Detection of early events in lipid oxidation by electron spin resonance spectroscopy

Heating of consumer cannabis oils can lead to free radical initiated degradation, causing CBD and THC depletion

Commercial cannabis oil products are widely available in Canada even though there is a significant gap in scientific information regarding them. Oils, such as vegetable oils, are known to undergo oxidative changes through free radical mechanisms when they are heated or aged, but the cannabis oils used in this study did not have expiry dates or best-before usage dates. This led to the question of how these products would be affected with time. We hypothesized that cannabis oils would produce increased concentrations of free radicals in aging-simulated conditions, which would be related to a decrease in cannabidiol (CBD) or Δ⁹-tetrahydrocannabinol (THC) content. Cannabis oils and their respective vehicles (oils) were heated using two protocols: One (moderate aging method) used a 2-day heating protocol at 50 °C, and the other (enhanced aging method) used a 14-day heating protocol at 70 °C. We used electron paramagnetic resonance (EPR) spectroscopy for free radical analysis using the spin trapping technique using 200 mM PBN and 0.02 mM CuCl₂ (for peroxide breakdown to free radicals). For active ingredient analysis (CBD, THC), we used LC/MS. Cannabis oils that contained unsaturated oils as their vehicles, such as olive or sunflower oil, all showed varying degrees of free radical formation. In both aged and unaged oils containing CBD or THC, less free radical formation was detected compared to the vehicle controls. Cannabis oils using medium-chain triglycerides (MCT) showed little or no free radical formation. The most significant decrease in CBD or THC was observed in the products using sunflower oil, to a lesser extent in MCT oil, and THC also decreased in olive oil. These findings are important for consumers and policymakers considering using such products in hot beverages or cooking and highlighting the importance of appropriate storage conditions.

Effect of soaking conditions on the formation of lipid derived free radicals in soymilk

Lipid derived free radical in soymilks were studied by combining 5,5-dimethyl-pyrroline-l-oxide (DMPO) spin trap, chloroform-methanol extraction and electron spin resonance (ESR) spectroscopy. Five lipid derived free radical adducts: DMPO-X, DMPO-L, DMPO-R, DMPO-LOO, and DMPO-RO were presented in soymilks. The total amounts of spins increased as the soaking temperature increased from 4 °C to 50 °C and the soaking pH increased from 3 to 9 and in paralleled with the diffusion of soybean exudates to soaking water. Prolonged soaking of soybean at 50 °C resulted in a higher signal intensity of DMPO-R than that of DMPO-LOO. Soybean lipoxygenases (LOXs) were responsible for the formation of lipid derived free radicals in soymilks. Soybean exudates affected the total amounts of lipid radicals in linoleic acid (LA) - LOX model system. The relative signal intensities of DMPO-R and DMPO-LOO were depended on the contents of soybean exudates in the system.

Effect of storage temperature on lipid oxidation and changes in nutrient contents in peanuts

Peanut, an important oil crop worldwide, is highly susceptible to oxidative damage during storage due to its high level of fats and unsaturated fatty acids which will affects its nutritional value and agricultural importance. Therefore, it is significantly important to research the physicochemical properties changes of peanuts during storage. Peanuts belong to two varieties were stored at various temperatures (15°C, 25°C, and 35°C) for 320 days. Peroxide value (PV), carbonyl value (CV), and malondialdehyde (MDA) content of oil extracted from peanuts were determined every 80 days to evaluate lipid oxidation degree. Proximate composition (fat, protein, total sugar, moisture, and ash), fatty acid, and amino acid compositions were also assessed. All samples exhibited increased CV and MDA contents during storage. The PV of peanuts increased continuously when stored at 15°C and 25°C, but the PV increased firstly and then decreased sharply when stored at 35°C. Storage significantly affected the contents of lipids, proteins, total sugars, and moisture in peanuts but did not influence the ash content. In general, the fatty acid and amino acid compositions changed significantly during storage at different temperatures. High temperatures lead to a high degree of lipid oxidation and nutrient loss. The results above of this study can provide a theoretical basis for the actual storage and preservation of peanuts.

Lipid Oxidation in Low-moisture Food: A Review

Overly high intake of saturated fat is an international problem contributing to global health issues. Low-moisture snacks account for a nutritionally significant proportion of the saturated fat in the diet, making these foods a key target for improving consumers' health. However, it is not currently feasible to maintain the same oxidative shelf life when replacing saturated fats with unsaturated fats, which are generally perceived to be more heart-healthy. This article summarizes current theories and available research on lipid oxidation in low-moisture foods in order to lay the groundwork for new lipid oxidation rate-reduction strategies. Research deficits needing attention and new methods for assessing lipid oxidation in low-moisture foods are also discussed.

Use of ESR and HPLC to follow the anaerobic reaction catalysed by lipoxygenases

The measurement of the 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) consumption by using ESR allows to follow the anaerobic reaction between linoleic acid (LH) and its 13-hydroperoxide (LOOH) catalysed by lipoxygenase. During this reaction, two types of radicals are initially obtained, alkyl (L) and alkoxyl (LO) radicals which formed two types of adducts (LT and OLT) with TEMPOL as characterised by HPLC. The stoichiometry of the adduct formation is two mole of TEMPOL consumed for one mole of LH and one mole of LOOH. Using ESR, the kinetic parameters and the mechanism of the anaerobic reaction have been determined at pH 6.5 for three different lipoxygenases, soybean, horse bean and wheat and compared to the values obtained at pH 9 for soybean lipoxygenase. Wheat lipoxygenase is very weakly active compared to the other enzymes. An uncompetitive inhibition of the anaerobic reaction catalysed by soybean and horse bean lipoxygenases was observed with 2,6-di-tert-butyl-4-methylphenol (BHT).

Oxidative signaling in seed germination and dormancy

Reactive Oxygen Species (ROS) play a key role in various events of seed life. In orthodox seeds, ROS are produced from embryogenesis to germination, i.e., in metabolically active cells, but also in quiescent dry tissues during after ripening and storage, owing various mechanisms depending on the seed moisture content. Although ROS have been up to now widely considered as detrimental to seeds, recent advances in plant physiology signaling pathways has lead to reconsider their role. ROS accumulation can therefore be also beneficial for seed germination and seedling growth by regulating cellular growth, ensuring a protection against pathogens or controlling the cell redox status. ROS probably also act as a positive signal in seed dormancy release. They interact with abscisic acid and gibberellins transduction pathway and are likely to control numerous transcription factors and properties of specific protein through their carbonylation.

ROS production and protein oxidation as a novel mechanism for seed dormancy alleviation

At harvest, sunflower (Helianthus annuus L.) seeds are dormant and unable to germinate at temperatures below 15 degrees C. Seed storage in the dry state, known as after-ripening, is associated with an alleviation of embryonic dormancy allowing subsequent germination at suboptimal temperatures. To identify the process by which dormancy is broken during after-ripening, we focused on the role of reactive oxygen species (ROS) in this phenomenon. After-ripening entailed a progressive accumulation of ROS, namely superoxide anions and hydrogen peroxide, in cells of embryonic axes. This accumulation, which was investigated at the cellular level by electron microscopy, occurred concomitantly with lipid peroxidation and oxidation (carbonylation) of specific embryo proteins. Incubation of dormant seeds for 3 h in the presence of hydrogen cyanide (a compound that breaks dormancy) or methylviologen (a ROS-generating compound) also released dormancy and caused the oxidation of a specific set of embryo proteins. From these observations, we propose a novel mechanism for seed dormancy alleviation. This mechanism involves ROS production and targeted changes in protein carbonylation patterns.

Contribution of mass spectrometry to assess quality of milk-based products

The vast knowledge of milk chemistry has been extensively used by the dairy manufacturing industry to develop and optimize the modern technology required to produce high-quality milk products to which we are accustomed. A thorough understanding of the chemistry of milk and its numerous components is essential for designing processing equipment and conditions needed for the manufacture and distribution of high-quality dairy products. Knowledge and application of milk chemistry is also indispensable for fractionating milk into its principal components for use as functional and nutritional ingredients by the food industry. For all these reasons, powerful analytical methods are required. Because of the complexity of the milk matrix, mass spectrometry, coupled or not to separation techniques, constitutes a key tool in this area. In the present manuscript, we review the contribution and potentialities of mass spectrometry-based techniques to assess quality of milk-based products.

Two types of radicals in whole milk powder. Effect of lactose crystallization, lipid oxidation, and browning reactions

Whole milk powder was stored in closed vials at 60 degrees C to induce crystallization of lactose within a short time scale. After an induction period of 3-4 days simultaneous crystallization of lactose, increase of water activity, formation of browning products, and increase of radical content took place. Radicals detected before lactose crystallization were characterized by a narrow ESR spectrum (g = 2.006) and could be depleted by removal of oxygen and therefore were assigned to oxidation processes. Late-stage radicals present after crystallization of lactose gave much wider spectra (g = 2.0048) and were independent of oxygen availability and assigned to late-stage Maillard reaction products. The study indicates that the processes of lactose crystallization, browning, and formation of radical species (g = 2.0048) are strongly coupled, while lipid oxidation is less dependent on the other processes.

Analysis of the early stages of lipid oxidation in freeze-stored pork back fat and mechanically recovered poultry meat

An analytical method that can detect low levels of oxidation in food earlier than a sensory panel would be a valuable tool for food manufacturers as well as research institutes. Two model matrixes, pork back fat and mechanically recovered poultry meat (MRPM), were freeze-stored in air at -20 degrees C for 26 weeks. Peroxide value, thiobarbituric acid reactive substances, volatiles analyzed with dynamic headspace gas chromatography-mass spectrometry (GC-MS) and a gas-sensor array technique (electronic nose), chemiluminescence, and front-face fluorescence were evaluated against sensory analysis with regard to detection of early oxidation and correlation with sensory data. Fluorescence and GC-MS could detect oxidative changes in pork back fat earlier than the sensory panel and the electronic nose at the same time. The three methods were highly correlated with sensory attributes (r = 0.8-0.9). GC-MS gave the best results with regard to detection of small oxidative changes in MRPM.