品种和后成熟对NFC苹果浊汁挥发性香气成分的影响

为了探讨果实品种和后成熟度对苹果浊汁风味的影响,采用顶空-固相微萃取结合气相色谱-质谱联用技术,基于多元数据分析手段,非靶向分析了富士、嘎啦、华硕、金冠、澳洲青苹等5个品种,在3个后熟度下制成的NFC苹果浊汁挥发性香气成分差异。结果表明:醇类（2-甲基-1-丁醇、1-己醇等）、醛类（己醛、（E）-2-己烯醛等）和酯类（2-甲基乙酸丁酯等）为苹果浊汁的主要挥发性香气成分。品种和后熟度对苹果汁的特征性挥发性香气成分的含量和组成影响显著。澳洲青苹果汁挥发性香气成分总量少且含量低,醛类是其主要的挥发性香气物质;富士、嘎啦和金冠果汁则表现出相似的香气组分特征,酯类、醛类和醇类物质含量丰富,具有浓郁的香甜水果气味和青草味;华硕苹果汁的挥发性香气成分以醇类和醛类为主,整体具有清淡的香味和生青味。另外,随着不断后熟,不同品种苹果浊汁挥发性香气成分的变化呈现不同趋势。澳洲青苹和富士苹果汁中的香气成分逐渐累积,分别有15和28种挥发性化合物含量显著增加;嘎啦和金冠苹果汁香气物质含量呈现先上升后下降的趋势,在第二个后熟阶段风味最好;用采摘初期华硕苹果原料制成的苹果汁香气最浓郁,但随着不断后熟,挥发性香气含量显著降低。本研究开展的苹果汁风味特性研究,可为苹果浊汁加工的原料选择提供理论基础。     

果色和成熟度对樱桃番茄（Solanum lycopersicum var. cerasiforme）果实挥发物分布的影响

为探究果色和成熟度对樱桃番茄果实挥发物的影响,用顶空固相微萃取-气相色谱-质谱联用法测定育种自交系材料金珠（橙）、黑樱桃1（紫）、1号（粉）、红珍珠（红）在绿熟期、转色期和红熟期的挥发物。分析发现,橙色番茄挥发物明显高于红色和粉色番茄。橙色番茄在绿熟期,紫色番茄在转色期和红熟期挥发物最高,而粉色番茄挥发物始终最低。气味强度由挥发物质量浓度和嗅觉阈值决定。3-甲基-丁醛、(E,E)-2,4-庚二烯醛、1-戊烯-3-酮、己醛、苯甲醛和(Z)-3-己烯-1-醇对番茄气味贡献较大。红色、橙色和紫色番茄分别在绿熟期、转色期和成熟期气味最浓。随着果实成熟,挥发物质量浓度持续增加,气味更加浓郁。果色和成熟度对挥发物有显著影响。     

Study of the volatile profile characteristics of longan during storage by a combination sampling method coupled with GC/MS

BACKGROUND: Longan (Dimocarpus longan Lour.) is a kind of subtropical fruit, but it has a very short shelf life under normal ambient conditions. In this work, a combination sampling method, including headspace solid phase micro‐extraction (HSSPME), simultaneous distillation extraction (SDE) and steam distillation (SD), was used to study the volatile profile characteristics of longan at the fresh and deteriorated storage phases followed by gas chromatography–mass spectrometry (GC‐MS) detection. The study would provide a method for investigating the volatile profile characteristics of longan during storage and some helpful clues for quality discrimination. RESULTS: In total, 28 and 22 volatile compounds of fresh and deteriorated longan were identified. Alkenes and esters were the main volatile components of longan. β‐ocimene accumulated, whereas allo‐ocimene and 3,4‐dimethyl‐2,4,6‐octatriene decreased during storage. Different volatile profile characteristics at the fresh and deteriorated storage phases obtained by HSSPME were specified by principal component analysis (PCA). Typical volatile compounds were distilled by a common model strategy. CONCLUSION: The volatile profiles of longan during storage were studied using a combination of sampling methods followed by GC‐MS detection. Five typical volatiles contributing significantly to the difference in volatile profile characteristics of longan at the fresh and deteriorated storage phases were distilled using a common model strategy. These compounds are potential bio‐markers for longan degradation. Tentative results suggest that combining HSSPME with conventional volatile isolation methods would provided more representative data on changes in the volatile compounds of longan during storage and some helpful clues for quality discrimination. Copyright © 2008 Society of Chemical Industry     

Effect of eugenol and guaiacol application on tomato aroma composition determined by headspace stir bar sorptive extraction

BACKGROUND: The present work was carried out because there is only a small amount of literature on how the volatile composition of tomatoes can be modified by the effect of exogenous substances in contact with tomato plants. This work studies how eugenol and guaiacol, either by foliar application and/or in the surrounding atmosphere, can affect the volatile composition of this fruit. An important work of this study was also conduced to validate the analytical method [headspace stir bar sorptive extraction–gas chromatography–mass spectrometry (HS‐SBSE‐GC‐MS)] to determine the composition of the volatiles in tomato. RESULTS: Analytical method validation parameters such as linearity, limit of detection, limit of quantification, and recovery proved that this method is suitable for the analysis of tomato volatiles. Their eugenol and guaiacol content changed, with an increase of 200 and 35 times, respectively, when foliar treatment was used, and an increase of 10, in both cases, when plants were in contact with the contaminated atmosphere. As consequence of the treatments other volatile compounds changed considerably. CONCLUSION: For first time, a HS‐SBSE‐GC‐MS method was successfully validated for the study of volatiles in tomatos. Results suggests that exogenous compounds in contact with the plants, such as eugenol and guaiacol, can be absorbed changing the global volatile composition of fruits, which could produce a negative or positive effect in their aroma. © 2012 Society of Chemical Industry     

Recent Advance in Aromatic Volatile Research in Tomato Fruit: The Metabolisms and Regulations

Aroma, an essential characteristic of tomato fruit, plays an important role in determining the perception and acceptability of tomato products by consumers. During tomato fruit ripening, associated with color changes from green to red involving the conversion of chloroplasts to chromoplasts are changes of aromatic volatile profiles. Although the biosynthetic pathways for some aromatic volatiles have been established in tomato fruit recently, our knowledge of regulatory mechanisms is still rudimentary. On the other hand, many internal and external factors modify volatile metabolism in tomato fruit. This review first summarizes the current knowledge of expression patterns and biosynthetic pathways of aromatic volatiles in tomato fruit along with the role of ethylene in their biosynthesis. The impact of internal and pre- and postharvest external factors on volatile composition is then discussed. This review will provide critical information for research on tomato aromatic volatiles and their manipulation.     

Auxin treatment of pre‐veraison grape (Vitis vinifera L.) berries both delays ripening and increases the synchronicity of sugar accumulation

Background and Aims: Pre‐veraison auxin treatments can delay grape berry ripening, but there is little information about their effects on berry development and wine composition. The aim of this study was to further investigate these effects and explore the practical implications of delaying ripening. Methods and Results: Treatment of pre‐veraison Vitis vinifera L. cv. Shiraz berries with 1‐naphthaleneacetic acid (NAA) significantly delayed ripening as measured by the accumulation of total soluble solids (TSS) and anthocyanins. The onset of the post‐veraison phase of berry size increase was delayed in NAA‐treated fruit, but these fruit were significantly larger than Control fruit at harvest. NAA‐treatments significantly increased the synchronicity of berry sugar accumulation. GC‐MS analysis of wine headspace volatiles showed significant, but largely small, differences in the concentration of 19 compounds. No significant difference in sensory properties was found between replicate small‐scale wine lots made from Control and NAA‐treated fruit. Conclusions: Auxin treatment delayed berry ripening, increased the synchronicity of sugar accumulation between berries, increased berry size and changed the levels of some volatile compounds, but did not affect wine sensory properties. Significance of the Study: We propose that NAA sprays might be used to delay grape berry ripening and increase the synchronicity of sugar accumulation, and therefore ripening, without deleterious effects on wine quality. This may be useful in controlling winery intake and fruit composition.     

Variety‐based discrimination of apple juices by an electronic nose and gas chromatography–mass spectrometry

The variety of raw material plays a crucial role in the quality and authenticity of fruit juices and juice products. To characterise and classify apple juices according to variety on the basis of their volatile compounds, electronic nose (EN) and gas chromatography–mass spectrometry (GC‐MS) were applied to detect the apple juices prepared by eight different varieties. The EN was used to analyse the mixture of volatile compounds as a whole and enabled rapid classification of juice samples when coupled with linear discriminant analysis (LDA). LDA showed a perfect discrimination of apple juices based on varieties. GC‐MS was utilised to illustrate the differences of volatile compounds among juice samples. Identification of volatile compositions and their contents provides useful access to differentiate juices from different varieties.     

The mozzarella cheese flavour profile: a comparison between judge panel analysis and proton transfer reaction mass spectrometry

Described in this paper is a comparison of results obtained in flavour profiling with two different approaches: classical sensory analysis and a novel instrumental technique. The mozzarella cheese flavour profile of seven different brands has been described by a sensory panel of eight judges. The same brands have been studied by means of proton transfer reaction mass spectrometry (PTR‐MS), a novel technique well suited for detecting volatile organic compounds (VOCs) down to the pptv level in air, without any need for sample concentration or trapping. The PTR mass spectra of the headspace of mozzarella samples held at 36 °C have been compared with the judge panel flavour profile. Multivariate statistical data analysis shows that the two methods perform comparable sample discrimination. Even though several questions are still open (definition of better instrumental parameters, improvements in sampling set‐up, spectral interpretation), the PTR‐MS technique appears to be a very promising method for the instrumental evaluation of the flavour sensory profile of food. This opens up new opportunities both in the control of quality and technological processes as well in the fundamental comprehension of the physiological processes of aroma perception. © 2000 Society of Chemical Industry     

Detection of Volatile Compounds of Cheese and Their Contribution to the Flavor Profile of Surface‐Ripened Cheese

The volatiles responsible for the typical aroma of cheese are produced mainly by lipolytic and proteolytic pathways and by the metabolism of lactose, lactate, and citrate. The volatile profile of cheese is determined by gas chromatography (GC), which includes the extraction, separation, and detection of volatiles. A wide range of extraction techniques is available, and technological improvements have been developed in GC separation and detection that enhance our understanding of the role of individual key volatiles to cheese flavor. To date, for surface‐ripened cheese, the main volatiles detected that contribute to flavor include acids, ketones, alcohols, and sulfur compounds. However, based on the limited number of studies undertaken and the approaches used, it appears that a significant degree of bias possibly exists that may have over‐ or underestimated the impact of specific chemical classes involved in the flavor of these types of cheese.     

Flavor of tomato and tomato products

Abstract

The characteristic sweet‐sour taste of tomato and its overall flavor intensity are due to the following components: reducing sugars (fructose and glucose), free acids (mainly citric’ acid), their ratio, as well as some volatile substances, not identified so far, and the interplay between the above‐mentioned groups of compounds. Of the minerals, potassium (by influencing the free acid content) and phosphate (due to its buffering capacity) indirectly affect the taste. The effect of the free amino acids (glutamic acid, glutamine, gamma‐aminobutyric acid, and aspartic acid) is not unambiguously proven.

The characteristic tomatolike flavor is predominantly determined by volatile substances. Volatile substances develop partly during ripening, partly during the comminution of the ripe fruit, as an effect of the enzymes activated. Volatile substances characterizing fresh tomato flavor are derived mainly from fatty acids and amino acids. Differences between the flavors of different varieties, the less characteristic, weaker flavor of hothouse‐grown tomatoes or artificially ripened ones, are explained by the different quantitative proportions of the volatile substances. So far no key substance playing a decisive role in the flavor of tomato has been detected. Of the approximately 400 volatile compounds so far identified, several were found, however, which have an important role in the flavor of fresh tomato (cis‐3‐hexenal, trans‐2‐hexenal, 2‐isobutylthiazole, hex‐anal, cis‐3‐hexen‐1‐ol, 2E,4E‐decadienal, 6‐methyl‐5‐hepten‐2‐one, etc.).

In the course of tomato processing the flavor substances undergo substantial qualitative and quantitative change, which may or may not be favorable. Depending on the extent of heat treatment and its duration, the reducing sugar and amino acid content decreases while the acid content (by the formation of pyrrolidone carboxylic acid) increases. A part of the volatile substances (mainly those providing “green” smell) evaporates and at the same time—traceable back to the breakdown of sugars and carotenoids—new components, among them those which characterize the “cooked” smell of tomato products, are formed (e.g., dimethyl sulphide, acetaldehyde). Although our knowledge as to the qualitative and quantitative composition of tomato flavor, the factors affecting it, and the effect of certain compounds on it has substantially increased, we are still not in the position to consciously develop the flavor during cultivation and processing. To achieve this further systematic research work is necessary.     

甜玉米成熟过程中挥发性风味物质的变化规律

以“仲甜9号”、“珠玉甜8号”、“珠玉甜1号”3 个品种甜玉米为材料,研究甜玉米籽粒成熟过程中挥发性风味物质的变化规律。采用顶空固相微萃取-气相色谱-质谱联用分析技术,结合NIST14质谱数据库比对、保留指数分析、气相色谱嗅闻分析等方法对挥发性风味物质进行鉴定,利用内标法测定其含量,构建甜玉米挥发性风味活性化合物组成谱,评价甜玉米香气品质与特征。结果表明：3 种甜玉米在成熟过程中共检测到61 种挥发性风味物质;成熟度对挥发性风味物质种类和含量有显著影响,随成熟度增加,壬酸乙酯、1-庚醇、1-己醇含量显著下降,苯乙烯、甲苯、乙苯、1,3-二甲基苯含量显著增加,籽粒成熟过程中以积累芳香烃为主。在气味特征方面,随着籽粒的成熟,脂香强度明显增强,青香强度明显减弱。甜玉米品种之间存在差异,“仲甜9号”甜玉米成熟期时挥发性风味物质种类和含量明显高于其他2 个品种,且整体风味强度最大。     

Effects of ripening, 1-methylcyclopropene and ultra-high-pressure pasteurisation on the change of volatiles in Chinese pear cultivars

BACKGROUND: Aroma is one important fruit sensory attribute influenced by the volatile constituents related to species, variety and technological treatments. We analysed the variations of volatile compounds in five pear cultivars and investigated their changes related to different pear organs, different ripening stages, 1‐MCP treatment and ultra‐high‐pressure pasteurisation. RESULTS: Considerable variations exist in the quantity of 10 volatile compounds among five pear cultivars. Their levels generally showed an increasing trend when collected at later harvest time in Ya pear. In Whangkeumbae pear, most volatile compounds reached their maximum levels in skin and pulp. After treating pears with 42 µmol L^?1 1‐methylcyclopropene (1‐MCP), the levels of volatiles remained basically unchanged or only slightly increased in Ya pear during a shelf life of 21 days. When Huangguan pear juice was pasteurised by using ultra‐high pressure, the levels of volatiles significantly changed during the shelf life. CONCLUSION: The volatile compositions of five different Chinese pear cultivars differ considerably. The levels of these volatiles vary along with ripening stages and pear tissues. A moderate concentration of 1‐MCP could keep the levels of volatile compounds basically unchanged during storage and ultra‐high‐pressure pasteurisation could change the levels of volatiles significantly during the following shelf life. Copyright © 2011 Society of Chemical Industry     

In Vitro and In Vivo Flavor Release from Intact and Fresh‐Cut Apple in Relation with Genetic,Textural, and Physicochemical Parameters

Abstract: Flavor release from 6 commercial apple cultivars (Fuji, Granny Smith, Golden Delicious, Jonagold, Morgen Dallago, and Red Delicious) under static conditions (intact or fresh‐cut samples) and during consumption of fresh‐cut samples (nosespace) was determined by proton transfer reaction mass spectrometry. Textural (firmness, fracturability, flesh elasticity, and rupture) and physicochemical (pH, acidity, and water content) properties of the apples were also measured. Static headspace analysis of intact fruits revealed Fuji and Granny Smith apples had the lowest concentration for all measured flavor compounds (esters, aldehydes, alcohols, and terpenes), whereas Red Delicious apples had the highest. Fresh‐cut samples generally showed a significant increase in total volatile compounds with acetaldehyde being most abundant. However, compared to intact fruits, cut Golden and Red Delicious apples had a lower intensity for ester related peaks. Five parameters were extracted from the nosespace data of peaks related to esters (m/z 43, 61), acetaldehyde (m/z 45), and ethanol (m/z 47): 2 associated with mastication (duration of mastication–t_con; time required for first swallowing event–t_swal), and 3 related with in‐nose volatile compound concentration (area under the curve–AUC; maximum intensity–I_max; time for achieving I_max–t_max). Three different behaviors were identified in the nosespace data: a) firm samples with low AUC and t_swal values (Granny Smith, Fuji), b) mealy samples with high AUC, I_max, t_swal values, and low t_con (Morgen Dallago, Golden Delicious), and c) firm samples with high AUC and I_max values (Red Delicious). Strengths and limitations of the methodology are discussed. Practical Application: Volatile compounds play a fundamental role in the perceived quality of food. Using apple cultivars, this research showed that in vivo proton transfer reaction mass spectrometry (PTR‐MS) could be used to determine the relationship between the release of volatile flavor compounds and the physicochemical parameters of a real food matrix. This finding suggests that in vivo PTR‐MS coupled with traditional physicochemical measurements could be used to yield information on flavor release from a wide range of food matrices and help in the development of strategies to enhance food flavor and quality.     

Influence of different banana cultivars on volatile compounds during ripening in cold storage

The aroma responsible for the flavor of fruits is highly susceptible to low temperatures in storage. The present study investigated the volatile composition of the Nanicão and Prata banana cultivars by testing pulp and whole fruit under cold storage conditions. The volatile fractions were characterized using headspace solid phase micro-extraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS). The cold storage induced changes in the volatile profile relative to the profile of the control group. The result of principal component analysis revealed that cold storage more strongly affects the Nanicão than the Prata cultivar. Esters such as 2-pentanol acetate, 3-methyl-1-butanol acetate, 2-methylpropyl butanoate, 3-methylbutyl butanoate, 2-methylpropyl 3-methylbutanoate and butyl butanoate were drastically reduced in the cold group of the Nanicão cultivar. Our results suggest that the metabolism responsible for the production of volatile compounds is related to the ability to tolerate low temperatures.     

The flavor of pomegranate fruit: a review

Despite the increasing commercial importance of pomegranate, especially because of its recently discovered health‐promoting benefits, relatively little is yet known regarding its sensory quality and flavor preferences, or about the biochemical constituents that determine its sensory characteristics. The perceived flavor of pomegranate fruit results from the combination of various taste, aroma and mouthfeel sensations. The taste is governed mainly by the presence of sugars (glucose and fructose) and organic acids (primarily citric and malic acids). The aroma evolves from the presence of dozens of volatiles, including alcohols, aldehydes, ketones, and terpenes, which provide a mixture of various ‘green’, ‘woody’, ‘earthy’, ‘fruity’, ‘floral’, ‘sweet’ and ‘musty’ notes. In addition, the sensory satisfaction during the eating of pomegranate arils is complemented by various mouthfeel sensations, including seed hardness and astringency sensations. In the present review we will describe the sensory quality and flavor preferences of pomegranate fruit, including the genetic diversity in flavor characteristics among distinct varieties. In addition, we will describe the dynamic changes that occur in fruit flavor during fruit ripening and postharvest storage. © 2013 Society of Chemical Industry     

Comparison of Volatile Release in Tomatillo and Different Varieties of Tomato during Chewing

ABSTRACT: The release of volatiles from tomatillos (Physalis ixocarpa Brot.) and tomatoes in the mouthspace and nosespace was measured in real-time using selected ion flow tube mass spectrometry (SIFT-MS). (Z)-3-Hexenal, (E)-2-hexenal, hexanal, and 1-penten-3-one increased, while isobutyl alcohol, nonanal, and methylbutanal showed no significant change in the first 30 s of chewing. Cherry tomato released more (E)-2-hexenal, (Z)-3-hexenal, and 1-penten-3-one than tomatillo, Roma tomato, and vine-ripened tomato during chewing. The proportion of the average concentration of volatiles in the mouthspace after swallowing to before swallowing (MSas/MSbs) varied from 2.8% to 73.9% between different volatiles and varieties. Methylbutanal, hexanal, and nonanal were retained at a higher percentage in the mouth after swallowing than (Z)-3-hexenal, (E)-2-hexenal, 1-penten-3-one, and isobutyl alcohol. The proportion of the average volatile concentration in the mouthspace, to the headspace in a glass container (MS/HS) of 1-penten-3-one, hexanal, methylbutanal, and nonanal, and the proportion of nosespace to headspace (NS/HS) for 1-penten-3-one, hexanal, (Z)-3-hexenal, and nonanal was significantly higher in tomatillo than in tomatoes. There was no difference between tomatoes of different varieties in NS/HS ratio. Practical Application: The real-time volatile release from tomatillos and tomatoes was measured and compared. The information obtained on the dynamic generation of volatile compounds provides a better understanding of volatile release in the headspace of tomatillo and tomatoes. The compounds and their volatile release patterns were similar for the tomatillo and tomatoes. The green aldehydes released during chewing were not significantly higher than most tomato varieties, except for Roma tomatoes. Cherry tomato released relatively more volatiles during chewing, whereas Roma tomatoes were generally poor in mouthspace volatiles. The lingering of volatiles in the mouth after swallowing was different for different volatiles and varieties, which may appear as a sensory difference detected by consumers.     

EATING QUALITY OF “FUJI” APPLES AFFECTED BY A PERIOD OF COLD AIR AFTER ULO STORAGE

ABSTRACT

Over two subsequent seasons, emission of volatile compounds, consumer acceptability and quality parameters were analyzed in “Fuji” apples. In both seasons, apples were harvested at the same maturity stage and stored for 19 or 30 weeks at 1C and 92% relative humidity under an ultralow oxygen (ULO) atmosphere (1% O₂ + 1% CO₂) or under an ULO atmosphere followed by different periods (2 or 4 weeks) in cold air. The results revealed, for both seasons, that 4 weeks of cold air storage after ULO storage helped to increase the emission of some volatile compounds for both storage period, including characteristic volatile compounds for the variety, and did not have a negative effect on quality parameters. Additionally, the consumer acceptability was superior for those fruits.

PRACTICAL APPLICATIONS

It is well known for various apple varieties that long‐term storage under ULO conditions reduces volatile production resulting in poor flavor and aroma compared with fruits stored in air. Consequently, there is often dissatisfaction among consumers with the flavor of fruits which have been subjected to cold storage. The strategy that is proposed in the present work could be recommended to enhance the aromatic quality of fruit provided by the apple industry and, in consequence, increase its acceptability by consumers.     

MAINTAINING POSTHARVEST QUALITY OF THE TOMATO FRUIT BY EMPLOYING METHYL JASMONATE AND ETHANOL VAPOR TREATMENT

ABSTRACT

The postharvest quality of tomato fruit (Lycopersicon esculentum L.) was evaluated after treatment with natural volatile compounds (methyl jasmonate [MJ] or ethanol) and storage at 13C during or following vapor exposure. The fruit treated with natural volatiles did not differ on fruit decay during vapor exposure, but following exposure and transfer to ambient air, the fruit had less decay at storage temperature. Volatile‐treated fruit tended to maintain firmness during exposure, and the effects were significant for ethanol‐treated fruit, following storage to ambient air. Sugar (i.e., fructose and glucose) concentration was stimulated in ethanol‐treated fruit following exposure and transfer to ambient air. Ascorbic acid concentration was stimulated in MJ‐treated fruit during exposure and persisted (including ethanol treatment) following transfer to ambient air. Total phenolics declined during vapor exposure and increased for MJ‐treated fruit after transfer to ambient air. Lycopene concentration did not differ during MJ exposure but increased following volatile exposure. The fruit samples treated with vapors had accelerated percentage weight loss compared with untreated fruit during ripening but without commercial interest, whereas citric acid content did not differ among the treatments. The results suggest that MJ and ethanol vapor may improve fruit quality‐related attributes on top of the well‐documented antimicrobial protection during fresh produce storage and transit.

PRACTICAL APPLICATIONS

The data presented in this work suggest that the use of natural volatiles is an innovative and useful tool as an alternative to the use of synthetic fungicides or other sanitation techniques in storage/packaging. Vapor enrichment may reduce disease development with a major contribution to limiting the spread of the pathogen by lowering the spore load (spore production) in the storage/transit atmospheres as well as the use of natural volatiles as an alternative food preservative. In addition to these, the improvement of fruit quality observed in the present work is of great market importance. The effects of natural compounds on individual microorganisms (fungi and bacteria), both responsible for spoilage and foodborne pathogens, as well as the minimum concentration to gain effectiveness without affecting fresh produce quality and storage deserve further research.

     

Effect of Pretreatment with Dehulling and Microwaving on the Flavor Characteristics of Cold‐Pressed Rapeseed Oil by GC‐MS‐PCA and Electronic Nose Discrimination

Raw and dehulled rapeseeds were treated with microwave energy (800 W) from 1 to 8 min with 1‐min intervals at a frequency of 2450 MHz to investigate the influence of microwaving and dehulling pretreatment on the flavor characteristics of rapeseed oil extracted by pressing. Headspace solid phase microextraction was used to isolate the volatile compounds of rapeseed oil, which were then identified by gas chromatography‐mass spectrometry analysis. The results indicated that microwave and dehulling pretreatment of rapeseed can significantly influence the kinds and content of volatile compounds. The key flavor compounds in rapeseed oil were oxidized volatiles, heterocyclic compounds, and degradation products of glucosinolates. A pungent compound, 4‐isothiocyanato‐1‐butene, was reduced by 97% in rapeseed treated for 3 min with microwaves energy when compared to the rapeseed oil without any treatment. The pyrazine compounds in the oil appeared after 6 min of microwave pretreatment and give a pleasant roasting flavor when compared to crude oils. Principal component analysis was able to differentiate between oils obtained using 4 pretreatment processes based on volatile compounds and electronic nose. The results showed that dehulling pretreatment could improve the flavor, yet microwaving had a greater effect on the flavor of rapeseed oils.