Effect of cultivar and storage time on the volatile flavor components of baked potato

Tubers of five cultivars of potato were stored at 4 degrees C for 2, 3, and 8 months and baked in a conventional oven. The flavor compounds from the baked potato flesh were isolated by headspace adsorption onto Tenax and analyzed by gas chromatography-mass spectrometry. On a quantitative basis, compounds derived from lipid and Maillard reaction/sugar degradation dominated the flavor isolates, with sulfur compounds, methoxypyrazines, and terpenes making smaller contributions. Levels of 37 of the >150 detected compounds were monitored in each cultivar with time of storage. Many significant differences were found in levels of individual compounds, compound classes, and total monitored compounds for the individual effects of cultivar and storage time and for their two-way interaction. Differences may be explained by variations in levels of flavor precursors and activities of enzymes mediating flavor compound formation among cultivars and storage times. In addition, differences in agronomic conditions may partly account for variations among cultivars. Overall, of the compounds monitored, those most likely having the greatest flavor impact were 2-isopropyl-3-methyoxypyrazine, 2-isobutyl-3-methoxypyrazine, dimethyl trisulfide, decanal, and 3-methylbutanal, with methylpropanal, 2-methylbutanal, methional, and nonanal also being probable important contributors to flavor.     

Generation of Maillard compounds from inulin during the thermal processing of Agave tequilana Weber Var. azul

During the cooking process of Agave tequilana Weber var. azul to produce tequila, besides the hydrolysis of inulin to generate fermentable sugars, many volatiles, mainly Maillard compounds, are produced, most of which may have a significant impact on the overall flavor of tequila. Exudates (agave juice) from a tequila company were collected periodically, and color, Brix, fructose concentration, and reducing sugars were determined as inulin breakdown took place. Maillard compounds were obtained by extraction with CH(2)Cl(2), and the extracts were analyzed by GC-MS. Increments in color, Brix, and reducing sugars were observed as a function of time, but a decrease in fructose concentration was found. Many Maillard compounds were identified in the exudates, including furans, pyrans, aldehydes, and nitrogen and sulfur compounds. The most abundant Maillard compounds were methyl-2-furoate, 2,3-dihydroxy-3,5-dihydro-6-methyl-4(H)-pyran-4-one, and 5-(hydroxymethyl)furfural. In addition, a series of short- and long-chain fatty acids was also found. A large number of the volatiles in A. tequilana Weber var. azul were also detected in tequila extracts, and most of these have been reported as a powerful odorants, responsible for the unique tequila flavor.     

Volatiles from roasted byproducts of the poultry-processing industry

Volatiles of roasted chicken breast muscle and byproducts, such as backbones, breastbones, spent bones, and skin, were investigated. Total volatile concentrations ranged from 2030 ppb in the roasted backbones to 4049 ppb in the roasted skin. The major classes of volatile compounds detected in roasted samples were aldehydes (648-1532 ppb) and alcohols (336-1006 ppb). Nitrogen- and/or sulfur-containing compounds were also detected in appreciable quantities (161-706 ppb) in all samples. For all samples, hexanal and 2-methyl-2-buten-1-ol were dominant among the aldehydes and alcohols, respectively. Among the nitrogen- and sulfur-containing compounds, Maillard reaction products, such as tetrahydropyridazines, piperidines, and thiazoles, were the major contributors to the total volatile content in all samples. The composition of volatiles observed in roasted byproducts was markedly different from that of the roasted breast muscle. Therefore, the blending of the byproducts in appropriate proportions or blending of volatile flavor extracts from different byproducts may be necessary to obtain an aroma that mimics roasted chicken aroma.     

Reducing acrylamide precursors in raw materials derived from wheat and potato

A review of agronomic and genetic approaches as strategies for the mitigation of acrylamide risk in wheat and potato is presented. Acrylamide is formed through the Maillard reaction during high-temperature cooking, such as frying, roasting, or baking, and the main precursors are free asparagine and reducing sugars. In wheat flour, acrylamide formation is determined by asparagine levels and asparagine accumulation increases dramatically in response to sulfur deprivation and, to a much lesser extent, with nitrogen feeding. In potatoes, in which sugar concentrations are much lower, the relationships between acrylamide and its precursors are more complex. Much attention has been focused on reducing the levels of sugars in potatoes as a means of reducing acrylamide risk. However, the level of asparagine as a proportion of the total free amino acid pool has been shown to be a key parameter, indicating that when sugar levels are limiting, competition between asparagine and the other amino acids for participation in the Maillard reaction determines acrylamide formation. Genetic approaches to reducing acrylamide risk include the identification of cultivars and other germplasm in which free asparagine and/or sugar levels are low and the manipulation of genes involved in sugar and amino acid metabolism and signaling. These approaches are made more difficult by genotype/environment interactions that can result in a genotype being "good" in one environment but "poor" in another. Another important consideration is the effect that any change could have on flavor in the cooked product. Nevertheless, as both wheat and potato are regarded as of relatively high acrylamide risk compared with, for example, maize and rice, it is essential that changes are achieved that mitigate the problem.     

鳙鱼皮水解物美拉德反应产物抗氧化活性研究

为进一步利用鱼类加工副产物,采用微波技术预处理鳙鱼皮,碱性蛋白酶酶解制备鳙鱼皮水解物(FSH),将其与葡萄糖、木糖和核糖进行美拉德反应,评价美拉德反应产物的抗氧化活性和挥发性风味物质。结果表明,美拉德反应显著提高了鳙鱼皮水解物的抗氧化活性,核糖美拉德反应产物的抗氧化活性最高,在135℃、35 min条件下,核糖美拉德反应产物的总氧化活性为2 156 μmol·L^-1 FeSO₄,DPPH自由基清除能力达到96.53%,超氧阴离子自由基清除能力达到88.08%。采用固相微萃取-气相色谱-质谱联用(SPME-GC-MS)分析美拉德反应产物的挥发性风味物质发现,呈肉香味的吡嗪、呋喃类杂环化合物相对含量增加,从而改善了鳙鱼皮水解物的风味。本研究结果为制备食品天然抗氧化剂提供了理论依据,为鱼类加工副产物高值化开发与利用提供了参考。     

Formation of sulfur aroma compounds in reaction mixtures containing cysteine and three different forms of ribose

The headspace volatiles produced from buffered and unbuffered cysteine model systems, containing inosine 5'-monophosphate, ribose 5-phosphate, or ribose, were examined by GC-MS. Sulfur compounds dominated the volatiles of all systems and included mercaptoketones, furanthiols, and disulfides. The inosine monophosphate systems produced much lower quantities of volatiles than ribose phosphate or ribose systems. In the systems buffered with phosphate or phthalate buffers, both ribose and ribose phosphate systems gave similar quantities of sulfur volatiles. However, in the absence of buffer, the ribose system was relatively unreactive, especially for volatiles formed via the 2,3-enolization route in the Maillard reaction, where 4-hydroxy-5-methyl-3(2H)-furanone is a key intermediate. A number of keto-enol tautomerisms, which are known to be acid-base-catalyzed, occur in the 2,3-enolization route. This may explain the catalysis of the ribose systems by the buffers. In the ribose phosphate systems, however, Maillard mechanisms probably played a less important role, because ribose 5-phosphate readily dephosphorylated to give 4-hydroxy-5-methyl-3(2H)-furanone on heating and thus provided an easier route to aroma compounds than the Maillard reaction.     

Characterization of odor-active volatiles in apples: influence of cultivars and maturity stage

The aroma and texture of three different apple cultivars, harvested at three maturity stages, were analyzed by sensory and instrumental analysis. The emphasis was on the identification of the most potent odorant volatiles, and the challenge was to separate the few most important flavor compounds, which may be trace chemicals, from the vast number of nonodorant compounds present in apple aroma extracts. Thirty-six odorant compounds were detected, 24 of which were common to all extracts. A significant correlation coefficient was found between the aroma intensity scores and overall quantity of the odorant volatiles, which shows that the development of sensory aroma is similar to that of odorant volatiles. This study also showed that the parameters measured by penetrometry and compression were highly correlated with sensory textural attributes. The determination of the optimal maturity stage for different apple cultivars by the usual parameters, such as color, diameter, total soluble solids, and titrable acidity, may not be sufficient to determine the optimal sensory quality for consumers. Moreover, the sensory quality of fruits changes during maturation in a different way from one cultivar to another, and this should be taken into account.     

Flavor Volatiles of Rice During Cooking Analyzed by Modified Headspace SPME/GC‐MS

The flavor volatiles in three Japanese rice cultivars, Nihonbare, Koshihikari, and Akitakomachi, during cooking were directly extracted by using a modified headspace solid‐phase microextraction (SPME) method and analyzed by gas chromatography‐mass spectrometry (GC‐MS). A total of 46 components were identified, including aldehydes, ketones, alcohols, and heterocyclic compounds, as well as fatty acids and esters, phenolic compounds, hydrocarbons, etc. The amount of key odorant compounds increased with cooking, while the amount of low‐boiling volatiles decreased. The similarities and differences of the three rice cultivars were determined through a comparison of their volatile components. Nihonbare was characterized by a higher amount of indole but an absence of the chemical class of fatty acid esters. In contrast, both Koshihikari and Akitakomachi had a higher amount of 4‐vinylphenol and an abundance of those esters. Koshihikari and Akitakomachi were quite similar in regard to those flavor volatiles. Furthermore, the observations in the research may suggest that the volatile components at cooking stage (I) were the representatives of the flavor volatiles of uncooked rice, while the volatile constituents at cooking stage (IV) were the representatives of the flavor volatiles of cooked rice.     

Influence of sulfur amino acids on the volatile and nonvolatile components of cooked salmon (Salmo salar)

Volatile and nonvolatile compounds, which could contribute to flavor, were analyzed in salmon. One hundred twenty-three volatile compounds were identified in the headspace of two different samples of cooked salmon, including lipid-derived volatiles, Maillard-derived volatiles, sulfur volatiles, Strecker aldehydes, nitrogen heterocyclic compounds, terpenes, and trimethylamine. Significant differences between samples were found for 104 of the volatiles. Although the levels of free cysteine and methionine were low in the salmon, sulfur volatiles were formed in the cooked fish, demonstrating that there were sufficient sulfur amino acids present for their formation. Notable differences in sulfur compounds between the samples suggested that small changes in sulfur amino acids could be responsible. When this hypothesis was tested, salmon heated with cysteine had increased levels of many thiophenes, thiazoles, alicyclic sulfides, and nitrogen heterocycles. With the addition of methionine, levels of dimethyl sulfides, two alicyclic sulfides, pyrazines, some unsaturated aldehydes, and alcohols and 2-furanmethanethiol increased. The largest difference found among the nonvolatile (low molecular weight water-soluble) compounds was in inosine monophosphate.     

Salt Tolerance of Four Potato Cultivars

Abstract

Tests are needed to evaluate the salt tolerance of new and untested potato cultivars under various cultural conditions. Two lysimeter experiments were conducted in two seasons to investigate the influence of irrigation water salinity on tuber yields of four potato (Solanum tuberosum L.) cultivars (Spunta, Alpha, Cara, and King Edward). Four salinity levels [EC_w 0.53 (control), 3.13, 6.25, and 9.38 dS m^?1] established by adding NaCI to fresh water, were used. Increasing irrigation water salinity reduced significantly total and average tuber yield for all cultivars in both seasons. Cara cultivar produced the highest tuber yield of all cultivars in both seasons. The salt tolerance curves of the potato cultivars in both seasons revealed that tolerant rating of the four cultivars can be assigned as follows: Cara > Alpha > Spunta > King Edward. The polynomial cubic equations developed for the four potato cultivars in fall and summer seasons were successful in predicting potato tuber yields response to irrigation water salinity.     

Content of free phenolic compounds in cultivars of potatoes harvested in Tenerife (Canary Islands)

Determination of free phenolic compounds in potato samples was optimized using a high-performance liquid chromatographic (HPLC) method with on-line diode array detection. This method was applied to samples of four cultivars of potatoes harvested in Tenerife (Canary Islands). The free phenolic compounds found in the potato samples were (+)-catechin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid. Potato samples belonging to Colorada cultivar, ssp. andigena, had mean concentrations of total phenolic compounds and chlorogenic acid higher than those found for Kerr's Pink and Cara cultivars, ssp. tuberosum, and for Negra cultivar, S. x chaucha. In contrast, p-coumaric acid was not detected in any potato samples of the Colorada cultivar. Traditional potatoes presented a higher mean concentration of ferulic acid than recently imported potatoes. A significant and negative correlation was established between (+)-catechin and p-coumaric acid. A considerable contribution to the daily intake of flavonoids was observed with the actual consumption of potatoes.     

Formation of 2-alkyl-(2H)-thiapyrans and 2-alkylthiophenes in cooked beef and lamb

2-Alkyl-(2H)-thiapyrans and 2-alkylthiophenes have been identified in the volatiles of cooked beef and lamb. The quantities of both groups of compounds were higher in the meat of animals fed lipid supplements high in n-3 polyunsaturated fatty acids. 2-Alkyl-(2H)-thiapyrans were formed when (E,E)-2,4-dienals (C(6)-C(11)) and hydrogen sulfide were heated at 140 degrees C for 30 min. This confirmed their proposed route of formation in cooked meat from lipid-derived aldehydes and hydrogen sulfide; the latter was produced from the degradation of cysteine, via the Maillard reaction. The mass spectra and NMR spectra of these thiapyrans are reported for the first time. Although 2-alkyl-(2H)-thiapyrans were found to have only low odor potency, the reactions by which they are formed may have important implications for meat flavor. These reactions may remove potent aroma compounds and their intermediates from meat, thus modifying the overall aroma profile.     

Reactions of monosaccharides during heating of sugar-casein systems: building of a reaction network model

The Maillard reaction is important during the heating and processing of foods for its contribution to food quality. To control a reaction as complex as the Maillard reaction, it is necessary to study the reactions of interest quantitatively. In this paper the main reaction products in monosaccharide-casein systems, which were heated at 120 degrees C and pH 6.7, were identified and quantified, and the reaction pathways were established. The main reaction routes were (i) sugar isomerization, (ii) degradation of the sugar into carboxylic acids, and (iii) the Maillard reaction itself, in which not only the sugar itself but also its reaction products react with the epsilon-amino group of lysine residues of the protein. Significant differences in reaction mechanism between aldose and ketose sugars were observed. Ketoses seemed to be more reactive in the sugar degradation reactions than their aldose isomers, and whereas the Amadori product was detected as a Maillard reaction intermediate in the aldose-casein system, no such intermediate could be found in the ketose-casein system. The reaction pathways found were put together into a model, which will be evaluated by kinetic modeling in a subsequent paper.     

Umami compounds are a determinant of the flavor of potato (Solanum tuberosum L.)

Vegetable flavor is an important factor in consumer choice but a trait that is difficult to assess quantitatively. The purpose of this study was to assess the levels of the major umami compounds in boiled potato tubers, in cultivars previously assessed for sensory quality. The free levels of the major umami amino acids, glutamate and aspartate, and the 5'-nucleotides, GMP and AMP, were measured in potato samples during the cooking process. Tubers were sampled at several time points during the growing season. The levels of both glutamate and 5'-nucleotides were significantly higher in mature tubers of two Solanum phureja cultivars compared with two Solanum tuberosum cultivars. The equivalent umami concentration was calculated for five cultivars, and there were strong positive correlations with flavor attributes and acceptability scores from a trained evaluation panel, suggesting that umami is an important component of potato flavor.     

Effect of urea on volatile generation from Maillard reaction of cysteine and ribose

Urea occurs naturally in many food products, and its presence affects food quality. However, little is known about its impact on flavor generation in food production. In this study, the urea contents in beef, pork, and chicken were determined. The effects of urea and pH on thermal flavor generation were investigated using the model system of cysteine with ribose, which was heated to the roasting temperature of 180 degrees C for 2 h at pH 5 and pH 8.5. The results revealed relatively large amounts of urea in these meats and demonstrated that pH affects aroma generation. Volatiles identified from the reaction system of ribose and cysteine showed that sulfur-containing compounds such as thiophenes, thiazoles, and thiophenethiols were the most abundant compounds. The addition of urea into the reaction mixture caused the disappearance or reduction in content of some sulfur-containing compounds but resulted in the generation of several important nitrogen-containing volatiles, like pyrazine, methylpyrazine, 2,5- (and 2,6-)dimethylpyrazine and other alkylpyrazines, which are known to elicit roasty, nutty flavor notes. A plausible explanation for this phenomenon is that ammonia can be released from urea upon heating and the formed ammonia competes with hydrogen sulfide to react with Maillard reaction precursors to produce nitrogen-containing compounds such as alkylpyrazines.     

Degradation of oligosaccharides in nonenzymatic browning by formation of alpha-dicarbonyl compounds via a "peeling off" mechanism

The formation of alpha-dicarbonyl-containing substances and Amadori rearrangement products was studied in the glycine-catalyzed (Maillard reaction) and uncatalyzed thermal degradation of glucose, maltose, and maltotriose using o-phenylenediamine as trapping agent. Various degradation products, especially alpha-dicarbonyl compounds, are formed from carbohydrates with differing degrees of polymerization during nonenzymatic browning. The different Amadori rearrangement products, isomerization products, and alpha-dicarbonyls produced by the used carbohydrates were quantified throughout the observed reaction time, and the relevance of the different degradation pathways is discussed. In the Maillard reaction (MR) the amino-catalyzed rearrangement with subsequent elimination of water predominated, giving rise to hexosuloses with alpha-dicarbonyl structure, whereas under caramelization conditions more sugar fragments with an alpha-dicarbonyl moiety were formed. For the MR of oligosaccharides a mechanism is proposed in which 1,4-dideoxyosone is formed as the predominating alpha-dicarbonyl in the quasi-water-free thermolysis of di- and trisaccharides in the presence of glycine.     

Investigation of volatiles in Charentais cantaloupe melons (Cucumis melo Var. cantalupensis). Characterization of aroma constituents in some cultivars

Volatile compounds of 15 Charentais melon cultivars, known to exhibit differences in their ripening behaviors and in their storage lives (wild, mid, and long shelf life), were investigated. Twenty-eight volatiles (11 esters, 8 sulfur compounds, 6 alcohols, and 3 carbonyl compounds) were isolated by direct dichloromethane extraction and analyzed by means of GC-MS and GC-FID. A considerable reduction in the aroma profile was observed for the long shelf life cultivars, in which total volatiles were 49-87% lower than in the wild or mid shelf life melons. Most of the esters such as ethyl 2-methylbutyrate, ethyl butyrate, ethyl hexanoate, hexyl acetate, and butyl acetate and sulfur compounds such as ethyl 2-(methylthio)acetate, 2-methylthioethanol, ethyl 3-(methylthio)propanoate, 3-(methylthio)propyl acetate, and 3-(methylthio)propanol with low odor values were 2-30-fold lower in long shelf life cultivars than in the others. Discrimination of long shelf life cultivars from wild and mid shelf life melons was achieved by statistical treatment of the data by principal component and variance analysis.     

Antioxidant properties of kilned and roasted malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.     

Volatile profiles of dry-cured meat products from three different Iberian x Duroc genotypes

Volatile profiles of two Iberian dry-cured products, dry-cured loin and ham, from three different Iberian x Duroc genotypes, was assessed. Three groups of 10 pigs, each (5 males and 5 females) from different genotypes, were studied: GEN1 = male Iberian x female Duroc1; GEN2 = male Duroc1 x female Iberian; and GEN3 = male Duroc2 x female Iberian. The genotype Duroc1 (DU1) corresponded to pigs selected for the production of dry-cured meat products (hams, loins, and shoulders), with a high level of fattening, while the genotype Duroc2 (DU2) corresponded to animals selected for meat production. Genotype slightly affected the volatile profiles of both dry-cured meat products, although dry-cured loin from GEN3 showed higher hexanal content. Dry-cured loin showed a volatile profile very different to that found in dry-cured ham. Volatile compounds of dry-cured meat products were mainly originated by lipid and protein degradation. Most of the volatile detected in both meat products came from lipid oxidation such as acids, aldehydes, ketones, alcohols, and hydrocarbons. In addition, a high proportion of volatile compounds from the Maillard reaction was found. Branched aldehydes and some sulfur and nitrogen compounds have their origin in the amino acids degradation by the Strecker reaction, while branched alcohols and acids come from the lipid oxidation of branched aldehydes. Dry-cured ham showed a higher number and a higher level of compounds with origin in protein and lipid degradation than dry-cured loin, which agrees with the longer ripening of the hams (24 months) with respect to the loins (4 months). In dry-cured loins, apart from these compounds, seasoning mixture provides high amount of volatiles, such as terpenes (from paprika and oregano) and sulfur compounds (from garlic), which have great importance in the overall aroma of this product.     

Effects of olive, canola, and sunflower oils on the formation of volatiles from the Maillard reaction of lysine with xylose and glucose

Some important edible oils (extra virgin olive oil, canola oil, and sunflower oil) were added to aqueous glucose-lysine or xylose-lysine model systems to investigate their effect on the formation of volatiles from the Maillard reaction (MR). The volatile compounds were extracted by a Likens-Nickerson apparatus and quantified. Pyrazines, Maillard reaction products with an important impact on food flavor, appeared to be particularly sensitive to the presence of the oils in both the xylose-lysine and glucose-lysine model systems. The unsubstituted pyrazine was formed more with olive oil, less with canola oil, and even less with sunflower oil, whereas 2-methylpyrazine, 2,5-methylpyrazine, and 2,3-dimethylpyrazine were formed less with olive oil, more with canola oil, and even more with sunflower. The oxidative states of the oils and their fatty acid fingerprints were determined: the results indicated that the relative amounts of the pyrazines are sensitive to the degree of unsaturation of the oil. The autoxidation of the volatile compounds generated from the MR, investigated by the addition of free radical modulators (antioxidants alpha-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and rosemary extract; or pro-oxidant alpha,alpha'-azobis-isobutyronitrile, a free radical initiator), was limited in respect to aqueous model systems.