Effect of dietary supplementation on lipid photooxidation in beef meat, during storage under commercial retail conditions.

The effects of feeding composition on the photosensitized oxidation of lipids from beef meat, were evaluated during storage under commercial retail conditions. Feeding was enriched with linseed oil (LO), Dl-α tocopheryl acetate (vE) and conjugated linoleic acid (CLA) at different doses and provided for diverse periods, resulting in 7 diet groups (A-G). After slaughtering and 2 weeks of holding period, meat slices were packed in vessels with transparent shrink film and exposed to white fluorescent light for 8h at 8 °C. Total cholesterol oxidation products (COPs) level varied from 4.0 to 13.0 µg/g of lipids, which corresponded to 0.1-0.6% oxidized cholesterol. The lowest peroxide value (PV) was found in the diet added with vE and LO for 90 days. Light exposure only had a significant impact on thiobarbituric acid reactive substances (TBARs). In general, Dl-α tocopheryl acetate supplemented for 90 days improved the oxidative stability of beef meat stored under commercial retail conditions.

A quick method for identifying radiolytic hydrocarbons in low-fat-containing food.

BACKGROUND: As radiation-induced alterations of the lipid fraction of foods are related to their initial fat content, concentrations of fat degradation products used as irradiation markers are expected to be lower when irradiating low-fat-containing foods. Thus the sensitivity required when applying analytical methods for identifying irradiation markers in foods eventually depends on their respective amounts of fat. The aim of this study was to perform the qualitative analysis of characteristic hydrocarbons resulting from irradiation of samples with a fat content as low as 25 g kg(-1). RESULTS: A rapid extraction using a small amount of ethyl acetate was the unique sample pretreatment required to accomplish the analysis of radiolytic markers by using on-line coupling of reverse phase liquid chromatography and gas chromatography with mass spectrometry detection (RPLC/GC/MS). Efficient elimination of the large volumes (up to 2170 µL) directly transferred from LC to GC was achieved by optimising the operation mode of the through-oven transfer adsorption/desorption system used as interface. CONCLUSION: The reported procedure allowed confirmation, in less than 65 min, of the occurrence of up to five irradiation markers, namely n-pentadecane, 1-hexadecene, 1,7-hexadecadiene, n-heptadecane and 8-heptadecene, in cooked ham irradiated at doses as low as 2 kGy.

Time-resolved diffuse optical spectroscopy up to 1700 nm by means of a time-gated InGaAs/InP single-photon avalanche diode.

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm.

Effect of roasting conditions on color and volatile profile including HMF level in sweet almonds (Prunus dulcis).

UNLABELLED: Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. PRACTICAL APPLICATION: The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.

Effects of gamma-irradiated fats on plasma lipid concentrations and hepatic cholesterol metabolism in rats.

Currently, there is a growing need for food irradiation that is effective in food preservation and quality improvement. Accordingly, this study was designed to observe the effects of gamma-irradiated dietary fat on plasma lipid concentrations and hepatic cholesterol metabolism in rats. Male rats were fed 5-kGy-gamma-irradiated beef tallow (gammaBT), corn oil (gammaCO), perilla oil (gammaPO), and nonirradiated fats (BT, CO, and PO) for 6 weeks. The gamma-irradiated fat feeding did not affect the plasma lipid concentrations. However, the hepatic cholesterol content was significantly higher in the rats fed gamma-CO as compared with the rats fed nonirradiated CO (40.0 vs. 28.2 mg/g liver). The hepatic HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase activities were not significantly different between the controls and the gamma-irradiated fat fed groups. However, the hepatic ACAT (acyl-CoA:cholesterol acyltransferase) activity was significantly lower in the gammaPO group as compared with its control group (138.2 vs. 404.5 pmol min(-1) mg(-1)). Among the nonirradiated groups, the ACAT activities of the CO and PO groups were higher than that of the BT group. The amounts of coprostanone, cholesterol, and total fecal neutral sterol were significantly higher in the gammaPO group as compared with the other groups. These results indicate that although slight changes in the lipid metabolism were observed as a result of 5-kGy-gamma-irradiated fat feeding, they were relative to the fat type and had no harmful consequences.

[Chemiluminescence method for the detection of radiation-induced oxidation products in fat-containing foods]. / Chemilumineszenzmethode zum Nachweis strahleninduzierter Oxidationsprodukte in fetthaltigen Lebensmitteln.

Radiation-induced oxidation of fatty foods was detected by a chemiluminescence method. Hazelnuts, peanuts and poultry were used as foodstuff samples. Additional investigations were performed with a model system and sunflower oil. The irradiation of the samples was carried out in a x-ray-fluorescence-apparatus. Thereby it is to note that the G-value of the x-ray-radiation is much higher than the G-value of a cobalt-60-source normally used for irradiation of food. A dependence of the integral of the light curve on the irradiation doses could be proved. Investigations with model systems which contained different amounts of alpha-tocopherol showed a decreasing chemiluminescence signal at low irradiation doses in presence of alpha-tocopherol. At higher doses the chemiluminescence signal enlarges with increasing amounts of alpha-tocopherol because irradiation products of alpha-tocopherol overlay its antioxidative effect. Irradiated poultry samples differ significantly from unirradiated samples after a deep-freeze storage of 26 weeks. A quantification of the doses is not possible without knowledge of the storage time, because the integrals decrease differently after irradiation during storage. In any case the chemiluminescence method is useful as a "screening method" for the detection of irradiation of foodstuffs with the possibility of automation and high sensitivity.

Food irradiation: the process and implications for dietitians.

Despite the limited use of irradiation for food preservation in the United States to date, the process provides an alternative to the use of some chemical pesticides and sprout inhibitors. The formation of random and varied radiolytic products (RPs) in foods that have been irradiated is the focus of criticism of the process, because RPs may affect the sensory and nutritive quality of foods processed with ionizing radiation. The FDA has deemed the process safe, within specified doses, for use on spices, some meats, fruits, and vegetables. Dietitians should be prepared to answer consumer questions related to irradiation as the process becomes more widespread.

Studies of lipid peroxide formation in irradiated synthetic diets and the effects of storage after irradiation.

The effect of irradiation doses of gamma-rays or electrons within the range 100--2000 krad has been studied on lipid peroxide formation in artificial food mixtures containing lard, corn oil or herring oil mixed with starch, casein or other proteins. Lipid peroxide formation after irradiation was very low in lard: starch or corn oil: starch mixtures but very large concentrations of peroxide were formed in irradiated herring oil: starch mixtures. This was mainly a result of the occurrence of the highly unsaturated C20:4, C20:5 and C22:6 fatty acids in the herring oil which readily form lipid peroxide. Lipid peroxide formation immediately after irradiation was much lower after doses of electrons given at a high dose-rate than after similar doses of gamma-rays given at low dose-rates but it increased rapidly in the samples irradiated with electrons during the period immediately following irradiation. Lipid peroxide formation changed rapidly during post-irradiation storage and was dependent on the type of radiation, the dose, the dose-rate, the time after irradiation and the temperatures of the post-irradiation storage. The concentration of peroxide in mixtures irradiated with gamma-rays formed after 2--3 days post-irradiation storage was dose-rate dependent and much greater after irradiation with gamma-rays given at a very low dose-rate than with gamma-rays given at a high dose-rate. Lipid peroxide increased after irradiation much more rapidly at 37 degrees C than at 4 degrees C or 21 degrees C but all irradiated samples a maximum concentration of peroxide was eventually formed, the time delay being temperature dependent. After reaching a maximum, the concentrations of both hydroperoxides and aledhyde breakdown products in all irradiated samples steadily fell to relatively low values. Peroxide yields were greater if the fat was dispersed in an inert medium such as starch than when irradiated in the pure form and were also dependent on the presence of water in the dispersant medium. Proteins such as casein or ovalbumin inhibited lipid peroxide formation in unsaturated fats.

Effects of antioxidants on lipid peroxide formation in irradiated synthetic diets.

The effect of the antoxidants, vitamin E, propyl gallate (PG), 2-t-butyl-4-methoxy phenol (BHA), 2,6-di-t-butyl-4-methoxy phenol (BHT), nordihydroguaiaretic acid (NDGA) and diphenyl-p-phenylene diamine (DPPD) in concentrations ranging between 0.001 per cent and 0.1 per cent have been tested on lipid peroxide formation in synthetic diet mixtures containing herring oil (10 per cent) mixed with starch (90 per cent) irradiated with gamma-ray doses of 100-2000 krad. On a weight basis NDGA, DPPD, BHA and BHT were most effective and vitamin E and propyl were least effective. An antioxidant concentration of 0.01 per cent normally protected against peroxide formation after a dose of 500 krad but if the dose was increased to 1000 or 2000 krad, much higher doses of antoxidant, up to 0.1 per cent, were required to give protection. Antioxidants prevented peroxide developing during post-irradiation storage even when added after irradiation. Antioxidants were partially or completely destroyed by irradiation with doses of 100 krad or more. The percentage of total antioxidant destroyed depended on the concentration; much greater destruction occurred in dilute solutions than in concentrated solutions. Vitamin E and propyl gallate were most sensitive whereas NDGA was relatively resistant. Antioxidant destruction was much enhanced if irradiation was carried out in presence of herring oil. Free radicals formed in unsaturated fatty acids of the herring oil are believed to be responsible. Lecithin and citric acid, which have been described as antioxidant synergists when added with vitamin E, caused a limited enhancement of its antioxidant action against radiation-induced peroxidation.