Influence of variety and growing location on the development of off-flavor in precooked vacuum-packed potatoes

Aroma characterization of tangerine hybrids by gas-chromatography-olfactometry and sensory evaluation

BACKGROUND

Tangerines have a distinct flavor among citrus fruit. However, information on tangerine volatiles remains limited. Volatile compounds from a breeding population of tangerines were earlier identified by gas chromatography-mass spectrometry. In this study, five hybrids with a distinct volatile profile were analyzed by gas-chromatography-olfactometry (GC-O) and descriptive sensory analysis.

RESULTS

Forty-nine aroma active compounds were found in a consensus by GC-O. Aldehydes were the most important group with odor activity, as well as monoterpenes, esters, alcohols and ketones. 1,8-Cineole, β-myrcene, (E,E)-2,4-nonadienal, hexanal, ethyl-2-methylbutanoate, and linalool were perceived with high intensity in most samples. Two 'Clementine' × 'Minneola' and one 'Fortune' × 'Murcott' hybrids with tangerine, sulfury and woody/spicy flavors had aroma active compounds with terpeney, fatty/vegetable and metallic/rubber descriptors. A tangerine with 'Valencia' orange in its parentage had a characteristic orange flavor, which could be explained by esters and ketones, high in fruity and floral odor intensities. A hybrid of unknown origin had a distinct fruity-non-citrus and pumpkin/fatty flavor; that sample had the lowest amount of aroma-active volatiles, with the least compounds with terpeney odors.

CONCLUSION

There was no one compound characteristic of tangerine flavor. Nevertheless, each sample sensory characteristic could be explained by a set of aroma-active volatile compounds.

Identification of an allele attributable to formation of cucumber-like flavor in wild tomato species (Solanum pennellii) that was inactivated during domestication

Carbon 6 (C6)-aldehydes formed by fatty acid 13-hydroperoxide lyase (13HPL) specific to fatty acid 13-hydroperoxides (13-HPO) are important flavor constituents in fresh tomato fruits. C9-aldehydes are usually formed by 9/13HPL showing dual specificity to 9- and 13-HPOs and are scarcely found in tomato fruits. Mature red fruits of one of the introgression lines, IL1-4, generated by hybridization of a cultivated tomato (Solanum lycopersicon) to its wild relative Solanum pennellii, form high amounts of C9-aldehydes upon homogenization. The IL1-4 fruits showed high 9/13HPL activity. One of the genes isolated from IL1-4 showed a high similarity to plant 9/13HPLs. Recombinant proteins expressed in Escherichia coli showed 9/13HPL activity. Cleaved amplified polymorphic sequence analyses indicated that the gene was specific to IL1-4 and S. pennellii. S. lycopersicon had a gene having high similarity to the S. pennellii gene. It was absent in IL1-4. Among the differences of amino acid residues found between the two genes, a Cys to Ser exchange may be responsible for the inactivation of resultant protein product of S. lycopersicon gene because the Cys is an essential amino acid residue for HPL activity. From these observations, it could be assumed that a tomato gene corresponding to S. pennellii 9/13HPL gene had been inactivated through domestication of tomatoes.

Origins and implications of drinking water odours in lakes and reservoirs of British Columbia, Canada

The relationship between commonly measured limnological parameters and odours was examined in 16 reservoirs and lakes used as sources for drinking water and three reference lakes. Odour analysis was conducted using flavour profile analysis (FPA) and, on select lakes, gas chromatography ion-trap mass spectrometry (GC-ITMS) for target compounds. Total phosphorus (TP) was the best single predictor of FPA intensity and multiple regression models accounted for 37-39% of intensity variance in the epilimnion and metalimnion, respectively. Earthy odours were more prevalent in reservoirs and lakes with higher TP, whereas decomposing vegetation and green vegetation+grassy odours almost exclusively occurred when TP was lower (<13 microg P/L). Only geosmin was identified with GC-ITMS, and it was found to occur in lakes and reservoirs of higher trophic status (e.g. more algal biomass). Infrequent episodic events in the Greater Victoria's principal reservoir (e.g. algal blooms) have previously been linked with taste and odour problems in their tap water. However, analysis of odours under the conditions of this study (i.e. no strong odour episodes in the source reservoir) suggest that typical odours prevalent in tap water originating from Sooke Lake Reservoir are derived from treatment processes or the distribution system, not directly from the reservoir. This study demonstrates the utility of employing relatively simple and established methods to better understand management issues of a drinking water system.

Formation of aroma compounds and lipoxygenase (EC 1.13.11.12) activity in unblanched leek (Allium ampeloprasum Var. Bulga) slices during long-term frozen storage

The content of aroma compounds (dynamic headspace) and catalytic activity of lipoxygenase (LOX) (EC. 1.13.11.12) were analyzed in 15 mm unblanched leek slices seven times during 12 months of frozen storage. The aroma profile changed from consisting of almost only sulfur compounds such as dipropyl disulfide [concentration in fresh leek (FL) = 0.197 mg/L, concentration after 12 months of frozen storage (12M) = 0.0409 mg/L] and propyl (E)-propenyl disulfide (FL = 0.0437 mg/L, 12M = 0.00452 mg/L) in the fresh leeks to being dominated by numerous saturated and unsaturated aldehydes, such as hexanal (FL = 1.53 mg/L, 12M = 3.63 mg/L), (E,E)-2,4-nonadienal (FL = 0.000 mg/L, 12M = 0.0647 mg/L), and (E,E)-2,4-decadienal (FL = 0.129 mg/L, 12M = 0.594 mg/L) at the end of the storage period. The catalytic activity of LOX diminished throughout frozen storage, but approximately 25% of the original activity was present after 12 months of storage.

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.

Comparison of volatile compounds isolated from the skin and flesh of four potato cultivars after baking

Four potato cultivars, Cara, Nadine, Fianna, and Marfona, were selected. Potatoes were baked in their skins prior to separating the skin and flesh and preparing extracts of the volatile flavor compounds using a modified Likens--Nickerson apparatus. The concentrated extracts were analyzed by gas chromatography--mass spectrometry. Volatiles were identified and classified according to their origin, that is, lipid, sugar degradation and/or Maillard reaction not involving sulfur amino acids, sulfur compounds, methoxypyrazines, and other compounds. Quantitative and qualitative differences were observed between isolates from flesh and skins and among cultivars grown at different sites. Strongest isolates from skin were obtained for Nadine. For flesh, Cara gave isolates approximately 10-fold more concentrated than the other three cultivars. For skin, sugar degradation and/or the Maillard reaction was by far the most important source in all cultivars except Nadine, for which 62% of the volatiles were accounted for by the sesquiterpene solavetivone. Lipid and sugar degradation and/or the Maillard reaction were the main origins of volatiles in flesh. Calculated aroma values for a selection of the key potato volatiles identified reinforce the effects of cultivar and growing site on baked potato flavor.