Methyl Anthranilate Content of Ohio Concord Grapes

Concord grapes grown at five locations in Ohio were collected in 1982 and 1983 for analysis of methyl anthranilate (MA) in free-run and heat-extracted juice samples. The MA content of free-run juice ranged from 0.33–2.05 mg/L in 1982 and 0.14–0.91 mg/L in 1983. The MA content was higher in heat-extracted juice than in free-run juice. Heat-extracted juice contained 0.19–2.60 mg/L of MA in 1982 and 0.22–3.50 mg/L in 1983. In general, the MA content increased with maturity and was highest in grapes grown in the coolest regions.     

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.     

热烫方式对草莓内源酶与主要品质影响的研究

主要研究了不同热烫方式（100。C蒸汽热烫1rain、1．5min、2min,100。C沸水热烫1min、1．5min、2min）对草莓的钝酶效果及主要品质的影响。结果表明,草莓过氧化物酶（POD）相对多酚氧化酶（PPO）热稳定性较强,热烫时间越长酶的钝化效果越好;热烫处理后草莓的色泽更加鲜艳,而可溶性固形物、PH、可滴定酸等变化不显著（P〉0．05）;热烫造成维生素C损失（P〈o．05）,而总酚及花青素含量显著增加（P〈O．05）;热烫处理后草莓的挥发性香气成分中酯类物质种类不变,相对含量增加,典型新鲜草莓香气成分反式--2-己烯醛显著减少（P〈o．05）,蒸汽热烫1mjn及1．5rain仍能保持草莓部分反式--2--己烯醛,热烫时间太长容易造成草莓清新青草风味的减弱。     

DETERMINATION OF ORTHO-NASAL AROMA THRESHOLD FOR MULTICOLORED ASIAN LADY BEETLE IN A CONCORD GRAPE JUICE

ABSTRACT

Sensory evaluation was used to determine the aroma threshold of Harmonia axyridis (multicolored Asian lady beetle [MALB]) in Concord grape juice. Prior to Concord grape juice preparation, MALB was added to the Concord grapes at concentrations of 0 and 8.4 MALB/kg fresh grapes. To determine the odor threshold, the three alternative forced‐choice method of sample presentation was used, with an ascending concentration series of 0.5, 1.5 and 4.5 MALB/kg fresh grapes. The panel aroma threshold concentration, calculated using the best estimate threshold over two panel sessions, was 1.8 MALB/kg fresh grapes. Individual detection thresholds ranged from 0.29 to 7.79 MALB/kg fresh grapes, with 75% of the panelists having a detection threshold at or below 0.87 MALB/kg fresh grapes. These results indicate the influence of low numbers of MALB on Concord grape juice aroma, and suggest the importance of quality control programs, including the implementation of established tolerance limits, to monitor grape quality.

PRACTICAL APPLICATIONS

Harmonia axyridis, the multicolored Asian Ladybeetle (MALB), was originally introduced as a method of biocontrol. However, its presence is now becoming problematic with respect to crop quality. In order to minimize economic losses to the Concord grape industry, determination of the number of MALB required to produce a detectable change in Concord grape juice is critical for juice producers in the establishment of their quality control programs. Therefore, the objective of this study was to determine the aroma threshold level of MALB in Concord grape juice. The panel aroma threshold concentration, calculated using the best estimate threshold was 1.8 MALB/kg fresh grapes, with 75% of the panelists having a detection threshold at or below 0.87 MALB/kg fresh grapes. These results indicate the influence of low numbers of MALB on Concord grape juice aroma, and suggest the importance of quality control programs, including the implementation of established tolerance limits, to monitor grape quality.

     

Physico-chemical changes in sugarcane (Saccharum officinarum var yellow cane) and the extracted juice at different portions of the stem during development and maturation

A study was conducted to determine the physicochemical differences between portions (top, middle, and bottom) of sugarcane at different maturation stages (between 3 and 10 months from planting). The variety used was Saccharum officinarum var. Yellow cane. The parameters analysed were weight, diameter, yield, total soluble solids (TSS), pH, titratable acidity, sugar content (sucrose, glucose, fructose). The weight, diameter, total soluble solids (TSS) and sucrose content increased significantly (P<0.01) in all portions (top, middle and bottom) up to the end of maturity. On the other hand, titratable acidity (TA), pH, juice yield, glucose and fructose contents decreased significantly (P<0.01) during maturation. However, significant differences were also detected in weight, diameter, TSS, sugar content, pH, TA and juice yield between the different portions during maturation. Sucrose content, juice yield and TSS were found to be the most suitable indicators of maturity, while TA, glucose and fructose contents were found to be poor maturity indicators. A suitable harvesting stage was found to be between 7 and 8 months after planting.     

Sugars and Acid Analysis and Effect of Heating on Color Stability of Northwest Concord Grape Juice

Changes during storage in color of Concord grape juice extracted after heating to different temperatures and the carbohydrate and nonvolatile acid composition of Concord grapes were studied. Heating crushed Concord grapes under pilot plant conditions to 88° and 99°C inactivated nearly all of the polyphenoloxidase, increased the extraction of anthocyanins (ACN) and reduced polymeric color in the grape juice. During storage of the juice for 8 months, the rate of ACN degradation and color density decrease was the same in all samples. Glucose, fructose and sucrose were the only sugars found in Northwest Concord grapes, while malic and tartaric acids were the major nonvolatile acids. Lesser amounts of phosphoric, citric and coumaric acids were present.     

不同品种草莓的特征香气成分

以"宝交""大将军"和"红宝石"3个品种的草莓为试材,采用顶空固相微萃取-气相色谱质谱联用技术(GC-MS)和嗅闻技术(GC-O)、感官评价以及快速气相电子鼻对果实的香气成分进行分析。3个品种共检测到71种挥发性成分,"宝交""大将军"和"红宝石"分别有60,70和66种。酯类物质种类最多(21~26种),而醛类物质含量最多(51.37%~63.63%)。其中,丁酸甲酯、丁酸乙酯、乙醛、己酸甲酯、(E)-2-己烯醛、己酸乙酯、乙酸己酯、芳樟醇在3个样品中具有较高的含量及香气强度,为草莓的主要特征香气物质。经感官评价,"宝交"较强甜香气的来源可能是由于2-戊酮的存在;"大将军"青香和花香更强,青香可能由于它具有更高的己醛和反式-2-己烯醛含量,而花香可能来源于芳樟醇、橙花叔醇和β-紫罗兰酮。由快速气相电子鼻可以显示出3个品种草莓很好的区分度。     

HS-SPME-GC-MS法测定不同成熟度蜜柑果汁挥发性成分

本文以未成熟、充分成熟、过熟三种不同成熟度的大叶尾张蜜柑果汁为原料,采用固相微萃取法进行抽取,然后经过GC-MS联机检测果汁中挥发性风味化合物,并对风味物质进行定量分析。结果表明:不同成熟度的大叶尾张蜜柑果汁中共有37种挥发性风味成分,主要包括酯类、酮类、醛类、醇类和烃类;在未成熟、充分成熟和过熟大叶尾张蜜柑果汁中分别检出34、32、33种挥发性化合物;其中,反式-3-蒈烯-2-醇、十八烷酸丙酯、1,3,8-对-孟三烯在柑橘品种的挥发性风味物质组成中未见报道;成熟度引起的大叶尾张蜜柑果汁挥发性风味化合物种类变化较小,但是柠檬烯、γ-松油烯、α-松油醇、香芹醇、β-甜橙醛等特征性风味物质含量有明显的变化;其中,醇类、醛类、酯类挥发性化合物均为在充分成熟果中含量最高。结合对果汁的物性分析得出,充分成熟果能保持大叶尾张蜜柑的香气特征。      

Electrodialytic Removal of Nitrate from Pineapple Juice: Effect on Selected Physicochemical Properties,Amino Acids,and Aroma Components of the Juice

This study aimed at investigating the effect of nitrate removal from pineapple juice by electrodialysis (ED) on selected properties of the ED‐treated juice. Single‐strength pineapple juice with reduced pulp content was treated by ED to reduce the nitrate concentration to 15, 10, or 5 ppm. After ED, the removed pulp was added to the ED‐treated juice and its properties, including electrical conductivity, acidity, pH, total soluble solids (TSS), color, amino acids, and selected aroma compounds, were determined and compared with those of the untreated juice. ED could reduce the nitrate content of 1 L of pineapple juice from an initial value of 50 ppm to less than 5 ppm within 30 min. A significant decrease in the electrical conductivity, acidity, pH, TSS, and yellowness, but a significant increase in the lightness, of the juice was observed upon ED. Concentrations of almost all amino acids of the ED‐treated juice significantly decreased. The concentrations of 8 major compound contributors to the pineapple aroma also significantly decreased. Adding the pulp back to the ED‐treated juice increased the amino acids concentrations; however, it led to a significant decrease in the concentrations of the aroma compounds.     

Harvest parameters to optimise storage life of European plum 'Oullins Gage'

European plum ( Prunus domestica L.) cv. 'Oullins Gage' was harvested according to firmness on five harvest dates. Fruit was analysed at harvest and during storage for weight loss, firmness, total soluble solids (TSS), titratable acidity (TA) and skin colour before and after a 3-day shelf-life period at 20 °C. Significant differences were found among harvest dates in fruit mass, skin colour, firmness, TSS and TA. Fruit mass, TSS and colour b * increased, whereas firmness and TA decreased significantly during the harvesting period. Firmness parameter as a maximum maturity index and TSS:TA (or b * colour, a non-destructive measurement) as a minimum maturity index could be used to distinguish maturity at harvest. It is suggested that the best post-storage quality of 'Oullins Gage' plums would be obtained when fruit is harvested with TSS:TA >9 or b * colour >30, but with a firmness >20N to assure a long storage life.     

Impact of Multicolored Asian Lady Beetles on the Sensory Properties of Concord and Niagara Grape Juice

ABSTRACT: The presence of Multicolored Asian Lady Beetles (MALB) in grape juice is increasingly problematic. The overall objective of this study was to determine the specific sensory impacts of MALB on Concord and Niagara grape juice. The aroma threshold for MALB-taint in both juices was determined and expressed as the best estimate threshold (BET). The aroma BET for MALB-taint in Concord grape juice was 1.8 and 0.65 MALB/L Niagara grape juice. The specific sensory attributes of the grape juices influenced by the presence of MALB were then described. In Concord grape juice, trained panelists (n = 9) found significant increases in vegetal aroma and earthy flavor as MALB concentration increased from 0.45 to 7.2 MALB/L. In Niagara grape juice, with increasing MALB concentration, trained panelists (n = 8) indicated significant decreases in honey and sweetness with corresponding increases in sourness, astringency, and vegetal and earthy aromas and flavors (P < 0.05). For both aroma and flavor, consumer rejection studies were performed using paired preference comparisons of control juice to MALB-tainted grape juice. For Concord grape juice, consumers (n = 60) rejected the aroma of MALB-tainted juice at 1.8 MALB/L and the taste/flavor of the MALB-tainted juice at 3.6 MALB/L. For Niagara juice, consumers rejected the aroma of the juice at 3.6 MALB/L. This study demonstrated the presence of MALB negatively impacts the sensory properties of Concord and Niagara grape juice. Grape juice processors may use this research for quality control measures and for establishing tolerance limits. Practical Application: The Multicolored Asian Ladybeetle (MALB), initially used for biocontrol, has been shown in previous literature to impact the sensory properties of wines. The presence of MALB in grape juice is now becoming problematic; however, there is little research describing the specific sensory impacts of MALB on grape juice. This study examined the sensory impact of MALB on both Concord and Niagara grape juice. While the threshold and trained panel evaluations from this study provide valuable sensory profile information, grape juice processors may be particularly interested in the consumer rejection of MALB-tainted grape juice as they can use this research for quality control measures and for establishing tolerance limits.     

Comparing the Effects of High Hydrostatic Pressure and Ultrahigh Temperature on Quality and Shelf Life of Cloudy Ginger Juice

The effects of high hydrostatic pressure (HHP) at 500 MPa for 10 min and ultrahigh temperature (UHT) at 110 °C for 8.6 s on the quality of cloudy ginger juice (CGJ) were investigated during storage for 91 days at 4 and 25 °C. The quality aspects studied were microbial stability and selected properties, including pH, total soluble solids (TSS), titratable acidity (TA), total phenols, gingerols, antioxidant capacity, color, and aroma composition. The results showed that HHP treatment led to a 3.0 log cycle reduction of microbial load but did not influence pH, TSS, TA, antioxidant capacity, and color (day 0). Total phenol content increased by 5.31 % after HHP treatment but decreased significantly by 14.74 % after UHT treatment (day 0). Gingerols increased by 14.43 and 14.18 % after HHP and UHT treatments (day 0), respectively. Monoterpenoids, which are the main volatile aroma compounds, did not change significantly after HHP treatment but decreased significantly by 2.27 % after UHT treatment (day 0). During storage, the decreases in total phenols, gingerols, and antioxidant capacity in the UHT-treated GCJ were more noticeable than those in the HHP-treated GCJ. Kinetic data of changes in total phenols, gingerols, and antioxidant capacity fitted into the combined model well. The changes in antioxidant capacity were positively and significantly correlated to total phenols and gingerols. Color darkened and aroma faded in both HHP-treated and UHT-treated CGJs during storage. The quality changes in samples stored at 25 °C were also more noticeable than those stored at 4 °C.     

杨凌地区‘媚丽’葡萄的采收期确定

目的：通过比较杨凌地区‘媚丽’葡萄不同采收期的果实香气、葡萄酒香气和葡萄酒颜色指标,确定出该地区‘媚丽’葡萄酿造红葡萄酒的最适采收时间。方法：进入转色期后对‘媚丽’果实进行定期采样,测定其理化成熟、酚成熟和果实香气变化;选取最佳理化成熟时间和酚成熟时间采收的‘媚丽’葡萄进行酿酒实验,测定香气成分和颜色指标。结果：8月24日,细胞成熟指数为0.061,种子成熟指数为0.521,为最佳酚成熟时间,该时间采收的葡萄酿造的葡萄酒香气最丰富,共检测到41?种香气化合物,总量为471.75?mg/L,且葡萄酒颜色亮度和红色色调也最符合干红葡萄酒的要求;最佳理化成熟时间相比酚成熟晚4?d,但其葡萄酒香气和颜色指标相比8月24日都较差。结论：杨凌地区‘媚丽’葡萄在达到酚成熟时所酿造的葡萄酒香气和颜色最佳。     

Maturity criteria for litchis (lychees)

Five varieties of litchi (lychee) were harvested from five different locations over a period of two years. The fruit varied from immature to almost fully mature. It was subjected to taste testing and analysed for total soluble solids (TSS) and titratable acidity (A). TSS (°Brix) was not suitable as a maturity indicator whereas titratable acidity and the TSS/A ratio were both good predictors of taste. A titratable acidity of 4.4 cmol H⁺ kg⁻¹ juice or a TSS/A ratio of 4.3 Brix.kg juice cmol⁻¹ H⁺ would be suitable maturity indexes.     

采后催熟对‘台农一号’芒果理化品质及营养特性的影响

采用外源乙烯利对‘台农一号’芒果进行催熟，乙烯利添加量0.1(w/w)，温度30℃，湿度40%～50%。探讨不同催熟阶段对芒果理化指标（硬度、色泽、可滴定酸、可溶性固形物），营养成分（类胡萝卜素、维生素C、可溶性蛋白质、总糖）和香气成分的影响。结果表明，在催熟过程中果实硬度从19.76 N下降到0.99 N，可滴定酸从1.37%下降至0.27%，而可溶性固形物从12.92%上升至23.64%。当催熟时间从0 h增加至60 h，黄色指数值显著（P<0.05）增加，约85%以上的果皮颜色转为黄色，类胡萝卜素含量可升高至4.90μg/g，维生素C从326.66 mg/100 g下降至180.00 mg/100 g，而总糖含量显著（P<0.05）增加；继续延长催熟时间至108 h，类胡萝卜素升高至10.93μg/g；维生素C、可溶性蛋白质和总糖等变化不显著。芒果果实香气物质主要是萜烯类化合物，其中异松油烯含量最高，在催熟60 h之内其含量迅速增大，外源乙烯利加快了果实中异松油烯的合成速率。综合评价催熟后果实理化及品质特性60 h后芒果色泽、香气等指标基本达到成熟。     

高压均质对NFC水蜜桃浊汁稳定性及品质的影响

本文采用高压均质技术,探究了均质压力（20~40 MPa）及次数（1~2次）对NFC水蜜桃浊汁的混浊度、离心沉淀率、粒径、Zeta电位等稳定性指标和pH、TSS、总酸、固酸比、还原糖、色泽、总酚、V_C等品质指标的影响。结果表明:高压均质（30~40 MPa/1、20~40 MPa/2）可有效提高NFC水蜜桃浊汁的稳定性,离心沉淀率较未处理组下降13.49%~24.22%,平均颗粒粒径由1853.67 nm降至501.10~665.27 nm,绝对Zeta电位值显著提高（P<0.05）。随着均质压力及次数的增加,浊汁中可溶性果胶含量上升,而残存果胶甲基酯酶活力逐渐降低。高压均质后,浊汁色泽显著改善,L*值升高,褐变指数BI值下降（P<0.05）;30 MPa/1下,品质保持最佳,总酚、V_C含量较未处理组显著提高（P<0.05）,而pH、TSS、总酸和固酸比无变化（P>0.05）;随着均质次数增加,pH、TSS、总酚和V_C含量显著降低（P<0.05）,品质下降。高压均质处理可有效提高NFC水蜜桃浊汁稳定性、抑制褐变,并提高总酚、V_C等营养物质含量。