The influence of carotenoids and tocopherols on the stability of safflower seed oil during heat-catalyzed oxidation

The stability and antioxidant effects of carotenoids and tocopherols in safflower seed oil were evaluated under thermal (75°C) and oxidative conditions and the oxidative stability index (OSI) determined. The antioxidant capability of butylated hydroxytoluene (BHT) was also compared with that of β-carotene in a model system. Lycopene and β-carotene (1 to 2000 ppm) were heated (75°C) and exposed to air (2.5 psi) in an oxidative stability instrument. β-Carotene had no antioxidant effect at concentrations below 500 ppm, because it did not alter the induction time. Lycopene increased the induction time only slightly at low concentrations. However, at concentrations greater than 500 ppm, both β-carotene and lycopene acted as prooxidants, significantly decreasing the induction period. At the highest concentration, 2000 ppm, lycopene was more prooxidative than β-carotene. α- and γ-Tocopherol (concentration, 1000 ppm) delayed the induction time by 16 and 26 h, respectively. There was no cooperative interaction between α-tocopherol and β-carotene in delaying the onset of oxidation. Furthermore, BHT was significantly more antioxidative than β-carotene. Thus, under thermal and oxidative conditions, β-carotene could not delay the onset of oxidation. The tocopherols and BHT were effective in suppressing the onset of oxidation, as determined by the oxidative stability measurement.     

Application of organic solvent nanofiltration for concentration of antioxidant extracts of rosemary (Rosmarinus officiallis L.)

The present investigation revealed the potential benefits of nanofiltration application in herbal extracts processing. Nanofiltrations of modelling solution of caffeic and rosmarinic acid in ethanol and ethanolic rosemary extract were carried out in a laboratory cross-flow system. Duramem™ 200 nanofiltration membrane was selected based on screening experiments. The experimental data and model predictions demonstrated the efficacy of a semi-batch cross-flow diafiltration process for concentration of fresh rosemary extracts. The observed absence of significant loss of antioxidant capacity in the retentate during the process and the degree of extract concentration achieved may allow retentate direct application as preservative and functional ingredient in the foods, cosmetics, neutraceuticals and medicines. The capability of the selected membrane to separate monophenolic acids from higher molecular weight antioxidant compounds in the extracts was also discussed. The dry solids content in the permeate was found sufficiently low as to permit its direct re-use in the extraction process thus bringing additional economical benefits.     

Effect of 5-caffeoylquinic acid on soybean oil oxidative stability

The antioxidant activity of 5-caffeoylquinic acid (5CQA) at concentration ranges of 0.01–0.08% (w/w) was compared with 0.02% (w/w) butylated hydroxytoluene (BHT) in soybean oil. The oil was stored in air at 55  °C and monitored by peroxide and conjugated diene measurements. Both 0.01% and 0.02% 5-CQA showed lower peroxide values than BHT only on the first day. However, on days 1, 2, 3 and 4, 0.04% 5-CQA reduced the peroxide value to 68%, 47%, 45% and 90% of that observed with BHT. Use of 5-CQA appears to delay the formation of peroxides and up to 0.04% (w / w) its antioxidative action increases with concentration for up to 3 days.     

生物柴油的抗氧化性研究

不饱和双键含量较多的生物柴油受到环境因素的影响,容易被氧化。试验中以BHA、BHT和TBHQ为抗氧化剂,分别在30℃和60℃且不通入加压空气的条件下,检测了抗氧化剂添加量分别为0.1‰、0.2‰和0.3‰时的过氧化值变化;结果表明,三种抗氧化剂对棕榈油生产的生物柴油的抗氧化效果为TBHQ>BHT>BHA。     

Primary Processes in the Catalytic Photooxidation of p-Cresol

Aerobic irradiation of organic compounds in aqueous suspensions of titanium dioxide (TiO₂) generally leads to rapid mineralization with little accumulation of intermediates. This environmentally advantageous feature, however, hinders attempts to obtain mechanistic information and, while expansion of the field continues unabated, details of reaction pathways in many cases remain obscure. We have developed a procedure that allows the identification and monitoring of principal primary products, and the outcome with p-cresol is reported. Extrapolation of primary product yield profiles to zero conversion enables us to account for approximately 50% of the initial mass loss of p-cresol. At least four pathways are in competition, including nuclear substitution by OH, side-chain oxidation, radical dimerization, and the hitherto undetected nuclear addition of OH. These findings allow the conflicting results reported by previous workers to be reconciled. Changing the solvent from water to 20% acetonitrile in water has little effect on the initial rate, but ring coupling is more favoured and there is some addition of O₂. Preliminary measurements with 2,6-di-tert-butyl-4-methylphenol (butylated hydroxytoluene, BHT), however, indicate that ortho-disubstitution with bulky tert-butyl groups substantially enhances the initial rate and changes the product profile significantly. The importance of both the extent of adsorption and substrate orientation on the catalyst surface is implicated in these results. © 1997 SCI.     

Effects of natural and synthetic antioxidants on changes in refined, bleached, and deodorized palm olein during deep-fat frying of potato chips

The effects of antioxidants on the changes in quality characteristics of refined, bleached, and deodorized (RBD) palm olein during deep-fat frying (at 180°C) of potato chips for 3.5 h/d for seven consecutive days in five systems were compared in this study. The systems were RBD palm olein without antioxidant (control), with 200 ppm butylated hydroxytoluene (BHT), 200 ppm butylated hydroxyanisole (BHA), 200 ppm oleoresin rosemary, and 200 ppm sage extract. Fried oil samples were analyzed for peroxide value (PV), thiobarbituric acid (TBA) value, iodine value (IV), free fatty acid (FFA) content, polymer content, viscosity, E^1% _{1 cm} at 232 and 268 nm, color, fatty acid composition, and C_18:2/C_16:0 ratio. Sensory quality of the potato chips fried in these systems prior to storage was also evaluated. The storage stability of fried potato chips for 14 wk at ambient temperature was also determined by means of the TBA values and sensory evaluation for rancid odor. Generally, in the oil, oleoresin rosemary gave the lowest rate of increase of TBA value, polymer content, viscosity, E^1% _{1 cm} at 232 and 268 nm compared to control and three other antioxidants. The order of effectiveness (P<0.05) in inhibiting oil oxidation in RBD palm olein was oleoresin rosemary > BHA > sage extract > BHT > control. Prior to storage, the sensory evaluation of fried potato chips for each system showed that there was no significant (P>0.05) difference in terms of flavor, odor, texture, and overall acceptability. The same order of effectiveness (P<0.05) of antioxidants was observed for storage stability study of fried potato chips by TBA values. However, there was no significant (P > 0.05) difference in sensory evaluation for rancid odor during storage periods.     

Antioxidant Activity of Oat Malt Extracts in Accelerated Corn Oil Oxidation

Oat cultivar AC Vermont was malted to concentrate antioxidants, milled to fractionate only the endosperm portion and extracted with methanol to isolate the crude antioxidants. The oat malt antioxidant fraction was assessed as a natural antioxidant based upon enhancing the stability of corn oil against oxidation and compared to the synthetic antioxidant butylated hydroxytoluene (BHT). The induction time (time required for the formation of 10 meq hydroperoxide per kilogram corn oil thermally oxidized) was used to measure antioxidant activity of oat antioxidant or BHT. The protection factor achieved by crude oat malt antioxidant extract concentrate at 0.26% (2,600 μg/g) was comparable to BHT (75 μg/g). The antioxidant activity of the oat and barley malt extract concentrates was not significantly different. However, the extract concentrate of oat malt had 44% less color compared to that of barley malt at equal concentrations showing its potential as a natural food antioxidant.     

Investigation of the effect of sumac extract and BHT addition on the quality of sucuk (Turkish dry‐fermented sausage)

The effect of sumac extract and BHT (butylated hydroxytoluene) addition on the quality (pH, colour, biogenic amine, TBARS values and sensory attributes) of sucuk (Turkish dry‐fermented sausage) were investigated during the ripening period. Addition of BHT decreased the TBARS value by about 23.7%, whereas sumac extract decreased it by 42.0%. Sumac extract decreased (P < 0.05) putrescine formation more than BHT addition. However, no significant difference (P > 0.05) was observed in histamine formation for both the sumac extract and BHT‐added recipe. The highest tyramine concentration was observed in a control recipe (R1) prepared without any antioxidants, and the lowest was in the sumac extract‐added recipe (R3) with mean values of about 96.62 and 63.17 mg kg^?1, respectively. The control recipe (R1) was found to be the worst (P < 0.05) sample with respect to overall sensory quality and addition of either sumac extract or BHT increased (P < 0.05) the overall sensory quality of sucuk. The pH and colour attributes of sucuk were not significantly different (P > 0.05) between the addition of sumac extract and BHT. This study demonstrated that sumac extract had more effect on the quality of sucuk during the ripening period, hence it could be easily utilised in sucuk to enhance quality. Copyright © 2006 Society of Chemical Industry     

气相色谱法测定食用植物油中抗氧化剂BHA、BHT

建立了气相色谱法测定食用植物油中的BHA、BHT的快速分析方法。采用乙醇萃取样品,上气相色谱仪进行定量分析。方法的线性范围在5-200毫克／升,相关系数均在0．999以上,分析加标实际样品,回收率为83．0％－97．2％,相对标准偏差为0．8-3．5％,方法完全符合食用植物油中抗氧化剂的快速分析要求。     

Lipid characteristics and essential minerals of native Turkish hazelnut varieties (Corylus avellana L.)

Five native hazelnut varieties from Turkey, namely, prime quality Tombul variety, and second grade quality Yass? Badem, Sivri, Karaf?nd?k, and Ham varieties were examined for their lipid characteristics (triacylglycerol, tocopherol, tocotrienol, phytosterol, and phytostanol composition) and 12 essential minerals. Among 12 triacylglycerols separated in all hazelnut varieties, OOO (61.0–77.5%) and OOL (10.5–22.8%) were the main components (where O = oleoyl and L = linoleoyl). Seven tocol isoforms (four tocopherols and three tocotrienols), seven phytosterols, as well as cholesterol, and one phytostanol were positively identified and quantified; among these, α-tocopherol and β-sitosterol were predominant in all hazelnut oils. Hazelnut varieties served as an excellent source of copper and manganese. Consumption of the recommended daily amount of 42.5 g of hazelnut from different varieties provides 44.4–83.6% of copper and 40.1–448% of recommended manganese intake for adults. These results suggest that second grade quality hazelnut varieties were as good sources of functional lipids and essential minerals as was prime quality Tombul hazelnut, with some exceptions (P < 0.05).