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R eceived 28 A pril 1995; revised 28 N o v em b er 1995; accepted 31 J a n u a ry 1996 AbstractCod fillets (Gadus morhua) were packed under modified atmospheres, with four differ ent gas com positions (60% CO2-10% Or 30% N 2, 60% COr 20% Or 20% N 2, 60% C O r 30% O2-10% N 2, 60% CO2-40% 0 2), and stored at 6°C. Plate counts were carried out after 3, 4, 5, 6 and 7 days, to follow the growth o f aerobic and anaerobic bacteria, lactic acid bacteria, H 2S-producing bacteria and Enterobacteriaceae. The production o f total volatile bases (TVB) and trimethylamine (TM A), and the changes in pH o f the fillets were measured. Modified atm osphere packaging (MAP) had in general an inhibitory effect on the growth o f the microflora but limited inhibition of the production o f TVB and TM A. Despite the fact th at increased oxygen proportions in the atm osphere contributed in a slightly lower production o f TM A, all the samples had a TVB and TM A content high enough to be considered as spoiled after 4 days' storage at 6°C. A total aerobic plate count at 25°C o f a IO6 cfu/g, combined with the presence o f only a IO3 cfu/g of H 2S-producing bacteria, which are normally considered as TM A O -reducing organisms in fish, cannot explain the strong increase in TM A. A high cell concentration o f m ore than IO8 cfu/g of Shewanella putrefaciens is required for production o f a TM A level normally found in spoiled fish. This suggests that there could be another type of bacterium in fish, n ot involved in the spoilage o f unpacked fish, which is resistant to 60% C 0 2, is not H2S-producing, and shows a high TM AO-reducing capacity. This bacterium could be Photobacterium phosphoreum.

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Commercially available oils (olive oil, sunflower oil, palm oil, and a vegetable shortening) were enriched in polyphenols, by adding olive leaf extract. Addition of the extract was performed in such way that the oils were enriched with 200 mg/kg polyphenols. Total polyphenols of both enriched and commercial oils were estimated by the Folin—Ciocalteau assay, while identification and quantification of individual simple phenolic compounds was performed by GC/MS and of oleuropein by HPLC analysis. The enrichment resulted in the supplementation of the commercial oils mainly with oleuropein, hydroxytyrosol, and quercetin. Antioxidant capacity and oxidative stability of the enriched oils and the commercial ones were assessed by the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•) scavenging assay and the Rancimat method, respectively. Both antioxidant capacity and oxidative stability were substantially improved for all the oils studied after supplementation. By the procedure adopted, oils rich in polyphenols, mainly in oleuropein, can be produced with olive leaf extract supplementation.

Content of trans,trans-2,4-decadienal in deep-fried and pan-fried potatoesTrans,trans-2,4-decadienal is a by-product of frying oil that is also transferred to fried food. This aldehyde has been found and quantified both in frying oils and fumes generated during frying. Furthermore, it has been reported that 2,4-decadienal has cytotoxic and genotoxic effects and promotes LDL oxidation. In the present work trans,trans-2,4-decadienal was detected directly in fried potatoes (french-fries). Moreover, the influence of frying conditions (deep-frying, pan-frying), the oil type (olive oil, sunflower oil, cottonseed oil, palm oil and a vegetable shortening) and the degree of thermal deterioration (eight successive frying sessions without replenishment) on the production of 2,4-decadienal in oil and potatoes was studied. The isolation of the aldehyde was performed by methanol extraction, while the identification and quantification was performed by RP-HPLC. The quantity of trans,trans-2,4-decadienal produced during successive pan-frying demonstrated a peak at the third and fourth frying session. The highest concentration of trans,trans-2,4-decadienal was detected in potatoes fried in sunflower oil, and the lowest in olive oil. The quantity of trans,trans-2,4-decadienal in fried potatoes decreased during successive deep-frying at the seventh frying session or remained stable, except for cottonseed oil. The quantity of trans,trans-2,4-decadienal in fried potatoes was considered to be dependent on the oil used, on the frying process and, to a lesser extent, on the oil deterioration. In all cases tested, the highest concentration of trans,trans-2,4-decadienal was detected during deep-frying. The unsaturation degree of the frying oil was considered to promote the formation of trans,trans-2,4-decadienal. Considering the quantity of 2,4-decadienal found in french-fries and in the respective frying medium, direct quantification of 2,4-decadienal is required in order to make an estimation of intake from french-fries.