Frying performance of a sunflower/palm oil blend in comparison with pure palm oil

Analysis of 8-oxooctanoate, 9-oxononanoate, fatty acids, oxidative stability, and iodine value during deep-frying of French fries in edible oils blended with palm oil

Four blended oils including palm + corn oil (PC), palm + grapeseed oil (PG), corn + grapeseed oil (CG), and palm + corn + grapeseed oil (PCG) were used as frying media. The 8-oxo and 9-oxo content, fatty acid composition, oxidative stability index, and iodine value of samples (n = 42) were analyzed. As the frying cycles increased, the content of 8-oxo and 9-oxo also increased significantly (p < 0.05) and showed the highest content of 965.56 ± 0.706 μg/g in 100 frying cycles of PCG. After 20-40 frying cycles in CG, the amount of palmitic, stearic, oleic and linoleic acid increased up to 15.5% (p < 0.05). The oxidative stability of palm oil was the highest at 16.76-18.33 h (p < 0.05). The iodine value of grapeseed oil was the highest at 144.96 ± 2.569-153.64 ± 2.233 g iodine/100 g oil (p < 0.05). Among the examined oils, PC was the most suitable alternative to palm oil.

Frying Performance of Gallic Acid and/or Methyl Gallate Accompanied by Phosphatidylcholine

This study shows the possibility of using gallic acid (GA) and/or methyl gallate (MG) accompanied by phosphatidylcholine (PC) instead of tert-butylhydoquinone (TBHQ) for frying purposes. The antioxidants and PC were added in the concentrations of 1.2 mM and 500-2000 mg/kg, respectively. Oxidative stability index (OSI) and the kinetics of change in conjugated dienes (LCD), carbonyls (LCO), and acid value (AV) were used to assess the antioxidative treatments. GA alone and GA/MG (50:50) plus PC at 2000 mg/kg yielded the same OSI as that of TBHQ (18.4 h). The latter was of the highest frying performance in preventing the formation of LCD (rn = 0.0517/h and tT = 10.6 h vs. rn = 0.0976/h and tT = 4.5 h for TBHQ), LCO (rn = 0.0411/h and tT = 12.7 h vs. rn = 0.15/h and tT = 4.3 h for TBHQ), and hydrolytic products (AVm = 37.8 vs. 24.0 for TBHQ); rn: normalized the maximum rate of LCD/LCO accumulation; tT: the time at which the rate of LCD/LCO accumulation is maximized; AVm: quantitative measure of hydrolytic stability.

Kinetics of chemical deteriorations over the frying protected by gallic acid and methyl gallate

The present work shows the possibility of use of gallic acid (GA) and methyl gallate (MG) as natural antioxidants replacing the powerful synthetic antioxidant TBHQ in frying process. Oxidative stability index (OSI) and the kinetics of change in lipid-peroxidation conjugated dienes (LCD), carbonyls (LCO), and acid value were adopted for the evaluation purposes. GA alone (1.2 mM) and in combination with MG (75:25) provided OSI values comparable to that of TBHQ (18.5-19.0 h). The GA/MG 75:25 exerted a frying performance quite better than TBHQ (r_n = 0.1351 vs. 0.1784 h^-1) in preventing the LCD formation. From the LCO formation standpoint, the GA/MG 75:25 (r_n = 0.0758 h^-1) and then MG (r_n = 0.1004 h^-1) provided better performances than TBHQ (r_n = 0.1216 h^-1). Lipid hydrolysis was also inhibited well by GA (AV_m = 8.6) and GA/MG 75:25 (AV_m = 7.9), respectively (AV_m = 9.2 for TBHQ).

An Evaluation Model for the Quality of Frying Oil Using Key Aldehyde Detected by HS-GC/MS

To establish a practical model for evaluating the oxidation of frying oil using aldehydes, the aldehydes of 10 commercial oils during frying at 180 °C were identified using headspace-gas chromatography/mass spectrometry, and the changes of common aldehydes and their correlation with carbonyl values (CV) were analyzed. The results showed that the total peak area of aldehydes increased significantly with heating time, which was related to the fatty acid and tocopherol contents of the oils. There were four common aldehydes with different trends during frying, namely, pentanal, hexanal, (E)-hept-2-enal, and nonanal. Moreover, pentanal with a high correlation with CV was selected as the quality evaluating index of frying oil due to its stable accumulation over time. Based on the linear fitting relationships between CV and pentanal, as well as the initial content ratio of linoleic acid to palmitic acid and total tocopherols in oils, a predictive model was established for evaluating the quality of frying oils with high precision and non-reagent by using mass spectrometry. In summary, this work provides theoretical support for using aldehyde as the quality evaluation index of frying oil and provides a new idea for evaluating oil deterioration from the perspective of volatile compounds.

Evaluation of glycerol core aldehydes formation in edible oils under restaurant deep frying

Glycerol core aldehydes (GCAs) are potentially toxic lipid oxidation products characterized by aldehydic acids bonded to glycerol via acyl groups. This study investigated the profile and change of GCAs in rapeseed oil (RO), high-oleic sunflower oil (HOSO) and cottonseed oil (CO) after frying chicken nuggets (CNs), fish nuggets (FNs) and French fries (FFs) for 60 h in real restaurant frying systems. Three GCAs (8-oxo, 9-oxo, and 10-oxo-8) were identified, with the GCAs (9-oxo) accounting for the highest value (60%), followed by GCAs (10-oxo-8) and GCAs (8-oxo). The total GCAs increased from 1.12 to 2.02 mg/g with frying time from 0 to 60 h in RO used for frying FNs. The FN frying systems produced the largest amount of GCAs, whereas the FF frying systems produced the least. RO contained more GCAs than CO and HOSO owing to its higher unsaturated fatty acid content (91.81%). Furthermore, the GCAs showed a high correlation with polymerized and oxidized products, indicating that the formation of GCAs were related to the oxidative stability of oils. These results may provide insight into the formation of GCAs and their control during frying.

Stability and Antioxidant Activity of Annatto (Bixa orellana L.) Tocotrienols During Frying and in Fried Tortilla Chips

Annatto tocotrienols (AnT3), which contain approximately 90% δ-tocotrienol (δ-T3), were added to mid-oleic sunflower oil used for frying tortilla chips over 3 d. The objectives were to evaluate their stability during frying, absorption by the fried food, and activity as antioxidants in frying oil and in tortilla chips during storage. AnT3 did not significantly affect the stability of the oil during frying or the sensory profiles of freshly fried chips. The naturally present α-tocopherol (α-T) in the oil degraded at a lower rate in the presence of AnT3, resulting in significantly higher α-T by the end of the frying study. Levels of tocopherols and tocotrienols in the chips mirrored oil levels. AnT3 did not affect the sensory profile of the chips after 1 wk of storage at 50 °C, but after 3 wk of storage, the control chips had higher levels of painty and rancid flavors compared to chips with AnT3. Headspace hexanal was also significantly higher in the control chips compared to the chips with AnT3 after 3 wk of storage.

PRACTICAL APPLICATION

Annatto tocotrienols, containing primarily delta- and gamma-tocotrienols, were added to mid-oleic sunflower oil used for frying tortilla chips. The tocotrienols were absorbed by the chips along with the oil. They slowed the degradation of α tocopherol during frying, and reduced levels of painty and rancid flavor scores as well as headspace hexanal in chips that were stored for 3 wk at elevated temperatures. The results indicated that fried snack foods such as tortilla chips may be a suitable and convenient vehicle for enriching tocotrienols in the diet, and that tocotrienols may also enhance the shelf-life of fried foods.

Electronic nose guided determination of frying disposal time of sunflower oil using fuzzy logic analysis

An electronic nose (e-nose), having 18 metal oxide semiconductor (MOS) sensors, guided determination of frying disposal time of sunflower oil is reported. The ranking and screening of MOS sensors, specific for volatile organic compounds, was performed using fuzzy logic. A correlation was examined between rancidity indices of fried oil (total polar compounds (TPC), and triglyceride dimers-polymers (TGDP), among others) and e-nose based odor index. Fuzzy logic screened 6 MOS sensors (LY2/G, LY2/AA, LY2/GH, LY2/gCT1, T30/1, and P30/1) to deconvolute the rancid fried oils using hierarchical clustering on principal component space. A good relationship was noted between rancidity indices and odor index (R²>0.85). Based on maximum discard limits of rancidity indices (25% TPC and 10% TGDP), the frying disposal time of 15.2h (TPC) vs. 15.8h (e-nose) and 15.5h (TGDP) vs. 16.3h (e-nose) was determined. The demonstrated methodology holds a potential extension to different fried oils and products.

The impact of cooking methods on the nutritional quality and safety of chicken breaded nuggets

The impact of cooking methods (industrial pre-frying, deep-fat frying and baking) on the nutritional quality and safety of chicken breaded nugget samples from supermarket and commercial brands was evaluated. The changes in the quality characteristics (nutritional composition, fatty acids profile, cholesterol and salt) of the fried food and frying oil, after ten consecutive frying operations, were evaluated. The total fat content of nuggets varied between 10.9 and 22.7 g per 100 g of edible portion and the salt content ranged from 0.873 to 1.63 g per 100 g. Taking into account one portion of nuggets, the daily intake of salt can reach 49%, which can have a significant impact on the health of those who regularly consume this type of food, especially considering the prevalence of hypertension around the world. The analysed chicken breaded nuggets are rich in unsaturated fatty acids, which have been related with potential health benefits, namely regarding cardiovascular diseases. The cholesterol content of baked samples was two times higher when compared with the fried ones. The trans fatty acids and polar compounds contents of the frying oil used for frying significantly increased, but the values were still away from the maximum recommended by legal entities for its rejection. From a nutritional point of view, it is possible to conclude that the applied cooking methods can significantly influence the nutritional quality and safety of the analysed chicken breaded nuggets. This study will contribute to important knowledge on how the applied cooking methods can change the nutritional quality and safety of foods, namely of chicken nuggets, and can be very useful for dietary recommendations and nutritional assessment.

The effect of frying on glycidyl esters content in palm oil

The changes in palm oil, as affected by frying temperature, and content of the glycidyl esters (GEs) were studied. Potato chips were fried intermittently in palm oil, which was heated for 8 h daily over five consecutive days. Frying was conducted at three frying temperatures: 150, 165 and 180 °C. Thermo-oxidative alterations of the oil were measured by acid and anisidine values, changes in fatty acid composition, total polar components, polar fraction composition and colour components formation. Content of GE was measured by liquid chromatography-mass spectrometry. Results showed that amount of products of hydrolysis, oxidation and polymerization (excluding decrease of degree of unsaturation) increased significantly as a function of frying temperature and time. Between GEs of fatty acids the most abundant were esters of palmitic and oleic acids. With increasing temperature and frying time, the content of GE decreased. The extent of GE decrease was correlated with degree of oil degradation.

Effect of frying on the rheological and chemical properties of palm oil and its blends

The aim of this research was to determine the changes in the physicochemical properties of palm oil and its blends by FTIR and rheological measurements. Application of heat produces some chemical compounds as impurities and even toxic compounds in oils and fats that give absorbance at different region. FTIR spectra of pure palm olein shows an absorbance at 3002 cm(-1) whereas other pure oils show maximum absorption at around 3007 cm(-1) due to C-H stretching vibration of cis-double bond (=C-H). By blending of high unsaturated oils with palm olein, a clear shift of 3007 cm(-1) band to 3005 cm(-1) occurs. Viscosity of palm olein was found higher among all oils while it subsequently and substantially reduced by blending with other oils. Since it is a function of temperature, viscosity of pure oils and their blends decreases with the increase of temperature. The loss modulus (G''), for all oil blends before and after frying, in rheological experiment was found higher for all oils than the storage modulus (G'), therefore, the viscous property was found higher than elastic property of oils and blends. However, the critical stress for all oil blends was found higher than that of pure oils.

Use of pilot plant scale continuous fryer to simulate industrial production of potato chips: thermal properties of palm olein blends under continuous frying conditions

Binary blends of palm olein (PO) with sunflower oil (SFO), canola oil (CNO), and cottonseed oil (CSO) were formulated to assess their stability under continuous frying conditions. The results were then compared with those obtained in PO. The oil blends studied were: (1) 60:40 for PO + SFO; (2) 70:30 for PO + CNO; and (3) 50:50 for PO + CSO. The PO and its blends were used to fry potato chips at 180°C for a total of 56 h of operation. The evolution of analytical parameters such as tocols, induction period, color, p-anisidine value, free fatty acid, smoke point, polar compounds, and polymer compounds were evaluated over the frying time. Blending PO with unsaturated oils was generally proved to keep most qualitative parameters comparable to those demonstrated in PO. Indeed, none of the oils surpassed the legislative limits for used frying. Overall, it was noted that oil containing PO and SFO showed higher resistance toward oxidative and hydrolytic behaviors as compared to the other oil blends.