Effect of flavonoids on the oxidative stability of corn oil during deep frying

To study the effect of flavonoids on the stability of frying oil, refined corn oil was analysed periodically for its peroxide value (PV), p‐anisidine value (p‐AV) and iodine value (IV) after its use for deep‐frying of French fries at 180 °C for varying periods of time, namely 30, 60 and 90 min. PV and p‐AV values increased with respect to time while a decrease in IV was observed with increase in time (P < 0.001). Deep‐frying of French fries in corn oil was then carried out in the presence of flavonoids, viz. pelargonidin, cyanidin, quercetin, myrecetin and gallic acid as antioxidants. All antioxidants effectively reduced the oxidation rate in the oil, as detected by decrease in PVs and p‐AVs and relatively low reduction rate in IVs (P < 0.001). The order of antioxidative activity was gallic acid > quercetin > myrecetin > cyanidin > pelargonidin.     

Deodorisation process variables for croaker (M. furnieri) oil

Fish oil is the major food source of the long-chain omega-3 polyunsaturated fatty acids. Deodorisation represents a critical step of the refining process since it involves high temperature that could induce degradation reactions which affect oil integrity and quality. The present study evaluated the effect of the deodorisation variables (temperature, time and steam) on the croaker (Micropogonias furnieri) oil refining process. The evaluated parameters were Lovibond color (LC), free fatty acids (FFA), peroxide (PV), Iodine (IV) and Saponification (SV) values. The best deodorisation conditions were at 220 °C, 60 min and 5% of steam (based in oil mass), resulting in oil with LC of 0.4 red and 30 yellow, FFA of 0.09%, PV of 0.53 meq/kg. IV and SV were not significantly affected. The obtained fish oil presented high quality and oxidative stability, as well as EPA and DHA contents of approximately 12% of total fatty acids.     

Physical Properties and Oxidation Rates of Unrefined Menhaden Oil (Brevoortia patronus)

ABSTRACT: Unrefined menhaden oil was evaluated for thermal and rheological properties and its temperature-dependent viscosity and lipid oxidation rate were determined. Peroxide value, free fatty acids, density, specific gravity, water activity, moisture content, and enthalpy of the unrefined menhaden oil were 5.70 meq/kg, 3.80%, 0.93 g/mL, 0.93%, 0.52%, 0.15%, and 20.2 kJ/kg, respectively. The melting point range of unrefined menhaden oil was found to be −69.5 to 27.21 °C. The menhaden oil exhibited non-Newtonian fluid behavior at lower temperatures (5 to 25 °C), while it behaved like a Newtonian fluid at 30 °C. The oil apparent viscosity at 5 °C (0.22 Pa.s) was significantly higher (P < 0.05) than that at 30 °C (0.033 Pa.s). The average magnitude of activation energy for viscosity of the unrefined menhaden oil was 50.37 kJ/mol. The predicted apparent viscosity agreed (R²= 0.9837) satisfactorily with the experimental apparent viscosity. The minimal lipid oxidation rate of the oil was found at 25 and 35 °C for 6 h, higher lipid oxidation rates were observed when the oil was heated for 6 h at 45 to 85 °C. The rate of lipid oxidation for unrefined menhaden oil was temperature dependent (R²= 0.9425). This study showed that the magnitude of the apparent viscosity and oxidation rate of the unrefined menhaden oil was greatly influenced by temperature.     

Optimisation of lipase-catalysed interesterification reaction for modulating rheological and heat transfer properties of frying oil

The present work reports the optimisation of enzyme interesterification reaction of rice bran oil (RBO) and refined, bleached, deodorized, palm olein (RBDPO) blend using immobilized 1,3-specific lipase, to improve the kinematic viscosity and heat transfer coefficient of oil, important for characterising heat transfer during the frying process. Four variables, namely RBO (20–80%) in RBO–RBDPO blend, reaction temperature (25–65 °C), enzyme concentration (1–13%, w/w) and reaction time (1–13 h) were selected and optimised using response surface methodology (RSM) coupled with central composite rotatable design (CCRD). The optimisation results predicted that optimum reaction conditions for preparing enzyme interesterified oil, having minimum kinematic viscosity (2.63 × 10⁻⁶ m² s⁻¹) and maximum heat transfer coefficient (262.0 Wm⁻² °C⁻¹) were at 62% RBO, temperature 65 °C, enzyme concentration 10% (w/w) and time 6.4 h. The predicted values were validated experimentally and corroborated with DSC melting profile and triacylglycerol molecular species data. This investigation could help snack food industries to develop suitable oils for frying operations.     

Sensory odour profiling and physical characteristics of edible oil blends during frying

Edible oil blends containing 80 parts of mustard oil (MO) or groundnut oil (GNO) or sunflower oil (SNO) and 20 parts of sesame oil (SO) or refined red palm oil (RPO) or rice bran oil (RBO) were studied to determine the changes in their physical and sensory characteristics during deep fat frying. Odour evaluation by the trained sensory panel revealed that successive fryings subdued the intensity of typical odour notes of the oil blends. Intensity of sulphury, pungent and vinegar (sour) notes of MO, nutty and sweet notes of GNO, sweet and seedy notes of SNO, seedy and earthy notes of SO, husk-like note of RPO and beany and branny notes of RBO decreased significantly by end of the 7th frying. Apparent viscosity of the oil blends increased on successive frying. Colour measured in CIE system indicated that the dominant parameters were a+ (redness) in RPO blends, b+ (yellowness) in blend containing SO or MO and a− (greenness) in RBO blends. The redness component decreased and yellowness increased with successive frying in SNO + RPO blend and GNO and RBO blend, respectively. Applying principal component analysis (PCA) to the data showed seggregation of various oil blends as distinct groups exhibiting their typical and characteristic attributes. PCA also revealed the pathway of change of oils during different frying cycles. MO and blend of MO + RPO were characterised by sulphury, pungent, harsh odour notes and red colour; GNO occupied a quadrant with fresh-oil-like, green and sweet notes, and SNO was characterised by fresh-oil-like, seedy odour and yellow colour. Addition of SO increased earthy note and lightness value, while blends containing RBO had distinct yellow colour, increased heated note and higher apparent viscosity.     

A novel rapid method for the determination of frying oil quality: development of prototype and equations and examination with respect to legislation criteria

The present work presents a prototype apparatus developed for a novel method based on capillary penetration for the determination of frying oil quality and examines the method and the performance of the prototype. The work further assesses the method results in comparison with the results of established methods and proposes equations for calculating frying oil quality parameters relevant to legislation criteria. The examination of the method is performed by using 184 oil samples produced by frying different foods in different oils for forty-five successive batches. Equations relating the method output with the total polar compounds, total polymers and viscosity are proposed. High correlation coefficients between legislation criteria and the method result are obtained: R² = 0.96, R² = 0.91 and R² = 0.86 for correlation with the oil viscosity, the polymer compounds and the TPC of the fried oils, respectively. The false-positive and false-negative answers of the method are below 2.5% for all cases.     

Correlation of fatty acid composition of vegetable oils with rheological behaviour and oil uptake

The fatty acid compositions of seven edible vegetable oils were investigated and correlated with their rheological behaviours and the amount of absorbed oils to fried products. All oil samples showed constant viscosity as a function of shear rate, exhibiting Newtonian behaviours. The highest viscosity was observed in hazelnut oil, followed by olive, canola, corn, soybean, sunflower, and grapeseed oils. In addition, a high correlation (R² = 0.94) demonstrated that the flow behaviours of vegetable oils were positively governed by their major components (18:1 and 18:2 fatty acids). It was also shown that a more rapid change in viscosity with temperature was observed in the oils containing more double bonds (R² = 0.71). Furthermore, even though the overall tendency was that the potato strips fried in the oils with high viscosity appeared to cause more oil uptake, a significant effect of oil types on oil uptake was not observed.     

Optimization of Bleaching Parameters in Refining Process of Kenaf Seed Oil with a Central Composite Design Model

Kenaf seed oil has been suggested to be used as nutritious edible oil due to its unique fatty acid composition and nutritional value. The objective of this study was to optimize the bleaching parameters of the chemical refining process for kenaf seed oil, namely concentration of bleaching earth (0.5 to 2.5% w/w), temperature (30 to 110 °C) and time (5 to 65 min) based on the responses of total oxidation value (TOTOX) and color reduction using response surface methodology. The results indicated that the corresponding response surface models were highly statistical significant (P < 0.0001) and sufficient to describe and predict TOTOX value and color reduction with R² of 0.9713 and 0.9388, respectively. The optimal parameters in the bleaching stage of kenaf seed oil were: 1.5% w/w of the concentration of bleaching earth, temperature of 70 °C, and time of 40 min. These optimum parameters produced bleached kenaf seed oil with TOTOX value of 8.09 and color reduction of 32.95%. There were no significant differences (P > 0.05) between experimental and predicted values, indicating the adequacy of the fitted models.     

Low Dielectric Constant Material from Hollow Fibers and Plant Oil

Abstract

A new low dielectric constant (k) material suited to electronic materials applications was developed using hollow keratin fibers (HF) and chemically modified soybean oil. High-speed microelectronics is facilitated by preventing the “rubber necking,” or slow-down of electrons on the printed wires through the use of low-k dielectrics. The unusual low-k value of the HF composite material derives both from the air (k = 1) in the hollow microcrystalline keratin fibers (k = 1.7), and the triglyceride molecules (k = 2.7), and is in the range of 1.7 to 2.7, depending on the HF fraction. These values are lower than that of the conventional silicon dioxide (k = 3.8 to 4.2) or epoxy dielectric insulators. Also, the HF dielectric is lightweight (SG < 1) and rigid (Modulus > 2 GPa), with fracture toughness (1.0 MPa m^1/2) and approximates the shape and feel of a silicon dioxide insulator. The coefficient of thermal expansion (CTE) of the new material (67.4 ppm/°C) is low enough for electronic materials applications. Multi-Chip-Module circuit printing results suggest that the low-cost composite made with HF (from avian sources) and plant oil (from soybean) has the potential to replace the dielectrics in microchips and circuits boards in the ever-growing electronic materials field, in addition to many applications as new lightweight composite material.     

Predicting Temperature-Dependent Viscosity of Amazonian Vegetable Oils and Their Mixtures from Fatty Acid Composition

Several studies on predicting the viscosity of oils and their mixes are found in the literature. However, data on Amazonian oils are relatively scarce. This study aimed to measure the viscosity and the influence of temperature and of the fatty acid composition of three Amazonian vegetable oils (buriti, pataua, and Brazil nut), as well as their mixtures. Models were applied from the literature and a new equation was presented to predict viscosity. Among the models assessed to estimate the viscosity of the oils and their mixtures as a function of temperature, the Andrade, modified Andrade, and Arrhenius models had the best fits. The models by Grunberg-Nissan and Kendall and Monroe can be used to predict the viscosity of mixtures from their compositions. The equation presented to predict viscosity was shown to be appropriate with R² values above 0.998 and error below 1.0723.     

Changes in chemical quality indices during long‐term storage of palm‐olein oil under heated storage and transport‐type conditions

Six quality indices, namely free fatty acids (FFA), peroxide value (PV), anisidine value (AV), oxidative stability index (OSI), total tocopherols and headspace volatiles (hexanal, t‐2‐hexenal and t,t‐2,4‐decadienal), were evaluated in a long‐term storage trial of 52 weeks at 50 °C of palm‐olein, a monounsaturated oil. Three concentrations of copper (0.035, 0.17 and 0.69 mg kg^?1) were added. FFA values for all the sample treatments increased slightly over the storage period but remained within acceptable limits. PV of the copper‐containing samples declined initially and then remained stable up to week 40, after which it increased slightly for the 0.035 and 0.17 mg kg^?1 samples. However, PV of the control (no added copper) increased steadily to above the acceptable limit. AV of the copper‐containing samples increased much more than that of the control. OSI and total tocopherol values of the copper‐containing samples were markedly lower than those of the control. t‐2‐Hexenal did not increase during the storage period, whereas hexanal increased in the copper‐containing samples but at a slower rate than in the control. Conversely, the copper‐containing samples had high levels of t,t‐2,4‐decadienal but the control had none. AV, OSI and total tocopherols are the most valuable quality indices for assessing monounsaturated oil quality, whereas FFA, PV and headspace volatiles can be misleading. Copyright © 2003 Society of Chemical Industry     

Comparative study of the functional,thermal and pasting properties of flours from different field pea (Pisum sativum L.) and pigeon pea (Cajanus cajan L.) cultivars

Physicochemical, functional, thermal and pasting properties of flours from field pea (LFP-48 and PG-3) and pigeon pea (AL-15 and AL-201) cultivars were determined and related to each other using Pearson correlation and principal component analysis (PCA). Field pea flours (FPF) were significantly (P < 0.05) different from pigeon pea flours (PPF) in their lower ash and higher fat and protein contents. FPF also exhibited higher L^∗, ΔE value, water solubility index (WSI), oil absorption capacity (OAC), foaming capacity (FC) and lower a^∗, b^∗ value, water absorption index (WAI) and water absorption capacity (WAC) in comparison to PPF. FPF differed significantly from PPF in exhibiting lower transition temperatures (T_o, T_p, T_c), enthalpy of gelatinization (ΔH_gel), peak height index (PHI) and higher gelatinization temperature range (R). PCA showed that LFP-48 and PG-3 flours were located at the far left of the score plot with a large negative score, while the AL-15 and AL-201 flours had large positive scores in the first principal component. Several significant correlations between functional, thermal and pasting properties were revealed, both by Pearson correlation and PCA. Pasting properties of the flours, measured using the rapid visco analyzer (RVA), also differed significantly. PPF were observed to have higher pasting temperature (PT), peak viscosity (PV), trough viscosity (TV), breakdown (BV), final viscosity (FV) and lower setback viscosity (SV) as compared to FPF.     

Production of lipase‐catalyzed solid fat from mustard oil and palm stearin with linoleic acid by response surface methodology

BACKGROUND: Solid fat was produced from mustard oil and palm stearin through lipase‐catalyzed reaction, in which linoleic acid was intentionally incorporated. For optimizing the reaction condition of melting point and ω6/ω3 fatty acids, response surface methodology (RSM) was employed with three reaction variables such as substrate mole ratio of mustard oil (MO) to palm stearin (PS) (X₁), reaction temperature (X₂) and reaction time (X₃). RESULTS: The predictive model for melting point of solid fat was adequate and reproducible due to no significant lack of fit (P = 0.0764), P‐value (0.0037) of the model, and satisfactory level of coefficient of determination (R² = 0.92). For the ω6/ω3 ratio model, R² and P‐value were 0.89 and 0.0132, respectively, but lack of fit was significant (P = 0.0389). The melting point of the produced solid fat was affected by substrate mole ratio, whereas reaction temperature and time had no significant effect. The ω6/ω3 ratio of solid fat was influenced by substrate mole ratio and reaction temperature but not by reaction time. Based on ridge analysis, lower ω6/ω3 ratio was predicted by decreasing substrate mole ratio and reaction time, and by increasing reaction temperature. CONCLUSIONS: For producing solid fat with a specific melting point of 34.57 °C, a combination of 1:2 (X₁), 65.17 °C (X₂) and 21.46 h (X₃) was optimized, and the optimization was confirmed under the same reaction conditions. The solid fat contained palmitic (37.8%), linoleic (24.8%), oleic (21.3%), and erucic acid (9.7%), and its solid fat content was 30.3% and 10.3% at 20 and 30 °C, respectively. Copyright © 2009 Society of Chemical Industry     

Dielectric Properties of Sweet Potato Purees at 915 MHz as Affected by Temperature and Chemical Composition∗

A process for rapid sterilization and aseptic packaging of sweet potato puree using a continuous flow microwave system operating at 915 MHz has been successfully developed. In microwave processing, dielectric properties have a major role in determining the interaction between purees and the electromagnetic energy. The objective of this research was to determine how dielectric properties are affected by temperature and chemical composition of purees derived from thirteen sweet potato cultivars with varying flesh colors. Results indicated that temperature, moisture, sugar and starch content had a pronounced effect (p < 0.001) on dielectric properties measured from 15°C to 145°C at 915 MHz. Dielectric constant decreased with increasing temperature, while dielectric loss factor increased quadratically. Power penetration depth of all cultivars decreased with increasing temperature. Predictive equations were developed for dielectric constant (R²?=?0.82) and dielectric loss factor (R²?=?0.90) as a function of temperature, moisture, sugar, and starch. The predictive equations would be useful in determining the dielectric properties of sweet potato purees for the microwave processing technology.     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

Application of Artificial Neural Networks to Predict the Oxidation of Menhaden Fish Oil Obtained from Fourier Transform Infrared Spectroscopy Method

Oxidation is a major cause of deterioration in fish oil, leading to considerable losses of quality and nutritional value. To date, the available methods to monitor lipid oxidation in foods are based on chemical analysis. Fourier transform infrared spectroscopy (FTIR) is an alternative technique for the study of molecular structure and compositional changes in a wide range of foods. The objectives of this study were to use attenuated total reflectance-FTIR for evaluating oxidative quality and application of artificial neural network analysis (ANN), a mathematical model, to predict the oxidative values of Menhaden fish oil. The oil was stored in the presence of light at room temperature. The oxidation was measured for primary and secondary oxidative change; peroxide value (PV) and anisidine value (AnV), respectively, using FTIR were compared with chemical analysis each day during the 3 weeks of storage. The wavenumber and absorbance values of FTIR spectra were applied to predict the oxidative values of the oil by using ANN. Inputs consisted of wavenumber and absorbance outputs were composed of PV and AnV. It was found that changes in the region between 3,500 and 1,700 cm^-1 and absorbance were related to PV and AnV of the chemical analysis (R ² > 0.85). FTIR spectroscopy with the aid of ANN demonstrates its potential as an alternative and rapid technique rather than a conventional method for prediction of food lipids oxidation.     

Effects of different crop starches on the cooking quality of Chinese dried noodles

To investigate the effects of seven starches made from different crop sources on noodle quality, Chinese dried noodles made from various reconstituted flours were prepared and analysed. Potato starch had better solubility and swelling power than the other starches, leading to higher water absorption, cooking loss and breakage ratio of the potato starch noodles. The correlation results unravelled that the cooking breakage ratio of noodles presented positive correlations with solubility, swelling power, peak viscosity (PV), trough viscosity (TV) and final viscosity (FV) values of starches. Besides, the adhesiveness of noodles showed a positive correlation with conclusion temperature (T_c) and setback viscosity (SV) values of starches. Moreover, the peak temperature (T_p) value of starches was negatively correlated with cooking loss; the granule size of starches had a positive correlation with noodles water absorption; and the peak time (PkT) value of starches represented positive relationships with noodles chewiness, shearing force and breaking strength.     

Quality assessment of packaged fried foods during storage based on oven storage test

Packaged fried foods have been appreciated worldwide, so monitoring quality deterioration during storage is very crucial. Twelve types of commercial packaged fried foods were selected to determine quality parameters such as moisture content (MC), hardness (HN), acid value (AV), peroxide value (PV), carbonyl value (CV), dielectric constant (DC), fatty acid compositions (FAC) and acrylamide (AA) every 3 days by Schaal oven tests. MC and HN showed a linear relationship with high correlation coefficient (R ≥ 0.821). PV increased from 2.65–8.51 meq/kg to 5.97–59.90 meq/kg. DC was highly correlated with MC, HN, PV, CV and AV (p ≤ 0.05). The content of unsaturated fatty acids slightly decreased, whereas that of saturated fatty acids marginally increased. AA content increased slightly during storage and varied from 43.07 to 226.82 μg/kg. These results revealed that DC can be used as an evaluation index of the quality deterioration of packaged fried foods during storage.     

Refining of high oleic safflower oil: Effect on the sterols and tocopherols content

The purpose of this work was to study the influence of the industrial process steps on free fatty acids, peroxide value (PV), p-anisidine value (PAV), trans fatty acids, tocopherols and sterols (free, esterified and total) in high oleic safflower oil. Degumming, bleaching and deodorization steps removed 91.4% of free fatty acids, 96.31% of oxidation primary products (PV), and 54.57% of oxidation secondary products (PAV), from crude high oleic safflower oil. Degumming neither affected the content of sterified sterols nor its proportion with respect to the crude oil. A significant increment (p<0.05) in the content of free sterols was observed during degumming and bleaching due to the acid-catalyzed hydrolysis of steryl esters. A significant reduction (p<0.05) in the content of total sterols during bleaching was observed, which is attributed to a reduction in the sterified sterol fraction. During deodorization, free sterols were distilled from oil, with a gradual reduction in the total sterol content as a function of the deodorization temperature. α- and γ-tocopherols represented 93.3% of the total tocopherols in high oleic safflower crude oil. The refining process removed 28.5% of the tocopherols. Deodorization was the main step which increased the level of trans fatty acids as an effect of temperature and heating time.