Modification of fish oil aroma using a macroalgal lipoxygenase

Abstract

The odor of fish oil is the major factor limiting its application in food. In this study, the addition of butylated hydroxytoluene to fish oil did not significantly inhibit the generation of fishy and rancid odors. To reduce the undesirable odors, fish oil was treated with lipoxygenase (LOX) to produce volatile compounds via position-specific cleavage of hydroperoxides. An extract of a green marine macroalga, Ulva conglobata, showed a high level of 13-LOX activity and 9-LOX to a lesser extent, and produced strong green, melon-like, and fresh-fishlike flavor notes from fish oil. The LOX-modified fish oil contained 99% of the highly unsaturated fatty acids (HUFA; containing three or more double bonds) originally present, total volatile compounds increased from 3477 to 3787 ppb after LOX treatment. Compounds with strong odors accounted for about 40% of the total volatiles. Increasing the level of LOX activity used to treat fish oil produced higher concentrations of the desirable unsaturated aldehydes, ketones, and alcohols, with odors resembling fresh fish, apple, citrus, melon, fruit, and oyster. These compounds were tentatively identified as E, Z-2,6-nonadienal, E-2-hexenal, E,E-2,4-octadienal, E,E-3-5-octadien-2-one, and alcohols E-2-pentenol and 2-butoxyethanol. The LOX treatment also slightly increased the content of the undesirable volatile components, including sour and rancid odors, tentatively identified as acetic acid and E,Z-and E,E-2,4-decadienals.

Fatty acid composition and volatile compounds of selected marine oils and meals

“…The small Euclidean differences found for the raw materials when comparisons were based on their fatty acid data, compared with those established by their volatile data, indicate different sources of variation of the two sets of data. Fatty acid composition seems to be solely dependent on biological factors (season and fish species used for raw materials), whereas volatile composition is also highly dependent on manufacturing techniques,17, 42, 43 storage conditions14, 25 and volatile extraction methods 28, 44. Thus it can be concluded that these additional factors seem to be strong sources of variation and therefore do not allow volatiles to be useful as traceability markers.…”

“…Salmon oil had a relatively repeatable volatile compound profile within its two batches (SO1 and SO2). The higher content of 2,4‐heptadienal in salmon oil could indicate a higher degree of oxidation of this oil, since levels of this compound have been found to increase with oxidation 14, 17…”

“…Although the flavour of fish has been examined extensively,3, 9–13 data on the volatiles of marine oils are scarce, apart from some on herring oil,14 menhaden oil,15, 16 cod liver oil17 and tuna oil 18. No data are available regarding the volatiles of marine meals.…”

Cryoprotective and antioxidative effects of gelatin hydrolysate from unicorn leatherjacket skin

“…The control showed the marked increase in 2, 4-heptadienal, approximately 10-fold after 6 freeze-thaw cycles. It was reported that the increase in 2, 4-heptadienal yielded an extremely rancid odour in fish oil (Hu and Pan, 2000). Moreover, pentanol was detected after freeze-thawing process in both control and sample added with NS-GH.…”

Characterization of Farmed Ovate Pompano (Trachinotus ovatus Linnaeus) Freshness during Ice Storage by Monitoring the Changes of Volatile Profile

“…1-Penten-3-ol has been identified in various fish species including tuna, gilthead sea bream, oyster, whiting (Duflos et al, 2005;Edirisinghe et al, 2007;Soncin et al, 2009;Zhang et al, 2009). 1-Penten-3-ol was reported to be the product of the action of lipoxygenases on ω-3 PUFA (German et al, 1992;Hu and Pan, 2000). 1-Penten-3-ol could also be caused by Pseudomonas species and can contribute to the stale and putrid off odors in fish (Miller et al, 1973;Olafsdottir et al, 2005).…”