44C-30 |
Are flavor aldehydes in cantaloupe endogenous or secondary compounds? |
J. M. LEA1, C. C. Grimm, and J. C. Beaulieu. (1) Food Processing and Sensory Quality, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70124 Formation of secondary compounds in fruits and vegetables are known to occur upon processing or sampling. Lipoxygenase (LOX) catalyzes incorporation of molecular oxygen into polyunsaturated fatty acids (linoleic acid and linolenic acid) to form hydroperoxides that are cleaved by hydroperoxide lyase (HPL) into various C6and C9 aldehyes such as hexanal, (E) 2-hexenal, (E, Z) 2, 6-nonadienal, and (E) 2-nonenal. Aldehydes are further reduced via alcohol dehydrogenase (ADH) into related alcohols, which are incorporated into flavor esters.Our goal was to compare endogenous versus secondary aldehyde production in cantaloupe mesocarp during tissue disruption or maceration. Aldehyde levels in mature and immature fruit were compared to blended juice ± LOX inhibitors such as n-propyl gallate (nPG), stannous chloride, and N2 atmosphere. Volatile compounds from immature and mature fruit cores as well as homogenized juice were monitored starting 13 days after pollination (DAP) through harvest with 5 different maturities (¼, ½, ¾, full-slip and over-ripe) that were processed and stored for 14 days at 4°C. Compound recovery was performed with SPME and GC-MS. In the immature fruit cores, few compounds were observed until 34 DAP and then only esters were detected, but in blended samples, aldehydes such as pentanal, hexanal, octenal, (E, Z) 2, 6-nonadienal, and (E) 2-nonenal were abundant. Hexanal, (E, Z) 2, 6-nonadienal, and (E) 2-nonenal were completely inhibited when nPG was added. In the fresh-cut mature cores mostly esters were recovered. However in blended samples, (E, Z) 2, 6-nonadienal, and (E) 2-nonenal were abundant but were not present when nPG was added, whereas key muskmelon flavor esters remained the same or increased.Our results indicate that most aliphatic aldehydes recovered from mesocarp tissue are secondary compounds. An attempt will be made to correlate LOX recovery and activity from pericarp versus mesocarp tissue with regard to aldehyde genesis.
Session 44C, Fruit & Vegetable Products: Chemistry
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