Studies on the aroma of five fresh tomato cultivars and the precursors of cis- and trans-4,5-epoxy-(E)-2-decenals and methional

Three tasty (BR-139, FA-624, and FA-612) and two less tasty (R-144 and R-175) fresh greenhouse tomato cultivars, which significantly differ in their flavor profiles, were screened for potent odorants using aroma extract dilution analysis (AEDA). On the basis of AEDA results, 19 volatiles were selected for quantification in those 5 cultivars using gas chromatography-mass spectrometry (GC-MS). Compounds such as 1-penten-3-one, ( E, E)- and ( E, Z)-2,4-decadienal, and 4-hydroxy-2,5-dimethyl-3(2 H)-furanone (Furaneol) had higher odor units in the more preferred cultivars, whereas methional, phenylacetaldehyde, 2-phenylethanol, or 2-isobutylthiazole had higher odor units in the less preferred cultivars. Simulation of the odor of the selected tomato cultivars by preparation of aroma models and comparison with the corresponding real samples confirmed that all important fresh tomato odorants were identified, that their concentrations were determined correctly in all five cultivars, and that differences in concentration, especially of the compounds mentioned above, make it possible to distinguish between them and are responsible for the differential preference. To help elucidate formation pathways of key odorants, labeled precursors were added to tomatoes. Biogenesis of cis- and trans-4,5-epoxy-( E)-2-decenals from linoleic acid and methional from methionine was confirmed.     

Similarities in the aroma chemistry of Gewürztraminer variety wines and lychee (Litchi chinesis sonn.) fruit

GC/O analysis of canned lychees indicated that cis-rose oxide, linalool, ethyl isohexanoate, geraniol, furaneol, vanillin, (E)-2-nonenal, beta-damascenone, isovaleric acid, and (E)-furan linalool oxide were the most odor potent compounds detected in the fruit extracts. However, on the basis of calculated odor activity values (OAVs), cis-rose oxide, beta-damascenone, linalool, furaneol, ethyl isobutyrate, (E)-2-nonenal, ethyl isohexanoate, geraniol, and delta-decalactone were determined to be the main contributors of canned lychee aroma. When these results were compared with GC/O results of fresh lychees and Gewürztraminer wine, 12 common odor-active volatile compounds were found in all three products. These included cis-rose oxide, ethyl hexanoate/ethyl isohexanoate, beta-damascenone, linalool, ethyl isobutyrate, geraniol, ethyl 2-methylbutyrate, 2-phenylethanol, furaneol, vanillin, citronellol, and phenethyl acetate. On the basis of OAVs, cis-rose oxide had the highest values among the common odorants in the three products, indicating its importance to the aroma of both lychee fruit and Gewürztraminer wines. Other compounds that had significant OAVs included beta-damascenone, linalool, furaneol, ethyl hexanoate, and geraniol. This indicated that while differences exist in the aroma profile of lychee and Gewürztraminer, the common odorants detected in both fruit and wine, particularly cis-rose oxide, were responsible for the lychee aroma in Gewürztraminer wine. When headspace SPME was used as a rapid analytical tool to detect the levels of selected aroma compounds deemed important to lychee aroma in Gewürztraminer-type wines, cis-rose oxide, linalool, and geraniol were found to be at relatively higher levels in Gewürztraminers. No cis-rose oxide was detected in the control wines (Chardonnay and Riesling), while lower levels were detected in the Gewürztraminer-hybrid wine Traminette. Gewürztraminers produced in the Alsace region showed differences in the levels of the 3 monoterpenes when compared to those from New York State, which could be attributed to differences in viticultural and enological practices between regions.     

滴灌水肥管理对温室冬春茬辣椒产量与风味的影响

  【目的】  探究滴灌水肥管理措施对温室辣椒产量与风味品质的影响,明确不同生育阶段适宜土壤含水量控制值,提出高产与增香提味的滴灌水肥管理方案。  【方法】  采用研发的全水溶滴灌专用肥,2019和2020年开展了温室冬春茬羊角型辣椒滴灌水肥协同试验。滴灌水量(W)和专用肥量(F)分别设计3个水平,共9个水肥组合处理。2019年总灌水量分别为1703.3 m3/hm2 (W1)、2423.3 m3/hm2 (W2)、3143.3 m3/hm2 (W3),总专用肥量分别为712.5 kg/hm2 (F1)、1087.5 kg/hm2 (F2)、1462.5 kg/hm2 (F3);2020年总灌水量分别为1913.3 m3/hm2 (W1)、2753.3 m3/hm2 (W2)、3593.3 m3/hm2 (W3),总专用肥量分别为412.5 kg/hm2 (F1)、825.0 kg/hm2 (F2)、1237.5 kg/hm2 (F3)。调查了辣椒阶段商品果产量、总商品果产量及构成、脐腐病果形成量,分析了鲜果辣味和挥发性香气成分,并监测了生育期间根区土壤含水量。  【结果】  灌水量对辣椒商品果总产量、总果实数、第4～10次滴灌施肥阶段采收的商品果产量和脐腐病果量的影响极显著(P<0.01),施肥量及其与灌水量的交互作用影响不显著。两年商品果总产量和2019年总果实数均表现为:W3>W2>W1,处理间差异显著;从第4次滴灌施肥开始,W2和W3处理采收的果实商品产量显著高于W1处理,在第6、7、9次施肥阶段,W3处理果实商品产量显著高于W2处理;W3处理显著降低了非商品果产量和脐腐病果量,氮磷钾总吸收量也显著高于W1处理。灌水量对鲜果中碳氢化合物、醛类、吡嗪类、呋喃类等主要香气组分含量,二氢辣椒素含量以及2-甲氧基-3-异丁基吡嗪(主体香气物质)、(E,E)-2,4-壬二烯醛等主要香气物质活度的影响极显著(P<0.01),施肥量对吡嗪类组分含量影响显著(P<0.05),水肥交互作用不明显。W1处理碳氢化合物、吡嗪类、呋喃类香气组分含量显著高于W2和W3处理,二氢辣椒素含量也最高,W1和W2处理醛类组分含量显著高于W3处理,W1处理2-甲氧基-3-异丁基吡嗪、(E,E)-2,4-壬二烯醛的活度显著高于W2,W2处理显著高于W3处理。F2和F3处理2-甲氧基-3-异丁基吡嗪的活度显著高于F1处理。W1、W2和W3处理全生育期根区土壤相对含水量平均分别为51%、77%和88%;从第2次滴灌施肥开始,W2、W3处理土壤含水量显著高于W1处理。  【结论】  适量降低滴灌水量可浓缩鲜果汁液,增加多种香气成分的积累,但是病果和畸形果较多;适量增加滴灌肥量有利于辣椒主体香气成分累积。增香提味兼顾产量较适宜的水肥组合(W2F2)灌水量为2423 m3/hm2和专用肥量为825 kg/hm2。     

Aroma components of cooked tail meat of American lobster (Homarus americanus)

Key aroma components of cooked tail meat of American lobster (Homarus americanus) were studied by gas chromatography-olfactometry (GCO) techniques. Components of low and intermediate volatility were evaluated by aroma extract dilution analysis of solvent extracts prepared by direct solvent extraction-high vacuum distillation and vacuum steam distillation-solvent extraction, whereas headspace volatile components were assessed by GCO of decreasing headspace (static and dynamic modes) samples. Forty-seven odorants were detected by all techniques. 3-Methylbutanal (chocolate, malty), 2,3-butanedione (buttery), 3-(methylthio)propanal (cooked potato), 1-octen-3-one (mushroom), 2-acetyl-1-pyrroline (popcorn), and (E,Z)-2,6-nonadienal (cucumber), were identified as predominant odorants by all four isolation methods. The highly volatile compounds methanethiol (rotten, sulfurous) and dimethyl sulfide (canned corn) were detected by headspace methods only. These eight odorants along with three unknown compounds with crabby, amine, fishy odors were found to predominate in the overall aroma of cooked lobster tail meat.     

Comparison of the most odor-active compounds in fresh and dried hop cones (Humulus lupulus L. variety spalter select) based on GC-olfactometry and odor dilution techniques

Application of aroma extract dilution analysis on the volatiles obtained from dried cones of Spalter Select hops grown in the German hop-growing area of Hallertau revealed 23 odorants in the flavor dilution (FD) factor range of 16-4096, 20 of which could be identified. On the basis of high FD factors, trans-4, 5-epoxy-(E)-2-decenal, linalool, and myrcene were identified as the most potent odorants, followed by ethyl 2-methylpropanoate, methyl 2-methylbutanoate, (Z)-1,5-octadien-3-one, nonanal, (E,Z)-1,3, 5-undecatriene, 1,3(E),5(Z),9-undecatetraene, propyl 2-methylbutanoate, 4-ethenyl-2-methoxyphenol, and 1-octen-3-one. Ten of the high-impact hop aroma compounds had previously not been identified as hop constituents and, in particular, 1,3(E),5(Z), 9-undecatetraene has not yet been reported as a food odorant. In an extract obtained from fresh hops, in addition to the odorants found in dry hops, (Z)-3-hexenal was characterized as a further key odorant rendering an additional green aroma note to the fresh material.     

Effects of abscisic acid and calcium on tomato fruit aroma volatiles

Aroma volatiles are derived from precursors, such as amino acids, fatty acids and carotenoids in tomato fruit. Volatiles enhance the main flavor components in the fruit, particularly sugars. Abscisic acid (ABA) is derived from the carotenoid pathway and there may be an indirect connection to this pathway. Therefore, the purpose of this study was to examine the influence of ABA on tomato fruit volatiles. This study identified five flavor volatile compounds that were consistently present in “Mt. Fresh Plus” tomato fruit tissue. They were 2-methyl furan, (E)-2-hexeanl, 1-hexanol, hexenal, and 6-methyl-5-hepten-2-one. ABA treatments did not have an effect on volatile concentrations in “Mt. Fresh Plus” tomato fruit. Majority of the volatiles identified did not differ between the ABA treated plants and the ABA control plants. However, ABA treatments did significantly decrease (E)-2-hexenal. These results indicated that ABA treatments did not have a major effect on the aroma volatile profile of the fruit.     

Occurrence of flavonols in tomatoes and tomato-based products

The flavonol contents of 20 varieties of tomato fruit were investigated in relation to variety, size, season, and country of origin. Ten commonly consumed tomato-based food products were also assessed. Free and conjugated flavonols were identified and quantified using reversed-phase HPLC. Ninety-eight percent of flavonols detected in tomatoes were found to occur in the skin. Tomatoes contained, primarily as conjugates, quercetin and kaempferol. The main quercetin conjugate was identified as rutin (quercetin 3-rhamnosylglucoside) by LC-MS. The total flavonol content of the different varieties of tomato that were analyzed varied from 1.3 to 22.2 microgram/g of fresh weight (fw). Smaller cherry tomato fruits originating from warm sunny climates, such as Spain and Israel, were found to contain the highest concentration of flavonols. Among the tomato-based products investigated, tomato juice and tomato purée were rich in flavonols, containing 14-16 microgram/mL and 70 microgram/g fw, respectively. In contrast to fresh tomatoes, most tomato-based products contained significant amounts of free flavonols.     

Solid-phase microextraction (SPME) technique for measurement of generation of fresh cucumber flavor compounds

Investigations were carried out to determine whether flavor compounds characteristic for fresh cucumbers could be rapidly determined using a solid-phase microextraction (SPME) dynamic headspace sampling method combined with gas chromatography and flame ionization detection. Cucumbers were sampled, during blending, for fresh cucumber flavor compounds (E,Z)-2,6-nonadienal and (E)-2-nonenal. The GC was such that the two target compounds were separated and baseline-resolved. Relative standard deviations for analysis of both (E,Z)-2,6-nonadienal and (E)-2-nonenal using this SPME sampling method were +/-10%. Utility of the analytical method was demonstrated by determining the effect of heat treatments on the ability of cucumbers to produce these flavor impact compounds.     

Determination of key aroma compounds in the crumb of a three-stage sourdough rye bread by stable isotope dilution assays and sensory studies

An investigation of the volatile fraction of a freshly prepared sourdough rye bread crumb by means of the aroma extract dilution analysis (AEDA), followed by identification experiments, revealed 22 flavor compounds in the flavor dilution (FD) factor range of 128 to 2048. Quantitations performed by stable isotope dilution assays (SIDA) and a calculation of odor activity values (OAV; ratio of concentration to odor threshold) revealed the following as contributors to the overall crumb flavor: 3-methylbutanal (malty), (E)-2-nonenal (green, fatty), (E,E)-2,4-decadienal (fatty, waxy), hexanal (green), acetic acid (sour, pungent), phenylacetaldehyde (honey-like), methional (boiled potato-like), vanillin (vanilla-like), 2,3-butandione (buttery), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (spicy), and 2- and 3-methylbutanoic acid (sweaty). Using either citrate buffer, starch, or deodorized crumb as model matrixes, the typical malty and sour rye bread crumb flavor was reproduced by adding a mixture of 20 reference odorants in the "natural" concentrations as quantitatively determined in the fresh crumb.     

Some unusual minor volatile components of tomato

The identities and possible origins of three minor unusual volatile components of tomato are discussed. These are pentyl nitrate, the first identification of a volatile alkyl nitrate in a fresh vegetable or fruit; 5-ethyl-2(5H)-furanone, which, besides its presence in tomato, was found to be a major autoxidation product of pure (Z)-3-hexenal; and 5-ethylcyclopentene-1-carbaldehyde, a likely unusual linolenic acid oxidation product.     

Effects of nitrogen application on flavor compounds of cherry tomato fruits

A pot experiment was conducted to determine the effects of N application on volatile compounds, taste compounds, and firmness of fresh tomato fruits. Each pot was filled with 8 kg of clean sand. The experiment consisted of six nitrogen (N)‐application rates with 0, 2.25, 4.50, 9.00, 18.00, and 36.00 mmol N L^–1 in the nutrient solution. Volatile compounds, soluble sugars, soluble solids, titratable acidity, and firmness of fresh tomato fruits were measured. The results show that increasing N application increased the concentrations of 1‐penten‐3‐one, hexanal, cis‐3‐hexenal, 2‐methyl‐4‐pentenal, trans‐2‐hexenal, 6‐methyl‐5‐hepten‐2‐one, titratable acidity, soluble sugars, and soluble solids. By contrast, increasing N supply decreased the concentration of phenylacetaldehyde and first increased and then decreased the concentrations of 2E–4E‐hexadienal and the firmness of fresh tomato fruits. Close relationships between the concentration of various volatile compounds, titratable acidity, soluble sugars, and soluble solids were found. However, concentrations of these flavor compounds were very poorly correlated with fruit firmness. Based on contributions of these compounds to tomato flavor, we assume that moderate high N supply improves tomato flavor, whereas excessive N supply can deteriorate it.     

Characterization of the most odor-active compounds in an American Bourbon whisky by application of the aroma extract dilution analysis

Application of the aroma extract dilution analysis (AEDA) on the volatile fraction carefully isolated from an American Bourbon whisky revealed 45 odor-active areas in the flavor dilution (FD) factor range of 32-4096 among which (E)-beta-damascenone and delta-nonalactone showed the highest FD factors of 4096 and 2048, respectively. With FD factors of 1024, (3S,4S)-cis-whiskylactone, gamma-decalactone, 4-allyl-2-methoxyphenol (eugenol), and 4-hydroxy-3-methoxy-benzaldehyde (vanillin) additionally contributed to the overall vanilla-like, fruity, and smoky aroma note of the spirit. Application of GC-Olfactometry on the headspace above the whisky revealed 23 aroma-active odorants among which 3-methylbutanal, ethanol, and 2-methylbutanal were identified as additional important aroma compounds. Compared to published data on volatile constituents in whisky, besides ranking the whisky odorants on the basis of their odor potency, 13 aroma compounds were newly identified in this study: ethyl (S)-2-methylbutanoate, (E)-2-heptenal, (E,E)-2,4-nonadienal, (E)-2-decenal, (E,E)-2,4-decadienal, 2-isopropyl-3-methoxypyrazine, ethyl phenylacetate, 4-methyl acetophenone, alpha-damascone, 2-phenylethyl propanoate, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, trans-ethyl cinnamate, and (Z)-6-dodeceno-gamma-lactone.     

Identification of characteristic aroma components of Thai fried chili paste

Three forms of Thai fried chili pastes (CP) were prepared, consisting of an unheated CP (UH-CP), a CP heated at 100 degrees C for 25 min (H25-CP, typical product), and a CP excessively heated for 50 min (H50-CP). The potent odorants in the CPs were investigated by two gas chromatography-olfactometry methods: dynamic headspace dilution analysis (DHDA) and aroma extract dilution analysis (AEDA). DHDA revealed that the predominant odorants in heated CPs were mainly sulfur-containing compounds, followed by lipid-derived compounds, Strecker aldehydes, and Maillard reaction products. Dimethyl sulfide, allyl mercaptan, 2- (or 3-) methylbutanal, ally methyl sulfide, 2,3-butanedione, 3,3'-thiobis(1-propene), and methyl propyl disulfide were among the most potent headspace odorants detected by DHDA. By AEDA, 2-vinyl-4 H-1,3-dithiin and diallyl trisulfide had the highest FD factors in H25-CP. On the basis of their high FD factors by both GCO methods, the predominant odorants in H25-CP were 3-vinyl-4 H-1,2-dithiin, allyl methyl disulfide, and allyl methyl trisulfide. Furthermore, dimethyl trisulfide and diallyl disulfide had the highest odor activity values in H25-CP, suggesting that these were also potent odorants in CP. In addition, methional, 3-methylbutanoic acid, 4-hydroxy-2,5-dimethyl-3-(2 H)-furanone, and 3-hydroxy-4,5-dimethyl-2( 5H)-furanone (sotolon) were indicated as potent thermally derived odorants of H25-CP.     

Chemical characterization of commercial Sherry vinegar aroma by headspace solid-phase microextraction and gas chromatography-olfactometry

The sensorial representativeness of the headspace solid-phase microextraction (HS-SPME) aroma extract from commercial Sherry vinegars has been determined by direct gas chromatography-olfactometry (D-GCO). Extracts obtained under optimal conditions were used to characterize the aroma of these vinegars by means of GCO and aroma extract dilution analysis (AEDA). Among the 37 different odorants determined, 13 of them were identified for the first time in Sherry vinegars: 2 pyrazines (3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine), 2 sulfur compounds (methanethiol, dimethyl trisulfide), 1 unsaturated ketone (1-octen-3-one), 1 norisoprenoid (β-damascenone), 1 ester (ethyl trans-cinnamate) and 6 aldehydes (2- and 3-methylbutanal, octanal, nonanal, (E)-2-nonenal and (E,E)-2,4-decadienal). The determination of the odor thresholds in a hydroacetic solution together with the quantitative analysis-which was also performed using the simple and fast SPME technique-allowed obtaining the odor activity values (OAV) of the aromatic compounds found. Thus, a first pattern of their sensory importance on commercial Sherry vinegar aroma was provided.     

Characterization of the aroma of a meatlike process flavoring from soybean-based enzyme-hydrolyzed vegetable protein

Defatted soybean meal was converted into enzyme-hydrolyzed vegetable protein (E-HVP) using the proteolytic enzyme Flavorzyme. Total free amino acids increased by 40-fold after enzyme hydrolysis, with leucine being the most abundant, followed by phenylalanine, lysine, glutamine/glutamic acid, and alanine. Volatile components from a meatlike process flavoring made from E-HVP were isolated by direct solvent extraction (DSE)-high vacuum transfer (HVT), dynamic headspace sampling and static headspace sampling and analyzed by gas chromatography (GC)-mass spectrometry and GC-olfactometry. Aroma extract dilution analysis was used to establish a flavor dilution chromatogram of the DSE-HVT extract. Results of these complementary techniques indicated the importance of odorants of high (hydrogen sulfide and methanethiol), intermediate (2-methyl-3-furanthiol, 3-mercapto-2-pentanone, 2-furanmethanethiol, and 3-(methylthiol)propanal) and low volatility (maltol and Furaneol) in the overall aroma of the meatlike process flavoring.     

Carotenoid pigmentation affects the volatile composition of tomato and watermelon fruits, as revealed by comparative genetic analyses

Tomato near-isogenic lines differing in fruit carotenogenesis genes accumulated different aroma volatiles, in a strikingly similar fashion as compared to watermelon cultivars differing in fruit color. The major volatile norisoprenoids present in lycopene-containing tomatoes and watermelons were noncyclic, such as geranial, neral, 6-methyl-5-hepten-2-one, 2,6-dimethylhept-5-1-al, 2,3-epoxygeranial, (E,E)-pseudoionone, geranyl acetone, and farnesyl acetone, seemingly derived from lycopene and other noncyclic tetraterpenoids. Beta-ionone, dihydroactinodiolide, and beta-cyclocitral were prominent in both tomato and watermelon fruits containing beta-carotene. Alpha-ionone was detected only in an orange-fleshed tomato mutant that accumulates delta-carotene. A yellow flesh (r) mutant tomato bearing a nonfunctional psy1 gene and the yellow-fleshed watermelon Early Moonbeam, almost devoid of carotenoid fruit pigments, also lacked norisoprenoid derivatives and geranial. This study provides evidence, based on comparative genetics, that carotenoid pigmentation patterns have profound effects on the norisoprene and monoterpene aroma volatile compositions of tomato and watermelon and that in these fruits geranial (trans-citral) is apparently derived from lycopene in vivo.     

Simultaneous transgenic suppression of LePG and LeExp1 influences fruit texture and juice viscosity in a fresh market tomato variety

Tomatoes are grown for fresh consumption or for processing of the fruit. Some ripening-associated processes of the fruit can either contribute to or degrade attributes associated with both fresh and processing quality. For example, cell wall disassembly is associated with loss of fresh fruit firmness as well as with loss of processed tomato product viscosity. Several enzymes contribute to cell wall polysaccharide disassembly. Polygalacturonase (PG, poly[1,4-alpha-d-galactouronide] glucanohydrolase, EC 3.2.1.15) is among the most abundant polysaccharide hydrolases in ripening tomato fruit and is the major contributor to pectin depolymerization. Expansin (LeExp1) is also abundant in ripening fruit and is proposed to contribute to cell wall disassembly by nonhydrolytic activity, possibly by increasing substrate accessibility to other enzymes. Suppression of either LePG or LeExp1 expression alone results in altered softening and/or shelf life characteristics. To test whether simultaneous suppression of both LePG and LeExp1 expression influences fruit texture in additive or synergistic ways, transgenic Lycopersicon esculentum var. Ailsa Craig lines with reduced expression of either LePG or LeExp1 were crossed. Fruits from the third generation of progeny, homozygous for both transgenic constructs, were analyzed for firmness and other quality traits during ripening on or off the vine. In field-grown transgenic tomato fruit, suppression of LeExp1 or LePG alone did not significantly increase fruit firmness. However, fruits suppressed for both LePG and LeExp1 expression were significantly firmer throughout ripening and were less susceptible to deterioration during long-term storage. Juice prepared from the transgenic tomato fruit with reduced LePG and LeExp1 expression was more viscous than juice prepared from control fruit.     

Changes in sugars,acids, and volatiles during ripening of koubo [Cereus peruvianus (L.) Miller] fruits

The columnar cactus Cereus peruvianus (L.) Miller, Cactaceae (koubo), is grown commercially in Israel. The unripe fruits are green, and the color changes to violet and then to red when the fruit is fully ripe. The content of soluble sugars was found to increase 5-fold during ripening. Glucose and fructose were the main sugars accumulated in the fruit pulp, and each increased from 0.5 to 5.5 g/100 g fresh weight during ripening. The polysaccharides content decreased during ripening from 1.4 to 0.4 g/100 g fresh weight. The titratable acidity decreased and the pH increased during ripening. The major organic acid found in the fruit was malic acid, which decreased from 0.75 g/100 g fresh weight at the mature green stage to 0.355 g/100 g fresh weight in ripe fruits. Citric, succinic, and oxalic acids were found in concentrations lower than 0.07 g/100 g fresh weight. Prominent accumulation of aroma volatiles occurred toward the end of the ripening process. The main volatile found in the ripe fruit was linalool, reaching concentrations of 1.5-3.5 microg/g fresh weight.     

Change in carotenoids and antioxidant vitamins in tomato as a function of varietal and technological factors

The change in the carotenoid and bioantioxidant content of tomato as a function of varietal and technological factors was investigated in the present work. No great differences were found between cultivars for fresh consumption (salad tomatoes) and those for processing in ascorbic acid content. The concentration of ascorbic acid ranged between 14.6 and 21.7 mg/100 g fresh weight of ripe tomato fruit. Processing cultivars contained higher amounts of tocopherols, particularly alpha-tocopherol than tomatoes for fresh consumption. Significant differences could be obtained between the examined varieties with regard to carotenoid concentration. The different tomatoes varied not only in the total carotenoid content but also in the qualitative distribution of some pigments such as lycopene, beta-carotene and lutein. During heat-based processing, ascorbic acid, tocopherols, and carotenoids showed different role and response. Ascorbic acid, alpha-tocopherol quinone, and beta-carotene were the most susceptible components toward thermal degradation.     

Evaluation of the key aroma compounds in beef and pork vegetable gravies a la chef by stable isotope dilution assays and aroma recombination experiments

Although the aroma compounds of meat processed as such have been studied previously, data on complete homemade dishes containing beef and pork meat were scarcely studied. Recently, 38 odor-active compounds were characterized in beef and pork vegetable gravies using GC-olfactometry. In the present investigation, the most odor-active compounds were quantitated in a freshly prepared stewed beef vegetable gravy (BVG) as well as a stewed pork vegetable gravy (PVG) by means of stable isotope dilution assays. Calculation of odor activity values (OAVs; ratio of concentration to odor threshold) revealed 3-mercapto-2-methylpentan-1-ol, (E,E)-2,4-decadienal, (E,Z)-2,6-nonadienal, (E)-2-decenal, (E)-2-undecanal, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone as the most potent odorants in both gravies. However, significantly different OAVs were found for 12-methyltridecanal, which was much higher in the BVG, whereas (E,Z)-2,4-decadienal showed a clearly higher OAV in the PVG. Aroma recombination experiments performed on the basis of the actual concentrations of the odorants in both gravies revealed a good similarity of the aromas of both model mixtures containing all odorants with OAVs > 1 with those of the original gravies.