A chemiluminescence study of the oxidation of vegetable oils and model compounds and the effects of antioxidants

Chemiluminescence was used to study the course of oxidation of sunflower oil samples at a number of temperatures between 70 and 121°C. The induction time was determined for each sample and used to estimate the shelf life of the oils at 25°C. In addition, Chemiluminescence during oxidation in air on alumina at 80°C was used to study both sunflower oil and, as a model compound, methyl linoleate with and without added artificial antioxidants. By using the method of inhibitors, the reaction rate and level of hydroperoxide were determined. It was also possible to determine the level of naturally occurring antioxidant in the vegetable oil.     

A kinetic study of oxidation development in sunflower oil under microwave heating: Effect of natural antioxidants

The antioxidative effects of carnosic acid and sesamol on sunflower oil under temperature-controlled microwave heating were investigated as a function of time and temperature. The concentration of conjugated diene hydroperoxide and p-anisidine value were determined spectrophotometrically, as measures of oxidation, during microwave heating of sunflower oil with or without added antioxidants at 40 °C, 60 °C and 80 °C. The kinetics of hydroperoxide formation was examined on the basis of previously proposed mechanisms and found to be of the half-order with respect to the concentration of conjugated diene hydroperoxide. The amounts of added antioxidants remaining in sunflower oil after different microwave heating periods at different temperatures were determined by HPLC-DAD. The results were interpreted in terms of antioxidative effects of carnosic acid and sesamol. Carnosic acid was found to be a more effective antioxidant than sesamol for sunflower oil.     

Effect of soyasaponin I on the oxidation of corn oil and lard

The antioxidant activity of soyasaponin I added to corn oil (100 and 1000 mg kg^?1) and lard (567 mg kg^?1) has been examined. In corn oil oxidised at 40°C no effect was observed as measured by the increase in conjugated diene hydroperoxide. In corn oil oxidised at 180°C there was no effect as measured by both thiobarbituric acid values and the loss of unsaturated fatty acids. Soyasaponin I conferred no additional stability to lard measured by an induction period on the Rancimat apparatus at 100°C. The results obtained do not support a recently implied antioxidant role for this saponin.     

Superoxide dismutase from hen’s egg yolk can protect fatty acids from peroxidative damage

Superoxide dismutase (SOD, EC1.15.1.1) is a family of enzymes, which remove superoxide anion (O ₂ ^·? ) from the cells of living organisms. The aim of this study was to describe antioxidative properties of SOD with regard to the protection of unsaturated fatty acids (UFA) from peroxidative damage and to compare this effect with butylated hydroxytoluene (BHT). In this experiment, Cu, Zn-SOD from hen’s egg yolk with a mass of 15.59 ± 0.38 kDa and pI 6.58 ± 0.10, 6.41 ± 0.08 and 6.30 ± 0.15 was used to protect fatty acids from peroxidative damage in vegetable oil (sunflower oil and olive oil) during 200 days of storage at different temperatures—4, 20 and 35 °C. Antioxidative properties of SOD and BHT were expressed as the ratio of unsaturated to saturated fatty acids (SFA) in samples after 50, 100 and 200 days of storage as well as the percentage content of selected fatty acids in the examined oils. SOD from egg yolk showed the same or better antioxidant properties with regard to the concentration of linoleic acid (C18:2) contained in sunflower oil and olive oil than the corresponding concentrations of BHT during 200-day storage at 4, 20 and 35 °C. The concentration of linoleic acid (C18:2) in the sample with SOD was significantly higher during storage at 35 °C on day 200. At all storage temperatures, the ratio of SFA to UFA in samples with the addition of SOD was statistically higher than in oils stored without the antioxidant. With regard to linoleic acid (C18:2), SOD proved to be a better antioxidant than BHT. The results demonstrated better antioxidant properties of SOD from hen’s eggs compared with the same concentrations of BHT at elevated temperatures (at 20 and 35 °C) in oil with a high content of UFA. No negative antioxidative effect (worse than that of BHT at a corresponding concentration) of the addition of SOD from egg yolk on fatty acid composition of the tested samples was observed. Though further research is necessary, SOD from hen’s egg yolk seems to be a promising natural antioxidant of vegetable oils.     

COMPARISON OF WET-CHEMICAL METHODS FOR DETERMINATION OF LIPID HYDROPEROXIDES

Five methods for determination of lipid hydroperoxides were evaluated, including two iodometric procedures involving a titration and a spectrophotometric micro method, and three other spectrophotometric methods namely the ferro, International Dairy Federation (IDF) and FOX2 (ferrous oxidation in xylenol orange). Peroxide values determined in a range of food products by these five methods gave different results. The ferro method required large amounts of solvent (50 mL/sample); the FOX2 method had a low range (0.005–0.04 μmol hydroperoxide); the end point detection of the titration method was subjective and required a large amount of sample (1 g); and the micro method was sensitive to interruptions during execution. Therefore, only the modified IDF method was chosen for further testing and validation. Stability tests of the standard curve showed a variation coefficient of 4% and within runs the highest variation was 5.9% (for blank) and a maximum of 9.6% between runs variation for the lowest concentration. Among the antioxidants tested, only ethylenedi-aminetetraacetic acid (EDTA) affected the peroxide determinations.     

A Rapid and Small-Scale Method for Estimating Antioxidative Potency of Peanut Sprouts

A method for estimating antioxidative potency (AOP) was achieved by incubating emulsified linoleic acid in a 1 mL iron/ascorbate system at 37 °C for 30 min followed by absorbance measurement at 234 nm to determine the conjugated diene hydroperoxide (CDHP) content. By that method, 100% AOP was obtained when 10 ppm butylated hydroxytoluene or 50 ppm α‐tocopherol was introduced. When freeze‐dried peanut sprouts were cooked with ground pork‐fat patties and the separated oils were stored at 60 °C for CDHP determination, the highest AOP was observed in the 144 h germinated sprout roots. After extracting the sprout roots with methanol and AOP evaluation by the iron/ascorbate and pork‐oil storage methods, both showed similar AOP trends as affected by extract concentration.     

Comparability of mineral oil testing for dry food and cardboard samples – Perspectives from different PT rounds

Mineral oil hydrocarbons (MOH) can be found in detectable levels in a multitude of foodstuffs. Therefore, chemical analysis of food for MOH gains importance. Different proficiency testing (PT) rounds on mineral oil testing have been performed in different matrices: cereals and rice as well as cardboard samples were examined. The laboratories participating in the PT rounds had to follow specific requirements for examination. The sample materials used contained different concentrations of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). The PT results were statistically evaluated according to ISO 13528:2005 and additionally the HorRat(R) value was calculated to gain information on the comparability of the mineral oil testing. It could be shown that for the examined sample materials and under the chosen specifications for testing a comparable determination of the mineral oil content is possible within the required relative standard deviations. A useful analytical determination can be achieved with an acceptable relative standard deviation of <50% from a concentration of defined mineral oil fractions at ≥1 mg/kg in food. In the concentration range for MOH in food of between 1 mg/kg and 2 mg/kg, relative standard deviations of 20–40% were achieved. MOH concentrations of ≥ 2 mg/kg food were determined with good relative standard deviations of around 20%. Moreover, due to the results gained within this work a statement concerning the comparability for MOSH and MOAH contents below concentrations of 1 mg/kg food is possible: under the chosen conditions for examination as part of this work, mineral oil determination below 1 mg/kg food showed high variability. To gain reliable information with regard to consumer protection on the risk of mineral oil contents in this low concentration range further standardisation of the test method is indicated.     

Antioxidant Properties of Aqueous Extract of Roasted Hulled Barley in Bulk Oil or Oil‐in‐Water Emulsion Matrix

Antioxidant properties of the aqueous extracts of hulled barley (Hordeum vulgare L.) that had been roasted at 210 °C for 20 min were determined in bulk oil and oil‐in‐water (O/W) emulsions. Bulk oils were heated at 60, 100, and 180 °C, and O/W emulsions were oxidized under riboflavin photosensitization. The content of phenolic compounds was analyzed by high‐performance liquid chromatography, and in vitro antioxidant assays were also conducted. The major phenolics contained in the aqueous extract of roasted hulled barley (AERB) were p‐coumaric, ferulic, protocatechuic, chlorogenic, 4‐hydroxybenzoic, and vanillic acids. Depending on the concentration and oxidation temperature, AERB had antioxidant or prooxidant properties in bulk oil. At 60 °C, AERB at a concentration of 0.5% acted as a prooxidant, whereas at 1.0% it acted as an antioxidant. At 100 °C, AERB acted as an antioxidant irrespective of concentration. In 180 °C conditions, 0.5% AERB acted as a prooxidant, whereas other concentrations of AERB acted as antioxidants. In the case of riboflavin photosensitized O/W emulsions, AERB showed antioxidant properties irrespective of concentration. Antioxidant abilities of AERB are affected by the food matrix, including bulk oil and O/W emulsions, and concentrations of AERB, even though diverse phenolic compounds may display high antioxidant properties in in vitro assays.     

Microencapsulation of fig seed oil rich in polyunsaturated fatty acids by spray drying

Fig oil is a nutritious vegetable based oil type which is rich in polyunsaturated fatty acids. In the present study, several attempts have been made to produce encapsulated oil with maximum efficiency. In the first step, the effect of feed concentration was observed at 140, 150 and 160 °C and 20 % dry matter was selected. In the second step, distribution of gum arabic (GA) and maltodextrin (MD) as a wall material was determined at different temperature levels (140, 150, 160, 170 and 180 °C), and optimum MD/GA ratio and temperature were found to be 8/1 and 150 °C, respectively. In the next step, impact of wall material/fig oil ratio on the encapsulation efficiency was investigated and it was determined to be 3.0. According to the results, optimum encapsulation ratio of MD/GA/oil and temperature were 8/1/3 and 150 °C, respectively. The physicochemical properties; particle size, peroxide value, dry matter content, and encapsulation efficiency of the oil encapsulated under this condition were determined. Water content and water solubility of the powder was determined as 2.875 and 97.85 %, respectively. At the optimum conditions particle of the fig oils showed smooth surface, non-homogeneous and spherical shape, and size of the most of the particles ranged between 8 and 40 μm.     

1-MCP Treatment Prolongs Postharvest Life of 'Santa Rosa'Plums

'Santa Rosa’plums were treated with concentrations of 0‐ (control), 0.5‐, or 0.75‐μL/L 1‐methylcyclopropene (1‐MCP) for 24 h at 1°C and stored at 1 °C for up to 40 d. Ethylene and CO₂ production, firmness, weight loss, Brix, acidity, color evolution, and ethanol and acetaldehyde concentrations were determined periodically after cold storage and after subsequent shelf life of 5 and 8 d at 20 °C. 1‐MCP strongly inhibited ethylene and CO₂ production. Higher values of firmness were observed in 1‐MCP‐treated plums compared with control. 1‐MCP treatment delayed color evolution, reduced acidity loss, and inhibited ethanol and acetaldehyde production. 1‐MCP did not affect weight loss or sugar content.     

Effect of corn oil and amylose on the thermal properties of native soy protein and commercial soy protein isolate

Differential scanning colorimetry (DSC) was used to estimate thermal property differences between a commercial soy protein isolate (SPI) and milled defatted soy protein flour (MDF). The measurements were determined in the presence of 15, 20, 25, and 30% corn oil and 2, 4, and 6% amylose. SDS-PAGE showed that the SPI material contains aggregates as a result of the isolation procedures and processing. Upon DSC, this protein isolate showed a 7S protein transition peak at 77 °C and an 11S peak at 170 °C, while the MDF sample had a 7S peak at 69 °C and 11S peak at 177 °C. The MDF sample showed ΔH values 4 times greater than that of the SPI sample. These values reflect the effect of the isolation process on the protein. In the presence of corn oil, the MDF sample showed three transition peaks while the SPI sample displayed only two. The MDF sample demonstrated more interaction with oil than did the SPI sample. The change in the ΔH was reflective of this interaction. The addition of amylose to the SPI sample resulted in the appearance of a third peak. Amylose had a mixed effect on the two proteins; peaks of the same protein reacted differently to amylose level. Increasing the amylose level had the most influence on the third peak of the MDF sample. Amylose influence on the two proteins was attributed to a reduction of the amount of free oil in the system.     

Viscosity changes and gel formation during storage of liquid micellar casein concentrates

Our objective was to determine the effects of temperature and protein concentration on viscosity increase and gelation of liquid micellar casein concentrate (MCC) at protein concentrations from 6 to 20% during refrigerated storage. Skim milk (∼350 kg) was pasteurized (72°C for 16 s) and filtered through a ceramic microfiltration system to make MCC and replicated 3 times. The liquid MCC was immediately concentrated via a plate ultrafiltration system to 18% protein (wt/wt). The MCC was then diluted to various protein concentrations (6–18%, wt/wt). The highest protein concentrations of MCC formed gels almost immediately on cooling to 4°C, whereas lower concentrations of MCC were viscous liquids. Apparent viscosity (AV) determination using a rotational viscometer, gel strength using a compression test, and protein analysis of supernatants from ultracentrifugation by the Kjeldahl method were performed. The AV data were collected from MCC (6.54, 8.75, 10.66, and 13.21% protein) at 4, 20, and 37°C, and compression force test data were collected for MCC (15.6, 17.9, and 20.3% protein) over a period of 2-wk storage at 4°C. The maximum compressive load was compared at each time point to determine the changes in gel strength over time. Supernatants from MCC of 6.96 and 11.61% protein were collected after ultracentrifugation (100,605 × g for 2 h at 4, 20, and 37°C) and the nitrogen distributions (total, noncasein, casein, and nonprotein nitrogen) were determined. The protein and casein as a percent of true protein concentration in the liquid phase around casein micelles in MCC increased with increasing total MCC protein concentration and with decreasing temperature. Casein as a percent of true protein at 4°C in the liquid phase around casein micelles increased from about 16% for skim milk to about 78% for an MCC containing 11.6% protein. This increase was larger than expected, and this may promote increased viscosity. The AV of MCC solutions in the range of 6 to 13% casein increased with increasing casein concentration and decreasing temperature. We observed a temperature by protein concentration interaction, with AV increasing more rapidly with decreasing temperature at high protein concentration. The increase in AV with decreasing temperature may be due to the increase in protein concentration in the aqueous phase around the casein micelles. The MCC containing about 16 and 18% casein gelled upon cooling to form a gel that was likely a particle jamming gel. These gels increased in strength over 10 d of storage at 4°C, likely due either to the migration of casein (CN) out of the micelles and interaction of the nonmicellar CN to form a network that further strengthened the random loose jamming gel structure or to a gradual increase in voluminosity of the casein micelles during storage at 4°C.     

Production and storage stability of concentrated micellar casein

Concentrated micellar casein (CMC) is a high-protein ingredient that can be used in process cheese product formulations. The objectives of this study were to develop a process to produce CMC and to evaluate the effect of sodium chloride and sodium citrate on its storage stability. Skim milk was pasteurized at 76°C for 16 s and cooled to ≤4°C. The skim milk was heated to 50°C using a plate heat exchanger and microfiltered with a graded permeability (GP) ceramic microfiltration (MF) membrane system (0.1 μm) in a continuous feed-and-bleed mode (flux of 71.43 L/m² per hour) using a 3× concentration factor (CF) to produce a 3× MF retentate. Subsequently, the retentate of the first stage was diluted 2× with soft water (2 kg of water: 1 kg of retentate) and again MF at 50°C using a 3× CF. The retentate of the second stage was then cooled to 4°C and stored overnight. The following day, the retentate was heated to 63°C and MF in a recirculation mode until the total solids (TS) reached approximately 22% (wt/wt). Subsequently, the MF system temperature was increased to 74°C and MF until the permeate flux was <3 L/m² per hour. The CMC was then divided into 3 aliquots (approximately 10 kg each) at 74°C. The first portion was a control, whereas 1% of sodium chloride was added to the second portion (T1), and 1% of sodium chloride plus 1% of sodium citrate were added to the third portion (T2). The CMC retentates were transferred hot to sterilized vials and stored at 4°C. This trial was repeated 3 times using separate lots of skim milk. The CMC at d 0 (immediately after manufacturing) contained 25.41% TS, 21.65% true protein (TP), 0.09% nonprotein nitrogen (NPN), and 0.55% noncasein nitrogen (NCN). Mean total aerobic bacterial counts (TBC) in control, T1, and T2 at d 0 were 2.6, 2.5, and 2.8 log cfu/mL, respectively. The level of proteolysis (NCN and NPN values) increased with increasing TBC during 60 d of storage at 4°C. This study determined that CMC with >25% TS and >95% casein as percentage of TP can be manufactured using GP MF ceramic membranes and could be stored up to 60 d at 4°C. The effects of the small increase in NCN and NPN, as well as the addition of sodium chloride or sodium citrate in CMC during 60 d of storage on process cheese characteristics, will be evaluated in subsequent studies.     

Antioxidant activity of ginger extract in sunflower oil

The antioxidant activity of dichloromethane extract from ginger was evaluated during 6 months of storage of refined sunflower oil at 25 and 45 °C. Free fatty acid (FFA) content, peroxide value (POV) and iodine value (IV) were used as criteria to assess ginger extract as an antioxidant. After 6 months of storage at 45 °C, sunflower oil containing 1600 and 2400 ppm ginger extract showed lower FFA contents (0.083 and 0.080%) and POVs (24.5 and 24.0 meq kg^?1) than the control sample (FFA contents 0.380%, POV 198.0 meq kg^?1). Sunflower oil containing 200 ppm butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) showed FFA contents of 0.089 and 0.072% and POVs of 26.5 and 24.7 meq kg^?1 respectively after 6 months of storage at 45 °C. Similarly, after 6 months of storage at 45 °C, IVs of sunflower oil containing 1600 and 2400 ppm ginger extract were 80 and 92 respectively, higher than that of the control sample (53). However, IVs of sunflower oil treated with 200 ppm BHA and BHT were 94 and 96 respectively after 6 months of storage at 45 °C. These results illustrate that ginger extract at various concentrations exhibited very strong antioxidant activity, almost equal to that of synthetic antioxidants (BHA and BHT). Ginger extract also showed good thermal stability and exhibited 85.2% inhibition of peroxidation of linoleic acid when heated at 185 °C for 120 min. Therefore the use of ginger extract in foods is recommended as a natural antioxidant to suppress lipid oxidation. © 2003 Society of Chemical Industry     

Dynamic Mechanical Analysis for Glass Transitions in Long Shelf-Life Bread

Dynamic Mechanical Analysis (DMA) showed three thermal transitions in meal, ready-to-eat (MRE) bread, resulting in various degrees of change in the viscoelastic property. The moisture-dependent transition at an extremely low temperature (-90°C to – 50°C) was due to humcctants added, while that at a higher temperature T1 was possibly due to ice melting and the polymer components. T1 increased from ～?10°C at 29% moisture to ～ 150°C as moisture decreased to 2%. This correlated with hardening of the sample. A moisture independent transition at ～ 10-15°C by DMA was identified as a melting process of lipids (shortening). During storage, the magnitude of tan 8 peak decreased but its peak temperature did not change. No evidence of any network could be observed by DMA throughout 3 yr storage.     

Modeling of Salt Diffusion in White Cheese during Long-Term Brining

Salt transport in white cheese was investigated at two brine concentrations (15 and 20% w/w) and at three temperatures (4, 12.5 and 20°C) for each brine concentration. Two mathematical models were developed based on treating the cheese samples as finite or semi-infinite bodies. Theoretical and experimental salt concentration profiles were in good agreement. The semi-infinite model was valid only for low Fourier numbers, i.e., Fo≤0.07. Effect of convectional flow was insignificant. Salf diffusivity remained constant with time, and an Arrhenius-type equation described its variation with temperature. Salt diffusivity in white cheese was estimated as 0.21 × 10^?9 m²/sec at 4°C and 0.31 × 10^?9 m²/sec at 12.5°C for both brine concentrations and as 0.39 × 10^?9 m²/sec for brine concentration 15% (w/w) and 0.34 × 10^?9 m²/sec at 20°C for 20% (w/w).     

Edible coating affects physico‐functional properties and shelf life of chicken eggs during refrigerated and room temperature storage

Effects of chitosan, whey protein concentrate (WPC), mineral oil (MO) and/or soybean oil (SO) coating on egg quality were compared at 25 and 4 °C, respectively, during 5 and 20 weeks of storage. Storage time and temperature, and type of coating significantly affected Haugh unit, yolk index, weight loss, albumen pH and emulsifying capacity. Shelf life was extended 4 weeks by MO and SO and 2 weeks by chitosan and WPC longer than that observed for noncoated eggs at 25 °C. MO‐ and SO‐coated eggs maintained AA grade for 20 weeks at 4 °C. Weight loss of SO‐coated eggs was <1% after 5 weeks at 25 °C and after 20 weeks at 4 °C. Yolk index and emulsifying capacity were more correlated at 25 °C than at 4 °C. MO and SO were more effective coating materials, with SO providing a more cost‐effective coating for extending egg shelf life.     

Technical note: Evaluation of the diagnostic accuracy of 2 point-of-care β-hydroxybutyrate devices in stored bovine plasma at room temperature and at 37°C

The use of point-of-care (POC) devices to measure blood metabolites, such as β-hydroxybutyrate (BHB), on farm have become an important diagnostic and screening tool in the modern dairy industry. The POC devices allow for immediate decision making and are often more economical than the use of laboratory-based methods; however, precision and accuracy may be lower when measurements are performed in an uncontrolled environment. Ideally, the advantages of the POC devices and the standardized laboratory environment could be combined when measuring samples that do not require an immediate result—for example, in research applications or when immediate intervention is not the goal. The objective of this study was to compare the capability of 2 POC devices (TaiDoc, Pharmadoc, Lübeck, Germany; Precision Xtra, Abbott Diabetes Care, Abingdon, UK) to measure BHB concentrations either at room temperature (RT; 20–22°C) or at 37°C compared with the gold standard test in stored plasma samples. Whole blood from multiparous Holstein dairy cows (n = 113) was sampled from the coccygeal vessels between 28 d before expected calving and 42 DIM. Whole-blood BHB concentrations were determined cow-side using the TaiDoc POC device. Plasma was separated within 1 h of collection and stored until analysis. A subset of stored plasma samples (n = 100) consisting of 1 sample per animal was chosen retrospectively based on the BHB concentrations in whole blood within the range of 0.2 to 4.0 mmol/L. The samples were analyzed for BHB plasma concentration using an automated chemistry analyzer (Hitachi 917, Hitachi, Tokyo, Japan), which was considered the gold standard. On the same day, the samples were also measured with the 2 POC devices, with samples either at RT or heated up to 37°C. Our study showed high Spearman correlation coefficients (>0.99) using either device and with samples at both temperatures compared with the gold standard. Passing–Bablok regression revealed a very strong correlation (>0.99), indicating good agreement between both POC devices and the gold standard method. For hyperketonemia detection, defined as BHB concentration ≥1.2 mmol/L, the sensitivity for both POC devices at RT and 37°C was equally high at 100%. Specificity was lowest (67.4%) for the TaiDoc used with plasma at RT and was highest (86.5%) when plasma was measured at 37°C with the Precision Xtra meter. Bland–Altman plots revealed a mean bias of 0.25 and 0.4 mmol/L for the Precision Xtra meter and TaiDoc, respectively, when tested on plasma at 37°C. Our data showed that both POC devices are suitable for measuring BHB concentration in stored bovine plasma, and accuracy was highest when samples were heated to 37°C compared with RT.     

Kinetic Studies of Oxygen Dependence During Initial Lipid Oxidation in Rapeseed Oil

Lipid oxidation was studied in rapeseed oil, stored at 35 or 50°C in 0.03, 0.3, 1.0 or 1.8% oxygen for 42 days. Peroxide value (PV), oxygen consumption, tocopherol consumption and production of volatile compounds were analyzed to follow the oxidation. At 50°C, lipid oxidation measured as oxygen consumption or PV was only slightly influenced by oxygen concentration ≥1%. Below 0.5% the influence was strongly enhanced. The production of volatiles showed different relationships to oxygen concentration and some compounds were produced in larger amounts at lower O₂, than at higher O₂, concentrations.     

不同温度下充氮低氧对赤拟谷盗各虫态致死效果与时间研究

了解低温对充氮低氧气调致死害虫过程和时间的影响程度,以及氮气气调过程中害虫异常行为反应与种群完全致死时间的关系可为低温充氮(低氧)与成功杀虫应用提供指导。分别在低温18℃、准低温23℃和常温28℃条件下,测定了赤拟谷盗的卵、幼虫、蛹、成虫各个虫态在控制氮气体积分数98%(氧气2%以下)过程中不同时间的死亡率及完全致死时间,以及视频监测下成虫行动异常和击倒反应率与种群完全致死的关系。98%氮气体积分数下,18、23、28℃时赤拟谷盗卵的死亡率-时间回归方程分别为y=3.61+5.47、y=3.92x+11.11和y=5.95x+5.83,完全致死时间分别为28、24、16 d;幼虫的相应回归方程分别为y=4.62x+10.16、y=6.08x+8.33和y=6.66x+21.67,完全致死时间分别为20、16、12 d;蛹的相应回归方程为y=3.69x+3.81、y=4.11+3.89和y=5.87x+13.33,完全致死时间分别为28、24、20 d;成虫的相应回归方程分别为y=6.33x-1.67、y=5.87x+13.33和y=7.29x+15.56,完全致死时间分别为16、16、...