Spirit recovered from heap-fermented grape marc: Nature,origin and removal of the off-odour

Spirit derived from heap-fermented grape marc was found to owe its undesirable odour to a series of unsaturated carbonyl compounds present in trace amounts. The principal odoriferous aldehydes in the spirit included trans-2-octenal, trans, trans-2,4-heptadienal, trans-2-nonenal, trans, trans-2,4-nonadienal, trans-2-undecenal and trans, trans-2,4-decadienal. The same compounds were found in a sample of autoxidised grape-seed oil. This implied that oxidation of the polyunsaturated fatty acids in the grape-seed oil was responsible for off-odours of the marc spirit. The odorous carbonyl compounds could be removed by passing the marc spirit through a strong anion-exchange resin in the bisulphite form. By analysing total acetaldehyde concentration in the treated spirit and relating this to the sensory characteristics of the spirit, an indirect analytical monitor of the efficiency of the deodorisation process was established.     

Oxidation of corn oil at room temperature: Primary and secondary oxidation products and determination of their concentration in the oil liquid matrix from H nuclear magnetic resonance data

The oil liquid matrix of several corn oil samples that have been stored at room temperature in closed receptacles for different periods of time is studied by means of ¹H nuclear magnetic resonance (¹H NMR), in order to further knowledge about this type of edible oil oxidation. As expected, the degradation of linoleic acyl groups predominates. In samples at early oxidation stages the presence of hydroperoxides and of (Z,E) conjugated-dienic systems is demonstrated, the concentration of the first group being higher than that of the second. In addition to these compounds, the presence of hydroxy derivatives supporting (Z,E) conjugated-dienic systems, as well as of hydroperoxy derivatives supporting (E,E) conjugated-dienic systems, in samples at intermediate and advanced oxidation stages, is also shown. Corn oil samples at advanced stages of oxidation also contain aldehydes, among which there are alkanals, (E)-2-alkenals, (E,E)-2,4-alkadienals, 4-hydroxy-(E)-2-alkenals, 4-hydroperoxy-(E)-2-alkenals and 4,5-epoxy-(E)-2-alkenals. The concentrations of the different kinds of intermediate compounds above mentioned as well as of the different kinds of aldehydes present in the oil liquid matrix were determined. These latter compounds can be either free or joined to truncated structures of triglycerides. In addition, a principal component analysis between storage conditions and oxidation level of the samples was carried out.     

Comparative study of extra virgin olive oil flavor profile of Koroneiki variety (Olea europaea var. Microcarpa alba) cultivated in Greece and Tunisia during one period of harvesting

The effects of geographical region, irrigation and ripening degree of olives on the profile of volatile compounds isolated by monovarietal virgin olive oils from Crete and Tunisia of Koroneiki variety (Olea europaea var. Microcarpa alba) using the SPME GC/MS technique were investigated. Fruits obtained from Greece (island of Crete) and Tunisia (Sfax region) were picked at three and two different growth stages respectively and then immediately processed. The most important compounds identified were esters, alcohols, carbonyl compounds and hydrocarbons. The main volatile compounds present in the oil samples were C6 derivatives, such as [E]-2-hexenal, [E]-2-hex-1-enol, [Z]-3-hexen-1-ol and 1-hexanol. In addition to C6 compounds, the aroma of the studied samples contained reasonable amounts of various classes of C5 components. The tested oil samples showed different volatile profiles. Specifically, the concentration of total esters, carbonyl, C6 and C5 compounds increased significantly with the ripening degree in Cretan, but not in Tunisian olive oils. Principal component analysis of the results indicated that primary maturity and geographical region rather than irrigation affected significantly the volatile’s profile of olive oil.     

Relationship between odour-active compounds and flavour perception in meat from lambs fed different diets

To identify the most important aroma compounds in 20 d-aged meat from castrated heavy Corriedale lambs fed one of four diets, grilled loin samples were subjected to a dynamic headspace-solid phase extraction (DHS-SPE) and gas chromatography–olfactometry (GC–O). Most of the important odorants were aldehydes and ketones. To evaluate the effect of finishing diet on carbonyl compounds, a derivatization of the headspace carbonyls using o-[(2,3,4,5,6-pentafluorophenyl)methyl]hydroxylamine hydrochloride (PFBHA) and analysis by GC–MS was conducted. Diet did not affect aliphatic saturated aldehydes. The meat from lambs finished on pastures, without a concentrate supplement, had very low concentrations of lipid-derived unsaturated aldehydes and ketones and Strecker aldehydes, possibly because of the protective effect of antioxidants that occur in the diet naturally. Lamb flavour was related to the concentration of heptan-2-one and oct-1-en-3-one, but rancid or undesirable flavours were not related to the abundance of carbonyl compounds.     

烹制方法对猪肉脂质氧化和挥发性风味物质的作用研究

研究对比了4种烹制方法(煮制、烤制、微波及油炸制(大豆油、花生油和葵花油))对猪肉脂质氧化及挥发性风味成分的影响。结果表明:烹制能够促进猪肉的脂质氧化,经不同方式烹制后,熟制猪肉的过氧化值(POV)和硫代巴比妥酸值(TBA)显著增加(P0.05)。不同熟制猪肉之间脂质氧化程度存在显著性差异(P0.05),其中烤制猪肉的脂质氧化程度最高,其次为微波和水煮,而炸制猪肉的氧化程度最低。气相色谱-质谱(GC-MS)联用技术从熟制猪肉中共分离鉴定出68种挥发性风味成分,主要包括醛类、脂肪烃类、醇类、酮类、酯类等,总挥发性风味化合物含量在221.09(大豆油炸制猪肉)-1084.61 AU×106/g(煮制猪肉)之间。醛类是主要的化合物,占总挥发性风味成分的73.78(葵花油炸制猪肉)-78.79%(烤制猪肉),而己醛是最主要的醛类物质。TBA值与醛类、醇类及总挥发性风味物质呈显著正相关(p0.05),而POV值与挥发性风味物质的相关性不显著(p0.05)。主成分分析法(PCA)能够很好地区分经不同烹制方法得到的熟猪肉。     

Effect of blackberry and raspberry juice on whey protein emulsion stability

The effect of raspberry and blackberry juice on oil-in-water (o/w) emulsion oxidative stability was investigated with different concentrations of whey proteins and rapeseed oil. The extent of lipid oxidation was measured by determining conjugated diene hydroperoxides and thiobarbituric acid reactive substances and that of protein oxidation by loss of natural tryptophan fluorescence and formation of protein carbonyl compounds. In addition, the anthocyanin colour stability and emulsion turbidity were measured. The increasing concentration of whey proteins and berry juices led to enhanced stabilization of the interface formed during emulsification. The anthocyanin concentration and colour decreased during oxidation leading to whiter emulsions. Raspberry juice provided a better overall antioxidant protection towards lipid and protein oxidation compared to blackberry juice. The antioxidant activity of berry juices towards lipid oxidation varied with concentration. The antioxidant activity increased with increasing concentration of berry juices. In conclusion, red berry juice anthocyanins, as well as other phenolic compounds, act as antioxidants improving the oxidative stability of whey protein emulsions. However, the antioxidant protection is different towards protein and lipid oxidation, and is also affected by other components present.     

Headspace composition of cod liver oil and its evolution in storage after opening. First evidence of the presence of toxic aldehydes

The headspaces of two samples of cod liver oil, when recently acquired, after five and after fifteen months from opening, were studied by solid phase microextraction, followed by gas chromatography/mass spectrometry. Nearly one hundred compounds were found, some of them identified for the first time as cod liver oil components. In both samples, the presence of the toxic 4-hydroxy-(E)-2-hexenal and of 4-oxo-(E)-2-hexenal was detected, as well as that 4,5-epoxy-2-heptenal in one of the samples; this is the first time that these toxic compounds have been described as being present in cod liver oil. In the early oxidation stages, taking place during storage, the compounds formed are mainly of low molecular weight; some of these could be adopted as oxidation markers of cod liver oil. The possibilities of using the technique to evaluate the oxidation level of cod liver oil are shown. These results suggest the need to monitor the levels of toxic oxygenated α,β-unsaturated aldehydes in cod liver oil in order to ensure its safety.     

Volatile oxidation compounds in a conjugated linoleic acid-rich oil

In this study, volatile oxidation compounds formed in a commercial conjugated linoleic acid (CLA)-rich oil were quantified and results compared to those found in safflower oil (rich in linoleic acid, LA). Intact oil samples and pure triacylglycerols obtained following elimination of tocopherols and minor compounds were oxidised at 60 °C, and volatile oxidation compounds were analysed by solid phase microextraction-gas chromatography with flame ionisation detector and mass spectrometer. Results showed that while, as expected, hexanal was the major volatile oxidation compound found in oil and triacylglycerols rich in LA, both hexanal and heptanal equally were the most abundant compounds in oil and triacylglycerols rich in CLA. Besides, samples rich in CLA also showed significantly high quantities of trans-2-octenal and trans-2-nonenal and the latter, along with heptanal, were absent in samples rich in LA. Results for CLA samples were not easy to interpret since major volatiles found are not expected from theoretically stable hydroperoxides formed in CLA and could in part derive from dioxetanes coming from 1,2-cycloadditions of CLA with oxygen. Overall, results obtained support evidence that oxidation mechanisms of CLA may differ than those of LA. Also, it was concluded that heptanal determination could serve as a useful marker of oxidation progress in CLA-rich oils.     

基于SPME-GC-MS和电子鼻分析薏苡仁油加速氧化过程挥发性成分变化

采用固相微萃取-气相色谱-质谱联用和电子鼻技术分析薏苡仁油氧化期间风味化合物动态变化。结果表明：薏苡仁油加速氧化期间特征挥发性风味物质主要为醛类、酮类、醇类化合物。新鲜油中相对气味活度值大于1的关键挥发性成分贡献度从大到小依次为(E)-2-壬稀醛、(E,E)-2,4-癸二烯醛、(E)-2-癸烯醛、(E,Z)-2,6-壬二烯醛、1-辛烯-3-酮、癸醛,赋予青草气味、油脂味、西瓜样品味;随着氧化时间的延长油脂品质劣变,60 ℃加速氧化30 d时醛类化合物相对含量为73.815%,与新鲜油相比,小分子醛、酸及醇类化合物相对含量增加;薏苡仁油加速氧化后关键风味化合物新增壬醛、辛醛、己醛、(E)-2-辛烯醛,赋予其酸败气味;电子鼻线性判别分析明显区分新鲜油与氧化油以及氧化初期及后期风味物质差异。结果表明(E)-2-壬稀醛、(E,E)-2,4-癸二烯醛等为新鲜薏苡仁油的特征化合物,壬醛、辛醛、己醛等小分子化合物为薏苡仁油加速氧化后的特征化合物。     

Comparative chemical composition,antioxidant and hypoglycaemic activities of Juniperus oxycedrus ssp. oxycedrus L. berry and wood oils from Lebanon

Juniper (Juniperus oxycedrus) is used in European cuisine for its distinguishing flavour. J. oxycedrus ssp. oxycedrus berry and wood essential oils were tentatively identified by GC and GC/MS. Fifty compounds were identified in the berry oil and 23 compounds were identified in the wood oil. The J. oxycedrus ssp. oxycedrus berry oil was characterised by high contents of α-pinene (27.4%) and β-myrcene (18.9%). Other important compounds were α-phellandrene (7.1%), limonene (6.7%), epi-bicyclosesquiphellandrene (2.3%) and δ-cadinene (2.2%) while, in the wood oil, δ-cadinene (14.5%) is a major main component, together with cis-thujopsene (9.2%) and α-muurolene (4.9%). In vitro evaluation of antioxidant activity by the DPPH method showed a significant activity for both oils with IC₅₀ values of 1.45 μl/ml for wood and 7.42 μl/ml for berries. Hypoglycaemic activity was investigated through the inhibition of α-amylase. The results revealed that oil obtained by hydrodistillation from J. oxycedrus ssp. oxycedrus wood exhibits an interesting activity with IC₅₀ of 3.49 μl/ml.     

Oxidation of aldehydes by xanthine oxidase located on the surface of emulsions and washed milk fat globules

The enzymatic activity of xanthine oxidase (XO) located within the native and recombined milk fat globule membrane (MFGM) on emulsion surfaces was investigated after successive washing with deionised water (DW) or simulated milk ultrafiltrate (SMUF). DW was more effective than SMUF at removing non-MFMG proteins from the globule surface. Surface XO activity on a protein basis increased after three washes due to loss of MFGM proteins to the serum phase. Recombined emulsions had higher surface enzymatic activity than washed native fat globule samples. The oxidation of acetaldehyde, 3-methylbutanal, 2-methylpropanol and 2-methylbutanal to the corresponding acids by XO on the globule surface was analysed. A higher proportion of aldehydes were depleted at higher XO activity when the initial aldehyde concentration was constant, and for higher initial concentrations of aldehydes. The recovery of aldehydes and acids was above 79%, indicating that the depleted aldehydes were mostly converted to the corresponding acids.     

HS-SPME-GC-MS联用及电子鼻分析不同提取方法油莎豆油香气特征

采用顶空固相微萃取-气相色谱-质谱联用对不同提取方法（超临界CO2萃取法、压榨法、浸出法、水酶法）获取的油莎豆油挥发性化合物的组成及相对含量进行分析，结合主成分分析（principal component analysis，PCA）及电子鼻进行比较，并以相对气味活度值（relative odor activity value，ROAV）确定关键风味化合物。结果表明：不同提取方法油莎豆油挥发性化合物的组成及相对含量存在明显差别，4 个样品共鉴定出101 种挥发性化合物，共有组分为22 种，主要为醛类、酮类、酯类及烷烃类，超临界CO2萃取法及压榨法样品中醛类物质相对含量最大分别为36.71%和25.64%，浸出法样品中烷烃类物质相对含量最大为31.07%，水酶法样品中酯类物质相对含量最大为45.66%；挥发性化合物的PCA及电子鼻分析可以将4 种方法很好区分；根据ROAV得出4 个样品的关键风味化合物，其中壬醛、柏木脑及D-柠檬烯为共有成分。     

Determination of aldehydes as pentafluorobenzyl derivatives in grape pomace distillates by HS-SPME-GC/MS

This work describes an analytic method that quantifies aldehydes in grape pomace distillates (Orujo). Diluted samples were derivatised with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine and then microextracted with a solid phase (SPME) for analysis by GC–MS. Twenty compounds, among them, short chain aldehydes having pungent notes (propanal, butanal, and Strecker aldehydes) and long chain aldehydes characterised by fatty odours were studied.     

HPLC–ESI-MS investigation of tyrosol and hydroxytyrosol oxidation products in virgin olive oil

The aim of this research is the characterisation of the oxidation products of several hydrophilic phenols of virgin olive oil (VOO), such as hydroxytyrosol (3,4-DHPEA) and tyrosol (p-HPEA) and, their identification in the product during storage. This work is aimed at finding analytical indicators that can be used both as molecular markers of VOO “freshness” and for the evaluation of the shelf life of the product itself. Two oxidation systems were examined for the oxidation of p-HPEA and 3,4-DHPEA: enzymatic oxidation and Fenton oxidation. Reaction products were different for the two systems and were identified as quinones, dimers, and acids. During the autoxidation process, Fenton reaction oxidation products, but not enzymatic oxidation products, were found in VOO.     

Inhibition of lipid oxidation and dynamics of polyphenol content in mechanically deboned meat supplemented with sea buckthorn (Hippophae rhamnoides) berry residues

Mechanically deboned meat (MDM) contains about 10 times more polyunsaturated fatty acids (PUFAs) and also more hemoproteins than hand deboned meat (HDM) and is essentially more susceptible to both chemical and biochemical oxidation. The oxidation, leading to the formation of potentially mutagenic and carcinogenic derivatives of PUFAs, can be inhibited by berry extracts rich in antioxidant polyphenols. Using the 2-thiobarbituric acid reactive substances (TBARS) method, we have established that the ethanol slurry of the juice-free solid residue of sea buckthorn (Hippophae rhamnoides – SB) berries inhibits oxidation of unsaturated fatty acids, of both chicken and turkey MDM. The polyphenols, mainly flavonols, responsible for this inhibition, are comparatively stable during short-term cooking and 6-day storage of cooked SB-MDMs at +6 °C. About half of the polyphenols are lost, obviously oxidised, during the storage of the uncooked samples of turkey 2%SB-MDM at +6 °C. The loss of polyphenols is much smaller in the case of chicken MDM, which is characterised by an in situ lower content of fatty acids, including the polyunsaturated ones. The liquid chromatography–diode array detection–tandem mass spectrometry (LC–DAD–ESI-MS/MS) method was used for identification and ranking of the potent polyphenolic antioxidants in the berry residue.     

Monitoring the oxidation of almond oils by HS-SPME–GC–MS and ATR-FTIR: Application of volatile compounds determination to cultivar authenticity

In this study, the oxidative process of Spanish and American almond oils was monitored by using headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Oxidative stability of samples was evaluated after thermal treatment at 100 °C for 1, 3, 5, 7, 10, 15 and 20 days, in order to accelerate the lipid oxidation process. Variations observed in bands of infrared spectra were used to monitor the progress of the oxidation process of almond oils. HS-SPME–GC–MS was used for isolation and determination of volatile compounds in oxidised almond oils. The following aldehydes were identified in all samples: hexanal, (E)-2-heptenal, (E)-2-octenal, nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal and (E,E)-2,4-decadienal. Determination of volatile compounds resulting from lipid oxidation from three different almond cultivars (Spanish Guara and Marcona and Butte from USA) was performed to obtain a set of parameters for discrimination between Spanish and American cultivars. Successful discrimination was obtained in samples kept under thermal treatment for 7 days, by using HS-SPME/GC–MS combined with multivariate stepwise linear discriminant analysis (LDA).     

1H NMR approach as an alternative to the classical p-anisidine value method

Aldehydes, formed as secondary oxidation products during the autoxidation process of oils and fats, are analytical markers used to assess the lipid deterioration status. Generally, the level of aldehydes is expressed as the p-anisidine value (AV). This deterioration index is based on the reaction of the carbonyl group with p-anisidine leading to the formation of an intensively coloured Schiff base which is determined spectroscopically (UV/ViS). ¹H NMR provides an alternative approach by enabling the quantification of individual aldehydes like n-alkanals, 2-alkenals or (E,E)-2,4-alkadienals. This work illustrates that the AV can be modelled as a linear combination of the NMR integrals of aldehydes. A functional relationship was derived on the basis of calibration experiments. The suitability of the model is shown by comparing the NMR-determined AVs with the classical AVs of 79 commercially available edible oils of different oil types.     

橄榄油氧化过程中风味化合物变化

橄榄油具有良好保健功能,是较为理想食用油脂;但在贮存过程中也存在氧化变质现象;橄榄油氧化将产生对人体有毒、有害副产物,其独特风味发生劣化,产生难以接受气味。该文详细介绍橄榄油氧化机理,总结引起橄榄油风味改变的醛、酮、醇、短链脂肪酸等氧化产物。     

Analysis of Aldehydes and Ketones in the Headspace of Heated Pork Fat

Volatile chemicals in the headspace above heated pork fat were purged into aqueous solutions of cysteamine, sodium bisulfite, or methylhydrazine to trap aldehydes and ketones. Nine aldehydes and four ketones were determined as thiazolidine derivatives in traps containing aqueous cysteamine or aqueous sodium bisulfite. The major compounds produced were hexanal, heptanal, and pentanal. In general, aqueous cysteamine was more efficient at trapping carbonyl compounds than was aqueous sodium bisulfite. However, formalydehyde and acetaldehyde were trapped better by sodium bisulfite solution than by cysteamine solution. Acrolein and malonaldehyde were determined as l-methyl-2-pyrazoline and 1-methylpyrazole, respectively, from the trap containing methylhydrazine. This represents the first time that malonaldehyde has been determined in the vapor phase.