Flavor stability of high-oleic peanuts stored at low humidity

Shelf-life studies were conducted on roasted high-oleic peanuts (HOP; F1250, BC93Q10) and a reference peanut with normal oleic acid content (NOP, Florunner). HOP contained at least 80% oleic acid and 3% linoleic acid, whereas normal-oleic peanuts contained 53% oleic and 27% linoleic acids. Peanuts were dry-roasted to a medium roast (Hunter lab L=50) and stored at 40°C at 18% relative humidity. Samples were removed from storage at different intervals (0, 2, 4, 7, and 10 wk) for sensory evaluation and chemical oxidation measurements. Sensory attributes rated included roasted peanutty flavor, sweetness, crunchiness, and oxidized flavors (cardboardy and painty). The two HOP lines were not significantly different from each other in flavor quality or stability during storage but had better flavor quality and stability than NOP. The latter oxidized faster and developed painty off-flavors to a greater extent than did the HOP lines. Chemical oxidation measurements confirmed higher levels of oxidation in NOP than in the HOP lines. Peroxide values at 10-wk storage were 47 meq/kg oil for NOP and <3 meq/kg oil for the HOP lines. Both HOP lines had greater shelf lives than NOP.     

Effect of high-oleic sunflower seed on the carotenoid stability of ground pepper

Mixtures of dehydrated pepper fruit (Capsicum annuum L.) with pepper seed (PS) and with high-oleic sunflower seed (SFS) in proportions of 0, 20, 30, and 40% (w/w) were subjected to heat degradation to compare the effect of a polyunsaturated medium (PS mixtures) and a monounsaturated medium (SFS mixtures) on the carotenoid fraction. The kinetic study carried out indicates that the carotenoid degradation, in both types of mixture and for all the proportions, fits a first-order mathematical model. The values of the kinetic constant k in each case and for the stage of commercial usefulness of the paprika, which ends when 50% of its initial coloring power has been lost, indicate that the presence of a higher percentage of seed, either pepper or high-oleic sunflower, in the mixture means a greater stability of the carotenoid fraction. However the presence of a lipid medium less sensitive to oxidation (SFS mixtures) strengthens this effect, prolonging the stage of practical usefulness of the product, so manufacture of paprika by grinding dehydrated pepper fruit with high-oleic SFS will provide a product with a longer shelf life. Also the improvement of the natural lipid substrate of the pepper fruit, to delay carotenoid degradation in the end product, is a possible line of investigation.     

The effect of roasting on the chemical composition and oxidative stability of pumpkin oil

This study is concerned with the effect of the process of roasting of naked pumpkin seeds prior to their pressing on the chemical composition and oxidative stability of the extracted oil. Ground seeds were roasted at temperatures of 90, 110, and 130°C for 30 and 60 min, according to the traditional technology of production of roasted pumpkin oil. Depending on the roasting conditions of the seeds, this treatment resulted in a significant increase of the contents of phospholipids (from 0.005 to 0.463%), total phenolic compounds (from 4.63 to 19.60 mg/kg), and total tocopherols (from 265.79 to 350.98 mg/kg) in oil. Higher contents of these minor components enhanced the oxidative stability of the oil, i.e., increased the induction period (from 4.50 to 12.93 h). However, at the same time, the applied thermal treatment generated an increase in the primary and secondary oxidation products, resulting in higher Totox values that could lower the quality of the oil.     

Comparison of the frying stability of regular and high-oleic acid sunflower oils

The frying stability of a regular sunflower oil (RSFO) was compared with that of a high-oleic acid sunflower oil (HOSFO). The rate of FFA formation was greater for HOSFO than RSFO during 72 h of frying. The content of tocopherols was much higher in RSFO and their degradation was markedly slower than that observed for HOSFO. The formation of total polar compounds, however, was similar for both oils despite the dramatic differences in FA composition. This study further confirms the limitations in predicting frying stability based solely on the FA composition and is consistent with earlier studies conducted in our laboratory.     

Effect of triacylglycerol composition and structures on oxidative stability of oils from selected soybean germplasm

The oxidative stability of soybean oil triacylglycerols was studied with respect to composition and structure. Crude soybean oils of various fatty acid and triacylglycerol composition, hexane-extracted from ground beans, were chromatographed to remove non-triacylglycerol components. Purified triacylglycerols were oxidized at 60°C, in air, in the dark. The oxidative stability or resistance of the substrate to reaction with oxygen was measured by determination of peroxide value and headspace analysis of volatiles of the oxidized triacylglycerols (at less than 1% oxidation). The correlation coefficients (r) for rates of peroxide formation (r=0.85) and total headspace volatiles (r=0.87) were related positively to oxidizability. Rate of peroxide formation showed a positive correlation with average number of double bonds (r=0.81), linoleic acid (r=0.63), linolenic acid (r=0.85). Rate of peroxide formation also showed a positive correlation with linoleic acid (r=0.72) at the 2-position of the glycerol moiety. A negative correlation was observed between rate of peroxide formation and oleic acid (r=−0.82). Resistance of soybean triacylglycerols to reaction with oxygen was decreased by linolenic (r=0.87) and increased by oleic acid (r=−0.76)-containing triacylglycerols. Volatile formation was increased by increased concentration of linolenic acid at exterior glycerol carbons 1,3 and by linoleic acid at the interior carbon 2. Headspace analysis of voltiles and high-performance liquid chromatography of hydroperoxides indicated that as oxidation proceeded there was a slight decrease in the linolenic acid-derived hydroperoxides and an increase in the linoleic acid-derived hydroperoxides. The oxidative stability of soybean oil triacylclycerols with respect to composition and structure is of interest to the development of soybean varieties with oils of improved odor and flavor stability. Presented at the 81st Annual American Oil Chemists' Society Meeting, Baltimore, MD, April 18–21, 1990.     

Factors affecting the shelf stability of sunflower nuts

Dehulled, raw, whole sunflower kernels of high-oleic acid (HOA) and high-linoleic acid (HLA) types were shelf-stable at 23 and 37°C for over one year. Dry-roasted HOA kernels were more stable than dry-roasted HLA kernels. Oilroasted HLA kernels were more stable than dry-roasted ones. Stability of roasting oil and storage temperature had no appreciable effect on shelf stability of kernels.     

Sensory stability of canola oil: Present status of shelf life studies

Sensory studies on autoxidation of canola oil, stored under several variations of Schaal Oven test conditions, suggest an induction period of 2–4 d at 60–65°C. Similar induction periods have been observed between canola and sunflower oils, whereas a longer induction period has been found for soybean oil. Canola oil seems to be more stable to storage in light than cottonseed and soybean oils but is less stable than sunflower oil. Storage stability of products fried in canola oil is similar to products fried in soybean oil. Storage stability of canola and cottonseed oils that had been used in the frying of potato chips showed that canola oil was more prone to autoxidation during storage at 40°C. The presence of light aggravated the oxidative effects and was similar for both oils. Advances in our knowledge about the shelf life of canola oil would be strengthened by standardization of Schaal Oven testing conditions and by specifying the testing protocol for photooxidation studies. Methods for training of panelists and for handling and evaluating oils and fried foods require definition. Rating scales used in the evaluation of oils need to be evaluated to ensure that reliable and valid measurements are achieved. Further progress is needed in the identification of chemical indicators that can be used to predict sensory quality of oils. Presented in part at AOCS Annual Meeting in Toronto, Ontario, Canada, May 1992.     

Effect of triacylglycerol structures on the thermal oxidative stability of edible oil

Different molecular species of TAG were assessed to determine the influence of TAG structure on the thermal oxidative stability of edible oil. TAG containing palmitic acid (16∶0, P) as saturated FA (SFA) and oleic acid (18∶1, O), linoleic acid (18∶2, L), or linolenic acid (18∶3, Ln) as unsaturated FA (UFA) were chemically synthesized and then heated at 180 or 150°C. Thermal oxidative stability of TAG was determined by evaluating the resultant UFA, polar compound, FFA, carbonyl compound, polymerized compound, and tocopherol contents. When TAG containing 16∶0 and 18∶2 in the ratio of 2∶1 (mol/mol) were heated at 180°C, a 2∶1 (mol/mol) mixture of saturated TAG (PPP) and unsaturated TAG (LLL) was found to be more susceptible to thermal oxidation than PPP/PLL (1∶1) and PPL. Similarly, a 2∶1 mixture of PPP and OOO or LnLnLn was more unstable toward thermal oxidation than PPO or PPLn, respectively. Thermal oxidative stability of TAG containing SFA and UFA (2∶1) was negatively correlated with the moles of UFA in a single TAG molecule. This tendency was also observed at 150°C. From these results, it is suggested that the TAG structure could be one of the factors determining the thermal oxidative stability of edible oil.     

Quality factors in exported peanuts from agrentina,China and the united states

In three crop years (1986–1988), peanuts exported from Argentina, China and the United States were evaluated for biochemical composition relative to flavor and shelf-life quality potentials and physical size conformity. Relationships were consistent in that oil stability was associated with high tocopherol and oleic/linoleic acid ratio, and with low free fatty acid, peroxide, carbonyl, and copper and iron content. Peanuts from specific origins had recurring component patterns, with highest indications for shelf life and flavor potential in United States samples. Although no single factor or group of factors can be relied on completely as predictors of flavor or quality, these data establish a significant positive relationship between oil quality factors and roasted peanut flavor quality potential. Argentina and United States peanuts were the most consistently sized, and China peanuts generally had the lowest count/weight.     

Improving the oxidative stability of polyunsaturated vegetable oils by blending with high-oleic sunflower oil

Mixing different proportions of high-oleic sunflower oil (HOSO) with polyunsaturated vegetable oils provides a simple method to prepare more stable edible oils with a wide range of desired fatty acid composition. Oxidative stability of soybean, canola and corn oils, blended with different proportions of HOSO to lower the respective levels of linolenate and linoleate, was evaluated at 60°C. Oxidation was determined by two methods: peroxide value and volatiles (hexanal and propanal) by static headspace capillary gas chromatography. Determination of hexanal and propanal in mixtures of vegetable oils provided a sensitive index of linoleate and linolenate oxidation, respectively. Our evaluations demonstrated that all-cis oil compositions of improved oxidative stability can be formulated by blening soybean, canola and corn oils with different proportions of HOSO. On the basis of peroxide values, a partially hydrogenated soybean oil containing 4.5% linolenate was more stable than the mixture of soybean oil and HOSO containing 4.5% linolenate. However, on the basis of volatile analysis, mixtures of soybean and HOSO containing 2.0 and 4.5% linolenate were equivalent or better in oxidative stability than the hydrogenated soybean oil. Mixtures of canola oil and HOSO containing 1 and 2% linolenate had the same or better oxidative stability than did the hydrogenated canola oil containing 1% linolenate. These studies suggest that we can obviate catalytic hydrogenation of linolenate-containing vegetable oils by blending with HOSO. Presented at the AOCS/JOCS joint meeting, Anaheim, CA, April 25–29, 1993.     

Microwave roasting effects on the physico-chemical composition and oxidative stability of sunflower seed oil

The purpose of the present study was to explore the influences of microwave heating on the composition of sunflower seeds and to extend our knowledge concerning the changes in oxidative stability, distribution of FA, and contents of tocopherols of sunflower seed oil. Microwaved sunflower seeds (Helianthus annuus L.) of two varieties, KL-39 and FH-330, were extracted using n-hexane. Roasting decreased the oil content of the seeds significantly (P<0.05). The oilseed residue analysis revealed no changes in the contents of fiber, ash, and protein that were attributable to the roasting. Analysis of the extracted oils demonstrated a significant increase in FFA, p-anisidine, saponification, conjugated diene, conjugated triene, density, and color values for roasting periods of 10 and 15 min. The iodine values of the oils were remarkably decreased. A significant (P<0.05) decrease in the amounts of tocopherol constituents of the microwaved sunflower oils also was found. However, after 15 min of roasting, the amount of α-tocopherol homologs was still over 76 and 81% of the original levels for the KL-39 and FH-330 varieties, respectively. In the same time period, the level of σ-tocopherol fell to zero. Regarding the FA composition of the extracted oils, microwave heating increased oleic acid 16–42% and decreased linoleic acid 17–19%, but palmitic and stearic acid contents were not affected significantly (P<0.05).     

Oil stability index correlated with sensory determination of oxidative stability in canola oil

The usefulness of the Oil Stability Index (OSI) as an accelerated oxidative stability test for canola oil was studied by correlating the OSI with the induction period as determined by sensory analysis. Canola oil was treated by holding it for differing times (0, 1, 2, 3, 4, and 6 d) at elevated temperature (60°C) in the dark with agitation. The sensory induction period (SIP) was determined by storing the five treatments of oil and the control at 60°C in the dark with agitation and removing aliquots of oil for a nine-member sensory panel to evaluate over a 9-d period. The time it took for a treatment to reach an average sensory score of 5 (10-point scoring scale) was defined as the treatment’s SIP. OSI values were obtained on day 0 using a heating block temperature of 110°C and an air pressure of 6 psi. The relationship between SIP and OSI had a 0.89 coefficient of determination (r ²). This relationship may be sufficiently strong to warrant use of the OSI in industry applications but may not be ideal for more precise experimental studies of canola oil shelf life.     

Effect of the full refining process on rice bran oil composition and its heat stability

The effects of the chemical refining process on the minor compounds of rice bran oil and its heat stability were investigated. After 8 h of heating, about 50% and 30% of total tocopherols remained in crude and refined rice bran oil, respectively. The individual tocopherols were differently affected by the refining process. The order of heat stability of tocopherols and tocotrienols in crude oil was found to be different from that in fully refined oil. A similar tendency was observed for sterols. After 8 h of heating, 65% and 72% of total sterols, and 14% and 46% of sterol esters, of crude or fully refined rice bran oil, respectively, disappeared. The heating process led to a 4% and 10.3% increase in polymer contents in crude and refined rice bran oil, respectively. Although refined rice bran oil showed good heat stability, when compared to crude oil its heat stability was decreased to some extent.     

Effect of fatty acid composition of oils on flavor and stability of fried foods

Effects of fatty acid composition of frying oils on intensities of fried-food flavor and off-flavors in potato chips and french-fried potatoes were determined. Commercially processed cottonseed oil (CSO) and high-oleic sunflower oil (HOSUN) were blended to produce oils with 12 to 55% linoleic acid and 16 to 78% oleic acid. Analytical sensory panels evaluated french-fried potatoes and pilot plant-processed potato chips. Initially, both foods prepared in CSO (16% oleic/55% linoleic acid) had the highest intensities of fried-food flavor; however, this positive flavor decreased with decreasing levels of linoleic acid. 2,4-Decadienal in potato chips also decreased with decreasing linoleic acid in the oils. Frying oil stability, measured by total polar compounds (TPC), and oxidative stability of potato chips, measured by volatile compounds, showed that HOSUN (78% oleic acid) produced the lowest levels of TPC and the lowest levels of hexanal and pentanal, indicating greater frying oil stability and oxidative stability of the food. However, fresh potato chips fried in HOSUN had the lowest intensities of fried-food flavor and lowest overall flavor quality. Fried-food flavor intensity was the best indicator of overall flavor quality in fresh potato chips. Volatile compounds, TPC, and oxidative stability index directly varied with increasing oleic acid, and were therefore not directly indicative of flavor quality. No oil analysis predicted flavor stability of aged potato chips. Compositions of 16 to 42% oleic acid and 37 to 55% linoleic acid produced fresh fried-food with moderate fried food flavor intensity, good overall flavor quality, and low to moderate TPC levels (chips only). However, in aged food or food fried in deteriorated oil, compositions of 42 to 63% oleic and 23 to 37% linoleic provided the best flavor stability.     

Effect of roasting temperature and time on the chemical composition of rice germ oil

Compositional changes of rice germ oils prepared at different roasting temperatures (160–180°C) and times (5–15 min) from rice germ were evaluated and compared with those of unroasted rice germ oil. The color development and phosphorus content of oils increased significantly as roasting temperature and time increased, whereas the FA compositions of rice germ oils did not change with roasting temperature and time. Four phospholipid classes, i.e., PE, PI, PA and PC, were identified. PE had the lowest stability under roasting conditions. There were no significant differences in γ-oryzanol levels of rice germ oils prepared at different roasting temperatures and times. Four tocopherol isomers (α−, β−, γ−, and δ-tocopherol) and three tocotrienol isomers (α−, γ−, and δ-tocotrienol) were identified, but no β-tocotrienol was detectable. The content of α− and γ−tocopherol in rice germ oil gradually increased as roasting temperature and time increased.     

Optimising the oil phases of aluminium hydrogel-stabilised emulsions for stable,safe and efficient vaccine adjuvant

To increase antibody secretion and dose sparing, squalene-in-water aluminium hydrogel (alum)-stabilised emulsions (ASEs) have been developed, which offer increased surface areas and cellular interactions for higher antigen loading and enhanced immune responses. Nevertheless, the squalene (oil) in previous attempts suffered from limited oxidation resistance, thus, safety and stability were compromised. From a clinical translational perspective, it is imperative to screen the optimal oils for enhanced emulsion adjuvants. Here, because of the varying oleic to linoleic acid ratio, soybean oil, peanut oil, and olive oil were utilised as oil phases in the preparation of aluminium hydrogel-stabilised squalene-in-water emulsions, which were then screened for their stability and immunogenicity. Additionally, the underlying mechanisms of oil phases and emulsion stability were unravelled, which showed that a higher oleic to linoleic acid ratio increased anti-oxidative capabilities but reduced the long-term storage stability owing to the relatively low zeta potential of the prepared droplets. As a result, compared with squalene-in-water ASEs, soybean-in-water ASEs exhibited comparable immune responses and enhanced stability. By optimising the oil phase of the emulsion adjuvants, this work may offer an alternative strategy for safe, stable, and effective emulsion adjuvants.     

Effect of processing on the composition and oxidative stability of coconut oil

The effect of various processing procedures on the composition and oxidative stability of coconut oil has been studied. The crude oil is relatively stable but major reductions in oxidative stability occur during the bleaching of oil degummed with phosphoric acid; during alkali refining; during the deodorization of oil degummed with citric acid and bleached; and during the deodorization of oil processed with a combined phosphoric acid degumming and bleaching operation. The reasons for the loss of oxidative stability during processing are discussed with reference to changes in the composition of the oil. Residual traces of citric acid or phosphoric acid play an important role in stabilizing processed oils. The tocopherol content is also important, although no additional stabilization of the oil occurs on adding levels of tocopherol above those present naturally in the crude oil. A combined phosphoric acid degumming and bleaching process leads to smaller losses of tocopherols than sequential treatments.     

Frying quality and oxidative stability of high-oleic corn oils

To determine the frying stability of corn oils that are genetically modified to contain 65% oleic acid, high-oleic corn oil was evaluated in room odor tests and by total polar compound analysis. Flavor characteristics of french-fried potatoes, prepared in the oil, were also evaluated by trained analytical sensory panelists. In comparison to normal corn oil, hydrogenated corn oil and high-oleic (80 and 90%) sunflower oils, high-oleic corn oil had significantly (P<0.05) lower total polar compound levels after 20 h of oil heating and frying at 190°C than the other oils. Fried-food flavor intensity was significantly higher in the normal corn oil during the early portion of the frying schedule than in any of the high-oleic or hydrogenated oils; however, after 17.5 h of frying, the potatoes fried in normal corn oil had the lowest intensity of fried-food flavor. Corn oil also had the highest intensities of off-odors, including acrid and burnt, in room odor tests. High-oleic corn oil also was evaluated as a salad oil for flavor characteristics and oxidative stability. Results showed that dry-milled high-oleic corn oil had good initial flavor quality and was significantly (P<0.05) more stable than dry-milled normal corn oil after oven storage tests at 60°C, as evaluated by flavor scores and peroxide values. Although the high-oleic corn oil had significantly (P<0.05) better flavor and oxidative stability than corn oil after aging at 60°C, even more pronounced effects were found in high-temperature frying tests, suggesting the advantages of high-oleic corn oil compared to normal or hydrogenated corn oils.     

Effect of dewaxing pretreatment on composition and stability of rice bran oil: Potential antioxidant activity of wax fraction

The effect of dewaxing pretreatment on rice bran oil composition and stability was investigated, as well as the possibility to use rice bran oil waxes as natural antioxidants at high temperatures. A correlation between wax content and dewaxing time was noticed. The pre‐dewaxing process led to a loss of minor compounds, which negatively affected the oxidative stability index (OSI) of the dewaxed oil. The addition of rice bran oil waxes improved the oil stability index and heat stability of sunflower oil. An increase of 60% of the OSI and a significant decrease in polymer formation (59.2%) were observed.