vinegar.     

冷冻保护剂葡聚糖-聚赖氨酸对冷冻皇冠梨品质的影响

为了解冷冻保护剂葡聚糖、聚赖氨酸对冷冻皇冠梨品质的影响,以氯化钙、氯化钙-葡聚糖、氯化钙-聚赖氨酸、氯化钙-葡聚糖-聚赖氨酸为冷冻浸渍液对皇冠梨进行冷冻处理.用无纸化温度记录仪测定冻结时间,分析样品冻结过程中温度随时间的变化,并对冻融后样品进行汁液损失、质构、水分分布等指标测定.结果表明:氯化钙、氯化钙-葡聚糖、氯化钙...     

2种浓缩方法对柠檬汁特性影响的比较

采用界面渐进冷冻浓缩法和真空蒸发法分别对柠檬汁进行界面渐进冷冻浓缩和真空蒸发浓缩。通过对 2种浓缩液处理前后柠檬汁香气成分含量的定性定量分析 ,以及柠檬汁色差、Vc含量、电导和 pH值的比较分析 ,证明了冷冻浓缩柠檬汁明显地比真空蒸发浓缩果汁能更好地保持柠檬汁的香气成分、Vc含量和原汁的香气协调性。     

酸甜佛手瓜加工技术

以佛手瓜为原料,以白砂糖、柠檬汁、酱油等为辅料,通过工艺和配方研究,制作出新型腌制产品—酸甜佛手瓜,并对产品进行感官、理化和微生物指标检测。结果表明,最佳加工工艺是:CaCl20.2%,切分厚度3 mm,发酵12 h,热烫1.5 min,糖渍浓度40%;最佳原料配方是:佛手瓜212 g(43%),白砂糖148 g(31%),柠檬汁21 g(4%),酱油107 g(22%);通过测定其总酸度为0.836 6%,VC含量0.088 52 mg/100 g,亚硝酸盐含量为19.38 mg/kg,大肠菌群<30个/100 g。根据上述方法制得的酸甜佛手瓜清爽脆口、酱香味浓、营养丰富、安全性高。     

不同澄清工艺对柠檬果汁品质影响及柠檬苦素贮存期间降解速率预测模型建立

为优化柠檬NFC果汁的加工工艺,本研究比较了琼脂絮凝法、酶解-吸附联用法、酶解-絮凝联用法和冻融细胞破碎法对柠檬原果汁的澄清效果,并建立了柠檬原果汁及经不同澄清工艺处理获得的柠檬清汁贮存期间柠檬苦素降解模型。结果显示,四种澄清工艺均可明显提高柠檬果汁的透光度并维持品质;酶解-吸附联用法对柠檬原果汁的澄清效果要优于其它三种方法,但显著降低了清汁中总酚和抗坏血酸含量(P<0.05),该法最优参数为果胶酶添加量0.3%,纤维素酶添加量0.15%,酶解时间2 h,活性白土添加量为4%;经澄清处理的柠檬清汁样品在贮存期间柠檬苦素含量降解的速率常数(k)与Arrhenius数学模型的相关性高,且模型为一级反应动力学方程。经酶解-吸附联用法澄清处理的柠檬清汁中柠檬苦素降解反应活化能(Ea)显著(P<0.05)低于其余三种澄清处理法,说明该体系下柠檬苦素更易发生降解。因此,琼脂絮凝法、酶解-吸附联用法、酶解-絮凝联用法和冻融细胞法均可用于柠檬NFC原果汁的澄清,但在实际果汁生产中应考虑使用对功能性物质破坏小的方法。     

猕猴桃冷冻破壁离心取汁工艺

根据缓慢冻结破坏细胞壁的原理,采用冻融离心取汁新工艺制取猕猴桃果汁,对冷冻破壁和离心工艺参数进行单因素和正交试验分析。结果表明：冷冻破壁离心取汁工艺所制备的果汁在出汁率、VC 含量、透光率及色泽方面都明显优于传统榨汁工艺,最佳工艺条件为切片厚度0.6cm、－ 14℃冷冻10h、30℃解冻30min、3000r/min 离心20min、100 目过滤。     

不同冻结方式对草鱼肉挥发性成分的影响

为探明冻结方式对草鱼肉挥发性风味物质的影响,以草鱼背肉和红肉为研究对象,采用新型材料MonoTrap作为固相萃取整体捕集剂,通过电子鼻和气相色谱-质谱联用技术对经过速冻、酒精浸渍冻结和冰柜直接冻结的草鱼背肉和红肉的挥发性风味成分进行分析和鉴定。结果显示,电子鼻可以良好区分新鲜和不同冻结方式处理草鱼背肉和红肉气味,主成分分析显示冰柜直接冻结样品的气味与新鲜样品的气味差异最大。通过气相色谱-质谱检测新鲜、速冻、酒精浸渍冻结及冰柜直接冻结草鱼背肉和红肉,从背肉中分别鉴定出45、33、28?种和22?种挥发性物质,红肉中分别鉴定出49、38、33?种和25?种挥发性物质,以醛类和醇类物质为主。结果表明,戊醛、己醛、庚醛、辛醛、2-辛烯醛、壬醛、2-壬烯醛、癸醛、2-癸烯醛、十一醛、2,4-癸二烯醛、己醇、2-辛烯醇、1-辛烯-3-醇、二甲苯等化合物对草鱼肉总体风味形成有重要贡献。3?种冻结方式中与新鲜样品挥发性物质的种类和相对含量最接近的是速冻后的样品,差异最大是冰柜直接冻结样品。速冻更有利于保持冻结草鱼肉的品质,冻结后草鱼肉的风味接近于新鲜鱼肉。