Characterisation of the key aroma compounds in a freshly reconstituted orange juice from concentrate

Application of an aroma extract dilution analysis on the entire volatile fraction isolated from an orange juice freshly reconstituted from concentrate revealed 40 odour-active constituents in the flavour dilution (FD) factor range of 4–2,048. Among them, ethyl butanoate and linalool showed the highest FD factor of 2,048, followed by octanal with an FD factor of 512. Thirty-six of the 40 odour-active compounds detected could be identified, all of which have previously been reported as volatile constituents of various orange juices. Quantification of 17 key odorants by stable isotope dilution assays followed by a calculation of odour activity values (OAVs) on the basis of odour thresholds in water or citrate buffer (pH 3.8), respectively, revealed the following most important odorants in the overall aroma of the freshly reconstituted juice: (R/S)-linalool, (R)-limonene and (S)-ethyl 2-methylbutanoate with the highest OAVs (>1,000) followed by octanal, (R)-α-pinene, ethyl butanoate, myrcene, acetaldehyde, decanal and (E)-β-damascenone with OAVs > 100. A model mixture containing all 14 aroma compounds with OAVs > 1 in their actual concentrations in the juice showed a good similarity with the aroma of the original orange juice under investigation, thus corroborating that the key odorants of a freshly reconstituted orange juice were characterised for the first time.     

Influence of different storage conditions on changes in the key aroma compounds of orange juice reconstituted from concentrate

Quantification of aroma compounds in an orange juice reconstituted from concentrate which had been stored at 37 °C for 4 weeks (forced storage) revealed an increase in the concentrations of, in particular, dimethyl sulphide, 2-methoxy-4-vinylphenol, α-terpineol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF) in comparison with the same orange juice before storage. On the other hand, clearly lower concentrations were found for octanal, decanal, (R)-α-pinene, linalool, and (E)-β-damascenone after storage, while the concentrations of vanillin and carvone remained nearly constant. Similar results were found for the same aroma compounds after storage of the orange juice at 20 °C for 1 year. Sensory experiments corroborated the importance of 2-methoxy-4-vinylphenol and dimethyl sulphide for the typical stale off-flavour of the stored orange juice, while the omission of e.g., α-terpineol in model mixtures could not be detected. Under both storage conditions (37 °C for 4 weeks or 20 °C for 1 year), the breakthrough odour thresholds of α-terpineol and 4-HDF were not reached, while the concentrations of dimethyl sulphide and 2-methoxy-4-vinylphenol clearly exceeded their breakthrough odour thresholds, thus confirming the crucial role of these odorants for the off-flavour of stored orange juice from concentrate. In addition, changes in the concentrations of selected orange juice odorants at various temperatures and times were investigated.     

橙汁饮料香气组分的初步分析

以橙汁饮料为研究对象,用SPME-GC-MS方法对其香气成分进行定性和定量分析,并以自制巴西橙浓缩汁勾兑饮料作对照,比较其香气成分在种类和含量上的差异,为橙汁饮料的增香调控提供理论依据。     

Effect of pulp reduction and pasteurization on the release of aroma compounds in industrial orange juice

ABSTRACT:  Release of aroma compounds in orange juice according to pulp content and pasteurization was performed by headspace-solid phase microextraction (HS-SPME), HS-SPME-GC-olfactometry, and by the determination of partition coefficients of aroma compounds between the juice and the headspace. Orange juices with 12% and 6% pulp contents were collected from a processing line before and after pasteurization. HS-SPME revealed that the 6% pulp juice was the most affected by pasteurization, with an increase in the release of several aroma compounds that are generated by heat treatment (that is, α- and β-terpinéol) and a decrease in the release of compounds sensitive to pasteurization (that is, neral and geranial). Principal component analysis of olfactometric data allowed discriminating fresh and pasteurized juices, regardless of the pulp content. The determination of the gas/liquid partition coefficients by the phase ratio variation method was possible for 7 aroma compounds. For the most hydrophobic ones, the release of aroma compounds in fresh juices was higher in the 6% pulp juice than in the 12% pulp juice. However, in pasteurized juices, the difference between their partition coefficients was less marked. Potential interactions between cloud proteins and hydrophobic aroma compounds may explain this phenomenon.     

加工条件对橙汁香气物质的影响

橙汁香气可以形成橙汁独特的风味,也是橙汁品质的重要指标。橙汁加工工艺类型和杀菌方式都会影响其香气组分和含量,非浓缩还原橙汁以及非热加工技术橙汁是当前的研究热点。文中概述了柑橘原料特性、橙汁工艺类型以及杀菌方式对橙汁香气物质产生的影响,并论述了提升橙汁香气物质在未来的研究趋势。     

加工和储藏条件对橙汁芳香成分的影响

橙汁的怡人香气是由多种挥发性化合物混合而成。鲜榨橙汁经热加工后性质更稳定,但对芳香物质影响较大。热处理会降低香气活性化合物含量,并产生异味物或其前体物。乙烯基愈创木酚、对伞花烃和香芹酮等异味物都是化学反应的产物,而丁二酮、愈创木酚和2,6-二氯苯酚则是微生物污染物。文中简述了橙汁的芳香物质组成,重点介绍了不同的加工方法、包装、储藏和微生物污染对橙汁芳香物质的影响的研究进展,并探讨了研究中存在的问题和未来的研究方向。     

Migration into food of polyethylene terephthalate (PET) cyclic oligomers from PET microwave susceptor packaging

A quantitative method has been developed to measure the migration of polyethylene terephthalate (PET) cyclic oligomers from aluminized PET susceptor film-type food packaging into several food types. Microwaveable French fries, popcorn, fish sticks, waffles and pizza sold in susceptor-type packaging were purchased in local markets, cooked according to package instructions and analysed for PET oligomers. Appropriate food blanks were cooked in glass containers. Quantities of PET oligomers found in the foods ranged from less than 0.012 micrograms/g to approximately 7 micrograms/g.     

Exposure to antimony from polyethylene terephthalate (PET) trays used in ready-to-eat meals

Antimony residues, a result of the use of a polycondensation catalyst in the production of polyethylene terephthalate (PET) oven-proof trays, were analysed in ready-to-eat meals. The toxicity of antimony has raised concerns about consumer safety; therefore, the migration of small fractions of these residues into ready meals and foods as a result of cooking directly in the PET trays was studied. A straightforward approach of measuring real samples was selected to obtain accurate exposure data. Background antimony concentration was determined separately from a series of lunch meals, which ranged from not detectable to 3.4 µg kg^-1. Microwave and conventional oven-cooking caused a distinct increase in the concentration of antimony in food and ready meals of 0-17 and 8-38 µg kg^-1, respectively, depending, to a certain extent, on the industrial preparations. The migrated quantities of antimony corresponded to 3-13 µg. For comparison, PET roasting bags and ready-made dough products in PET baking dishes were also evaluated. About half of the products prepared at a temperature of 180°C exceeded the specific migration limit set for food contact material by the European Commission. However, the migrated amounts of antimony relative to the accepted tolerable daily intake (TDI) show that exposure from this type of food is currently not of toxicological concern.     

Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants

The migration characteristics of the UV stabilizer Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis (1-methyl-1-phenylethyl)phenol) into food simulants has been measured from polyethylene terephthalate (PET) using HPLC with UV detection. Ethanol/water, isooctane and a fractionated coconut oil simulant (Miglyol®) were used as food simulating solvents. The migration characteristics were measured at temperatures in the range of 40-70°C. Diffusion coefficients were determined to be in the range of 1 × 10^-14 cm² s^-1 to 1 × 10^-18 cm² s^-1. At 40°C, the amount of migration into 95% ethanol after 10 days was 2 μg dm^-2. Isooctane is determined to be a good fatty food simulant that provides similar results for PET to those of fatty foods.     

市售橙汁抗氧化活性物质的研究

利用1,1-二苯基-2-三硝基苯肼（1,1-Diphenyl-2-picrylhydrazyl radical,DPPH）法和铁离子还原能力（Ferric reducing antioxidant power,FRAP）法、福林酚法以及超高效液相-四极杆飞行时间串联质谱（Ultra-high performance liquid chromatography-quadruple time-of-flight-mass spectrometry,UPLC-QTOF-MS）法,分别对市售橙汁的抗氧化活性、总酚含量以及抗氧化活性物质种类进行了研究,以达到明确橙汁的抗氧化活性有无,以及研究其主要抗氧化活性物质种类的目的。实验结果表明橙汁甲醇提取液具有清除DPPH自由基的能力[（1023±9.56）μg/m L,VCEAC（Vitamin cequivalent antioxidant capaciy）]和还原铁离子能力[（804.49±7.57）μg/m L,VCEAC],并且总酚含量丰富[（601.57±9.92）μg/m L,阿魏酸当量]。橙汁中鉴定出的主要的酚类化合物为柚皮素和橙皮苷,其中柚皮素是主要的抗氧化活性物质之一。      

苹果汁香气物质研究进展

香气成分是构成苹果汁典型风味、影响其整体品质的重要因素。研究其香气化合物对于保持苹果汁的特征香气、提高苹果汁的整体香气品质具有重要意义。该文概述了苹果汁中主要的香气成分、苹果汁香气物质分析方法、香气活性物质及其阈值的研究、苹果汁香气的主要来源和影响因素,以期为进一步深入研究和工业化生产提供理论指导。      

苹果汁香气物质研究进展

香气成分是构成苹果汁典型风味、影响其整体品质的重要因素。研究其香气化合物对于保持苹果汁的特征香气、提高苹果汁的整体香气品质具有重要意义。该文概述了苹果汁中主要的香气成分、苹果汁香气物质分析方法、香气活性物质及其阈值的研究、苹果汁香气的主要来源和影响因素,以期为进一步深入研究和工业化生产提供理论指导。     

Influence of flavour absorption by food-packaging materials (low-density polyethylene, polycarbonate and polyethylene terephthalate) on taste perception of a model solution and orange juice

The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic films after dark storage at 20°C. Owing to absorption, the amount of flavour compounds in the model solution exposed to LDPE decreased substantially. From the model flavour solution valencene was almost completely absorbed by LDPE, followed to a lesser extent by decanal, hexyl acetate, octanal and nonanone. Less flavour compounds were absorbed from the model solution by PC and PET. In contrast to LDPE, valencene was absorbed in the lowest amounts and decanal in the highest. Limonene was readily absorbed from orange juice by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene, myrcene and decanal. Although the flavour content between controls and polymer-treated samples differed substantially, the loss of flavour compounds due to absorption by LDPE, PC and PET did not influence taste perception of a model solution and orange juice significantly up to 29 days of dark storage at 20°C as determined by triangular taste panel tests.     

SiOx layer as functional barrier in polyethylene terephthalate (PET) bottles against potential contaminants from post-consumer recycled PET

The barrier effect of a silicon oxide (SiOx) coating on the inner surface of PET bottles, in terms of the ability to reduce the migration of post-consumer compounds from the PET bottle wall into food simulants (3% acetic acid and 10% ethanol), was investigated. The barrier effect was examined by artificially introducing model substances (surrogates) into the PET bottle wall to represent a worst-case scenario. Test bottles with three different spiking levels up to approximately 1000 mg kg(-1) per surrogate were blown and coated on the inner surface. The SiOx-coated bottles and the non-coated reference bottles were filled with food simulants. From the specific migration of the surrogates with different bottles wall concentrations, the maximum surrogate concentrations in the bottle wall corresponding to migration of 10 microg l(-1) were determined. It was shown that the SiOx coating layer is an efficient barrier to post-consumer compounds. The maximum bottle wall concentrations of the surrogates corresponding to migration of 10 microg l(-1) were in the range of 200 mg kg(-1) for toluene and approximately 900 mg kg(-1) for benzophenone. Consequently, the SiOx coating allows use of conventionally recycled post-consumer PET flakes (without a super-clean recycling process) for packaging aqueous and low alcoholic foodstuffs (under cold-fill conditions) and protects food from migration of unwanted contaminants from post-consumer PET.     

Evolution of aroma compounds in sparkling ciders

This paper reports the influence of yeast strain and aging time on the volatile composition of sparkling cider made according to the traditional method. Two sparkling ciders were obtained from the same base cider using a selected cider yeast strain (Saccharomyces bayanus) and a commercial wine yeast strain (Saccharomyces cerevisiae). Analysis of volatile compounds (alcohols, esters and carbonylic compounds) were performed every 3 months, from 3 to 15 months. The analysis of variance revealed that the majority of differences between sparkling ciders are due to the aging time. Acetaldehyde and acetoin decrease with time, while higher alcohols, ethyl acetate, ethyl lactate and ethyl octanoate significantly increase during aging in contact with lees. The concentrations of methanol, 2-phenyletanhol, ethyl lactate and ethyl octanoate were higher in the cider made with the selected yeast strain (S. bayanus).     

Ascorbic acid,aroma compounds and browning of orange juices related to PET packaging materials and pH

The ascorbic acid content of orange juice made from concentrate was measured after 9 months of storage at 20 °C in glass, standard monolayer polyethylene terephthalate (PET₁), multilayer PET (PET₂) and plasma‐treated PET (PET₃) containers. Glass enabled the best preservation of ascorbic acid and, in plastic packaging materials, ascorbic acid losses were correlated with their oxygen permeability. PET₂ and PET₃, which exhibit oxygen permeability 10 times less than that of PET₁, enabled a gain of 100 mg L^?1 after 9 months of storage. Freshly hand‐squeezed orange juice samples were adjusted to various pH values using sodium hydroxide; a rise in the pH from 3.2 to 4.0 significantly reduced the amounts of off‐flavours (i.e., furfural and α‐terpineol) appearing during storage, by 79% and 65%, respectively. Moreover, an increase in the pH from 3.2 to 4.0 enabled the protection of ascorbic acid levels without detrimentally increasing non‐enzymatic browning. Copyright © 2006 Society of Chemical Industry     

Leak detection in polyethylene terephthalate bottles filled with water and pulped and unpulped orange juice using a vacuum decay system

This research evaluated an offline vacuum decay leak detection system for 1775-ml polyethylene terephthalate (PET) bottles. These bottles were filled with water and pulped and unpulped orange juice and induction sealed with an aluminum liner and an outer 38-mm continuous thread polypropylene cap. The objectives of this study were to evaluate (i) minimum leak size sensitivity of the instrument; (ii) ability to identify weak but nonleaking seals; (iii) effect of varying fill heights on the equipment's sensitivity; and (iv) percentage of false-positive and negative results likely to be obtained during a normal test run. To meet these objectives, leaks 5, 10, 15, 20, 30, 40, and 50 microm were created in the PET bottles. A second set of bottles was induction sealed at high voltage and 1, 1.5, 2, 2.5, 3, 3.5, and 4 s of dwell time. A third set of bottles with good seals was filled with differing headspace measurements of brimful, 1, 2, 3, 4, and 5 cm. After optimizing the equipment, leak tests on random sets of leaking and nonleaking bottles showed 0.0% false-positive and 0.0% negative identifications. Results showed 5-microm minimum leak size detection for bottles filled with all products. Optimum seal conditions were >2 but <3 s at high voltage. Product fill heights >2 to < or =3 cm did not affect the efficiency of the equipment. These results show that this vacuum decay system has potential for use in identifying leaks in PET bottles used for food packaging.     

SiO x layer as functional barrier in polyethylene terephthalate (PET) bottles against potential contaminants from post-consumer recycled PET

The barrier effect of a silicon oxide (SiO _x ) coating on the inner surface of PET bottles, in terms of the ability to reduce the migration of post-consumer compounds from the PET bottle wall into food simulants (3% acetic acid and 10% ethanol), was investigated. The barrier effect was examined by artificially introducing model substances (surrogates) into the PET bottle wall to represent a worst-case scenario. Test bottles with three different spiking levels up to ～1000 mg kg^?1 per surrogate were blown and coated on the inner surface. The SiO _x -coated bottles and the non-coated reference bottles were filled with food simulants. From the specific migration of the surrogates with different bottles wall concentrations, the maximum surrogate concentrations in the bottle wall corresponding to migration of 10 µg l^?1 were determined. It was shown that the SiO _x coating layer is an efficient barrier to post-consumer compounds. The maximum bottle wall concentrations of the surrogates corresponding to migration of 10 µg l^?1 were in the range of 200 mg kg^?1 for toluene and ～900 mg kg^?1 for benzophenone. Consequently, the SiO _x coating allows use of conventionally recycled post-consumer PET flakes (without a super-clean recycling process) for packaging aqueous and low alcoholic foodstuffs (under cold-fill conditions) and protects food from migration of unwanted contaminants from post-consumer PET.     

葡萄汁主要芳香物回收工艺的研究

以玫瑰香葡萄为实验材料,采用瑞士Unipekth公司生产的芳香物回收设备,研究了在这一装置上从浓缩葡萄汁生产中回收芳香成分的最佳蒸发比,真空度,温度和回流化。结果表明：减压蒸馏法回收玫瑰香葡萄汁芳香成分时,系统压力为0.0192MPa,温度是60℃,蒸发比为50％,回流比为7：1时芳香回收物浓度最高,是该装置回收玫瑰香葡萄汁香物的适宜条件。