Contribution of Free and Glycosidically Bound Volatile Compounds to the Aroma of Muscadine Grape Juice

Free and glycosidically bound volatile compounds were isolated and identified from muscadine grape juice. Most abundant in free and bound form was the muscadine character-impact aroma compound 2,5-dimethyl-4-hydroxy-3(2H)-furanone (Furaneol). Other aroma compounds, such as o-aminoacetophenone and 2-phenylethanol were found in free and bound forms. A high level of 2-phenylethanol was intheglycosideformand many bound monoterpenes were identified. p-Vinylguaiacol, a potential off-flavor in muscadine juice was found at a low level in bound form. Enzymatic hydrolysis of glycoside precursors could lead to release of volatile compounds with both potentially positive and deleterious effects on the overall aroma.     

Factors Influencing Ellagic Acid Precipitation in Muscadine Grape Juice During Storage

Ellagic acid sedimentation in white muscadine grape juice was monitored following different processing treatments and storage temperatures. High storage temperatures (40°C) greatly accelerated sediment formation, and pasteurization (100°C, 10 min) resulted in a faster sediment formation than sterile filtration. Sediment also increased substantially after juice was hydrolyzed (121°C and pH 2 for 10 min). Ultrafiltration of juice through a 10,000 or 30,000 dalton membrane resulted in significantly less sediment formation in the juice. Treatment of juice with polyvinylpolypyrrolidone (0.1– 0.2 g/L juice), egg albumen (6–10 mg/L juice) or gelatin (0.05 – 0.4 g/L juice) resulted in a significant reduction of juice phenolics and sediment formation. A commercial pectinase added to the grapes increased sediment formation and total phenolics in the juice. Levels of ellagic acid in juice were very low and did not correlate well with amount of sediment formed.     

Stability of Non-Pasteurized, Refrigerated Muscadine Grape Juice

The stability of nonpasteurized muscadine grape juice processed with and without 100 mg/L potassium metabisulfite was monitored during storage at 3°C. The muscadine flavor intensity, sweetness, off-flavor levels, and color of white juices remained stable, and ethanol levels remained low for 7 wk. However, the flavor intensity and sweetness of nonsulfited white juice decreased, and off-flavor and ethanol levels increased after 7 wk. Sulfite lowered microbial levels in white juice throughout 9 wk. Red juices did not develop significant levels of off-flavors or ethanol during 9 wk, although the flavor intensity declined, especially in nonsulfited red juice. Sulfite lightened the color of red juice, but the color was stable in both sulfited and nonsulfited red juices.     

酶解处理对葡萄汁芳香物回收工艺的影响

以玫瑰香葡萄为试材 ,采用NOVOferm1 2酶制剂对葡萄中键合态芳香物质进行酶解处理 ,并结合感官评定 ,研究了酶解处理对葡萄汁芳香物回收工艺的增香效果。结果表明 ,酶解处理葡萄汁芳香物回收液中葡萄典型芳香物质总含量比未酶解处理葡萄汁芳香物回收液增长了 30 2 1 4μg/L ;感官分析表明 ,酶解处理对葡萄汁芳香物质回收工艺具有明显的增香调控作用     

Identification of Natural Antimicrobial Substances in Red Muscadine Juice against Cronobacter sakazakii

ABSTRACT: Red muscadine (Vitis rotundifolia Michx.) juices with natural organic, phenolic acids and polyphenol compounds were tested against Cronobacter sakazakii. The concentration of total phenolic compounds of commercial baby juices ranged from 176.7 to 347.7 mg/mL. Commercial baby juices showed poor antimicrobial activity, reducing less than 1-log of C. sakazakii in juice samples for 2 h at 37 °C. Red muscadine juices, regardless of processing methods (filtration, pasteurization, and sterilization), achieved a 6-log reduction of C. sakazakii in the same time period (2 h). The mixture of synthetic organic acids (malic and tartaric acids) and polyphenolic acid (tannic acid) showed strong antimicrobial activity against C. sakazakii. Among synthetic organic acids, tannic acid was undetected in commercial baby juices. Tannic acid showed the highest antimicrobial activity (1.4- to 3.8-log reduction) against C. sakazakii, while malic and tartaric acids showed less than 0.5-log reduction. These results suggest that red muscadine juice could be utilized as a natural antimicrobial in baby food formulations to inhibit C. sakazakii.     

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)。     

低温对赤霞珠葡萄香气和单体酚含量的影响

目的:通过不同低温处理赤霞珠葡萄,研究果皮内主要功能性物质如香气成分及单体酚的溶出程度,旨在探究提高葡萄酒品质的低温处理方案。方法:对葡萄果粒分别进行4、-8、-20℃和-32℃低温处理,16℃为对照组,采用气相色谱-质谱和高效液相色谱对葡萄皮和葡萄汁处理前后的香气成分和单体酚含量进行分析。结果:赤霞珠葡萄果皮和果肉中检测出共有香气成分34种,-8、-20℃和-32℃能够在不同程度上增加葡萄汁中香气总量及酯类、醇类、酸类含量,减小其在葡萄皮中的含量;4℃处理不能增加葡萄汁中的香气成分,反而能使葡萄皮中香气成分增加;共检测出18种单体酚,低温及冷冻处理能在不同程度上减少果皮中单体酚类物质含量,增加葡萄汁中的含量,但是温度与作用效果之间没有明显的变化趋势。结论:低温冷冻处理能够增加酯类、酸类和醇类等香气成分及多种酚类物质在葡萄汁中的含量,降低葡萄皮中的含量。     

石榴汁糖苷键合态香气前体物质的初步研究

本文运用紫外可见光谱初步确定石榴汁糖苷键合态香气前体物质的特征吸收峰;利用高效液相色谱法和气相色谱-质谱联用法测定石榴汁酶解前后的糖基部分和配体部分,通过石榴汁酶解前后理化指标的测定来分析石榴汁中糖苷键合态香气前体物质。研究表明:紫外可见光谱分析得到糖苷键合态香气前体物质的特征吸收峰;理化指标测定中发现石榴汁酶解液TSS和还原糖含量增加较明显;HPLC检测到石榴汁中糖苷键合态香气前体物质的糖基主要以葡萄糖和果糖为主;GC-MS分析在酶解后的石榴汁中共检测出36种挥发性芳香化合物,其中石榴汁键合态物质有芳香醇类、萜烯类和醛类等,主要以正己醇、叶醇、四氢芳樟醇和苯乙醇等芳香醇类物质为主。本实验结果为进一步阐明石榴汁中糖苷键合态香气前体物质的结构提供依据。     

蜜柑鲜汁与巴氏灭菌汁香气成分比较研究

采用顶空-固相微萃取法提取蜜柑鲜果汁与巴氏灭菌果汁的香气成分,用气相色谱-质谱进行分离鉴定,应用色谱峰面积归一化法测定各成分的相对含量。实验结果显示:鲜果汁与巴氏灭菌果汁分别鉴定出78和79个香气成分。蜜柑鲜汁中的主要香气成分是D-柠檬烯(69.82%)、芳樟醇(3.35%)、γ-松油烯(1.61%)、4-松油醇(1.01%)和α-松油醇(0.81%)等;灭菌后的蜜柑汁中的主要香气成分为D-柠檬烯(58.20%)、α-松油醇(8.02%)、γ-松油烯(1.65%)、4-蒈烯(1.29%)、β-松油醇(1.11%)。灭菌后,果汁原有的愉悦的香气成分如丁酸乙酯未检出;α-松油醇、癸醛的含量增加使果汁风味变劣;产生的二甲基硫醚、糠醛、p-乙烯基愈疮木酚也影响果汁品质。     

Impact of Harvesting and Processing Conditions on Green Leaf Volatile Development and Phenolics in Concord Grape Juice

ABSTRACT: The disruption of plant cell walls during fruit juice processing results in the enzymatic formation of herbaceous-smelling green leaf volatiles (GLVs). Our objective was to assess the impact of thermal processing conditions on resulting levels of GLVs (hexanal, trans-2-hexenal, hexanol, cis-3-hexenol, and trans-2-hexenol), total phenols, monomeric anthocyanins, and percent polymeric color in Concord grape juice. The effects of fruit maturity and stage of juice processing on juice GLV content was also assessed. Of the GLVs studied, only trans-2-hexenal routinely exceeded its published sensory threshold in finished juice. We observed an inverse linear correlation between berry maturity (total soluble solids) and trans-2-hexenal levels in finished juice (P < 0.05, R ²= 0.91). Trans-2-hexenal was at a maximum immediately following crushing (569 μg/kg, >30-fold over detection threshold [DT]), decreased to 100 μg/kg following depectinization, pressing, and pasteurization, and to 32 μg/kg following cold-stabilization. The loss of trans-2-hexenal could be explained primarily by its reduction to trans-2-hexenol, which increased from 53 μg/kg after crushing to 500 μg/kg after cold-stabilization. High temperature pretreatment of must immediately following crushing (“hot break”) resulted in 5- to 6-fold higher concentrations of trans-2-hexenal in the final bottled juice as compared to conventional hot press. Contrary to expectations, no significant increase in phenolics and anthocyanins were observed in hot break conditions. These results indicate that hot break procedures may thermally inactivate enzymes responsible for transforming trans-2-hexenal under normal processing conditions and potentially alter the flavor qualities of the finished Concord juice. Different equivalent pasteurization regimes (82 to 93 °C) prior to bottling had no significant effect on GLV content of the finished Concord juices (P > 0.05). Practical Application: Introducing new processing techniques to fruit juice production can potentially result in undesirable changes to organoleptic properties. We have observed significantly higher levels of trans-2-hexenal, a potent herbaceous off-flavor, in Concord grape juice prepared with an initial high temperature heat treatment (“hot break”). Concord juice producers should be cautious in using hot break processing, especially with immature fruit, as it may result in persistence of green aromas in juice.     

葡萄全汁乳酸发酵菌株筛选及其风味分析

为葡萄全汁乳酸发酵饮料研制提供优良菌株资源.以“桂葡1号”葡萄果汁为原料,以耐酸性及风味评价为指标,筛选葡萄果汁乳酸发酵的优良菌株,研究优选菌的单菌及复配发酵对果汁风味物质的影响.植物乳杆菌R23及副干酪乳杆菌R37能耐受pH值3.0高酸,其发酵香与葡萄果香协调;两菌复配生长是共生型,其发酵风味比单菌更饱满丰富;乳酸发...     

葡萄汁过量氧化研究进展

葡萄汁过量氧化是白葡萄酒酿造中的一项新技术，并逐渐引起了酿酒师的广泛重视。探讨了葡萄酒中类黄酮及其褐变机理；论述了过量氧化在实际应用中所涉及的工艺措施，如氧气供给数量、供给方式、分析控制以及SO2的添加等；讨论了过量氧化对葡萄酒微生物及其品质，如风味、色度及其香气等方面的影响；同时阐述了过量氧化存在的一些问题及其应用前景。     

固相微萃取结合GC-O分析两种葡萄柚汁香气成分

固相微萃取(solid phase microextraction,SPME)-气质联用(gas chromatography-mass spectrometry,GC-MS)对白葡萄柚和红葡萄柚汁的挥发性成分进行分析,分别检测出45种和41种挥发性成分,相对含量分别为84.43%和89.16%。通过气相色谱质谱联用-嗅觉检测法(gas chromatography-olfactometry,GC-O)分析发现两种葡萄柚汁中呈现气味的化合物分别有20种和21种,白葡萄柚中香气较强的组分是3-羟基-丁酸乙酯,乙酸香叶酯和RI=1006(水果香、清香、松油),红葡萄柚中有较强气味的是2-甲基丙酸乙酯、2-甲基丁酸乙酯、反式-2-己烯-1-醇、庚醛、1-辛烯-3-醇、α-松油烯、3-羟基己酸乙酯、香芹酮和3种未知化合物(RI=971、1156、1390)。气味轮廓分析发现白葡萄柚以果香为主,红葡萄柚以木头/树叶味为主。     

树莓汁中键合态香气物质提取方法及糖基组成的研究

本文采用Amberlite XAD-2树脂吸附洗脱分离的方法和甲醇直接提取法对树莓汁中的键合态香气物质进行了分离,对得到的键合态香气物质进行了酶水解释放,采用GC-MS分析方法对水解得到的键合态香气物质进行了分析鉴定,重点比较了这两种方法的提取效果,并对酶水解后的糖基部分进行了分析研究。结果显示,甲醇直接提取法只提取得到4种键合态香气物质,总含量为77.1μg/kg,包括2种苯系物和2种脂肪醇类物质;Amberlite XAD-2树脂吸附洗脱提取法共提取得到20种键合态香气物质,包括11种苯系物,6种醇类物质及3种萜烯类物质,总含量达3042μg/L。两种方法提取得到的键合态香气物质在种类和含量上存在很大的差异,Amberlite XAD-2树脂吸附提取法提取得到的键合态香气物质种类丰富。树莓汁中糖苷键合态香气物质的糖基部分含有甘露糖和葡萄糖两种单糖。     

巨峰葡萄浓缩汁快速酿造葡萄酒工艺

研究利用巨峰葡萄的浓缩汁酿制葡萄酒.结果表明,果胶酶酶用量0.1mL/kg,酶解温度55℃,酶解时间40min,为提高葡萄出汁率的最佳条件.所酿制的葡萄酒的理化指标符合国家标准,其有机酸的含量与传统工艺基本相同,保持了葡萄酒的口味和保健功能.     

应用HS-SPME技术分析葡萄果皮与果肉挥发性香气物质

采用顶空固相微萃取(HS-SPME)和气质联用法(GC-MS)快速测定葡萄中的挥发性香气成分,定量分析了蛇龙珠、品丽珠、赤霞珠和梅鹿辄4种葡萄果皮与果肉中的香气成分。在4种葡萄中,果皮中的化合物总量高于果肉,含有较多的酯类、芳香族化合物、挥发性有机酸和挥发酚,这些化合物在果皮中的含量是果肉中的1.58～20.54倍。不同的风味化合物在葡萄果皮与果肉中含量差别较大,其中有19种化合物在果皮中含量较多,茴香脑、(S)-3-乙基-4-甲基戊醇、萘在4种葡萄皮中含量远高于果肉。不同品种葡萄果皮中,高含量化合物是不同的,主要风味成分浓度也是不一样的。     

葡萄胡萝卜复合果蔬汁饮料的研制

选用葡萄、胡萝卜为主要原料,研制复合果蔬汁饮料,进行了配方工艺优化研究。通过正交试验确定了葡萄胡萝卜复合果蔬汁的最佳配方为：砂糖10％,葡萄胡萝卜混合汁20％,柠檬酸0．1％。使用混合稳定剂,参数为黄原胶0．4g／L、羧甲基纤维素0．6g／L、海藻酸钠0．8g／L,稳定效果较好。     

基于GC-MS和香韵法分析阳光玫瑰葡萄贮藏过程香气特征变化

探索温度对贮藏期阳光玫瑰葡萄香气特征变化的影响,采用顶空固相微萃取气相色谱质谱联用（Headspace-Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry,HS-SPME-GC-MS）对4个贮藏温度（0、4、10与15 ℃）下葡萄果实挥发性成分定性定量,通过香气活性值（Odor Activity Value,OAV）、香气轮廓及香韵分析法对特征物质及香气特征鉴定分析。GC-MS共鉴定出55种挥发性成分,包括醛20种,醇6种、酯6种、萜烯16种及其他7种,其中16种物质被鉴定为活性香气成分（OAV>1）,特征香气物质为萜烯及醛类。冰温（0、4 ℃）与低温（10、15 ℃）贮藏条件下葡萄果实特征香气轮廓变化分别趋于一致,贮藏过程特征香气变化差异主要为花香类,特别是铃、茉、兰、玫与鸳香韵。0 ℃贮藏更能保持葡萄新鲜果香,但花香特征损失明显;4 ℃与10 ℃贮藏8周后特征香气发生劣变,15 ℃贮藏6周后特征香气发生劣变。综上所述,冰温贮藏初期极易引起花香特征的减损,低温贮藏则不能在较长贮藏期内维持果实的特征香气品质。     

Use of Rectified Grape Juice in Yogurt Edulcoration

ABSTRACT: Plain yogurt was prepared by adding 5 or 10% rectified grape juice (RGJ) or 3% sucrose to concentrated milk. Influence of the sweeteners addition on fermentation, and on syneresis, rheological, and sensorial properties after 14 d of storage was analyzed. Addition of a 10% RGJ increased the fermentation and reduced the lactic acid production; however after 14 d of storage the pH and L-lactic production were similar to the control. Syneresis was not affected by sweeteners addition. The storage modulus (G') andloss modulus (G") were slightly different from the control in samples added to a 5 or 10% RGJ. The panelists found that yogurt added to a 10% RGJ was significantly ( P < 0.001) sweeter than the control and also significantly ( P < 0.001) sweeter than those added to a 3% of sucrose.