Oxidative Stability Instrument Research Articles

Fortification of Potato Chips with Natural Plant Extracts to Enhance their Sensory Properties and Storage Stability

AbstractThis study evaluated the effectiveness of grape seed extracts (GSE), green tea extracts (GTE), or butylated hydroxytoluene (BHT) on lipid oxidation reduction of potato chips stored for up to 90 days. The highest (P ≤ 0.05) phenolic contents were detected in GSE (6134.5 mg gallic acid equivalent/100 g) followed by GTE and other plant extracts (oregano, thyme, terebinth, parsley, and bouncing bet). BHT had the greatest antioxidant activity (% inhibition) value (53.0) followed by GSE (42.6) and GTE (31.7). The GSE and GTE exhibited significantly higher antioxidant activities (measured by oxidative stability instrument) than the other plant extracts. The BHT and GSE at 1,000 ppm level was significantly the most effective in minimizing the peroxide value development during 90 days of storage. Descriptive results showed that higher levels of GSE and GTE (750 and 1,000 ppm) prevented the astringency development during 60 days of storage and minimized the off‐notes, i.e., astringency and rancidity, during 90 days of storage. The cardboard attribute was not noticed when GSE and GTE, and BHT were added at 750 and 1,000 ppm levels. The GSE and GTE have a great potential for use as natural antioxidants to preserve the potato chips.

Effects of Green Tea and Grape Seed and TBHQ on Physicochemical Properties of Baladi Goat Meats

The effect of natural extracts of green tea or commercial grape seed in combination with synthetic tert methyl-butylhydroquinone at different concentrations on lipid oxidation and the redness of goat meats stored at 5°C for 9 days was evaluated. Fresh boneless Baladi goat meats were ground and mixed at varying concentrations of green tea or grape seed extract alone or combined with tert methyl-butylhydroquinone. The color values of raw goat meat and the thiobarbituric acid-reactive substance values of raw and cooked goat meats were determined following 0, 3, 6, and 9 days of storage at 5°C. The antioxidant activity of the plant extracts and the tert methyl-butylhydroquinone ranged from 4.6–10.2 h induction time using an oxidative stability instrument. Thiobarbituric acid-reactive substance values ranged from 0.21 to 1.21 and 0.31 to 4.57 mg malondialdehyde/kg (goat meat) for the raw and cooked goat meats, respectively. Tert methyl-butylhydroquinone and plant extracts significantly decreased lipid oxidation of the goat meats, with a higher level of addition being more effective in minimizing lipid oxidation. Grape seed extract significantly increased the redness, while green tea extract decreased it; no effect of tert methyl-butylhydroquinone on the redness of goat meats was observed. This study has shown that inclusion of natural extracts of green tea and grape seed in goat meat could reduce lipid oxidation during its storage.

INFLUENCE OF POWER ULTRASOUND ON OXIDATIVE RANCIDITY OF POTATO CHIPS

ABSTRACT Removal of some lipids on the surface, or from a layer adjacent to the surface of potato chips, was investigated as a means to extend the oxidative stability. Classic potato chips purchased from a local grocery store were subjected to sonication in n‐hexane at room temperature for 1 min. Oxidative stability of the potato chips with and without surface lipids removed was examined by accelerated oxidative stability testing, where samples were stored in an environmental chamber set at 35C. The oxidative stability index was measured with an oxidative stability instrument. As compared with the nonsonicated potato chips, the oxidative stability of sonicated samples was improved by 25, 14, 11, 6 and 21% during the 0, 2, 4, 6 and 8th week of storage, respectively. In average, sonication resulted in 15% improvement of the oxidative stability of potato chips during the 8 weeks of storage at 35C. Thus, it was observed that removing some lipids from the surface of the potato chips by power ultrasound improved the storage oxidative stability.PRACTICAL APPLICATIONSSonication treatment used in this study was capable of reducing peanut lipid rancidity. This research demonstrated the potential of power ultrasound to remove lipids from the potato chips and improve oxidative stability during storage. This research indicated that sonication could provide an alternative for improving the oxidative stability and eventually shelf life and quality of potato chips.

Oxidation of Corn Oils with Spiked Tocols

AbstractStripped corn oils with added tocopherols and tocotrienols, at concentrations between 100 and 5,000 ppm, were used to evaluate antioxidant activity of these tocol compounds. The formation of lipid hydroperoxides, measured as peroxide value (PV), was accelerated at 60 °C in the dark for 5 days. Resistance to oxidation as induction period (IP) was also measured using an oxidative stability instrument (OSI) at 100 °C. For PV inhibition, the oils containing α‐tocols exhibited decreasing effectiveness with increasing concentration. At day five, samples with 100 ppm α‐tocols had the lowest PVs of about 40 mequiv/kg and samples containing 5,000 ppm had the highest values, ranging from 150 to 200 mequiv/kg. At concentrations above 700 ppm of α‐tocols, there was an inversion of antioxidative properties as α‐tocols promoted lipid oxidation. The opposite concentration effect was observed with δ‐tocols and γ‐tocotrienol (T3) for which antioxidant effectiveness increased with concentration. OSI‐IP hour at 100 °C increased with increasing tocol concentrations for all tocol homologs, although with diminishing effectiveness at greater than 700 ppm. The α‐tocols were less effective in extending the IP (~9 h at 5,000 ppm) than the δ‐tocols and γ‐T3 (13–14 h at 5,000 ppm). Therefore, the antioxidant or prooxidant activities of different tocols are different and the outcomes are different depending on the evaluation methods used.

Oxidation of Crude Corn Oil with and without Elevated Tocotrienols

AbstractKernels and oil from corn with increased concentrations of tocotrienols (T3) due to the transgenic expression of a homogentisic acid geranylgeranyl transferase (HGGT) gene from two growing years were characterized for tocol and fatty acid compositions. The crude extracted oil was analyzed for oxidative properties and compared to non‐transformed material derived from the plants grown at the same location and during the same year. No significant difference was observed in composition of major fatty acids. Both the seed (kernel) and extracted crude oil from the HGGT expressing corn had a 18‐fold increase in tocotrienol content from 300 to 5,400 ppm in oil. There was a concurrent 18% decrease in tocopherol content, 1,150 ppm total tocopherols in control oil declining to 940 ppm in HGGT oil. Although tocopherols and tocotrienols are generally considered antioxidants, they may exhibit prooxidant effects at higher concentrations and they should be tested. Crude oil was extracted from control and transformed corn produced during 2005 and 2006 yielding four oil samples that were evaluated for their oxidative properties. The formation of lipid hydroperoxides, a primary oxidation product, was evaluated at 60 °C over 9 days by measuring the peroxide value (PV). Resistance to oxidation or induction period (IP) was measured using an Oxidative Stability Instrument. There was a slight decrease in hydroperoxide formation in the HGGT oil compared to the corresponding control but was less than the year to year differences. The induction period was the same for the 2005 oils, with or without the increased tocotrienol content, but the crude oil with enhanced tocotrienol had a longer IP than the control crude oil in the 2006 samples.

Application of High-Power Ultrasound to Improve Adhesion of Honey on Roasted Peanuts to Improve Oxidative Stability

The extent of honey-coating retention on the surface of sonicated peanuts was studied to evaluate the efficacy of sonication to improve adhesion of honey on peanuts. Samples (150 g each) were sonicated in 450 ml petroleum ether for 5, 10, and 15 min. Following sonication, 25 ml of honey was poured and stirred over the peanuts then roasted in an oven at 177 °C for 10 min. Honey adhesion was determined by measuring the weight of 50 g peanuts before and after coating. The effect of honey and sonication on oxidative stability was measured every 7 days by oxidative stability instrument. The results showed that the weight of honey coating was 7, 16, 19, 21, and 21 g on the control, dipped, 5-, 10-, and 15-min sonicated sample, respectively. Sonication improved adhesion of honey on peanuts by 64%, 68%, and 67% after 5, 10, and 15 min of sonication, respectively, relative to the control. Oxidative stability of dipped, 5-, 10-, and 15-min sonicated samples was improved by 22%, 36%, 46%, and 32%, respectively, in relative to the control. Therefore, removing lipids from peanut surface by high-power ultrasound improved adhesion of honey coating and the oxidative stability.

Effect of Grape Seed Extracts on the Physicochemical and Sensory Properties of Corn Chips during Storage

AbstractThis study evaluated the effectiveness of grape seed extracts (GSE) on lipid oxidation of corn chips stored for 90 days in comparison to tert‐butylhydroxytoluene (BHT). Proximate chemical analysis results showed that corn chips contained low moisture contents (less than 2%) and also that no significant differences were found in the dry matter values in ash, fat, protein, and fiber. Antioxidant activity of the GSE measured by an oxidative stability instrument ranged from 1.6 to 9.3 h of induction time, while BHT prevented oxidation by 18.8 h. GSE (800 ppm) increased the redness and decreased the brightness and yellowness of the corn chip samples, whereas no significant differences were observed for other concentrations of the GSE compared to the control. The peroxide values (PV) for the control and the lower concentration (200 ppm) of GSE increased from 4.5 to 32.7 mequiv/kg, and from 4.4 to18.7 mequiv/kg, respectively, while no increase in PV was found for the higher level (400 and 800 ppm) of GSE or BHT. These changes were observed after 90 days of storage. Descriptive and consumer results showed that the control and the low concentration of GSE were associated with an increase in rancidity and the appearance of off‐flavor, while no noticeable increase in either rancidity or off‐flavor was observed when using a higher concentration of GSE or BHT. GSE has great potential for use as a natural antioxidant to preserve the extruded corn chips.

Total Phenolics, Antioxidant Activities, and Anthocyanins of Different Grape Seed Cultivars Grown in Jordan

The total phenolics, antioxidant activities, anthocyanins, vitamine E, and tert-butylhydroxytoluene (BHT) of different cultivars of grape seed extracts (GSE) grown in Jordan were evaluated. In addition, antioxidant activities of GSE were investigated using olive oil substrate by oxidative stability instrument (OSI). Results of chemical composition showed that Baladi black and Asbani black had the highest amount of fat content 14.52 and 14.22 g /100 g seed, respectively, followed by Baladi green (13.28 g /100 g seed), Ajloni green (12.24 g/100 g seed), and Khudari green (10.92 g/100 g seed), respectively. The total phenolics and anthocyanins of GSE ranged from 4.66 to 5.12 g/100 g extracts and 0.14 to 0.68 g/100 g extracts, respectively. Antioxidant activities of GSE ranged from 66.4 to 81.40%, while vitamin E and BHT were 90.34 and 94.70%, respectively. Antioxidant activity of the extracts using OSI ranged from 3.10 to 41.13 h induction time, while vitamin E and BHT had 16.33 and 17.20 h, respectively. GSE had high amounts of antioxidants and can be used to retard lipid oxidation in a variety of food products.

Antioxidant activities of compounds isolated from Dalbergia odorifera T. Chen and their inhibition effects on the decrease of glutathione level of rat lens induced by UV irradiation

Four compounds were isolated from the root of Dalbergia odorifera T. Chen and identified by chemical and spectroscopic methods as 2′- O-methyl-isoliquiritigenin ( 1), odoriflavene ( 2), 5′-methoxy-vestitol ( 3) and formononetin ( 4). Their antioxidant activities were investigated in lard by the oxidative stability instrument; their inhibitory effects on the decrease of glutathione level of rat lens induced by UV irradiation were studied using a rat lens UV-damage model, and their in vitro cytotoxicity was measured on human SH-SY5Y neuroblastoma cells. Results indicated that all four compounds had obvious antioxidant effects, while none of them showed any synergistic effects on butylated hydroxytoluene or α-tocopherol. When FeCl 3 (4.0 μM) was added, the antioxidant activities of the four compounds markedly decreased. The inhibitory effects of compounds 1, 2 and 4 on the decrease of glutathione level of rat lens induced by UV irradiation were comparable to that of α-tocopherol. All four compounds showed cytotoxic activity when evaluated against a SH-SY5Y cell line in vitro.

Composition of total sterols (4-desmethyl-sterols) in extravirgin olive oils obtained with different extraction technologies and their influence on the oil oxidative stability

The composition and antioxidant activity of total sterols in extravirgin olive oils obtained with different extraction technologies from olives harvested at two ripening stages, were studied. The antioxidant activity was evaluated with an oxidative stability instrument (OSI), by using a model system (made of a mixture of treated/untreated commercial refined peanut oil) enriched with the total sterol fractions of the extravirgin olive oils. No correlation was found between the OSI time and the extraction technologies, the ripening stages or the actual amount of sterols added. No significant differences were observed in the percent composition of sterols of extravirgin olive oils produced with different technologies during the same harvesting period. The latter, however, had a significant effect on the percent of β-sitosterol and 5-avenasterol in extravirgin olive oils produced with the same technology.

Antioxidant properties of natural components from Salvia plebeia on oxidative stability of ascidian oil

Six compounds hispidulin-7-glucuronide ( 1), β-sitosterol ( 2), conferyl aldehyde ( 3), 2′-hydroxyl-5′-methyoxybiochanin A ( 4), and hispidulin-7- O- d-glycoside ( 5), 6-methoxyluteolin-7-glycoside ( 6) were isolated from Salvia plebeia and identified by UV, IR, Mass, 1H and 13C NMR spectra. Their antioxidant activities were investigated individually and compared with α-tocopherol by the oxidative stability instrument (OSI) at 40 °C. The oils extracted from Styela clava and Ciona intestinalis Linnaeus with supercritical fluid (SCF) CO 2 and ethyl acetate, respectively, were used as substance oils, which were rich in polyunsaturated fatty acids (PUFA), especially in the long chain PUFA icosapentaenoic acid (EPA, 20:5 n − 3) and docosahexaenoic acid (DHA, 22:6 n − 3). β-Sitosterol, 2′-hydroxyl-5′-methyoxybiochanin A and 6-methoxyluteolin-7-glycoside exhibited strong antioxidant activities, which increased markedly with increasing concentration, and even stronger than α-tocopherol. The results indicate that the components extracted from S. plebeia should preserve the quality of ascidian oil from ascidian oxidative deterioration.

Evaluation of the Antioxidant Capacity of Individual Phenolic Compounds in Virgin Olive Oil

Virgin olive oil has a high resistance to oxidative deterioration due to its tryacylglycerol composition low in polyunsaturated fatty acids and due to the presence of a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. We isolated several phenolic compounds of extra virgin olive oil (phenyl-ethyl alcohols, lignans, and secoiridoids) by semipreparative high-performance liquid chromatography (HPLC) and identified them using ultraviolet, atmospheric pressure chemical ionization, and electrospray ionization MS detection. The purity of these extracts was confirmed by analytical HPLC using two different gradients. Finally, the antioxidant capacity of the isolated compounds was evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl radical, by accelerated oxidation in a lipid model system (OSI, oxidative stability instrument), and by an electrochemical method.

Oxidative stability of soybean oil fatty acid methyl esters by oil stability index (OSI)

AbstractBiodiesel, an alternative diesel fuel derived from transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long‐chain FA alkyl esters. During long‐term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern with respect to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise quality by adversely affecting kinematic viscosity, acid value, or PV. This work examines the oil stability index (OSI) as a parameter for monitoring the oxidative stability of soybean oil FAME (SME). SME samples from five separate sources and with varying storage and handling histories were analyzed for OSI at 60°C using an oxidative stability instrument. Results showed that OSI may be used to measure relative oxidative stability of SME samples as well as to differentiate between samples from different producers. Although addition of α‐tocopherol or TBHQ increased OSI, responses to these antioxidants varied with respect to SME sample. Variations in response to added antioxidant were attributed to aging and other effects that may have caused oxidative degradation in samples prior to acquisition for this study. Results showed that OSI was more sensitive than iodine value in detecting the effects of oxidative degradation in its early stages when monitoring SME during storage.

Free Radical Generation Assays: New Methodology for Accelerated Oxidation Studies at Low Temperature in Complex Food Matrices

A novel method for the rapid screening of antioxidant efficacy and oxidative stability in food and feed matrices has been developed. The analyses are described as free radical generation (FRG) assays. The new procedure combines the use of azo-initiators with analytical equipment that is widely used for antioxidant research such as the oxidative stability instrument and the oxygen bomb. The use of initiators instead of high temperatures as a driving force to increase the rate of oxidation improves the correlation between the accelerated screening of foodstuffs and real shelf life. The improved correlation can be mainly explained by the fact that food products are analyzed in their original status, maintaining all interfacial phenomena of the food matrix. Furthermore, the lower temperature of analysis reduces differences between the reaction kinetics of the assay and those of the oxidation during actual shelf life. Consequently, the correlation between the accelerated analysis and shelf life is improved, particularly when compared to accelerated oxidation at high temperatures. The FRG assays could be used successfully to evaluate the efficacy of natural antioxidants in heat-sensitive food products such as emulsions and meat products. A good correlation was observed between the accelerated tests and the oxidation parameters obtained from standard shelf-life evaluation. It was possible to successfully compare the efficacy of several antioxidants and to predict shelf life for these heat-sensitive food matrices.

Antioxidants from a Chinese medicinal herb – Psoralea corylifolia L

The powder and extracts of Psoralea corylifolia L. were tested in lard at 100 °C by using the oxidative stability instrument (OSI) and were found to have strong antioxidant effects. Six compounds, bakuchiol, psoralen, isopsoralen, corylifolin, corylin and psoralidin were isolated from the herb and identified by UV, IR, Mass, 1H and 13C NMR spectra and melting point. Their antioxidant activities were investigated individually and compared with butylated hydroxytoluene (BHT) and α-tocopherol by the OSI at 100 °C. The results showed that bakuchiol, corylifolin, corylin and psoralidin had strong antioxidant activities, and especially psoralidin (stronger antioxidant property than BHT), but psoralen and isopsoralen had no antioxidant activities at 0.02% and 0.04% levels. The antioxidant activities of the compounds decrease in the following order: Psoralidin > BHT > α-tocopherol > bakuchiol > corylifolin > corylin > isopsoralen ∼ psoralen.

Total phenolics and antioxidant activities of fenugreek, green tea, black tea, grape seed, ginger, rosemary, gotu kola, and ginkgo extracts, vitamin E, and tert-butylhydroquinone.

The total phenolics and antioxidant activities of fenugreek, green tea, black tea, grape seed, ginger, rosemary, gotu kola, and ginkgo extracts, vitamin E, and tert-butylhydroquinone, were determined. Grape seed and green tea were analyzed for their phenolic constituents using high-performance liquid chromatography. The total phenolics of the plant extracts, determined by the Folin-Ciocalteu method, ranged from 24.8 to 92.5 mg of chlorogenic acid equivalent/g dry material. The antioxidant activities of methanolic extracts determined by conjugated diene measurement of methyl linoleate were 3.4-86.3%. The antioxidant activity of the extracts using chicken fat by an oxidative stability instrument (4.6-10.2 h of induction time) followed a similar trend in antioxidant activity as determined by the Folin-Ciocalteu method. Seven phenolics in grape seed and green tea extracts were identified that ranged from 15.38 to 1158.49 and 18.3 to 1087.02 mg/100 g of extract, respectively. Plant extracts such as green tea and grape seed extracts can be used to retard lipid oxidation in a variety of food products.

Antioxidant activity and components of Salvia plebeia R.Br. — a Chinese herb

The antioxidant properties of the extracts from Salvia plebeia R.Br. which was screened out of over 700 species of Chinese herbs, were tested in lard at 110°C using the Oxidative Stability Instrument. The ethyl acetate extract of the herb was re-extracted by solvents (with increasing polarity) into petroleum ether-, diethyl ether-, acetone-and-ethanol-soluble fractions. The fractions obtained were then separated according to their acidic properties. From the most active sub-fractions, namely the acidic sub-fraction of the petroleum ether-soluble fraction and the weakly acidic sub-fraction of the diethyl ether-soluble fraction, three antioxidant components were isolated and identified as royleanonic acid, hispidulin and eupatorin. The royleanonic acid was a novel compound and eupatorin was isolated for the first time from the herb. Though royleanonic acid and hispidulin prolonged the induction period significantly, their antioxidant activities were much weaker than the crude extracts, implying that synergistic effects might be responsible for the high activity of the crude extracts.

Oil stability index correlated with sensory determination of oxidative stability in light‐exposed soybean oil

AbstractValidity of the oil stability index (OSI) as an accelerated test of oxidative stability has been questioned because of its high holding temperature, 110°C, which may cause reactions that would not occur at lower temperatures. The purpose of this study was to characterize the usefulness of OSI as an accelerated oxidative stability test for oil of varying metal catalyst content by correlating OSI with the sensory induction period of light‐exposed soybean oil. Five 400‐g aliquots of soybean oil were placed in Erlenmeyer flasks and treated with increasing levels of a metal pro‐oxidant, Cu2+ 2‐ethylhexanoate. Pro‐oxidant concentration ranged from 0 to 3.13×10−5 M. Five‐gram aliquots were taken from duplicate flasks and immediately tested using the Oxidative Stability Instrument. Heating block temperature was 110°C. Sample flasks were then exposed to 800 footcandles of light and held at ambient temperature for 3 wk. One‐gram aliquots were regularly withdrawn and evaluated for rancidity by 10 trained panelists to determine the sensory induction period of each sample. Aliquots were also taken to determine OSI of light‐exposed oil samples. Sensory induction periods were correlated with OSI, resulting in a squared partial correlation coefficient (r2) of 0.920. The r2 for OSI of light‐exposed oil samples ranged from 0.897 to 0.979. OSI appears to be an acceptable accelerated method for measuring the oxidative stability of light‐exposed soybean oil that varies in metal catalyst content.

Antioxidant activity of compounds isolated from Salvia plebeia

Abstract Six compounds, hispidulin-glucuronide (1), hispidulin-7-O- d -glucoside (2), 6-methoxy-luteolin-7-glucoside (3), β-sitosterol (4), 2′-hydroxy-5′-methoxybiochanin A (5) and coniferyl aldehyde (6), were isolated from Salvia plebeia and identified by UV, IR, Mass, 1H and 13CNMR spectra. Their antioxidant activities were investigated individually and compared with butylatedhydroxytoluene (BHT) (8) and α-tocopherol (7) by the oxidative stability instrument (OSI) at 100°C. Compounds 3, 4 and 5 had strong antioxidant activities, but compounds 1, 2 and 6 had low antioxidant activities at 0.02 and 0.04% levels.

The protective role of different green tea extracts after oxidative damage is related to their catechin composition.

The antioxidant activities of three different green tea extracts were investigated and compared by two different methods. By the first method, which evaluated the direct protective effect of the green tea extracts on lipid peroxidation, the extracts were added, at different concentrations, to a lipid model system, made by refined peanut oil, freshly submitted to a further bleaching and subjected to forced oxidation at 98 degrees C, by an oxidative stability instrument. By the second method, the effectiveness of the same extracts was checked in cultures of neonatal rat cardiomyocytes exposed to a free radical-generating system by evaluating conjugated diene production and lactate dehydrogenase release. All of the extracts revealed a strong antioxidant activity by both the methods, and a particular effectiveness was demonstrated by the extracts having higher amounts of (-)-epigallocathechin-3-gallate and (-)-epigallocathechin, as analyzed by reverse-phase HPLC analysis.