Application of rapid methods and ultrasound imaging in the assessment of the microbiological quality of aseptically packed starch soup

The application of rapid microbiological methods such as automated turbidometry and microcolony count using the direct epifluorescence technique (DEFT) was tested for the quality control of aseptically packed ultra-high temperature-treated starch-based soup. In addition, a non-destructive method using ultrasound imaging through the packages prior to the microbiological analysis was evaluated. The results showed that ultrasound could be a promising non-destructive testing method in quality control schemes for starch-based foods. Certain problems associated with calibration may arise in the application of turbidometry for heat-treated food material. Neither method studied in this work was sufficiently sensitive without a pre-incubation step.     

Provision of visually appetising and high-energy maize soup as an in-between meal for older consumers

The objective of this study was to investigate the effects of enriched energy density and visual topping on maize soup’s intake, overall liking, taste liking, food-evoked emotion and perceived familiarity among older home-dwelling people. This study consisted of two tests: in the first test, the most appetising soup was chosen from six high-energy soups topped with different condiments by testing participants’ rankings based only on appearance; while in the second test, participants tasted the most visually appealing maize soup (high-energy maize soup topped with parsley), as well as topping-free high-energy maize soup and low-energy maize soup. Enriched energy density significantly increased the energy intake of maize soup, and visual topping significantly increased both the weighed intake and energy intake of high-energy maize soup. A combined sensory dimension modification of maize soup by enriching energy density and adding visual topping positively affected weighed intake, energy intake, overall liking and food-evoked emotion of maize soup. Slight changes of meal appearance by adding visually appetising toppings could be an effective method to encourage older consumers’ food consumption. In addition, combined sensory enhancement for food could have synergetic effect on older people’s food consumption and eating experience.     

A new medium for determining the total plate count in food

SimPlate for Total Plate Count-Color Indicator (TPC-CI, IDEXX Laboratories, Inc., Westbrook, Me.) is a new medium that incorporates the redox dye resazurin to detect and quantify bacteria in food. Enumeration is achieved by the most probable number method using a SimPlate device. Viable bacteria are detected in each well of the SimPlate device by the biochemical reduction of resazurin, which is blue, to the pink resorufin or the clear dihydroresorufin indicators. Results after 24 h of incubation for TPC-CI are highly correlated with standard plate count agar after 48 h of incubation. Correlation coefficients from studies conducted at five laboratories ranged from 0.94 to 0.98 in side-by-side comparisons against standard plate count agar. Four additional test sites, using alternative methods for determining the aerobic plate count in food, reported similar results in comparison studies (r = 0.91 to 0.97). The slopes from linear regression analysis at all sites ranged from 0.91 to 0.98, with y intercepts ranging from 0.11 to 0.84. Samples used for the validation of TPC-CI included raw food products (i.e., liver and grains), which may contain natural enzymes that interfere with enzyme-based detection methods. No interference was seen from the foods tested. These results suggest that TPC-CI is a suitable alternative to existing plate count methods and has reduced incubation time.     

超高压耦合热处理对鳙鱼鱼糜凝胶特性和水分迁移的影响

研究不同压力（100~500 MPa）耦合热处理（40 ℃/30 min,90 ℃/20 min）对鳙鱼（Aristichthys nobilis）鱼糜凝胶特性及水分迁移的影响,考察了不同处理条件下鳙鱼鱼糜的凝胶强度、持水性（WHC）、白度、质构、微观结构、SDS-PAGE电泳及水分迁移的变化,并进行相关性分析。研究发现,超高压耦合热处理能显著改善鳙鱼鱼糜的凝胶特性。超高压条件为300 MPa/15 min的压力耦合热处理（记为300PH）样品的凝胶强度和不易流动水单位质量峰面积（A22）显著性高于其他处理组（p<0.05）。与传统二段热处理样品相比,300PH样品的凝胶强度和WHC分别提高了88.40%、4.75%。与鱼糜凝胶的凝胶强度具有高度相关性的指标分别是破断强度、凹陷深度、硬度、弹性、胶着性、咀嚼性和A22。结合水单位质量峰面积（A21）与鱼糜凝胶强度具有中度相关性,这些表明300PH样品形成致密的凝胶网络结构,锁住更多结合水,限制不易流动水向自由水迁移,从而改善鱼糜凝胶的凝胶特性。该研究旨在为超高压技术鱼糜凝胶制品加工中的产业化应用、优质淡水鱼鱼糜制品的加工提供数据参考。     

Comparison of rapid tests for assessing UHT milk sterility

Samples of UHT milk were contaminated at two levels (10(2) and 10(4) cfu/ml) with 52 bacterial strains associated with spoilage. Samples were assayed, using various tests, to determine efficiency in detecting non-sterility after an incubation period shorter than that advised in standard procedures. The tests performed were colony count, titratable acidity and pH modification, organoleptic assessment, stability towards ethanol (68, 80 and 88% v/v), resazurin and nitrate reduction. After 3 d incubation at 30 degrees C every case was detected by the resazurin test with a good statistical probability (P = 0 x 999). Reliability was not so high in all other tests, even after 14 d incubation.     

氯化钙复合脂肪酶处理工艺对鸡汤腥味的影响

为探究鸡汤中存在的两种异味成分(庚醛和(E)-2-壬烯醛)与鸡汤腥味的相关性,并研究有效降低鸡汤腥味的方法。以河田母鸡为原料,对鸡肉进行焯水处理与氯化钙和脂肪酶复合前处理工艺后制备鸡汤,采用气相色谱-质谱联用(GC-MS)技术测定鸡肉前处理后和鸡汤中两种异味化合物的浓度,并对鸡汤腥味等方面进行感官评价。结果表明:2次焯水鸡汤中两种异味化合物浓度较0次焯水鸡汤显著下降(P<0.05);采用氯化钙和脂肪酶复合前处理后焯水的制备工艺,显著增加了焯水过程中两种化合物的溶出量,制成的鸡汤中两种化合物浓度较对照组显著降低(P<0.05);感官评价结果表明庚醛和(E)-2-壬烯醛浓度与鸡汤腥味评分呈显著负相关(r=-0.987,P<0.05;r=-0.981,P<0.05),与鸡汤总体感官品质呈显著负相关(r=-0.976,P<0.05;r=-0.965,P<0.05)。氯化钙和脂肪酶复合前处理后2次焯水的鸡汤制备工艺能有效降低鸡汤中的腥味,提升鸡汤的总体感官品质。     

Sensory and Nutritional Quality of Split Peas (Pisum Sativum) Stored up to 34 Y in Residential Storage

ABSTRACT: The sensory and nutritional quality of split peas stored up to 34 y was determined. Nine samples of split peas representing 5 retail brands packaged in Nr 10 cans and stored at room temperature were obtained from donors. Duplicate cans of a fresh sample of split peas were purchased as controls. Can head space oxygen ranged from 0.255% to 20.1%. Water activity of the raw split peas ranged from 0.41 to 0.56. The green color of the raw split peas decreased over time as shown by increasing CIE a* values. Flavor, appearance, texture, and overall liking hedonic scores (9-point scale) of split-pea soup made from each sample ranged from 3.7 to 6.7 and decreased over time. Hedonic scores for appearance were correlated with the decrease in raw product green color (r²= 0.65). Hedonic scores for soup texture declined over time, which corresponded with increasing hardness of the cooked peas as measured by a TA.XT2 texture analyzer. All samples were judged to be acceptable in an emergency situation by over 75% of sensory panelists. Available thiamin was significantly lower in older samples while riboflavin remained unchanged. The results indicate that split pea quality declines over time, but the product maintains sufficient sensory acceptance to be considered for potential use in emergency storage and other applications where minimal stock rotation is a common practice.     

浓缩预处理对速食银耳羹干燥品质的影响研究

对干燥前的银耳羹进行浓缩预处理以减少速食银耳羹块的干燥时间，探究去除水分程度（10%~50%）对速食银耳羹块品质的影响，结果表明：与无预处理样品相比，当去除汤羹40%以内的水分时，速食银耳羹块的复水能力、流变特性及摩擦特性无明显差异，复原性较好，每批次的干燥时间最多可减少9.5 h。当去除汤羹中50%的水分时，初始复水时间内银耳叶片团聚较多，吸水速度慢，产品复水速率较慢，复水能力降低幅度较大。因此，通过浓缩预处理去除汤羹中40%以内的水分以减少速食银耳羹块的冷冻干燥时间。     

超高压和热处理对果蔬中 四种香气合成酶活性与结构的影响

以果蔬香气代谢过程中四种关键纯酶为原料,研究超高压和热处理对酶活性、结构及其之间相关性的影响。结果表明,脂氧合酶(LOX)、磷脂酶A2(PLA2)、酰基转移酶(AAT)活性经过不同热处理和高压处理后呈降低趋势,乙醇脱氢酶(ADH)呈上升趋势;通过SDS-PAGE电泳发现四种酶的一级结构没有发生变化,二级和三级结构均发生不同变化。LOX经过超高压处理后,α-螺旋含量降低,β-折叠含量明显增加,荧光强度均比空白组高;ADH的二级结构变化中主要是无规则卷曲增加明显,荧光强度均比空白组低。在两类处理中均发现LOX活性与α-螺旋,PLA2与荧光强度显著相关。     

蒸煮方式对鳕鱼头汤呈味特性的影响

以太平洋鳕鱼头为原料，通过测定总固形物相对含量、色泽、感官评分、氨基酸态氮质量浓度、蛋白质量浓度、呈味核苷酸质量浓度、有机酸质量浓度、风味特征（电子鼻）、滋味特征（电子舌）和挥发性物质（气相色谱-质谱）等指标，研究常压蒸煮（AP）、高压蒸煮（HP）、常压-高压蒸煮（AP-HP）、高压-常压蒸煮（HP-AP）4 种方式对鳕鱼头汤呈味特性的影响。结果表明：HP组鳕鱼头汤中的总固形物相对含量和呈味核苷酸总质量浓度显著高于其他3 组（P＜0.05），白度、氨基酸态氮质量浓度、蛋白质量浓度也高于其他3 组；AP-HP组鳕鱼头汤的感官评分、有机酸质量浓度显著高于其他3 组（P＜0.05）。电子舌测试结果显示，3 组高压蒸煮样品的鲜味值高于AP组，其他滋味无明显差异。电子鼻测试结果显示，HP组和AP-HP组气味特征相接近，但与HP-AP组和AP组有明显差异，HP组与其他3 组芳香族化合物、氮氧化合物、氨类、烷烃类、甲烷、乙醇等气味组分均有明显差异。GC-MS检测到AP、HP、AP-HP、HP-AP组样品中挥发性物质分别为27、25、28、40 种。综上，高压蒸煮可能是更适用于鳕鱼头加工鳕鱼头汤的一种方式。     

排骨莲藕汤关键加工工艺研究

以猪排骨、莲藕为原料制作排骨莲藕汤,分析不同前处理方式、料水比、加盐时间点和灭菌方式对排骨莲藕汤感官品质和营养成分的影响,并对排骨莲藕汤感官品质和营养成分的相关性进行研究。结果显示：排骨莲藕汤制汤最佳料水比为1:2(m/V),加盐时间点选在起锅时,灭菌方式为高压灭菌;不同的加工工艺对排骨莲藕汤汤中可溶性固形物含量、呈味核苷酸、可溶性糖和可溶性蛋白质含量有显著性影响(P ＜ 0.05);排骨莲藕汤的滋味与可溶性固形物和游离氨基酸含量呈正相关(P ＜ 0.05),排骨莲藕汤的综合感官品质与可溶性固形物、游离氨基酸和总可溶性糖含量呈正相关(P ＜ 0.05)。     

不同工艺制备的鱼头汤营养品质及风味特征比较研究

为了解不同工艺对鱼头汤营养品质及风味特征的影响,本试验以革胡子鲶鱼鱼头的骨肉泥为原料,分别采用普通熬煮（Ordinary boil, OB）、超声辅助普通熬煮（Ultrasound-assisted ordinary boil, U-OB）、酶解（Enzymatic hydrolysis, Eh）和超声辅助酶解（Ultrasound-assisted enzymatic hydrolysis, U-Eh）四种工艺制备出四组鱼头汤,并进行营养成分、GC-MS、GC-IMS和电子鼻的分析。结果表明:超声辅助处理组（U-OB）的水溶性蛋白含量显著高于未经超声处理组（OB）;Eh和U-Eh中的钙、硒含量高于OB和U-OB;Eh和U-Eh的氨基酸含量远高于OB和U-OB,但苦味氨基酸含量高于鲜味和甜味氨基酸,鱼头汤中还检测出牛磺酸、肌肽等物质;电子鼻结果显示四种鱼头汤气味区分明显,没有出现重叠现象,U-Eh滋味轮廓与其他三个样品距离较远,风味较为丰富;GC-IMS技术共定性出33种物质,主要为醛类和酮类,OB与U-OB之间和Eh与U-Eh之间比较,它们的挥发性有机物（VOCs）种类相似,但含量差异较大;四组样品之间共性的VOCs只有壬醛（二聚体）、2-庚酮和壬醛（单体）,均对鱼头汤的风味有较好的修饰作用。     

A HYGIENIC MILK SUPPLY

The importance of hygiene at all stages of producing and processing milk is discussed. The value of the resazurin test to measure the cleanliness of production is questioned. With modern methods of milk production and storage the only meaningful test is the plate count, but it should be accompanied by frequent farm inspections. Pasteurized milk should have a negative coliform result (in 0.1 ml) and retail outlets should have adequate refrigeration.     

超高压结合酶法消减南美白对虾虾肉中的过敏原

以虾肉为原料,研究超高压对酶法消减南美白对虾虾肉过敏原的强化作用。将南美白对虾去头、去尾、去壳、去肠线后用匀浆机匀浆,制成虾肉酱,分别采用超高压法、超高压处理后再用木瓜蛋白酶水解、超高压条件下直接酶解的方法消减其过敏原,用间接酶联免疫吸附法检测过敏原消减效果,确定消减过敏原的条件。结果表明：采用超高压法处理,其最佳条件为：压力200Mpa、温度40℃、保压时间35min,此条件下产物与抗体反应的OD492nm值为0.1986;先超高压处理再用木瓜蛋白酶水解,其水解的最佳条件为：底物质量浓度10g/100mL、温度60℃、酶与底物质量比1:200,此条件下产物与抗体反应的OD492nm值为0.0487;超高压条件下直接用木瓜蛋白酶处理,其最佳条件为：压力300Mpa、温度40℃、保压时间35min,产物与抗体反应的OD492nm值为0.0516。由此可见,超高压处理对南美白对虾过敏原有消减作用,先超高压处理再用木瓜蛋白酶水解和超高压条件下直接酶处理对过敏原的消减效果更好。     

Simplified resazurin rennet test for diagnosis of mastitis.

A simplified resazurin rennet test for diagnosis of bovine mastitis was devised. A tablet of resazurin and rennet was placed in a sterile test tube to which 10 ml of milk were added directly from a teat. The test tube was incubated for 1 h at 37 C. After incubation the change in color of resazurin and the time required for coagulation by the rennet were observed. From the results the milk samples tested were classified into four types. Cell count, modified California Mastitis Test, coagulase positive staphylococci, and contents of solids-not-fat, lactose, and protein differed among the four types. This method is simple and practically useful for diagnosis of bovine mastitis.     

粉末香辛料投放方式对减盐卤鸭腿品质特性的影响

研究粉末香辛料投放方式对减盐卤鸭制品品质特性的影响.以八角、桂皮、花椒、山柰、小茴香、辣椒质量比10:10:25:5:5:40的比例配制复合香辛料,按复合香辛料使用量为3％配制卤汤,以未粉碎的香辛料本体为对照,将香辛料粉碎至60～100目,分别采用装袋投入卤汤、直接投入卤汤分散、预先熬汁过滤、与卤制品定量混合拌匀4种投...     

超高压处理协同低温贮藏对卤牛肉品质的影响

为了探究不同处理技术对卤牛肉品质的影响,以卤牛肉为原料,研究4 ℃贮藏、超高压处理、超高压结合4 ℃处理后对卤牛肉品质的影响。以常温贮藏为对照组,4 ℃贮藏、超高压处理、超高压结合4 ℃为处理组,为卤牛肉新型保鲜方式提供参考。结果表明:与对照组相比,4 ℃贮藏、超高压处理、超高压结合4 ℃处理后的卤牛肉的感官评分均高于对照组。贮藏16 d后,处理组的质构、挥发性盐基氮（TVB-N）、pH、TBA等指标的变化趋势均慢于对照组,其中超高压结合4 ℃处理组TVB-N值为15.254 mg/kg,TBA值仅增大5%,菌落总数为1.78 lg CFU/g,而常温对照组第8 d已达到5.21 lg CFU/g。通过电子鼻分析,超高压结合4 ℃处理组气味未发生明显变化, 各项指标在贮藏16 d后仍接近0 d,与其他处理组相比,超高压结合4 ℃处理可以更好的延长卤牛肉的贮藏期。综合可知,超高压结合4 ℃处理组为贮藏卤牛肉的最优前处理方法。     

不同减盐配方下卤鸭和卤汤盐含量测定及变化规律分析

以鸭腿(肉鸭腿、老鸭腿)为原料,以不同KCl和NaCl组成的减盐配方卤制,采用滴定法与原子吸收法,分别测定不同减盐配方组卤鸭制品及卤汤的盐分(以氯离子计)的变化,比较两种方法所测得卤鸭制品及卤汤的盐分变化规律。结果表明:两种方法测定肉鸭制品与老鸭制品的盐分含量变化规律基本一致,盐含量随着KCl的增加而减小,老鸭卤肉、卤后卤汤中氯离子含量均略高于肉鸭卤肉及卤后卤汤。用火焰原子吸收法测定卤鸭肉和卤汤中的钠离子、钾离子的含量,结果表明,钠离子含量随着KCl的增加而降低且降低比例接近,钾离子含量随着KCl的增加而增大,卤肉中的钠、钾含量均低于卤汤中的值,约为卤后卤汤的60%、卤前卤汤的90%;氯离子含量约为卤后卤汤的60%、卤前卤汤的80%。     

蒙顶黄芽不同加工工序中色泽变化与品质相关性研究

研究不同加工工序制成的蒙顶黄芽干茶、汤色及叶底色泽,并进行色素成分检测及品质审评,分析干茶、汤色及叶底色泽L*a*b*值与各审评因子得分、色素含量、品质总分的相关性,为黄茶闷黄程度及色泽的评价提供一定的参考依据。以蒙顶黄芽加工过程中的茶样为试验材料,采用色彩色差计CR410测定干茶、汤色及叶底的L*a*b*值,再与干茶、汤色、叶底得分做显著性分析,与茶色素、叶绿素及品质总分做相关性分析。结果表明,干茶L*、a*、b*值与干茶色泽审评得分呈显著或极显著相关（P<0.05, P<0.01）,茶汤L*、a*、b*值与汤色审评得分均呈极显著相关（P<0.01）,其相关系数分别为?0.93、0.97、0.93,叶底L*、a*、b*值与叶底得分均呈极显著相关（P<0.01）,其相关系数分别为?0.96、0.97、0.98;干茶、汤色及叶底的L值与茶色素含量呈极显著负相关（P<0.01）,a*、b*值与茶色素含量呈极显著正相关（P<0.01）;干茶、汤色及叶底的L*值与叶绿素含量呈极显著正相关（P<0.01）,a*、b*值与叶绿素含量呈极显著负相关（P<0.01）。蒙顶黄芽感官品质与L*、a*、b*值及色素之间的相关性表现为:与干茶 L *值、汤色L *值、叶底L *值、叶绿素a*、叶绿素b*含量均呈极显著负相关（P<0.01）,与干茶a*b*值、汤色a*b*值、叶底 a*b*值及茶色素含量均呈显著或极显著正相关（P<0.05, P<0.01）,除干茶a*值外,相关系数均在0.80以上。本试验表明,就各审评因子及品质总分而言,采用色泽Lab值测定方法可为黄茶色泽与品质相关性研究提供一定的理论基础。     

多酚氧化酶对普洱茶渥堆发酵过程中品质变化的影响

本文探讨了添加不同浓度多酚氧化酶对渥堆发酵过程中普洱茶理化指标和感官品质的影响。实验结果表明:经不同浓度多酚氧化酶处理后的普洱茶,其部分品质成分在渥堆发酵过程中的变化差异显著(p0.01),与对照组相比,实验组的渥堆平均温度相对较高,茶多酚、儿茶素指标变化速度加快,且与多酚氧化酶的添加量呈负相关;茶黄素发酵前期生成速度加快,后期转化速度提高;茶褐素有较快积累。加入多酚氧化酶的普洱茶发酵18d后,在外形、汤色、滋味、香气、叶底等感官品质上基本具有熟茶的品质,其中1.6U/g、3.2U/g多酚氧化酶组可达到陈年普洱汤色红浓明亮,滋味醇厚回甘,香气浓郁的品质特点。本研究为缩短发酵周期,改善普洱茶品质提供新的思路和方法。