Fresh sunflower seed oil and used oil were compared as media for deep fat frying of cod fillet. The oxidized oil had more rancid, varnish like and intensive fried flavours. Hydroperoxides present in used frying oil were decomposed into benzidine-active compounds. The sample fried in used oil had lower overall sensory quality, especially poorer flavour and odour. The flavour profile of the fried product was modified by oxidation products in used oil as well. The latter prome consisted of SignifKantly more intensive rancid and stale flavours and significantly stronger old meat flavour. In contrast to this, the product fried in fresh oil had slightly stronger meat flavour. There was no difference in the intensity of fish flavour.Frying oils are rapidly oxidized and decomposed during deep fat frying. More than 220 volatile products .were identified in fats heated under frying conditions [I], some of which contribute without doubt to the agreeable flavour of fried food. The amounts of these compounds are correlated with the sensory value of oil [2]. For instance, carbonyl derivatives containing4,6, and 10-12 carbon atoms impart frying oil a pleasant fried flavour while carbonyl derivatives containing 3,5, and 7 carbon atoms, produced in severely abused oils, are objectionable.Additional flavour-active compounds are produced by the interaction between food and frying oil, e. g. various amino acids, particularly methionine, yield products of interesting flavour [4]. The interaction of frying fats with protein is accompanied by production of volatile flavour-active compounds as well [5].Fish is particularly sensitive to production of off-flavour. It is therefore very important to use frying fats of superior quality in order to obtain a fried product of good quality [6] because even slight rancid fats impart the fried products an objectionable taste and flavour.The subject of this study was to determine how much the frying in used frying fat will influence the sensory quality of fried products. Experimental MaterialFresh sunflower seed oil (fatty acid composition by GLC: palmitic acid 5.07%, stearic acid 2.60% olek acid 17.2%, linoleic acid 74.5%) and sunflower seed oil used for deep fat frying for 20 h flab. 1) were used. Cod fillet (Frionor, Norway) and consumer bread (mixed rye and wheat) were purchased on the market immediately before frying.

During deep-fat frying of chicken muscle in sunflower seed oil the content of thermolabile hydroperoxides reaches a value of about 5 mmoleikg while the amount of benzidine-active substances depends on the original amount of hydroperoxides in frying oil. Oxidation products in frying oil deteriorate the quality of odour, flavour and of the overall sensory value of fried chicken muscle. The flavour quality is mainly affected by increasing intensity of rancid, oily, and fishy off-flavours by interaction of lipid oxidation products with the fried substrate. Breast muscle is more affected by the oxidation products present in frying oil than thigh muscle.

During cold storage of fried poultry muscle the peroxide value of the fat fraction increased after a short induction period. The benzidine value increased during the induction period, and then decreased. The overall sensory quality slowly (insignificantly) deteriorated during the induction period, relatively rapidly afterwards. Changes of odour and especially those of the flavour were more pronounced than changes of other organoleptic properties. Greater changes took place in fried duck muscle than in fried chicken muscle. Changes of the flavour profile were characterized by increasing intensity of the following partial flavours: gluey, fishy. rancid, stale, old (stored) meat, both in duck and in chicken muscle. The oxidative changes were almost the same in fried breast muscle as in fried thigh muscle but the sensory quality changed more in case of breast muscle. In the flavour profile the intensity of rancid flavour increased more distinctly in thigh muscle while the intensity of stale flavour rose more rapidly in fried breast muscle. The deterioration of sensory quality was partly due to peroxids decomposition products and their interaction with amino acids and proteins.