Oxidation progress in an emulsion made from metmyoglobin and different triacylglycerols

Influence of interfacial properties/structure on oxygen diffusion in oil-in-water emulsions

Oxygen diffusion played an important role in the lipid oxidation of food emulsions. In this study, a simple method was developed to quantitatively observe the oxygen diffusion in the oil-water biphasic system, and it was further applied to investigate the relationship between the oxygen diffusion and lipid oxidation in O/W emulsions. Various factors that related to the emulsion oxidation were considered, from their influence on the oxygen diffusion and lipid oxidation in the emulsions. Results showed that there was obvious correlation between the oxygen diffusion and lipid oxidation in O/W emulsions, which reveals the inhibition of oxygen diffusion could apparently slow down the lipid oxidation. Moreover, the changes of oil phase, water phase and interfacial layer of the emulsions, which were related to the oxygen diffusion, could improve the oxidative stability of the emulsions effectively. Our findings are helpful for deep understanding the mechanisms of the lipid oxidation in food emulsions.

New method for the extraction of volatile lipid oxidation products from shrimp by headspace-solid-phase microextraction-gas chromatography-mass spectrometry and evaluation of the effect of salting and drying

A new method based on headspace-solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) was developed, aimed at evaluating the formation of volatile lipid oxidation products (VLOPs) in shrimp during the salting and drying process. Of the four fibers evaluated, the fiber coated with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) was the most adequate for the quantification of the VLOPs. The best analytical conditions were obtained by homogenization in an ultraturrax followed by extraction at 40 °C for 30 min. The optimized method allowed for the rapid and simple extraction of the VLOPs, with low detection (≤0.15 ng g(-1)) and quantification (≤0.50 ng g(-1)) limits and satisfactory precision (≤12.67%) and extraction efficiency (≥94.28%). The salting and drying negatively affected shrimp quality, reducing the fatty acid content and increasing the VLOPs, especially hexanal.

Hydroperoxide formation in different lean meats

Peroxide is one of the compounds that are indicated to be toxic in the human digestion system. Lean fresh meat samples were collected from beef, lamb, pork and chicken to investigate their hydroperoxide formation potential. Total peroxides of fresh comminuted raw meat were determined by analysing protein-bound peroxides and hydroperoxide compounds in water-methanol and chloroform extracted phases. The amount of total peroxides was ranked as: beef>pork>lamb>chicken. Hydroperoxide formation was examined at different pH values and at different incubation times, using beef and chicken samples. All peroxides were transient, with a maximum value after 2-4 h of incubation at 37 °C. When pH fell from 7 to 1.5, the different peroxides fell by 10-20%. Non-polar peroxide formation could largely (70%) be described by variation in fatty acid composition and hemin content of the meat, while protein-bound peroxide variation was less explained by these variables. Liposome addition increased (40%) the amount of protein-bound peroxides.

Oxidative Stability of Polyunsaturated Edible Oils Mixed With Microcrystalline Cellulose

The oxidative stability of mixtures of edible oils containing polyunsaturated fatty acids (PUFA) and microcrystalline cellulose (MCC) was investigated. The mixtures studied consisted of oils of either camelina (CAM), cod liver (CLO), or salmon (SO) mixed with either colloidal or powdered MCC. A 50:50 (w/w) ratio of oil:MCC resulted in an applicable mixture containing high levels of PUFA edible oil and dietary fiber. The oxidative stability of the formulated mixtures and the pure oils was investigated over a period of 28 days. The peroxide value (PV) was assessed as a parameter for primary oxidation products and dynamic headspace gas chromatography mass spectrometry (GC/MS) was used to analyze secondary volatile organic compounds (VOC). CAM and the respective mixtures were oxidatively stable at both 4 and 22 °C during the storage period. The marine oils and the respective mixtures were stable at 4 °C. At 22 °C, an increase in hydroperoxides was found, but no increase in VOC was detected during the time-frame investigated. At 42 °C, prominent increases in PV and VOC were found for all oils and mixtures. Hexanal, a common marker for the degradation of n-6 fatty acids, propanal and 2,4-heptadienal (E,E), common indicators for the degradation of n-3 fatty acids, were among the volatiles detected in the headspace of oils and mixtures. This study showed that a mixture containing a 50:50 ratio of oil:MCC can be obtained by a low-tech procedure that does not induce oxidation when stored at low temperatures during a period of 1 month.