Headspace Oxygen Content Research Articles

Effects of relative humidity and neutral emulsifier on oxidative stability of corn oil during room temperature storage

The effects of tween 20, one of neutral emulsifiers, on oxidative stability of corn oil were determined under a relative humidity (RH) range of 0–93 % at room temperature after 350 days of storage. The degree of oxidation was determined by headspace oxygen content and conjugated dienoic acids analyses. Moisture content and α-tocopherol were also analyzed. The degree of lipid oxidation was significantly influenced by the concentration of tween 20 and relative humidity. Samples without addition of tween 20 showed the highest oxidative stability in 11 % RH, whereas oxidative stability was lowest at 93 % RH. Adding 0.5 and 1.0 % tween 20 increased the rate of lipid oxidation in a concentration dependent manner. Samples containing tween 20 had higher moisture content than those without an amphiphilic compound. Stability of α-tocopherol was depending on the content of moisture and amphiphilic compounds in bulk oil.

Synergism of phosphatidylcholine on the antioxidant properties of α‐tocopherol in corn oils under different relative humidity

SummaryThe effects of phosphatidylcholine on the antioxidant properties of α‐tocopherol (84 ppm) were determined in stripped corn oil with various moisture contents at 60 °C. The degree of oxidation in the oils was determined by analysing headspace oxygen content and conjugated dienoic acids (CDA). Generally, phosphatidylcholine acted as an antioxidant in stripped corn oils, whereas it accelerated the rate of lipid oxidation in nonstripped corn oils. As the relative humidity and moisture content increased, the antioxidant properties of phosphatidylcholine increased significantly (P < 0.05). Strong synergistic antioxidant effects were observed in samples containing both phosphatidylcholine and α‐tocopherol compared to samples with only phosphatidylcholine or α‐tocopherol. Oils containing phosphatidylcholine or α‐tocopherol under different moisture contents had different oxidative stabilities.

Antioxidant properties of ascorbic acid in bulk oils at different relative humidity

The effects of relative humidity (RH) on the antioxidant properties of ascorbic acid (10, 20, 42, and 84ppm) were investigated in stripped corn oils stored at 60°C. The degree of oxidation in oils was determined by analysing headspace oxygen content and conjugated dienoic acids. The oxidative stability of bulk oils without addition of ascorbic acid was significantly different depending on the RH. As the concentration of ascorbic acid increased from 10 to 84ppm, oxidative stability increased significantly irrespective of RH (p<0.05). Generally, oils containing ascorbic acid at low RH had higher oxidative stability after storage at 60°C than those at high RH. The antioxidant properties of ascorbic acid were greatly influenced by both the moisture content in the oil and the ascorbic acid concentration.

Oxidative stability of solid fats containing ethylcellulose determined based on the headspace oxygen content

Solid fat was developed by blending fully hydrogenated soybean oil, palm oil, and canola oil, and organogels were prepared using selected solid fats and ethylcellulose. The oxidative stability of organogel was tested at 100 and 180°C using a headspace oxygen assay. Addition of ethylcellulose produced a firmer organogel solid state in selected solid fats ranging from 15.8 to 24.6% saturation at room temperature. Addition of ethylcellulose generally decreased the oxidative stability of organogels prepared using canola oil. The oxidative stability of some organogels made using solid fats changed depending on the concentration of added ethylcellulose (10 or 15%, w/w), and the oxidation temperature. Development of an organogel with a relatively low saturation and a high oxidative stability suitable as a food ingredient is possible.

Antioxidant activities of Vine Tea (Ampelopsis grossedentata) extract and its major component dihydromyricetin in soybean oil and cooked ground beef

Antioxidant activities of Ampelopsis grossedentata extract (EXT) and its major component dihydromyricetin (DHM) were analysed and compared with BHA in two model systems, soybean oil and cooked ground beef. Oxidation of soybean oil samples was measured using peroxide value, anisidine value, headspace volatiles and headspace oxygen content. TBARS (thiobarbituric acid reactive substances) test was used to measure the oxidation of cooked beef. DHM was more potent than BHA in preventing soybean oil oxidation. EXT was not as effective as BHA or DHM in soybean oil. In cooked beef, all three antioxidants significantly lowered oxidation compared to control, but there were no differences between the three. Mechanisms and potentials of EXT and DHM as natural food antioxidants need to be studied on a case-by-case basis.

Effects of light and lipids on chlorophyll degradation

Stability of chlorophylls was studied in a system of paraffin oil with added oleic acid or triolein under 1,700 lx and in the dark. Chlorophyll contents were determined using HPLC. Sample oxidation was evaluated using the headspace oxygen content based on GC and the peroxide value. The chlorophyll content decreased with time and was higher and decreased faster under light than in the dark. Singlet oxygen was involved in chlorophyll degradation under light. Chlorophyll degradation was lower and slower in samples with added lipids than in samples without lipids. Protection of chlorophyll from photodegradation was greater using triolein than using oleic acid. Oxidation was slightly higher in samples with added lipids than in samples without lipids, however, there was no significant (p>0.05) difference between samples with added oleic acid or triolein. Decreased chlorophyll degradation under light by lipids is due to competition between lipids and chlorophyll for singlet oxygen.

Effects of relative humidity on the antioxidant properties of α-tocopherol in stripped corn oil

The effects of relative humidity (RH) on the antioxidant properties of α-tocopherol (10, 20, 42, and 84ppm) were determined in stripped corn oil oxidised at 60°C. The degree of oxidation in oils was determined by analysing headspace oxygen content and conjugated dienoic acids (CDAs). Changes in moisture and α-tocopherol content were also monitored. The oxidative stability of stripped corn oil and stability of α-tocopherol differed significantly depending on the RH. As the concentration of α-tocopherol increased from 10 to 84ppm, oxidative stability decreased significantly irrespective of RH. The remaining α-tocopherol content decreased as RH increased, suggesting an important role for moisture content in the stability of α-tocopherol. Antioxidant properties of α-tocopherol were greatly influenced by both moisture content in oil and α-tocopherol concentration.

Effect of ultraviolet‐B irradiation on antioxidative properties of aqueous extracts from shiitake (Lentinus edodes) mushrooms

SummaryAntioxidant properties of aqueous extracts from Lentinus edodes treated with UV‐B irradiation were examined in vitro systems including DPPH, ABTS and oxygen radical absorbance capacity (ORAC) assays and in riboflavin‐photosensitised oil‐in‐water (O/W) emulsions. Changes in total phenolics, total flavonoids and vitamin C were also analysed. Lentinus edodes receiving 25 kJ m−2 UV‐B treatment showed high radical scavenging ability based on DPPH and ABTS assays compared with samples with 0, 50 and 75 kJ m−2, while those with 50 kJ m−2 had higher antioxidant capacities than other samples from ORAC assays. Samples with 25 kJ m−2 UV treatment had significantly 7.1% higher total phenolic content, 12.0% higher total flavonoid content and 8.0% higher vitamin C content than UV‐B‐untreated sample (P &lt; 0.05), respectively. In O/W emulsions under riboflavin photosensitisation, 25 and 50 kJ m−2 UV treatment significantly increased the oxidative stability compared with other samples based on headspace oxygen content and lipid hydroperoxide analyses (P &lt; 0.05). Aqueous extracts of UV‐B‐treated mushrooms possessed enhanced antioxidant properties compared with untreated mushrooms.

Oxidative Stability in Bulk Oil Containing Carbohydrates Such as Glucose, Sucrose, Maltose, Mannitol, and Starch

AbstractEffects of carbohydrates including glucose, sucrose, maltose, mannitol, and starch on the oxidative stability of corn oils were evaluated at 40 °C for 51 days, at 100 °C for 17 h, and at 180 °C for 90 min. The degree of oxidation was determined by headspace oxygen content, conjugated dienoic acid (CDA) assay, or p‐anisidine value (p‐AV) and the moisture content of the oils was analyzed. Starch showed pro‐oxidant properties whereas mannitol acted as an antioxidant at all tested temperatures. However, glucose, sucrose, and maltose showed different properties depending on the temperature and type of assays. At 40 °C, glucose, sucrose, and maltose showed antioxidant properties in headspace oxygen and CDA assays. There were no significant differences in CDA between samples at 100 and 180 °C. p‐AV in samples containing glucose were significantly higher than those in controls at 180 °C, which may be due to the formation of volatiles from caramelization rather than lipid oxidation. Moisture content of oils containing glucose and starch was significantly higher than that of controls, whereas that of oils containing mannitol was lower than in the control (p &lt; 0.05). Changes in moisture content of oils may be due to the migration of moisture from added carbohydrates into the oils.

Effect of retail display illumination and headspace oxygen concentration on cured boiled sausages

Abstract The objective of this study was to investigate the influence of various commercial lamps and residual oxygen on discoloration and oxidation of cured boiled sausage. The wavelength dependence of different spectral bands on sausage color and oxygen absorption was investigated. A model packaging system, simulating a gastight package was used to compare the influence of fluorescent tubes, metal halide lamps, color optimized fluorescent tubes and LEDs. Sausages exposed to daylight fluorescent tubes showed significantly ( p

Effect of α‐, β‐, γ‐, and δ‐Tocotrienol on the Oxidative Stability of Lard

AbstractDespite the structural similarity of tocopherols, the antioxidative activities of tocotrienol homologues have not been studied often. In this study, the antioxidant activities of α‐, β‐, γ‐, and δ‐tocotrienols at various concentrations from 100 to 1,000 ppm in lard were evaluated. Headspace oxygen content of the lard without tocotrienol decreased from 21.1 to 10.7 % and the peroxide value increased from 0.4 to 33.4 mequiv/kg after 7 days of storage at 55 °C in the dark. α‐Tocotrienol at 100 ppm and β‐tocotrienol at 100 and 200 ppm effectively improved the oxidative stability of lard; however, the antioxidative activities of α‐ and β‐tocotrienol reduced as the concentration increased to 1,000 ppm. The γ‐ and δ‐tocotrienols improved the oxidation stability of lard and the effectiveness was essentially same at all concentrations (p &gt; 0.05). The antioxidative activities of tocotrienols in the autoxidation of lard increased in the order of α‐, β‐, γ‐, and δ‐tocotrienols. The activities of tocotrienols in lard were different depending on the type of homologues and concentrations.

Effects of Deuterium Oxide on the Oxidative Stability and Change of Headspace Volatiles of Corn Oil

AbstractEffects of deuterium oxide and deuterium oxide‐free water on the oxidative stability and formation of headspace volatiles were determined for corn oils to evaluate the role of moisture as an active influential factors during lipid oxidation. Mixtures of corn oil and water with different ratios of deuterium oxide were prepared, and the mixtures were stored at 60 °C for 2 days. Headspace oxygen contents, conjugated dienoic acid (CDA) values, and p‐anisidine values (p‐AV) were analyzed as a measure of oxidative stability, and headspace volatiles were analyzed by solid phase microextraction and a gas chromatography mass selective detector to determine the involvement of deuterium in volatiles. Deuterium oxide accelerated the rate of lipid oxidation in corn oil compared to oils with deuterium‐free water based on the results of headspace oxygen content, CDA, p‐AV, and total volatile content. Fragmented mass to charge ratios (m/z) of 73.1/72.1 for d1‐pentane/pentane and 57.0/56.0 for d1‐2‐propenal/2‐propenal from samples containing deuterium oxide were significantly higher than those from deuterium oxide‐free water, implying that moisture participated to form volatiles in corn oil oxidation under air‐tight condition. Deuterium oxide appeared to accelerate the rate of lipid oxidation in corn oils and participated to form volatiles from oils during oxidation.

Effect of α‐, β‐, γ‐, and δ‐Tocotrienol on the Singlet Oxygen Oxidation of Lard

AbstractThe impacts of four different types of tocotrienol homologues on the singlet oxygen oxidation of lard were evaluated by measuring the headspace oxygen content and the peroxide value. Singlet oxygen oxidation of lard was induced by chlorophyll photosensitization. Samples of 0.100, 0.250, and 0.400 M lard in methylene chloride containing chlorophyll and α‐, β‐, γ‐, or δ‐tocotrienol were prepared and stored under light at 3,000 lux for 4 h. All tocotrienol homologues at 1.20 mM significantly prevented the singlet oxygen oxidation of lard. Chlorophyll under light produced singlet oxygen at 1.09 μmol oxygen/mL headspace/h. A steady state kinetic study showed that tocotrienols reduced the singlet oxygen oxidation of lard by quenching the singlet oxygen. Singlet oxygen reacted with lard at 6.50 × 104M−1 s−1. α‐, β‐, γ‐, and δ‐tocotrienol quenched singlet oxygen with the rate of 2.16, 1.99, 2.05, and 0.800 × 107M−1 s−1, respectively. Among them, α‐tocotrienol significantly prevented singlet oxygen oxidation of lard.

Evaluation of Oxygen‐Limitation on Lipid Oxidation and Moisture Content in Corn Oil at Elevated Temperature

AbstractThe role of oxygen‐limitation on lipid oxidation and moisture content were tested in corn oil heated to 60, 100, and 140 °C. The degree of oxidation was determined by analyzing headspace oxygen content, conjugated dienoic acids (CDA), and p‐anisidine value (p‐AV). The moisture content in bulk oil was analyzed by the Karl Fischer method. Oxygen‐limited samples heated to 100 and 140 °C had significantly more lipid oxidation than oxygen‐unlimited samples at early timepoints (p &lt; 0.05). After this period, the oxygen‐unlimited samples had more lipid oxidation based on CDA and p‐AV assays. During those initial periods, oxygen‐limited samples had significantly higher moisture content than oxygen‐unlimited samples (p &lt; 0.05), which implies that moisture content in oils plays an important role in the rate of lipid oxidation. The increased moisture content in bulk oil under oxygen‐limited conditions is due to headspace moisture rather than moisture inside the oil. However, the effects of oxygen‐limitation on lipid oxidation were less clear at 60 °C than at 100 or 140 °C.

Role of moisture on the lipid oxidation determined by D2O in a linoleic acid model system

The possibility of moisture, as an active substance for lipid oxidation, was determined in linoleic acid model systems containing deuterium oxide (D2O) and deuterium free H2O, by measuring the headspace oxygen content and headspace volatiles. Mixtures of D2O and H2O, at the ratio of 3:0, 2:1, 1:2, and 0:3 (w/w), were added to linoleic acid and oxidised at 60°C. The existence of deuterium in headspace volatiles, was indirectly determined by comparing the amount of fragmented mass to charge ratio (m/z), which was 73.1/72.1 for d1-pentane/pentane, 57.0/56.0 for d1-2-propenal/2-propenal, 101.1/100.1 for d1-hexanal/hexanal, 113.1/112.1 for d1-t-2-heptenal-D/t-2-heptenal, and 153.2/152.2 for d1-2,4-decadieanl/2,4-decadieanl. As the oxidation time increased to 12h, the ratio of 73.1/72.1 (m/z) for pentane and 57.0/56.0 for 2-propenal increased significantly with a concentration dependent manner of deuterium oxide, which implies water was incorporated as a substrate during volatile formation. However, hexanal, t-2-heptenal, and 2,4-decadieanl did not follow the patterns of pentane and 2-propenal, implying that the formation mechanisms of these volatiles may not share the same pathways with pentane and 2-propenal. This study showed that moisture participates for the formation of volatiles and moisture may act as a substrate for lipid oxidation.

Effects of visible light irradiation on the oxidative stability in rice bran

Raw rice bran was treated with or without visible light exposure at room temperature or stored at 40 °C in the dark for 10 days and rice bran oil (RBO) was recovered from each rice bran. Headspace oxygen content from rice bran and conjugated dienoic acid (CDA) value, acid value, content of γ-oryzanol, and fluorescence intensity in RBO were analyzed to determine the effects of visible light on the oxidative stability in rice bran. Headspace oxygen content in visible light irradiated rice bran (RBL) decreased by 12.8% for 10 days while those in the dark (RBD) and stored at 40 °C (RBT) decreased by 5.87 and 5.35%, respectively, implying visible light irradiation accelerates the consumption of oxygen. CDA values in RBO from RBL were significantly higher than those in RBO from RBD and RBT (p < 0.05). However, acid values in RBO were not significantly different among samples (p > 0.05). Both γ-oryzanol content and fluorescence intensity in RBO from RBL were significantly lower than those in RBO from RBD and RBT (p < 0.05). Fluorescence intensity, which is related to the content of chlorophylls, decreased in samples under light only, implying that chlorophyll photosensitization may play important roles in the acceleration of lipid oxidation in rice bran.

Prooxidative and antioxidative properties of β-carotene in chlorophyll and riboflavin photosensitized oil-in-water emulsions

Effects of β-carotene on the oxidative stability of chlorophyll or riboflavin photosensitized oil-in-water (O/W) emulsions were determined by analysing the depleted headspace oxygen content, lipid hydroperoxides, fluorescence intensity, and headspace volatiles. As the concentration of β-carotene increased from 0 to 10, 100, and 1000μM, the oxidative stability of samples containing chlorophylls decreased in a concentration-dependent manner under light, indicating that β-carotene acted as a prooxidant. However, in riboflavin photosensitized O/W emulsions, 100 and 1000μM β-carotene inhibited lipid oxidation. Although β-carotene protected both photosensitisers in O/W emulsions, β-carotene displayed antioxidative or prooxidative properties, which depended on the polarity of the photosensitisers. The development of t-2-heptenal and 1-octen-3-ol increased greatly in chlorophyll sensitised O/W emulsions with an increase in β-carotene concentration, implying that more singlet oxygen oxidation occurred due to the higher levels of remaining chlorophylls. However, the content of t-2-heptenal and 1-octen-3-ol in the riboflavin sensitised O/W emulsions was not significantly correlated with the β-carotene concentration, which indicates that β-carotene in the lipid particles effectively quenched singlet oxygen.

Effects of lipophilic and hydrophilic antioxidants in oil-in-water emulsions under chlorophyll photosensitization

Antioxidative or prooxidative properties of α-tocopherol, Trolox, ascorbic acid, and ascorbyl-palmitate at the concentration of 0.1 and 1.0 mM were determined in oil-in-water (O/W) emulsions under chlorophyll photosensitization. Headspace oxygen depletion, lipid hydroperoxides, and headspace volatile analyses were conducted to determine the oxidative stability of O/W emulsions. For 32 h visible light irradiation, depleted headspace oxygen content in O/W emulsions were in the order of samples containing Trolox, ascorbic acid, ascorbyl palmitate, α-tocopherol, without antioxidants under light, and samples in the dark, which implies that all the added compounds acted prooxidant. These prooxidative properties of added compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. Samples containing ascorbic acid and ascorbyl palmitate retained higher chlorophyll content than those containing Trolox up to 16 h. Increases of concentration of Trolox, ascorbic acid, and ascorbyl palmitate from 0.1 to 1.0 mM increased the lipid oxidation products whereas α-tocopherol decreased the degree of lipid oxidation implying α-tocopherol may not share the same prooxidant mechanisms compared to other compounds in chlorophyll sensitized O/W emulsions.

Effect of Added Conjugated Linoleic Acid and Iodine Concentrations on Conjugated Linoleic Acid‐Rich Soy Oil Oxidative Stability

Jain and Proctor [1] reported pilot scale production of 20 % conjugated linoleic acid (CLA) in soy oil by photoisomerization of soy oil linoleic acid (LA) in oil triacylglycerides to CLA using an iodine catalyst. Recently, we reported in a food oil oxidation study of freshly produced CLARSO that the pro-oxidant effect of CLA and iodine was independent of concentration [2]. However, the study did not distinguish between the effect of CLA and iodine on CLA oxidation. Removal of iodine may be important if iodine is identified as prooxidant. However, if CLA is the major pro-oxidant, storage conditions and added antioxidants may be very important after iodine removal to protect against oxidation. The objective of the following study was to distinguish between the effect of added CLA and added iodine concentration on soy oil oxidative stability. Commercial RBD (Refined, bleached, and deodorized) soy oil was obtained from Riceland Foods (Stuttgart, AR) containing 52 % linoleic and 6 % linolenic acid. Resublimed iodine crystals were used as a catalyst (Alfa Aeser, Ward Hill, MA). Commercial CLA triacylglyceride (Tonalin TG80) consisting of a 50:50 mixture of cis-9, trans11 and trans-10, cis-12 was obtained from Cognis Nutrition and Health (Cincinnati, OH). Nine RBD soy oil treatments containing combinations of 0, 0.175, and 0.35 % iodine; 0, 10 and 20 % commercial CLA triacylglyceride (Tonalin TG80) were prepared. CLARSO oxidative stability was studied by gravimetric analysis [3] and headspace oxygen determination. The 500-mg samples of soybean oil treated with combinations of CLA and iodine were weighed into aluminum pans. Samples were stored in an oven in the dark at 65 C for 10 days and weighed daily. Results were expressed as change in weight (mg per 500 mg of oil). To measure headspace oxygen, 3 g of oil was weighed into 10-mL amber colored glass vials and the vials were stored in an oven in the dark at 65 C for 10 days. The headspace oxygen content in each vial was determined daily by using Oxygen Analyzer-Quantek Model 905 (Quantek Instruments, Grafton, MA). Data were analyzed as a full-factorial design by analysis of variance (ANOVA) and mean comparison of triplicate runs was done by a student’s t test (p 0.05) using JMP 9.0 (SAS Institute Inc., Cary, NC). RBD soybean oil was used in this study in place of CLARSO because the CLA in CLARSO may not allow for the effects of iodine to be determined independently. Figure 1 shows the effects of iodine and CLA concentration on weight change of RBD soy oil. The presence of iodine in the oils resulted in shorter induction time, more rapid weight increase, and therefore greater oxidation. However, there was no increase in induction time with increasing iodine levels. At 0 % CLA, both 0.175 and 0.35 % iodine had an induction period of 1 day. However, at 10 % CLA, 0.175 % iodine had an induction period of 0 days, and 0.35 % iodine had a 1-day induction period. At 20 % CLA, the two iodine concentrations again showed similar behavior with a 1 day induction period. The main general observation was that the presence of iodine increased oxidation but increasing the concentration did not. This agreed with our previous finding in CLARSO [2]. In the absence of iodine in the oil, there was increasing oxidation with an increasing CLA concentration with the 20 % CLA oil weight increase being most rapid followed by 10 % CLA oil. The change in weight was affected by iodine concentration, CLA concentration, time (day), and all interactions (p 0.05). The % iodine 9 % R. R. Yettella C. Castrodale A. Proctor (&) Department of Food Science, University of Arkansas, 2650 N. Young Avenue, Fayetteville, AR 72704, USA e-mail: aproctor@uark.edu

Modelling the degradation kinetics of vitamin C in fruit juice in relation to the initial headspace oxygen concentration

Abstract In the presence of oxygen, ascorbic acid (AA) is readily degraded to dehydroascorbic acid (DHA), which is prone to further degradation, hereby losing its vitamin C activity. In this study, the influence of different initial headspace O 2 concentrations on the oxidation of AA and the subsequent formation and breakdown of DHA was investigated in a model fruit juice. Kinetic rate constants for solely AA degradation were estimated using zero and first order kinetics, while first order irreversible and reversible consecutive models were used to describe the degradation kinetics of AA combined with the oxidative formation and irreversible breakdown of DHA. A linear relationship was found between the first order AA degradation constants and the initial headspace oxygen concentrations. Further, a similar relationship was found for a commercial fruit juice. In this way a tool is provided to predict the AA content in fruit juices at different stages during storage, knowing the residual headspace oxygen concentration after packaging, the O 2 -permeability of the packaging material and the initial AA and DHA concentration.