Frying performance of palm oil liquid fractions

Palm oil liquid fractions were used as frying media in household and industrial fryers and were compared to standard edible oils and fats, such as soybean, groundnut, sunflower, rapeseed and tallow. The analytical evaluation covered free fatty acids, viscosity, smoke and flame points, oxidized fatty acids, nonelution material (NEM), UV differential spectra, polymers and foam index. These values measure the extent of the oil degradation, i.e., oxidation, hydrolysis, splitting and polymerization. Moreover, they were combined with other analytical procedures (fatty acid composition, keeping qualities such as the time necessary for an oxygen-absorbing sample to reach a -0.5 psi pressure in a closed system) in order to have a large analytical control during the frying processes. The data collected show the suitability of edible oils and fats for frying purposes and indicate that palm oil liquid fractions perform satisfactorily as frying media. They have low degradation and produce fried foods with acceptable keeping qualities. Presented at the ISF/AOCS World Congress, New York, April 1980.     

Frying performance of low-linolenic acid soybean oil

The frying performance of low-linolenic acid soybean oil from genetically modified soybeans was examined. Partially hydrogenated and unhydrogenated low-linolenic acid soybean oils were compared to two partially hydrogenated soybean frying oils. Frying experiments utilizing shoestring potatoes and fish nuggets were conducted. Frying oil performance was evaluated by measuring free fatty acid content, p-anisidine value, polar compound content, soap value, maximal foam height, polymeric material content, and Lovibond red color. The hydrogenated low-linolenic soybean oil (Hyd-LoLn) consistently had greater (P<0.05) free fatty acid content and lower p-anisidine values and polymeric material content than did the other oils. Hyd-LoLn generally was not significantly different from the traditional oils for polar content, maximal foam height, and Lovibond red color. The low-linolenic acid soybean oil (LoLn) tended to have lower soap values and Lovibond red color scores than did the other oils. LoLn had consistently higher (P<0.05) p-anisidine values and polymeric material content than did the other oils, and LoLn generally was not different (P<0.05) from the traditional oils for polar content, maximal foam height, and free fatty acid.     

Frying stability of high-oleate and regular soybean oil blends

The objective of this work was to study the frying stability of soybean oil (SBO) with reduced linoleate (18∶2) and linolenate (18∶3) and elevated oleate (18∶1) contents. High-oleate SBO [HO SBO, 79% oleic acid (OA)] and a control (conventional SBO, 21.5% OA) were tested as is, as well as blended in different ratios to make three blended oils containing 36.9, 50.7, and 64.7% OA, abbreviated as 37%OA, 51%OA, and 65%OA, respectively. In addition, a low-linolenate (LL) SBO containing 1.4% 18∶3 and 25.3% 18∶1 was tested. Bread cubes (8.19 cm³) were fried in each of 18 oils (6 treatments×3 replicates). We hypothesized that stability indicators would be indirectly related to the total 18∶2 plus 18∶3 percentages and/or the calculated oxidizability. In general, the results were fairly predictable based on total 18∶2 and 18∶3 concentrations. The overall frying stability of the six oil treatments, from the best to the poorest, was: 79%OA, 65%OA, 51%OA, LL≥37%OA, and the control, with respective total compositions for 18∶2 plus 18∶3 of 10.3, 23.6, 36.3, 59.6, 48.9, and 62.8%. The greatly reduced concentration of 18∶3 in the LL SBO made it more stable than the 37%OA, even though the combined composition of 18∶2 and 18∶3 of LL was greater than that of the 37%OA. Blending conventional SBO with HO SBO had a profound effect on the oxidative stability index and color of the blended oils, but the values were not linearly predictable by the percentage of control in the blended oil. Other stability indices, including calculated oxidizability, calculated iodine value, conjugated dienoic acid value, and viscosity, changed in linear response to an increased proportion of the control in the blends.     

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

The aim of this study was to test the performance of a vegetable oil blend formulated as alternative to pure palm oil as frying medium. For this purpose, the evolution of many analytical parameters (free acidity, spectrophotometric indices, total polar components, fatty acid composition, short‐chain fatty acids, tocopherol and tocotrienol content and composition, color, flavor evaluated by means of an electronic nose) of the selected blend (sunflower/palm oil 65 : 35 vol/vol) has been monitored during a prolonged frying process (8 h discontinuous frying without oil replenishment) in comparison to pure palm oil. Sensory attributes of the fried food were also evaluated. The blend proved to keep qualitative parameters comparable to those shown by palm oil during the prolonged frying process. Even if some oxidation indices, such as spectrophotometric indices, short‐chain fatty acids and total polar components, increased faster in the blend, it showed a higher tocopherol content and a lower increment in free fatty acids as compared to pure palm oil. Chips fried in the two oils did not show significantly different sensory profiles.     

Frying stability of canola oil in presence of pumpkin seed and olive oils

Frying performance of canola oil (CO) was investigated in the presence of 5, 10, and 15% levels of virgin olive oil (VOO) and pumpkin seed oil (PSO) during frying of potatoes at 180°C. Acid value, carbonyl value, total polar compounds content, and total tocopherols content of the oil samples were determined during the frying process. VOO and PSO addition improved the frying stability of the CO. Frying performance of the CO increased more in the presence of PSO than in the presence of the VOO. The PSO levels higher than 5% exerted pro‐oxidant effects, indicating the necessity of investigation at lower levels. The better antioxidative effect of PSO was attributed to its probably different phenolic composition.     

Frying performance of the hull oil unsaponifiable matter of Pistacia atlantica subsp. mutica

The anti‐rancidity effect of the hull oil unsaponifiable matter (USM, 100 ppm) of Pistacia atlantica subsp. mutica (Bene) on sunflower oil (SFO) during frying at 180 °C was investigated and compared to that of tert‐butylhydroquinone (TBHQ, 100 ppm). The unsaponifiable constituents of the Bene hull oil (BHO) were separated into hydrocarbons (3.7%), carotenes (3.6%), tocopherols and tocotrienols (24.7%), linear and triterpenic alcohols (0.9%), methylsterols (5.7%), sterols (3.2%), triterpenic dialcohols (4.7%), and triterpenic dialcohol methylesters (4.5%), by means of silica gel TLC. The results obtained from the measurements of total polar compounds, conjugated diene value, carbonyl value, and acid value during 32 h of frying showed that the frying stability of SFO improves more in the presence of the USM of BHO than in the presence of TBHQ. Moreover, compared to TBHQ, the USM had a better protective effect on the indigenous tocopherols of SFO during frying.     

Frying oil and fat quality measured by chemical,physical, and test kit analyses

The performance of soybean oil (SBO) and a partially hydrogenated soybean oil (PHSBO) was monitored by chemical, physical, and test kit analyses during 50 h of deep-frying of potatoes in SBO and 50 h of deep-frying of potatoes in PHSBO. The oxidative stability of SBO and PHSBO was measured by the iodine value, color index, FFA content, total polar compounds, and FA analysis of deep-frying SBO and PHSBO. SBO, with higher levels of unsaturated FA, had the faster rate of formation of geometric and positional isomers of unsaturated FA as measured by GC with standards. PHSBO performance under deep-frying conditions was significantly better than SBO with respect to iodine value, color index, and total polar compounds. The results from analyses using test kits had a good correlation with analytical parameters.     

The Effects of Microwave Frying on Physicochemical Properties of Frying and Sunflower Oils

Deep fat frying is a method of food preparation which has been popular for quite a number of years. During deep frying, the quality of oil and the finished product decreases as the result of heat treatment of the oil exposed to air at high temperature. Application of heat by microwave as an alternative to the conventional method of frying has become popular in recent years. In this research, the effects of microwave frying on the changes in the quality indices of used oil have been investigated. To achieve this, potato slices were fried in both frying and sunflower oils by application of medium power microwave (550 W) for 20 min, three times a day, for five consecutive days, and oils were sampled for analysis. The results obtained from the chemical tests demonstrated that used frying oil had lower polar compounds, a higher induction period, and more saturated fatty acids than sunflower oil. The interesting point observed was that peroxides formed as the result of oxidation chain reactions were not broken down and were built up due to the lower temperature and shorter period of frying. Therefore microwave frying might be considered as a suitable alternative to the conventional frying due to less degradation of the oil and consequently a lower production of artifacts.     

Investigation of Artefacts Formed in Frying Fats

The investigation of frying fats and artefacts formed in edible oils both under actual industrial frying conditions and under experimental conditions is discussed. The potential importance of instrumental liquid chromatography for the characterization and identification of oxidized oils is shown. Separation schemes and methods for the isolation and identification of fractions are discussed. Classes of artefacts consisting of dimeric fatty acids and more polar monomeric fatty acids may be isolated by preparative column, thin layer, and gel permeation chromatography and further characterized by GLC, TLC, derivatization, and mass spectrometry. The use of methoxylation, silylation, and labeling techniques for double bond and hydroxy group position determination in artefact classes by mass spectrometry is discussed.     

Vacuum Frying of Carrot Chips

Abstract

Vacuum frying is an alternative method to produce high quality vegetable or fruit chips. The effect of frying temperature and vacuum degree on moisture content, oil content, color, and texture of fried carrot chips were investigated. During the early stage of vacuum frying, the rate of moisture removal and oil absorption increased with increasing frying oil temperature and degree of vacuum. Statistical analysis of the color data showed that there were no significant differences P > 0.05) in lightness (L), redness (a), and yellowness (b) of carrot chips as a function of vacuum degree and temperature. The breaking force of carrot chips decreased with increasing frying temperature and vacuum degree. The statistical analysis also showed that there were no significant differences P < 0.05) in the breaking force as a function of temperature, but the breaking force was significantly (P < 0.05) affected by the vacuum degree.     

Regeneration of Used Frying Oil

Used frying oils were purified in a packed column using different amounts of silica gel (SG), aluminum oxide (AO), activated charcoal (AC), bentonite (B), magnesol XL (M), calcium carbonate (CC), zeolite (Z), bleaching earth (BE) and/or their binary, triple, and quaternary combinations. SG (15 g) improved total polar material (TPM) by 100 %, conjugated diene (CD) content by 84 %, and p-anisidine value (AV) by 104 %, while AO and M improved free fatty acid (FFA) contents by 103 and 105 %, respectively. On the other hand, AC and M bleached the color by 100 and 90 %, respectively. As the amount of adsorbent in the column increased, FFA, CD, AV, and color improved. When the amount of used sunflower oil (UO1) loaded in the column containing SL was increased, FFA, CD, AV and color values increased, while no change was observed in TPM up to 60 g of UO1. Loading UO1 at 150 °C in the column caused the absorbance values at 460 nm to decrease from 0.740 to 0.240, while the amount of adsorbed tocopherol increased compared to UO1 at 25 °C. The increasing number of adsorbents within the column further improved the physicochemical properties of UO1 when it was used 30 g. However, as the amount of different type of used oils (UO2, UO3 and UO4) was increased to 300 g, improvement ratios of all parameters decreased.     

The use of hydrogenated fish oil to extend vegetable oil

During the last four years, national production of fish oil has increased appreciably due to the expansion of the "reduction" industries (fish flour). Nevertheless, this production is almost totally destined to industrial use (lubricants, tannery, etc.). In contrast, some countries like Japan, Canada and Peru have been using oil from different fish species for human consumption. In view of the above, the objectives of the present work were: first, to establish the experimental conditions for obtention of a hydrogenated fish oil and second, the formulation of fish and vegetable oil mixtures for use in the food industry. The methodology followed comprised: 1) characterization of crude fish oil through physical and chemical analysis; 2) adaptation of the vegetable oil refining procedures to fish oil, and 3) development of fish oil with vegetable oils. A hydrogenated fish oil with a melting point of 36 degrees C, iodine index of 80, and lovibond color, yellow 20, red 13, was produced. Based on the results of the sensory test, the possibility of using up to 30% extension of this oil with vegetable oils for frying, and up to 50% extension for baking, without affecting acceptability of product, was established.     

我国原油供应战略安全分析

石油是国家的重要资源,是支撑国民经济发展的重要保障。原油供应安全对国民经济的发展起到举足轻重的作用。本文从7个比较重要和具有代表性的评价指标方面详细分析了我国原油供应安全的现状和未来的发展趋势。经过分析发现我国原油的供应状况正处于极度危险的状况。     

Flexible pipe puts oil well back in use

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Accumulation of 2-tert-Butyl-1,4-Benzoquinone in Frying Oil and Fried Food during Repeated Deep Fat Frying Processes

2-tert-Butyl-1,4-benzoquinone (TBBQ), the main oxidation product of tert-butyl-hydroquinone (TBHQ) during frying, is cytotoxic and its residual levels in frying oils and foods are unknown. In this study, TBBQ residues have been evaluated during the preparation of french fries. Results showed that frying at 140 °C resulted in the highest TBBQ peak concentration (48.42 mg kg⁻¹) compared with frying at 190 or 170 °C. This unexpected finding can be attributed to more extensive hydrolytic reaction when frying at the lower temperature, generating more peroxyl radicals. TBBQ concentrations proved to be independent of the oil type among various unsaturated oils. However, higher TBBQ levels were observed in saturated palm oil and crude soybean oil than in unsaturated oil or refined oil. Continuous frying leads to the accumulation of a large amount of TBBQ in fried food. After frying 1–5 batches, TBBQ levels in both the frying oil and fries were above 10 mg kg⁻¹, exceeding its critical cytotoxic concentration (IC₅₀ value of 10.71 mg kg⁻¹ for RAW 246.7 cells in our previous study), warranting concern with respect to the safety of fried food. FTIR has been utilized as an effective tool for visually monitoring the degree of oxidation in the frying medium with respect to its hydrogen peroxide level, which contributes to the increased level of TBBQ derived from TBHQ therein.     

Choice of Simple Methods for Quality Control of Frying Fat during Deep Frying of Potato Products

Studies have been carried out to choice methods which could assess in best way the complex changes in fat during deep frying of French fries and potato crisps. A special emphasis was laid on the estimation of usefulness of simple and quick “methods” which could practically indicate the utilization time of fats (soybean oil, low erucic acid rapeseed oil, ?Sofryt”? -hardened soybean oil), used in deep-fat frying of potato products. Besides the oxidized fatty acid content, proposed by DGF (German Society for Fat Science) as a basic test for the quality assessment of used frying fats, following control tests during the deep-fat frying of potato products have been appointed: colour tests with bromthymol blue and 2,6-dichlorphenol-indophenol, sensoric evaluation, dielectric constant and colour by iodine scale. For these tests suitable limits, qualifying the utility of oils and fats for further frying of French fries and potato crisps, have been estimated.