巴氏灭菌对南香果汁香气成分的影响

采用顶空-固相微萃取法提取南香鲜果汁与巴氏灭菌果汁的香气成分,用气相色谱-质谱进行定性定量分析。试验结果表明：鲜果汁与巴氏灭菌果汁分别鉴定出62和28种香气成分。南香鲜汁中的主要香气成分是己醛、2-辛醇、D-柠檬烯、（4R）-3,4-开环-5α-胆甾炕-3-酸4-羟基-4-甲基-ε-内酯等;灭菌后的南香汁中的主要香气成分为D-柠檬烯和己醛等;灭菌后果汁原有的愉悦的香气成分如内酯物质未检出;2-甲基-6-（2-丙烯基）-吡嗪的出现使果汁呈现烘烤香味,癸酮则使果汁风味变劣。     

巴氏灭菌对不同品种菠萝蜜汁挥发性香气成分的影响

巴氏灭菌是果汁加工中常用的灭菌手段,为探究巴氏灭菌对菠萝蜜汁香气成分的影响程度,采用顶空固相微萃取结合气相色谱质谱联用技术分析6 个不同品种菠萝蜜汁巴氏灭菌前后的香气成分,并采用聚类分析方法,结合香气成分相对含量对菠萝蜜汁巴氏灭菌前后香气成分进行分类。结果表明：巴氏灭菌前后6 个品种菠萝蜜汁分别鉴定出58 种和55 种化合物。 巴氏灭菌后减少的香气组分是乙酸乙酯、乙酸丙酯、异戊醇、乙酸叶醇酯、乙酸庚酯、乙酸癸酯、2,4-十二碳二烯醛、1,9-十二碳二烯醛和反油酸乙酯;增加的香气组分为丁酸丙酯、己酸乙酯、异戊酸己酯、2-甲基丁基己酸酯、α-香柑油烯、苯甲酸-2-甲基丁酯、十六碳烯酸乙酯和亚麻酸乙酯。聚类分析结果表明：马来西亚1号果汁（m1）,马来西亚3号果汁（m3）和马来西亚5号果汁（m5）香气成分受巴氏灭菌影响较小;马来西亚2号果汁（m2）,马来西亚4号果汁（m4）和马来西亚6号果汁（m6）香气成分受巴氏灭菌影响较大,尤其是m6和m4。     

粮食香气成分分析方法的研究

用顶空-固相微萃取法和同时蒸馏萃取法研究了酒用粮食中的挥发性香气成分,采用不同极性和不同膜厚的萃取头进行顶空固相微萃取,使用二氯甲烷、乙醚等作为有机溶剂进行同时蒸馏,用GC/MS对萃取成分进行定性检测。结果表明,顶空-固相微萃取法宜采用中等极性和中等膜厚的萃取头,同时蒸馏萃取法用二氯甲烷作为有机溶剂较合适,两种方法结合可以更全面地测定粮食的香气成分。     

巴氏灭菌前后沃尔卡姆柠檬汁挥发性成分的分析比较

为探究巴氏灭菌对新鲜沃尔卡姆柠檬汁香气的影响,采用顶空固相微萃取-气相色谱-质谱联用法（HS-SPME-GC-MS）分析巴氏灭菌前后新鲜柠檬汁的挥发性成分。结果表明,巴氏灭菌前后的柠檬汁中分别共鉴定出86种和94种挥发性成分,主要挥发性风味物质的种类及其相对含量均有不同。巴氏灭菌后,醇类、酯类化合物相对含量分别增加了9.15%和0.86%,而烷烯类、醛酮类物质相对含量分别下降了10.77%、0.40%。巴氏灭菌后原有的挥发性成分有所变化,同时也生成了新的物质,但是柠檬汁中柠檬烯、萜品油烯、β-蒎烯、α-松油醇、4-萜烯醇、月桂烯、香茅醇、1-β-红没药烯等主体挥发性成分没有发生明显变化。     

基于SPME-GC-MS与PCA的不同萃取头萃取刺梨汁香气成分效果比较

为提高刺梨汁香气成分气相色谱分析的准确可靠性,比较不同纤维涂层萃取头萃取刺梨汁香气成分的效果及灵敏度。采用50/30μm DVB/CAR/PDMS、75μm CAR/PDMS、65μm PDMS/DVB、100μm PDMS 4种萃取头进行刺梨汁香气成分的富集和浓缩处理,气质联用仪检测其香气成分,通过主成分分析法,对其香气成分的数量、含量进行比较,建立香气品质评价模型。结果表明,刺梨汁香气成分以酯类、醇类、萜烯类为主,不同萃取头萃取的化合物存在明显差异,50/30μm DVB/CAR/PDMS萃取化合物59种,相对含量最多为93.96%,其中酯类、醇类呈香物质含量最高;65μm PDMS/DVB萃取出38种化合物,相对含量为91.19%;100μm PDMS萃取出29种化合物,相对含量92.79%;75μm CAR/PDMS萃取出26种化合物,相对含量92.08%。在4种纤维涂层萃取头中,以50/30μm DVB/CAR/PDMS为富集刺梨汁香气成分的最佳萃取纤维。     

柑橘酒酿造过程香气成分变化的研究

通过固相微萃取结合GC-MS技术分析柑橘汁与柑橘酒的香气成分及其变化趋势。结果表明,柑橘汁的香气物质主要是烯类和酯类;随着酿造过程的进行,烯类物质逐渐减少,到了发酵后期,烯类物质几乎消失;酯类物质随着酿造的进行呈逐步上升变化趋势,醇类是先上升后下降,然后持平趋势;酚类、酮类、醛类含量都较少,而且在发酵、贮存过程中没有大变化。     

不同方法提取费约果叶片香气成分的比较研究

分别采用索氏抽提法、超声波辅助溶剂萃取法和顶空固相微萃取法对费约果叶片中所含香气成分进行提取,经GC-MS进行分析,结合谱库检索技术,采用峰面积归一化法进行定性和定量分析。结果表明,索氏抽提法所得香气物质中鉴定出挥发性成分20种,占总挥发性成分的70.357%,且以烷烃为主,超声波辅助溶剂萃取法所得香气物质中鉴定出挥发性成分17种,占总挥发性成分的65.222%,且以酯类为主,顶空固相微萃取法所得香气物质中鉴定出挥发性成分最多,有42种,占总挥发性成分的76.899%,且以萜烯类为主。由此可见,在费约果叶片香气成分分析中顶空固相微萃取法能得到最多的香气组分,索氏抽提法次之,超声波辅助溶剂萃取法得到的香气物质最少。      

气质联用结合多元分析法比较甜橙汁与宽皮柑橘汁的香气成分差异

比较宽皮柑橘汁和甜橙汁中香气物质的差异性,为宽皮柑橘制汁加工提供数据基础。榨取常见甜橙和宽皮柑橘各8个品种的果汁,通过顶空固相微萃取-气相色谱-质谱对柑橘汁样品中香气成分进行定性和定量,采用香气活度值(odor active value,OAV)计算特征香气,并利用主成分分析进行比较和区分。结果表明,16种柑橘汁中共检出77种香气成分,其中甜橙汁特有香气物质有14种,宽皮柑橘汁特有香气物质有7种。通过计算得到47种OAV> 1的特征香气成分,其中芳樟醇、正己醛、壬醛对两类柑橘汁的主体香气贡献极大。选取31种香气物质进行主成分分析,两类柑橘汁均可被明显区分开。研究表明两类柑橘汁中萜类化合物的种类和含量均最多,但甜橙汁中的酯类和醇类化合物的种类和含量远高于宽皮柑橘汁。     

青砖茶的香气成分分析

采用感官审评法和顶空固相微萃取法结合气相色谱-质谱联用技术,对16个典型青砖茶样品挥发性成分进行分析鉴定。结果表明,青砖茶的香气以陈香纯正为优,有菌香和木香,分析鉴定出72种香气成分,相对含量较高的成分有己醛、芳樟醇、壬醛和甲苯,醛类和酮类为主导香气化合物;相关性分析显示(E,E)-2,4-庚二烯醛、(Z)-氧化芳樟醇、樟脑、1-甲基萘和长叶环烯与香气品质得分的相关性达到极显著水平(P0.01),(E)-2-己烯醛、1-甲氧基-4-甲基苯、(E)-2-壬烯醛、2,2,6-三甲基环己烷酮及脂肪醛中的烯醛占醛类的比例与香气品质得分的相关性达到显著水平(P0.05);主成分分析显示前6个主成分方差累计贡献率达到82.250%,主要代表性成分为β-环柠檬醛、β-紫罗酮、β-二氢紫罗酮、己醛、(E)-2-戊烯醛、(E)-2-己烯醛、庚醛、壬醛、癸醛、萘、1-甲基萘、柠檬烯和6-甲基-5-庚烯-2-酮等,它们是影响青砖茶香气品质的关键香气成分,可基本反映青砖茶的香气特征。     

5种黑茶香气成分的比较分析

本研究采用感官审评法和顶空固相微萃取法,结合气相色谱-质谱仪联用技术,对5种黑茶样品挥发性成分进行了分析鉴定。结果表明,5种黑茶共检出83种香气化合物,共有成分30种,主要包括醇类、醛类、酮类、芳香烃类、烯类和酯类等;不同产区黑茶香气特征及组成存在明显差异:青砖茶陈香纯正,以醛类和酮类化合物为主,包括(E,E)-2,4-庚二烯醛、β-紫罗酮、己醛;茯砖茶\     

Pasteurization of Fresh Orange Juice Using Low-Energy Pulsed Electrical Field

ABSTRACT: Using the hurdle approach, temperature, acidity, and number of pulses were varied to maximize microbial inactivation in orange juice. The effect of PEF combined with the addition of nisin, lysozyme, or a combination of both to orange juice was also investigated. Optimal conditions consisting of 20 pulses of an electric field of 80 kV/ cm, at pH 3.5, and a temperature of 44 °C with 100 U nisin/ml resulted in over a 6-log cycle reduction in the microbial population. The process was most influenced by a change in temperature (p < 0.0001). Following treatment, there was a 97.5% retention of vitamin C, along with a 92.7% reduction in pectinmethylesterase activity. The microbial shelf-life of the orange juice was also improved and determined to be at least 28 d when stored at 4 °C without aseptic packaging. Gas chromatography revealed no significant differences in aroma compounds before and after pulsing.     

Absorption of Aroma Volatiles of Orange Juice into Laminated Carton Packages Did Not Affect Sensory Quality

Orange juice was stored in glass bottles and polyethylene/barrier material laminated cartons at 4°C for 24 wk. Studies were carried out on the absorption of 19 orange juice aroma compounds (e.g ethyl butyr-ate, d-limonene) into low density polyethylene (LDPE). Sensory evaluations were performed on the same orange juice in different packages over the storage period. A reduction of d-limonene of up to 50% by absorption into the LDPE inside coating was observed. However, an experienced sensory panel did not distinguish between orange juice stored in glass bottles and polyethylene laminated cartons.     

Microbial, Enzymatic, and Chemical Changes During Storage of Fresh and Processed Orange Juice

Microbial, enzymatic, and chemical comparisons were made on orange juice stored at 4°C without pasteurization, with light pasteurization (66°C, 10 sec) directed at vegetative microorganisms, and with full pasteurization (90°C, 60 sec) directed at the heat stable isozyme of pectinesterase. Effects of oxygen-barrier and nonbarrier packaging were also examined. Oxygen-barrier packaging did not benefit unpasteurized juice. However, lightly and fully pasteurized juices in barrier cartons exhibited lower microbial counts, greater ascorbic acid retention, and apparent slowing of cloud loss by the third week of storage. During the first 22 days storage, microbial, cloud, sugar, and ascorbic acid values for lightly pasteurized juice were similar to those of juice receiving full pasteurization.     

固相微萃取-气质联用分析塔罗科血橙汁香气成分

采用顶空固相微萃取对塔罗科血橙汁的香气成分进行提取,用气相色谱-质谱对香气化合物进行分析,结合谱库检索技术和保留指数对化合物进行鉴定,应用峰面积归一化法测定各成分的相对含量,共鉴定出39种香气成分,相对总量为87.23%。主要香气成分为烃类(55.13%),酯类(13.67%)、醇类(13.17%)、醛类(4.59%),还有2种酮类(0.67%)。其中相对含量最高的是柠檬烯(50.40%),其次是丁酸乙酯(7.67%)、乙醇(5.38%)、3-羟基己酸乙酯(3.92%)、己醛(3.73%)、芳樟醇(3.32%)、β-月桂烯(1.87%)、α-松油醇(1.50%)、巴伦西亚桔烯(1.50%)、己酸乙酯(1.07%)。     

Pasteurization of Fresh Orange Juice Using Gamma Irradiation: Microbiological, Flavor, and Sensory Analyses

Recent concern about the presence of disease‐causing bacteria in unpasteurized juice has highlighted the need to develop alternative means of pathogen control that preserve sensory properties and nutrient content. The objectives of this study were to determine the effects of different doses of gamma irradiation on reducing the microbial pathogens L. monocytogenes and Salmonella enterica in fresh orange juice, and to determine whether significant reduction could be achieved without compromising sensory qualities. While irradiation was effective in destroying pathogens, the development of off flavors precludes its use as an alternative processing technology.     

Flavor Losses in Orange Juice during Ultrafiltration and Subsequent Evaporation

Losses of volatile compounds in orange juice during ultrafiltration and subsequent evaporation were studied. Alcohols and esters predominated in the permeate, while terpenes (d-limonene and valencene) and nonpolar aldehydes (octanal and decanal) were distributed in the retentate from the ultrafiltration (UF) system. Fractions of some flavor compounds were lost during ultrafiltration process. An aqueous phase essence was recovered from the permeate during evaporative concentration. No oil phase was observed. When whole juice was concentrated, both oil and aqueous phases were recovered. Essence recovery efficiency of individual compounds was 3 to 13% when concentrating permeate and <5% when concentrating whole juice.     

固相微萃取-气相色谱-质谱联用法分析荔枝汁贮藏过程中香气成分的变化

以荔枝果汁为研究对象,研究其在贮藏过程中香气成分的变化,旨在为荔枝汁生产和品质控制提供理论依据。采用SPME/GC-MS法分别对4℃和25℃贮藏的荔枝汁于贮藏4、5、6、7、8周后进行香气成分检测。结果表明：荔枝汁中香气成分总量在4℃和25℃贮藏4周后分别比贮藏前增长39.10%及31.99%。贮藏5周后呈显著下降趋势(P＜0.05),贮藏8周后香气保留率分别为96.17%及74.49%。其中醇类、酸类香气成分均在贮藏4周时含量最高,此后随着贮藏时间延长含量呈缓慢下降趋势;酯类物质在冷藏6周后达到最高,之后出现显著降低趋势(P＜0.05);烯类香气成分随着贮藏时间的延长逐渐减少,呈现显著下降趋势(P＜0.05);醛类香气成分含量在贮藏4周时变化不大,在4℃和25℃贮藏8周后保留率分别为59.86%和55.3%。荔枝汁中几种典型的香气成分如香叶醇、香茅醇、苯乙醇,β-月桂烯,D-柠檬烯,香叶醛的含量也是在贮藏4周达最大,此后逐渐降低。通过对4℃冷藏和25℃常温贮藏的荔枝汁主要香气类型及典型香气成分的比较分析表明,4℃冷藏后香气总量和绝大多数典型香气成分的含量显著高于同期常温贮藏(P＜0.05)。     

Effect on Orange Juice of Batch Pasteurization in an Improved Pilot-Scale Microwave Oven

ABSTRACT:  The effects on orange juice batch pasteurization in an improved pilot-scale microwave (MW) oven was evaluated by monitoring pectin methyl-esterase (PME) activity, color, carotenoid compounds and vitamin C content. Trials were performed on stirred orange juice heated at different temperatures (60, 70, 75, and 85 °C) during batch process. MW pilot plant allowed real-time temperature control of samples using proportional integrative derivative (PID) techniques based on the infrared thermography temperature read-out. The inactivation of heat sensitive fraction of PME, that verifies orange juice pasteurization, showed a  z -value of 22.1 °C. Carotenoid content, responsible for sensorial and nutritional quality in fresh juices, decreased by about 13% after MW pasteurization at 70 °C for 1 min. Total of 7 carotenoid compounds were quantified during MW heating: zeaxanthin and β-carotene content decreased by about 26%, while no differences ( P  < 0.05) were found for β-cryptoxanthin in the same trial. A slight decrease in vitamin C content was monitored after MW heating. Results showed that MW heating with a fine temperature control could result in promising stabilization treatments.     

Identification of Predominant Aroma Compounds in Muscadine Grape Juice

The aroma components of muscadine (Vitis rotundifolia Michx) grape juice were analyzed by gas chromatography (GC)/mass spectrometry and GC/olfactometry (aroma extract dilution analysis). 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (furaneol), with a burnt sugar-like aroma, was the most intense aroma in the juice. Other predominant compounds included 2,3-butanedione, ethyl butanoate, ethyl 2-methylbutanoate, 2-phenylethanol, and o-aminoacetophenone. These compounds were described as buttery/cream cheese, bubble gum/fruity, green apple/fruity, rosy, and foxy, respectively. Furaneol and o-aminoacetophenone were thought to be responsible for characteristic candy and foxy-like aroma notes of muscadine grape juice. Flavor dilution chromatograms were similar for juices prepared from grapes harvested on different dates and from different locations.