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The frying performance and stability of pure soybean oil (PSBO), soybean oil blended with palm kernel olein and PSBO with an antioxidant mixture of butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), propyl gallate and citric acid were compared. The oils were subjected to intermittent frying (up to 15 fryings, without any 'topping up') of potato slices, at 180 degrees C for a period of and 337 min. Analytical determinations on the oils included the peroxide value (PV), iodine value (IV), free fatty acid (FFA) value, saponification value (SV) and the refractive index (RI). Changes in the product at the sensory level were also assessed. Results showed that (1) fat oxidation hence, reduction of unsaturated fatty acids, as indicated by changes in the IV, was non-significant in the treated oils, (2) hydrolysis of fats, as shown by changes in the FFA value from the first to last frying, was lowest in the blended oil but highest in PSBO, (3) the same trend as above was observed for PV, an indicator of fat oxidation and rancidity, (4) changes in SV were non-significant in the treated soya oils while PSBO with the antioxidant showed the least change in RI, (5) treated oils exhibited no visual increase in viscosity or turbidity and (6) PSBO with the antioxidant had the lightest colour at the end of the frying period. Taste panellists were unable to discriminate between products fried in the treated oils and in PSBO. Sensory assessment showed an improved quality of the chips fried in the blend. Chips fried in PSBO scored the lowest ratings. Thus, the overall results showed an improved behaviour and quality of the treated oils in terms of themal stability during frying.

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PurposeThis paper aims to determine the effects of processing pineapple fruits into different products and storage of the processed products on the ascorbic acid content.Design/methodology/approachPineapples (variety “Queen Victoria”) were processed into juice, jam and sorbet. Vitamin C was analysed by the 2‐6 dichloroindophenol titrimetric method and tests were performed during preparation and storage of the products. The pineapple juice was stored for nine days at 8°C, whilst the jam and sorbet were kept for two months at 22‐25°C and −18°C respectively.FindingsFresh peeled pineapple fruit contains an average ascorbic acid content of 24.8 mg/100 g of fruit. During the juice making process, peeling led to the highest percentage loss of vitamin C (41.8 per cent) followed by exhausting (23.7 per cent). Processing of pineapples into jam was revealed to be most destructive towards ascorbic acid (a loss of 46.8 per cent) as compared to juice making (38.5 per cent) and sorbet preparation (15.5 per cent). Storage of the three processed products in the specific conditions led to a significant decrease (p<0.05) in vitamin C content, and the highest rate of degradation was in pineapple juice (0.6 mg loss per day).Originality/valueThis paper deals with the retention of vitamin C potency in pineapple products, which is important both to consumers concerned with maintaining good health, and to pineapple processors, who are interested in quality assurance, nutrient labelling and product storage.

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