Olive R&D
The new research assessed the effect of deep frying in various cooking oils on the nutritional profiles and palatability of foods with different fat contents.
Countering the myths about high heat cooking with olive oil, recently-published research by the Modern Olives Laboratory team provides science-based evidence about the benefits of making EVOO your go-to cooking medium for deep frying. It’s great information to share with consumers at your farmers market stalls or farm shops, existing and potential new local stockists, and chefs wanting that healthful point of difference, so we’ve prepared a precis of the report for easy grower reference.
Research shows deep frying in EVOO improves nutritional value Introduction
When deep frying food, the quality of the frying oil and the fried food are intimately related, as the oil is absorbed during the frying process. When oil or fat is re-used multiple times it takes in moisture and air, resulting in thermal and oxidative decomposition, and the formation of elements harmful to health. Volatile decomposition products affect the flavour of the food, while the non-volatile compounds affect how long the oil can be used for frying. Naturally present or added antioxidants in oils and foods influence oil quality during deep-frying. The oxidative breakdown of lipids also causes significant changes to the sensory properties and consumer acceptance of foods, affecting odour, flavour, colour, and texture, and sensory quality decreases with the number of frying cycles. The aim of this study was to assess the effect of various cooking oils on the nutritional profiles and palatability of foods with different fat contents. Frozen chips, chicken, and broccoli were deep-fried in three cooking oils - extra virgin olive oil, canola oil, and grapeseed oil - and then evaluated for taste and other chemical changes such as products of degradation and antioxidants. This work is a continuation of the research
project Evaluation of chemical and physical changes in different commercial oils during heating.
Methodology
The trials consisted of four cycles of deepfrying at 180°C for four minutes, each using three litres of extra virgin olive oil (EVOO), canola and grapeseed oils. Standardised sample sizes of chicken nuggets, pre-cooked chips and broccoli were cooked separately, and added fresh to each cycle of cooking. Samples of foods and oils were taken untreated and samples of used oil were taken after each cycle. Samples of food were taken after each cycle for sensorial analysis and after the first and fourth cycles for chemical analysis. The experiments were carried out in triplicate.
Analysis
Sensory evaluation was performed blind by a nine-member untrained consumer panel. Samples were randomly coded and three sensory parameters (colour, texture, and flavour) were individually evaluated based on a nine-point hedonic scale (1: dislike and 9: extremely like). Using recognised scientific methodologies
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the fat content in food samples was determined, along with chemical and nutritional elements of both the oils and foods including fatty acid content (FAC), total phenols, Vitamin E, squalene, free fatty acids (FFA), specific absorbance coefficient (K232 and K270), polar compounds and smoke point.
Results and discussion
Nutritional and organoleptic impact When comparing the taste and preference of the food cooked with different oils, a statistically significant difference was only found between EVOO and canola oil on cooked chips. EVOO was preferred, with a fish odour and flavour detected in the food cooked with canola oil. This is consistent with previous research that shows that the oxidation of the linolenic acid in canola oil during deep-frying increases fishy odour and decreases fruity and nutty flavour, even at low concentrations. Fat transfer between food and oils In general, there were significant changes in fatty acid composition - saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) - of both the foods and oils used. These changes were greater when the food initially had less fat.
