Frying stability of virgin and refined sesame oils as compared to refined olive oil

Frying stability of two virgin (VSO) and refined (RSO) sesame oils was compared with that of a refined olive oil (ROO). The oils were used to fry potato stripes at 180 °C and conjugated dienes (CDV), total carbonyls (CV), and thermo-oxidative and hydrolytic polar components were monitored over time. The rate of change in CDV (mmol l–1 h–1) was significantly lower for ROO (0.72) than for VSO (1.00) and RSO (1.84). The change in CV for ROO (2.31 μmol g–1 h–1) was significantly much faster than those for RSO (1.89) and VSO (1.17). Based on the thermo-oxidative polar components, the calculated frying times for VSO, RSO, and ROO were on the order of 32.1, 13.9, and 15.4 h. However, VSO contained significantly the highest contents of hydrolytic polar components over time and RSO exhibited more resistance than ROO on this basis.

N-Way NIR Data Treatment through PARAFAC in the Evaluation of Protective Effect of Antioxidants in Soybean Oil

The use of chemometric tools is progressing to scientific areas where analytical chemistry is present, such as food science. In analytical food evaluation, oils represent an important field, allowing the exploration of the antioxidant effects of herbs and seeds. However, traditional methodologies have some drawbacks which must be overcome, such as being time-consuming, requiring sample preparation, the use of solvents/reagents, and the generation of toxic waste. The objective of this study is to evaluate the protective effect provided by plant-based substances (directly, or as extracts), including pumpkin seeds, poppy seeds, dehydrated goji berry, and Provençal herbs, against the oxidation of antioxidant-free soybean oil. Synthetic antioxidants tert-butylhydroquinone and butylated hydroxytoluene were also considered. The evaluation was made through thermal degradation of soybean oil at different temperatures, and near-infrared spectroscopy was employed in an n-way mode, coupled with Parallel Factor Analysis (PARAFAC) to extract nontrivial information. The results for PARAFAC indicated that factor 1 shows oxidation product information, while factor 2 presents results regarding the antioxidant effect. The plant-based extract was more effective in improving the frying stability of soybean oil. It was also possible to observe that while the oxidation product concentration increased, the antioxidant concentration decreased as the temperature increased. The proposed method is shown to be a simple and fast way to obtain information on the protective effects of antioxidant additives in edible oils, and has an encouraging potential for use in other applications.

Effects of Continuous Deep-fat Frying on the Physicochemical Properties of Assorted Brands of Edible Cooking Oils Sold in Greater Metropolitan Kampala

Aims: To investigate the effects of continuous deep fat frying of white (Irish) potatoes on the physical and chemical attributes of ten brands of edible cooking oils: Fortune Butto, Roki, Tamu, Best Fry, Mukwano, Golden Fry (hard oils); Sunseed, Sunny, Sunvita and Sunlite (soft oils) sold in Kampala, Uganda. Place and Duration of the Study: Oil samples of approximate manufacturing dates were obtained from Mega Standard supermarket in Greater Metropolitan Kampala, Uganda. Oil samples were also obtained from local Irish potato fryers in Makindye division of Kampala during ten deep frying cycles. Irish potatoes was procured from Nakasero market, Kampala. Physicochemical analyses were performed at the Quality Control Laboratory of Mukwano Industries Limited, Kampala Industrial area, Kampala. The research was conducted between May 2018 to December 2018. Methodology: 400g of Irish potato slices (1cm × 1cm × 3cm) were submersed in 1500mL of oil maintained at 140°C for 6 minutes in an Electric Deep Fryer with a frying time of 10 minutes.The color value (CV) and the acidification of the oils as free fatty acid (FFA), peroxide value (POV), paraanisidine value (AnV), iodine adsorption value (IV) and total oxidation (TOTOX) value before and between ten successive frying cycles were determined using ISO and AOCS official methods.The maximum number of reuses of an oil was estimated from the frying round before its POV or AnV surpassed the maximum permissible statutory or Codex Alimentarius limit for edible oils. Results: For fresh oils, the statistical physicochemical parameter ranges were: CV (0.4R 3.4Y-7.7R 70Y), FFA (0.0430±0.30-0.1508±0.30), POV (0.5951±0.03-6.6134±0.23 meqO2/Kg), AnV (0.90±0.01-4.30±0.19) and IV (57.62±0.17-128.35±0.02gI2/100g). By the 10th fry, the ranges were CV (3.0R 23Y-20.4R 70Y), FFA (0.2286±0.01-0.4817±0.01), POV (11.1138±0.01-15.7525±0.01meqO2/Kg), AnV (10.31±0.03-22.16±0.01) and IV (53.66±0.01-126.03±0.02gI2/100g). Considering oxidizability as TOTOX values, frying stability of the selected brands of cooking oils during the frying cycles followed the order: Roki > Fortune Butto > Sunvita > Sunny > Sunlite > Mukwano > Tamu > Best Fry > Golden Fry > Sunseed. Conclusion: Reuse of the oils for continuous frying of Irish potatoes on the same day can be done only up to 7 times on average for hard oils and 6 times for soft oils with the oils still regarded as safe for human consumption. Hard oils should be preferred to soft oils for deep frying of Irish potato chips.Further research should elucidate the variation of physicochemical properties of other oil brands on the Ugandan market such as Nile, Fortune, Kimbo, Star Fry, Cow boy and Ufuta and should use other food samples such as fish, cassava, chicken, sweet plantain, dough, meat and edible grasshoppers.

Frying performance of two virgin oils from Cornicabra olives with different ripeness indices

The frying performance of two virgin olive oils (VOO) from Cornicabra olives of different ripeness indices, 2.08 for VOO1 and 4.13 for VOO2, was evaluated. Thermal, oxidative and hydrolytic alterations were determined throughout 40 frying operations with potatoes. The initial oils showed similar fatty acid compositions and oxidative stability indices as determined by Rancimat, but VOO1 presented higher amounts of total polyphenols and tocopherols. The oils showed high and similar frying performance. No significant differences in the levels of polar compounds (PC) were found between the two oils during frying. Therefore, the frying stability of Cornicabra VOOs appears to be unconnected with olive fruit ripeness. The limit of degradation at 25% PC as established in different countries was calculated to occur at 55 frying operations in the two oils. As oil toxicity is related to the levels of compounds formed, the use of Cornicabra VOOs for frying is highly recommended.