New aroma compounds of leek oil

Summary Six leek oils of Turkish origin have been analysed for their aroma compounds. In order to achieve a comprehensive aroma spectrum different extraction methods were used: steam-distillation extraction according to Likens-Nickerson, and static and dynamic headspace analyses. Eighty-five compounds are recorded in leek oil for the first time, 28 of them having already been recorded for otherAllium varieties.

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Neue Aromastoffe in Porree-Ölen

Zusammenfassung Sechs Porreeöle türkischer Herkunft wurden auf ihre Aromastoffzusammensetzung hin untersucht. Um eine möglichst umfangreiche Extraktion der verschiedenen Verbindungsklassen zu erzielen, wurden neben der simultanen Wasserdampfdestillation-Extraktion nach Likens-Nickerson auch statische und dynamische Kopfraum-Analysen eingesetzt. 85 Verbindungen des Porree-Aromas werden neu vorgestellt, von denen 28 Verbindungen bereits bei anderenAllium-Arten beschrieben wurden.

     

Changes in volatile flavour compounds in field pea cultivars as affected by storage conditions

The impact of storage conditions on volatile flavour profile of field pea cultivars was evaluated. Seeds were kept at 4 °C, room temperature (approximately 22 °C) and 37 °C for 12 months. Headspace solid‐phase microextraction gas chromatography–mass spectrometry was used for extraction and identification of volatile flavour compounds (VFCs). Significant (P < 0.01) differences in the concentration of VFCs were observed during storage. All cultivars kept at 22 and 37 °C had higher mean value of aldehydes compared to those kept at 4 °C. Alcohols, hydrocarbons, ketones, terpenes and esters were higher in samples stored at 4 °C compared to those at higher temperatures. 1‐Hexanol, hexanal, styrene, 2‐butanone, dimethyl sulphide, 3‐carene, ethyl acetate and 2, 3‐diethyl‐5‐methyl pyrazine were the most abundant compounds found in peas. Results from this study could be useful in identifying improved conditions of storage to enhance flavour properties of peas.     

Changes in flavour and volatile components during storage of whole and skimmed UHT milk

Six batches of commercial UHT milk, submitted to direct treatment, three whole and the other three skimmed milk, were stored at 25±2°C for 4 months. Non-casein nitrogen (NCN) and sensorial analysis were carried out on packs opened every month. Volatile composition was analysed every 15 days, using a purge-and-trap concentrator coupled on-line to a GC–MS instrument. NCN increased during storage; the increase was greater in skimmed milk samples. Sensory characteristics were slightly better in the whole samples, although the scores decreased for both groups in the third month. Quantification of about 40 volatile components in whole milks showed no changes until 90 days (the legal shelf-life in Spain); the main change was the increase of methyl ketones. New components appeared in skimmed samples after 65 days storage; they could be related to both proteolysis and Maillard reaction. This is consistent with the poorer sensory quality found in skimmed milk samples.     

Changes in the physicochemical property and sensory quality of heat-processed beef flavour in the storage process

This study aimed to investigate changes in the quality of heat-processed beef flavour (HPBF) during 168-day storage period at 4, 20 and 50 °C through evaluating 10 physicochemical indexes and sensory profiles. The sensory score of HPBF reduced dramatically at 50 °C compared with those at other temperatures. The correlation analysis indicated that among the 10 physicochemical indexes, oxidation–reduction potential (ORP), which is positively correlated to lipid oxidation, possessed the strongest association with the total sensory score of HPBF. The kinetic analysis showed that the increasing rate of ORP during the first 50-day period at 50 °C was more than 10 times larger than those at 4 and 20 °C. These results suggested that lipid oxidation played a major role in affecting the quality of HPBF, especially during the early storage period. Reducing lipid oxidation via for instance maintaining a relatively low storage temperature should be given better attention for obtaining high-quality HPBF.     

Changes in flavour volatiles of whole pasteurized milk as affected by packaging material and storage time

Changes in volatile profiles of whole pasteurized milk stored under fluorescent light at 4 °C, packaged in different containers were monitored for a period of 7 days in a study designed to differentiate between light-induced oxidative and purely autoxidative effects related to packaging material. Changes in volatiles were measured using solid-phase microextraction–gas chromatography/mass spectroscopy, while microbiological and sensory analyses were used to assess milk quality. Two distinct patterns of milk flavour deterioration were observed. In light-exposed samples, a light-induced oxidation mechanism prevailed while in light-protected samples, an autoxidation mechanism was apparent. Under both conditions, the concentration of selected odorous compounds increased with storage time. Microbiological data correlated poorly with both sensory and GC/MS data. Sensory data correlated well with selected volatile compounds pointing to dimethyl disulphide, pentanal, hexanal and heptanal as potential markers of fresh milk quality. Based on sensory analysis, the optimal shelf life of the whole pasteurized milk used in this study was approximately 5 days.     

不同贮藏方式下橘皮精油含量的变化

为探讨橘皮在不同贮藏方式下精油含量的变化规律,以温州蜜柑皮、椪柑皮和柚皮为原料,分别采用-20℃和-40℃低温冻藏,以及避光、不避光常温干藏4种方式贮藏橘皮,并定期测定橘皮中精油含量。结果表明:不同品种柑橘皮中精油含量不同;贮藏期间,3种橘皮精油含量均有不同程度的减少;温州蜜柑皮和椪柑皮-40℃低温冻藏,柚皮避光和不避光常温干藏,均能较好地保留其中精油。     

Frozen storage conditions and rancid flavour development in lamb

Frozen storage of lamb at temperatures of −5 or −10°C before ultimate storage at −35°C induced changes that led to rancidity development (as assessed by a taste panel) continuing at a more rapid rate at the lower temperature. Parallel storage regimes, but with storage at −35°C first, then ultimate storage at −5°C or −10°C, led to much less storage flavour development.

No significant flavour changes occurred even after 40 weeks storage at −15°C followed by 20 weeks storage at −35°C.

These studies emphasise the importance of order of time-temperature holding treatments in studies of rancid flavour development and indicate that time-temperature effects may not be truly additive.     

韭籽粕提取物对韭菜籽油微胶囊理化特性及体外消化的影响研究

目的 研究韭籽粕提取物对韭菜籽油微胶囊理化特性的影响。方法 通过扫描电子显微镜、溶解性和流动性实验、热重分析、傅里叶变换红外光谱等,探究韭籽粕提取物对韭菜籽油微胶囊微观结构、包埋率、储存稳定性、溶解性及流动性等的影响;利用体外模拟消化实验探究韭菜籽油在消化道中的释放情况。结果 添加韭籽粕提取物的微胶囊颗粒形状规则,表面光滑、致密;韭籽粕提取物能把微胶囊的包埋率提升至93.272%,有效抑制微胶囊的氧化,提高微胶囊的溶解性和流动性;随着温度的升高,添加韭籽粕提取物的微胶囊最大失重率有所下降,韭籽粕提取物对微胶囊起到了一定保护作用;红外光谱结果证明了微胶囊化效果好,包埋成功;在体外模拟消化实验中,添加韭籽粕提取物的微胶囊能更有效地释放韭菜籽油,提高了韭菜籽油在人体内的生物利用率。结论 本研究为韭菜籽油微胶囊产品开发、应用体系的构建提供了理论参考。     

韭菜籽油微胶囊的制备及工艺优化

为提高韭菜籽油的资源利用率和产品附加值,本研究以韭菜籽油作为芯材,分别以明胶-阿拉伯胶、明胶-CMC、HI-CAP 100-明胶以及HI-CAP 100-麦芽糊精4种组合作为壁材,利用复凝聚法制备微胶囊,并对比冻干和喷雾干燥两种干燥方式对微胶囊的影响。以韭菜籽油微胶囊包埋率、光学显微镜和扫描电镜结构表征图为反应指标,在反应pH、壁材浓度、壁材比及芯壁比四种不同因素下,确定最佳组合壁材为HI-CAP 100-麦芽糊精,喷雾干燥制备得到的微胶囊性能优于冻干法。通过单因素实验和响应面优化分析,确定韭菜籽油微胶囊最佳优化工艺条件：反应pH为4.56,壁材比为1.07：1,芯壁比为1.28：1,壁材浓度为1.04%,在此条件下微胶囊包埋率可达90.80%。该研究为韭菜籽油的高值化利用提供了理论依据。     

充氮储藏的菜籽油食用期品质变化

以不添加抗氧化剂的一级菜籽油为原料,酸价、过氧化值、p-茴香胺值为监测指标,在模拟家庭食用期储藏条件下,探讨了充氮储藏的菜籽油(2. 5 L/桶)在3个月食用期内的品质变化规律。结果表明:充氮储藏的菜籽油在3个月的食用期内酸价(KOH)未超过一级菜籽油的限量值0. 2 mg/g;充氮储藏的菜籽油比空白对照组的过氧化值达到5. 0 mmol/kg的时间延长了20 d;充氮储藏的菜籽油p-茴香胺值的变化较为平缓,在前30 d内变化不大。充氮储藏提高了菜籽油的氧化稳定性,该储藏方法可以成为菜籽油的一种新型绿色的储藏技术。     

Changes in volatile flavour components of soybeans during roasting

Volatile concentrates were prepared from whole soybeans, roasted at 200°C for 10, 20 and 30 min, by steam distillation under reduced pressure followed by ether extraction, and analysed by gas chromatography and gas chromatography-mass spectrometry, in comparison with the volatile concentrate from raw soybean flour.Major flavour components of raw soybean, such as n-hexanol, 1-octen-3-ol and n-hexanal, decreased during the course of roasting, but the rate of this decrease was not rapid, especially between 10 and 20 minutes' roasting. During the roasting period, alkylated pyrazines, oxygenated furans, oxygenated pyrroles and phenols were formed or increased markedly. On the other hand, sensory evaluation showed that a flavour change to ‘desirable’ from ‘beany’ or ‘objectionable’ occurred between 10 and 20 minutes' roasting. These results suggest that roast flavour masks the ‘beany’ flavour in soybean.     

Heat and storage effects on the flavour of peanuts

Two peanut varieties, Giza 4 and Giza 5 were subjected to different heat treatments such as drying in solar drier at air speed 0.5 and 2 m/sec with average temperature 45 and 60°C and heating in oven at 120 and 150°C. The sensory evaluation of the two varieties showed insignificant differences among varieties and heating processes. A correlation between the sensory and instrumental data was found. The high sensory scores of samples heated at 150°C were attributed to the presence of high concentration of pyrazines which were thought to contribute to flavour and aroma of fresh roasted peanut. A comparative study between the main chemical classes retained in peanut samples after storage for 3 months at room temperature showed that the aldehydes derived lipids increased significantly in the solar dried samples. The antioxidative components produced via Maillard reaction resulted in oxidative stability of the samples heated in oven     

油菜花粉油脂贮藏过程中挥发性成分变化研究

采用顶空固相微萃取与气相色谱质谱联用技术对油菜花粉油脂在贮藏前后挥发性成分进行了分析。结果表明,新鲜油菜花粉油脂特殊风味物质的主要成分为D-柠檬烯(13.66%)、3-蒈烯(7.95%)、二甲基富烯(5.72%)、β-水芹烯(4.58%)、苯甲醛(3.15%)、氧化石竹烯(2.27%)、苯乙醇(1.16%)和β-蒎烯(1.12%)等化合物。经过常温贮藏6个月后油脂的主要挥发性成分为醛类和酯类化合物。油菜花粉油脂中的高含量亚麻酸导致其易氧化酸败。经分析鉴定出油菜花粉油脂氧化产物含有丙醛、(E)-2-戊烯醛、正己醛、(E)-2-己烯醛、(E,E)-2,4-己二烯醛、(E)-2-辛烯醛、壬醛和(E,E)-2,6-壬二烯醛和2,4-庚二烯醛等。其中2,4-庚二烯醛的含量最高,可作为油菜花粉油脂产品质量优劣的指标。     

The influence of storage conditions on flavour changes in human milk

The effects of freeze-storage on human milk have been investigated with regard to sensory changes and modifications in the molecular composition of constituent odour-active volatiles. Sensory evaluation showed that fishy-metallic odour attributes are generated during storage, as are rancid-sweaty odour notes, which were described by panellists to be highly unpleasant. To monitor the dynamics of off-odour development in human milk, sensory evaluation in both orthonasal and retronasal mode was performed at defined time intervals of storage, with parallel evaluation of human milk samples that had been heated prior to freeze-storage. Heating was found to induce slight flavour changes, with generation of a predominantly egg-white-like note, but with no further generation of off-odour formation upon subsequent storage. This suggests that the formation of the off-odour in non-heated milk resulted from metabolic processes in the milk, although may also be due to the specific composition of human milk. In comparison, similar off-odour development was not observed in bovine milk. Molecular identification of the off-odour substances, most specifically free fatty acids and oxidation derivatives of polyunsaturated fatty acids, indicated both lipolytic and peroxidative processes of components of the native human milk. Finally, these results indicate that human milk is obviously a highly sensitive food material, specifically with regard to its characteristic fatty acid composition.     

Changes in flavour and texture during the ripening of strawberries

The amount of total volatile compounds, total acidity, total sugar content (degrees Brix) and fruit firmness were used to characterize the degree of ripeness of three strawberry varieties (Carezza, Darselect and Marmolada). A novel concept using solid phase microextraction (SPME) and measurement of total volatile compounds to distinguish between various stages of strawberry ripeness was applied. The carboxene/polydimethylsiloxane SPME fibre was found to be best suited to differentiate between the stages of ripeness. The amount of total volatile compounds rapidly increased near to maturity (between the three-quarters red stage and the dark-red stage). Most of the volatile compounds identified were esters, followed by aldehydes, and alcohols. The most abundant volatile compounds were propyl butanoate, 3-phenyl-1-propanol, butyl butanoate, isobutyl butanoate, 3-methyl butyl butanoate and isopropyl hexanoate. The concentration of green aroma components such as hexanal, trans-2-hexenol and cis-3-hexenyl acetate progressively decreased during the maturation process until they became minor components in mature strawberries.     

SPME-GC-MS对菜籽毛油和精炼菜籽油挥发性风味成分的分析

以菜籽毛油和精炼菜籽油为原料,采用固相微萃取(SPME)装置顶空取样,用气相色谱-质谱法(GC-MS)对挥发性风味成分进行鉴定.结果表明:菜籽毛油的主要挥发性风味成分为硫甙降解产物、氧化挥发物(醛、醇、酮等)及杂环类物质,其中硫甙降解产物以2-甲代-1-丙烯基-氰、4-甲硫基-丁腈、3-苯基丙腈及4-异硫氰基-1-丁烯为主,氧化挥发物以1,5-己二烯-3-醇和反-2-反-4-癸二烯醛为主要成分,杂环类物质则以吡嗪类化合物为主;精炼菜籽油的挥发性风味成分主要为氧化挥发物,以反-2-反-4-庚二烯醛、反-2-反-4-癸二烯醛、反-2-癸烯醛为主,其菜籽油特征性风味不足,主要源于精炼过程中硫甙降解产物及杂环类芳香物质的减少.     

Soybean variety and storage effects on soymilk flavour and quality

Soymilk prepared from five soybean cultivars, grown in Ontario, were analysed for protein, oil, mineral composition, viscosity, colour, lipoxygenase (LOX) activities and flavour profile. Among the five soybean cultivars, the Vinton 81 variety contained the highest protein and the lowest fat. The yield of soymilk from all five cultivars was similar. Major differences were observed in viscosity and in the composition of both the soymilk and the okara. Higher protein and fat extractability was found in soymilk made from S08‐80 and Vinton 81 varieties. Their okara protein contents were also among the highest. Minimum extractability was observed with S03W4 cultivar. Soymilk made from S 03W4 and Vinton 81 cultivars had the whitest colour (lowest ΔE values). Viscosity values were the highest for S08‐80, FG1 and S20‐20 varieties. Headspace solid‐phase microextraction gas chromatography was used to analyse volatile compounds in soymilk. A total of fourteen volatiles were identified, among which aldehydes and their corresponding alcohols were the major compounds. Similar volatile compounds were identified in all the samples analysed but at different concentrations. The highest LOX activity was observed in the Vinton 81 and S20‐20 soybean cultivars, which had the highest total volatile and hexanal contents. A positive correlation (correlation coefficient = 0.82) between enzymatic activity and the total volatiles was observed. Vinton 81 cultivar was subjected to storage (at 18 °C and 50% relative humidity) for a period of 10 months. Soymilk was prepared at different times during storage. The results showed that the soymilk colour, LOX and total volatiles were significantly (P < 0.05) affected by the storage of the soybeans over time.     

Changes in lycopene and beta carotene contents in aril and oil of gac fruit during storage

Gac fruits were physically measured and stored under ambient conditions for up to 2 weeks to observe changes in carotenoid contents (lycopene and beta carotene) in its aril. Initial concentrations in the aril of lycopene were from 2.378 mg/g fresh weight (FW) to 3.728 mg/g FW and those of beta carotene were from 0.257 to 0.379 mg/g FW. Carotenoid concentrations in the aril remained stable after 1 week but sharply declined after 2 weeks of storage. Gac oil, pressed from gac aril, has similar concentrations of lycopene and beta carotene (2.436 and 2.592 mg/g, respectively). Oil was treated with 0.02% of butylated hydroxytoluene, or with a stream of nitrogen or untreated then stored in the dark for up to 15 or 19 weeks under different temperatures (5 °C, ambient, 45 and 60 °C). Lycopene and beta carotene in control gac oil degraded following the first-order kinetic model. The degradation rate of lycopene and beta carotene in the treated oil samples were lower than that in the control oil but the first-order kinetic was not always followed. However, both lycopene and beta carotene degraded quickly in gac oil with the first-order kinetic under high temperature conditions (45 and 60 °C) regardless of the treatments used.     

Changes in the sterol content of soybean oil after its thermal processing

A study was made of alterations in the composition of soybean oil sterols after thermal treatment. It was established that in heat-exposed oils, the content of total sterols dropped 20 to 50%. Analysis of a sample of free sterols from soybean oil heated for 13 h demonstrated a slight decrease in the content of stigmast-5-en-3 beta-ol at the expense of a rise in the concentration of delta 5-avenasterol, citrostadienol, and 24-methylene cycloartanol.