Volatile lipid oxidation products

Evidence-Based Challenges to the Continued Recommendation and Use of Peroxidatively-Susceptible Polyunsaturated Fatty Acid-Rich Culinary Oils for High-Temperature Frying Practises: Experimental Revelations Focused on Toxic Aldehydic Lipid Oxidation Products

In this manuscript, a series of research reports focused on dietary lipid oxidation products (LOPs), their toxicities and adverse health effects are critically reviewed in order to present a challenge to the mindset supporting, or strongly supporting, the notion that polyunsaturated fatty acid-laden frying oils are "safe" to use for high-temperature frying practises. The generation, physiological fates, and toxicities of less commonly known or documented LOPs, such as epoxy-fatty acids, are also considered. Primarily, an introduction to the sequential autocatalytic peroxidative degradation of unsaturated fatty acids (UFAs) occurring during frying episodes is described, as are the potential adverse health effects posed by the dietary consumption of aldehydic and other LOP toxins formed. In continuance, statistics on the dietary consumption of fried foods by humans are reviewed, with a special consideration of French fries. Subsequently, estimates of human dietary aldehyde intake are critically explored, which unfortunately are limited to acrolein and other lower homologues such as acetaldehyde and formaldehyde. However, a full update on estimates of quantities derived from fried food sources is provided here. Further items reviewed include the biochemical reactivities, metabolism and volatilities of aldehydic LOPs (the latter of which is of critical importance regarding the adverse health effects mediated by the inhalation of cooking/frying oil fumes); their toxicological actions, including sections focussed on governmental health authority tolerable daily intakes, delivery methods and routes employed for assessing such effects in animal model systems, along with problems encountered with the Cramer classification of such toxins. The mutagenicities, genotoxicities, and carcinogenic potential of aldehydes are then reviewed in some detail, and following this the physiological concentrations of aldehydes and their likely dietary sources are considered. Finally, conclusions from this study are drawn, with special reference to requirements for (1) the establishment of tolerable daily intake (TDI) values for a much wider range of aldehydic LOPs, and (2) the performance of future nutritional and epidemiological trials to explore associations between their dietary intake and the incidence and severity of non-communicable chronic diseases (NCDs).

Experimental rice seed aging under elevated oxygen pressure: Methodology and mechanism

Seed aging during storage results in loss of vigor and germination ability due to the accumulation of damage by oxidation reactions. Experimental aging tests, for instance to study genetic variation, aim to mimic natural aging in a shorter timeframe. As the oxidation rate is increased by elevating the temperature, moisture, and oxygen levels, this study aimed to (1) investigate the effect of experimental rice seed aging by an elevated partial pressure of oxygen (EPPO), (2) elucidate the mechanism of dry-EPPO aging and (3) compare aging under dry-EPPO conditions to aging under traditional moist-controlled deterioration (CD) conditions and to long-term ambient storage. Dry seeds from 20 diverse rice accessions were experimentally aged under EPPO (200 times higher oxygen levels), at 50% relative humidity (RH), along with storage under high-pressure nitrogen gas and ambient conditions as controls. While no decline in germination was observed with ambient storage, there was significant aging of the rice seeds under EPPO storage, with considerable variation in the aging rate among the accessions, with an average decline toward 50% survival obtained after around 21 days in EPPO storage and total loss of germination after 56 days. Storage under high-pressure nitrogen gas resulted in a small but significant decline, by an average of 5% germination after 56 days. In a second experiment, seven rice seed lots were stored under EPPO as compared to a moist-CD test and two different long-term ambient storage conditions, i.e., conditioned warehouse seed storage (CWSS) and traditional rice seed storage (TRSS). Untargeted metabolomics (with identification of lipid and volatile compounds profiles) showed a relatively high increase in levels of oxidized lipids and related volatiles under all four storage conditions. These compounds had a high negative correlation with seed viability, indicating oxidation as a main deteriorating process during seed aging. Correlation analysis indicated that EPPO storage at 50% RH is more related to aging under TRSS at 60% and CD-aging at 75% ERH rather than CWSS at 40% ERH. In conclusion, aging rice seeds under EPPO conditions is a suitable experimental aging method for analyzing variation among seed lots or genotypes for longevity under storage.

Volatile Compounds in Pulses: A Review

The worldwide demand for pulse-based products is increasing in the face of climate change, but their acceptability is limited due to the presence of off-flavours. Off-notes contribute to negative perceptions of pulses (beany notes). Volatile compounds belong to a large variety of chemical classes. They are mainly produced from the oxidation of unsaturated free fatty acids and the degradation of amino acids during seed development, storage, and transformation (dehulling, milling, and starch or protein production). This review aims to provide an overview highlighting the identification of these molecules in different pulses, their potential origins, and their impact on perceptions. However, data on odour-active compounds in pulses are sparse, as they are limited to those of two studies on peas and lupins. A better knowledge of the volatile compounds involved in the off-notes and their origins should allow for drawing efficient strategies to limit their impact on overall perception for more acceptable healthy food design.

Development of Beef Volatile Flavor Compounds in Response to Varied Oven Temperature and Degree of Doneness

Beef volatile flavor compound (VFC) development at the center, mid, and surface layers of cooked steaks was evaluated through 18 cookery treatment combinations consisting of oven cooking temperature (OT; 177°C, 246°C, and 343°C) and final internal steak temperature (IT; 57°C, 63°C, 68°C, 74°C, 79°C, and 85°C). In total, 72 VFC were measured representing the Maillard reaction and lipid degradation. Five VFC were impacted by a three-way interaction of OT × IT × layer (P ≤ 0.030). Two VFC were impacted by a two-way interaction of OT × IT (P ≤ 0.010). Sixteen VFC were impacted by a two-way interaction of OT × layer (P ≤ 0.050). Sixteen VFC were impacted by a two-way interaction of IT × layer (P ≤ 0.050). Twenty VFC were impacted by the main effect of layer (P ≤ 0.010). Eight VFC were impacted by the main effect of IT (P ≤ 0.050). Maillard compounds were formed primarily at steak surfaces, with a general increase in content with greater final IT, and OT to a lesser extent. Lipid-derived compounds were diverse. Methyl esters and aldehydes had lower contents at steak surfaces and were primarily found within the inner portions of steaks. Conversely, certain alcohols and ketones were more prominent at steak surfaces. Development of compounds among layers was also consistently influenced by IT and OT. It may be concluded that flavor-contributing compounds vary among cooked beef steaks at different depths and cookery temperatures. As a result, OT and final IT may be utilized to mediate the final volatile compound composition.

Quality Parameters of Wheat Bread with the Addition of Untreated Cheese Whey

Τhe present study was carried out to evaluate wheat bread of three different flour compositions prepared by replacing water with untreated cheese whey (WCB). Bread prepared with water was taken as the control (CB). All breads were stored at 24 ± 1 °C for up to 6 days. Microbiological, physicochemical, and sensory analyses were determined as a function of storage time. WCB had lower total viable counts (TVC) (3.81 log cfu/g for CB and 2.78 log cfu/g for WCB on day 2 of storage) and showed delayed mold growth by 1 day (day 4 for CB and day 5 for WCB). WCB also had lower pH (5.91 for CB and 5.71 for WCB on day 0), higher titratable acidity values (TTA) (2.5-5.2 mL NaOH/10 g for CB and 4.5-6.8 mL NaOH/ 10 g for WCB), and higher protein content (PC) (PC 7.68% for CB and 8.88% for WCB). WCB was characterized by a more intense flavor, reduced hardness but similar cohesiveness, springiness, and adhesiveness compared to CB. Based primarily on sensory (appearance/mold formation) data, the shelf life of WCB was 4-5 days compared to 3-4 days for CB stored at 24 ± 1 °C. The proposed use of whey in bread preparation contributes decisively to the environmentally friendly management of whey.

Effects of extraction pH on the volatile compounds from pea protein isolate: Semi-Quantification method using HS-SPME-GC-MS

HS-SPME-GC-MS is widely used to characterize the profile of volatile compounds despite some bad uses with a lack of information on the precision and repeatability of this technique. This work proposes a method, including a calibration step, to determine the global volatile compounds profile of a pea protein isolate at different pH of extraction. At the same time, nine compounds of interest were semi-quantified: hexanal, nonanal, 2-nonenal, 3-methylbutanal, benzaldehyde, 1-octen-3-ol, 3-octen-2-one, 2-pentylfuran, and 2,5-dimethylpyrazine. The variation coefficient of the method for a single fiber was 15%. Semi-quantification was done by external calibration. The global volatile compounds profile was composed of 39 compounds including 13 aldehydes, 9 alcohols, 13 ketones, and 4 furans. The quantification of the nine compounds of interest at different extraction pHs showed the importance of pH for aroma release from pea protein isolates. For example, hexanal release was found 59% higher with extraction using pH 4.5 than with pH 6.5.

Comparative study of accelerated assays for determination of equivalent days in the shelf life of roasted high oleic peanuts: Chemical and volatile oxidation indicators in accelerated and room temperature conditions

Lipids present in peanuts are susceptible to oxidation, which affects food quality and safety, for this reason shelf-life studies are carried out. The objective was to determine the relation between accelerated oxidation conditions and room temperature storage for roasted peanuts. Lipid oxidation indicators and roasted flavour volatiles were measured. There was a negative correlation between roasted and oxidation volatiles. In this research, 2,5-dimethylpyrazine and 2-ethyl-3,6-dimethylpyrazine were good indicators of the storage conditions of roasted peanuts, and the peroxide value (PV) was the most important oxidation indicator. For the comparision of equivalent days, it was used the peroxide value which reached 7.90, 2.47 and 0.89 Meq.O₂/kg after 21 days at 25, 45 and 60 °C, respectively. The accelerated storage condition of 60 °C is optimal for estimation of the shelf life at 25 °C wherein 1 day at 60 °C is equal to 8.79 days at 25 °C.

Comparative 1H NMR-Based Chemometric Evaluations of the Time-Dependent Generation of Aldehydic Lipid Oxidation Products in Culinary Oils Exposed to Laboratory-Simulated Shallow Frying Episodes: Differential Patterns Observed for Omega-3 Fatty Acid-Containing Soybean Oils

Soybean oil is the second most exported oil from the United States and South America, and is widely marketed as a cooking oil product containing numerous health benefits for human consumers. However, culinary oils with high polyunsaturated fatty acid (PUFA) contents, are known to produce high quantities of lipid oxidation products (LOPs), including toxic aldehydes upon exposure to high-temperature frying episodes. Previous studies have demonstrated causal links between aldehyde ingestion and inhalation with deleterious health perturbations, including mutagenic and carcinogenic effects, along with cardiovascular and teratogenic actions. In this study, aldehydic LOPs were detected and quantified in commercially available samples of soybean, avocado, corn and extra-virgin olive oil products before and after their exposure to laboratory-simulated laboratory frying episodes (LSSFEs) using high-resolution 1H nuclear magnetic resonance (NMR) analysis. Results acquired demonstrated that PUFA-rich soybean and corn oils gave rise to the highest concentrations of oil aldehydes from the thermo-oxidation of unsaturated fatty acids, whereas monounsaturated fatty acid (MUFA)-laden avocado and olive oils were much more resistant to this peroxidation process, as expected. Multivariate chemometrics analyses provided evidence that an orthogonal component pattern of aldehydic LOPs featuring low-molecular-mass n-alkanals such as propanal, and 4-oxo-alkanals, arises from thermo-oxidation of the ω-3 fatty acid (FA) linolenic acid (present in soybean oils at levels of ca. 7% (w/w)), was able to at least partially distinguish this oil from corresponding samples of thermally-stressed corn oil. Despite having a similar total PUFA level, corn oil has only a negligible ω-3 FA content, and therefore generated significantly lower levels of these two aldehyde classes. In view of the adverse health effects associated with dietary LOP ingestion, alternative methodologies for the incorporation of soybean oils within high-temperature frying practices are proposed.

The effects of soybean storage under controlled atmosphere at different temperatures on lipid oxidation and volatile compounds profile

This study aimed to evaluate the effects of low oxygen partial pressure (pO2) and high carbon dioxide partial pressure (pCO2) combined with different temperatures on the oil acidity and peroxide values of two soybean cultivars (NA 5909 RG and FEPAGRO 37 RR). The volatile compounds correlated to lipid oxidation were also evaluated. Soybeans were stored for seven months under ambient and controlled atmosphere (CA) conditions at three temperatures (20, 25, and 30 °C). Storage under ambient conditions increased acidity and peroxide value regardless of the temperature. CA storage with low pO2 reduced oil acidity and its combination with high pCO2 had no positive effects on oil acidity and peroxide values. Grains of FEPAGRO 37 RR stored under ambient air showed higher 1-octne-3-ol amount compared to CA. The higher storage temperature increased (E)-2-heptenal and decanal amount in grains of cultivar NA 5909 RG. In addition, the ambiente air storage provide higher γ-Butyrolactone in relation to CA storage. Moreover, in both cultivars the CA storage technique provides lower (E)-2-hexenal content. This compound, together with hexanal are potential lipid deterioration markers of soybeans. CA storage is a promising tool for soybean grains preservation and the effect is mainly due to the oxygen reduction, with no additional effect of CO2 increasing.

Occurrence and Development of Off-Odor Compounds in Farmed Hybrid Catfish (Clarias macrocephalus × Clarias gariepinus) Muscle during Refrigerated Storage: Chemical and Volatilomic Analysis

The goal of this study was to examine the changes in chemical parameters, major volatile compounds, and sensory aspects in farm-raised hybrid catfish (i.e., dorsal, lateral line and ventral muscles) during a 15-day period of refrigerated storage. Trichloroacetic acid-soluble peptides, free fatty acid, total volatile base-nitrogen (TVB-N), and non-heme iron levels in all muscles increased as storage time proceeded. The levels of trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (2-MIB) were higher than their thresholds, which was connected to a stronger earthy odor. The concentrations of geosmin and 2-MIB in all muscles increased, although there was a consistent trend of earthy odor throughout storage; this phenomenon could be attributed to the masking effect of other off-odors. During storage, the largest lipid oxidation was found in ventral muscle, as measured by peroxide value and thiobarbituric acid reactive substances. During storage, the formation of the most volatile products increased in the lateral line and ventral muscle, whereas the dorsal muscle had the lowest concentration. As storage time proceeded, the strength of spoiled, fishy, rancid, and overall off-odor intensity of all tested muscles tended to rise. Those alterations were linked to higher levels of TVB-N and trimethylamine, as well as all other volatile lipid oxidation products (e.g., hexanal, propanal, 2,4 heptadienal, 1-octen-3-ol, octanal, nonanal, trans-2-heptenal, and 1-hexanol).

The stability of paintings and the molecular structure of the oil paint polymeric network

A molecular-level understanding of the structure of the polymeric network formed upon the curing of air-drying artists' oil paints still represents a challenge. In this study we used a set of analytical methodologies classically employed for the characterisation of a paint film-based on infrared spectroscopy and mass spectrometry-in combination with solid state NMR (SSNMR), to characterise model paint layers which present different behaviours towards surface cleaning with water, a commonly applied procedure in art conservation. The study demonstrates, with the fundamental contribution of SSNMR, a relationship between the painting stability and the chemical structure of the polymeric network. In particular, it is demonstrated for the first time that a low degree of cross-linking in combination with a high degree of oxidation of the polymeric network render the oil paint layer sensitive to water.

Flavor of rapeseed oil: An overview of odorants, analytical techniques, and impact of treatment

As one of the three major vegetable oils in the world, rapeseed oil is appreciated for its high nutritional value and characteristic flavor. Flavor is an essential attribute, determining rapeseed oil quality and consumer acceptance. The present manuscript provides a systematic literature review of recent advances and knowledge on the flavor of rapeseed oil, which focuses on aroma-active as well as off-flavor compounds, flavor analysis techniques (i.e., extraction, qualitative, quantitative, sensory, and chemometric methods), and effects of treatments (storage, dehulling, roasting, microwave, flavoring with herbs, refining, and oil heating) on flavor from sensory and molecular perspectives. One hundred thirty-seven odorants found in rapeseed oil from literature are listed and possible formation pathways of some key aroma-active compounds are also proposed. Future flavor analysis techniques will evolve toward time-saving, portability, real-time monitoring, and visualization, which aims to obtain a "complete" flavor profile of rapeseed oil. The changes of volatile compounds in rapeseed oil under different treatments are summarized in this view. Studies to elucidate the influence of different treatments on the formation of aroma-active compounds are needed to get a deeper understanding of factors leading to the variations of rapeseed oil flavor.

Release Kinetics Studies of Early-Stage Volatile Secondary Oxidation Products of Rapeseed Oil Emitted during the Deep-Frying Process

The research concerns the use of proton transfer reaction mass spectrometer to track real-time emissions of volatile secondary oxidation products released from rapeseed oil as a result of deep-frying of potato cubes. Therefore, it was possible to observe a sudden increase of volatile organic compound (VOC) emissions caused by immersion of the food, accompanied by a sudden release of steam from a potato cube and a decrease of the oil temperature by more than 20 °C. It was possible to identify and monitor the emission of major secondary oxidation products such as saturated and unsaturated aldehydes, namely acrolein, pentanal, 2-hexenal, hexanal, 2-nonenal and 2-decenal. Each of them has an individual release characteristic. Moreover, the impact of different initial frying temperatures on release kinetics was investigated. Subsequently, it was possible to approximate the cumulative emission by a second-degree polynomial (R² ≥ 0.994). Using the proposed solution made it possible for the first time to observe the impact of the immersion of food in vegetable oil on the early emission of thermal degradation products oil.

Walnut (Juglans regia L.) Volatile Compounds Indicate Kernel and Oil Oxidation

Kernel oxidation susceptibility and pellicle darkening are among the biggest concerns regarding walnut quality. Monitoring oxidation is crucial to preserve quality from production to consumption. Chemical oxidation parameters (peroxide value and UV absorbances), fatty acid profile, tocopherols, phenols, and volatiles in ‘Chandler’ and ‘Howard’ kernels were studied at different time points during 28 weeks of storage to evaluate potential oxidation markers. During storage, peroxide value, UV absorbances, and volatiles concentration increased; oxidative stability, phenols, and tocopherols decreased, while fatty acid profile was unaffected. ‘Chandler’ had a lower peroxide value, K₂₃₂, and K₂₆₈; and higher kernel and oil oxidative stability compared to ‘Howard’. Phenols and tocopherols decreased 1.2-fold in ‘Chandler’ and 1.3-fold in ‘Howard’. Using multivariate analysis, samples were discriminated in three groups according with their oxidative levels. Increases of volatiles in oil and kernel were associated with higher oxidative levels. Pentanal, 2-methylpropanal, hexanal, (E)-2-pentenal, 3-octanone, octanal, (Z)-2-penten-1-ol, hexanol, (E)-2-octenal, 1-octen-3-ol, benzaldehyde, (E,E)-2,4-nonadienal, and hexanoic acid in kernels were adequate at distinguishing oxidation levels and as oxidative markers in walnuts. Kernel volatiles is a useful measurement for walnut oxidation during storage without any prior fat extraction.

Screening of volatile decay markers of minced pork by headspace-solid phase microextraction-gas chromatography-mass spectrometry and chemometrics

Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the volatile compounds of minced pork meat during storage. The origin of aromatic hydrocarbons in pork was verified by migration test. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were applied to characterize the profile of volatile compounds in pork meat and identify the potential volatile markers associated with the spoilage of pork. A total of 41 compounds were identified. Migration test showed that the aromatic hydrocarbons in raw pork are from packaging. Three compounds: ethanol, 2,3-butanediol and 2-ethyl-1-hexanol were selected based on the loading plot and their variables importance in the projection (VIP) values, since they contribute mainly to the discrimination of pork with different storage times. These compounds can be used as additional indicators for quality control of pork.

Detection of Lipid Oxidation in Infant Formulas: Application of Infrared Spectroscopy to Complex Food Systems

 Fish- or algal oils have become a common component of infant formula products for their high docosahexaenoic acid (DHA) content. DHA is widely recognized to contribute to the normal development of the infant, and the European Commission recently regulated the DHA content in infant formulas. For many manufacturers of first-age early life nutrition products, a higher inclusion level of DHA poses various challenges. Long-chain polyunsaturated fatty acids (LC-PUFAs) such as DHA are very prone to oxidation, which can alter the organoleptic property and nutritional value of the final product. Traditional methods for the assessment of oxidation in complex systems require solvent extraction of the included fat, which can involve harmful reagents and may alter the oxidation status of the system. A rapid, efficient, non-toxic real-time method to monitor lipid oxidation in complex systems such as infant formula emulsions would be desirable. In this study, infrared spectroscopy was therefore chosen to monitor iron-induced oxidation in liquid infant formula, with conjugated dienes and headspace volatiles measured with GC-MS as reference methods. Infrared spectra of infant formula were recorded directly in mid- and near-infrared regions using attenuated total reflectance Fourier-transform (ATR-FTIR) and near-infrared (NIRS) spectrophotometers. Overall, good correlation coefficients (R2 > 0.9) were acquired between volatiles content and infrared spectroscopy. Despite the complex composition of infant formula containing proteins and sugars, infrared spectroscopy was still able to detect spectral changes unique to lipid oxidation. By comparison, near-infrared spectroscopy (NIRS) presented better results than ATR-FTIR: prediction error ATR-FTIR 18% > prediction error NIRS 9%. Consequently, NIRS demonstrates great potential to be adopted as an in-line or on-line, non-destructive, and sustainable method for dairy and especially infant formula manufacturers.

Chemical composition and oxidative stability of eleven pecan cultivars produced in southern Brazil

Nuts are considered highly nutritious foods and a source of health-promoting compounds. Therefore, the aim of this study was to evaluate the chemical composition (proximate composition, fatty acids, volatile compounds, total phenolics, squalene, and β-sitosterol) of eleven pecan cultivars harvested in Rio Grande do Sul State (Brazil) and investigate their oxidative stability by the Rancimat method. 'Barton' is the main cultivar produced in Brazil and presented the highest protein, linoleic acid, and linolenic acid values and the lowest saturated fatty acid values, which provide health benefits. 'Mahan' showed the highest oxidation induction time, both in extracted oil and ground samples, low abundance of lipid oxidation compounds, low polyunsaturated fatty acids, high levels of oleic acid and β-sitosterol, which suggests potential for storage. 'Stuart' and 'Success' had the highest total dietary fiber values. Moreover, analysis showed that 'Chickasaw' and 'Success' had large quantities of compounds correlated to lipid oxidation, suggesting low stability for long-term storage. These results imply that the physicochemical characteristics and proximate composition of pecan nut cultivars from southern Brazil have variable parameters that may depend on their genetic variability.

Packing black ripe olives in acid conditions

The type of container (airtight and pouches with different O₂ permeability) and packing conditions (cover brine, air or N₂ atmosphere) has been studied to preserve black ripe olives in acid medium for a year. Unlike the traditional sterilized product, these acidified olives only needed pasteurization to assure its microbial safety, the absence of acrylamide being an additional advantage. Surprisingly, an increase in the oxygen diffusion through the films (i) faded the black color of the olives, (ii) softened the fruit that lost around 33% of its initial firmness in only 6 months, and (iii) produced the lipid́s oxidation forming volatile compounds that transmitted an abnormal flavor which tasters identified as rancid. Therefore, ripe olives in acid medium must be packed in airtight containers such as glass jars, cans o metallic pouches with cover brine or N₂ atmosphere. The addition of calcium is recommended to avoid olive softening.

Effect of Substitution of Rice Flour with Quinoa Flour on the Chemical-Physical, Nutritional, Volatile and Sensory Parameters of Gluten-Free Ladyfinger Biscuits

The present study investigates the effect of partial or total substitution of rice flour (RF) with quinoa flour (QF) (at 25%, 50%, 75% and 100%) on the chemical-physical, nutritional, and sensory characteristics, as well as the volatile compounds, of ladyfinger biscuits. All quinoa-based formulations positively affected the crust colour, endowing it with lower ‘lightness’ and higher ‘redness’ values, giving the biscuits a more appealing crust colour. Biscuits with higher percentages of QF also had better structure, as they were softer. The substitution of RF with QF significantly improved the nutritional profile of the biscuits, as a result of the increase in protein, lipid, ash, total soluble (SP) and insoluble polyphenol (IP), flavonoid, and antioxidant activity levels, which increased linearly with the substitution rate. Quinoa supplementation led to an increase in volatile compounds that were nearly always characterised by positive olfactory attributes. Sensory analysis revealed that the maximal substitution rate of QF able to maintain an adequate consumer acceptability rating is probably 50%, as higher percentages impaired acceptability due to the presence of herbaceous and bitter tastes, even if the consumers also rated these samples as healthier and softer to touch.

Uncovering lead formate crystallization in oil-based paintings

Lead carboxylates are an extensive group of compounds studied for their promising industrial applications and for their risky behavior when they are formed in oil paintings as corrosion products of lead-based pigments, leading to serious deterioration of paintings. Although the processes leading to the formation of aggregates, protrusions or inclusions, affecting undesirably the appearance of paintings, are assumed to be long term, neo-formed lead carboxylates are detectable in the early stage of paint drying. To uncover the chemical changes in lead pigments during the drying of oil paint films, model systems consisting of minium (Pb3O4) and four common drying oils were studied by X-ray powder diffraction (XRPD), 13C and 207Pb solid state NMR (ssNMR) spectroscopy and Fourier-transformed infrared spectroscopy (FTIR). For the first time, a degradation mechanism of Pb3O4via the crystallization of lead formate (Pb(HCOO)2), at the end of oxidative polymerization of oil paint films, was uncovered. The formation of formic acid in oils was proved by gas chromatography-mass spectrometry (GC-MS). Vapor experiments evidenced the susceptibility of Pb3O4 to react with volatile formic acid released during the autoxidation of oils comparably to the direct pigment-binder interactions in paint films. The investigation of the local environment of lead atoms in the paint film by 207Pb WURST-CPMG NMR spectroscopy showed that Pb(ii) atoms reacted with linseed oil preferentially to form highly crystalline Pb(HCOO)2, while the local chemical environment of Pb(iv) atoms did not change. The results proved the co-existence of (i) highly crystalline Pb(HCOO)2, (ii) a highly mobile amorphous phase corresponding to free carboxylic acids or a nascent lead soap phase and (iii) the remaining Pb3O4 in the polymeric/ionomeric network. Pb(HCOO)2 is assumed to be an intermediate for the conversion of Pb3O4 to lead soaps and/or lead carbonates.

Potential Adverse Public Health Effects Afforded by the Ingestion of Dietary Lipid Oxidation Product Toxins: Significance of Fried Food Sources

Exposure of polyunsaturated fatty acid (PUFA)-rich culinary oils (COs) to high temperature frying practices generates high concentrations of cytotoxic and genotoxic lipid oxidation products (LOPs) via oxygen-fueled, recycling peroxidative bursts. These toxins, including aldehydes and epoxy-fatty acids, readily penetrate into fried foods and hence are available for human consumption; therefore, they may pose substantial health hazards. Although previous reports have claimed health benefits offered by the use of PUFA-laden COs for frying purposes, these may be erroneous in view of their failure to consider the negating adverse public health threats presented by food-transferable LOPs therein. When absorbed from the gastrointestinal (GI) system into the systemic circulation, such LOPs may significantly contribute to enhanced risks of chronic non-communicable diseases (NCDs), e.g. cancer, along with cardiovascular and neurological diseases. Herein, we provide a comprehensive rationale relating to the public health threats posed by the dietary ingestion of LOPs in fried foods. We begin with an introduction to sequential lipid peroxidation processes, describing the noxious effects of LOP toxins generated therefrom. We continue to discuss GI system interactions, the metabolism and biotransformation of primary lipid hydroperoxide LOPs and their secondary products, and the toxicological properties of these agents, prior to providing a narrative on chemically-reactive, secondary aldehydic LOPs available for human ingestion. In view of a range of previous studies focused on their deleterious health effects in animal and cellular model systems, some emphasis is placed on the physiological fate of the more prevalent and toxic α,β-unsaturated aldehydes. We conclude with a description of targeted nutritional and interventional strategies, whilst highlighting the urgent and unmet clinical need for nutritional and epidemiological trials probing relationships between the incidence of NCDs, and the frequency and estimated quantities of dietary LOP intake.

Volatile compound profiling from soybean oil in the heating process

Soybean oil heating or cooking is a very complicated process. In order to better understand the composition of the volatile compounds from soybean oil during heating process, volatile profiling was carried out through vacuum-assisted headspace solid-phase microextraction combined with GC-MS. As a result, a total of 72 volatile compounds were detected and identified during this process, including aldehydes (27), alcohols (14), ketones (10), furans (6), aromatic compounds (9), acids, and esters (6). And the forming temperature of each volatile was determined. Results show most of volatile aldehydes and alcohols were formed at 120°C leading to release off-flavor largely, which was considered as a critical temperature point for the formation of soybean oil flavor during the whole heating process. Meanwhile, ketones and furans were formed at 150°C, and acids were detected at 180°C. The content of most volatile compounds increased significantly with the temperature raised. Simultaneously, results of principal component analysis demonstrate that flavor characteristics of soybean oil have a big difference between higher and lower temperature in the heating process.

Relationship of Glucosinolate Thermal Degradation and Roasted Rapeseed Oil Volatile Odor

This study aims to investigate the effect of glucosinolate (GSL) degradation on the volatile odor of rapeseed oil (RO) during roasting. Volatile compounds of RO and individual GSL contents in the seeds were identified and measured during roasting, separately. Total GSL content decreased by 30.47-84.44%. Nitriles were the key volatile compounds that were negatively correlated with GSLs for all samples. Results indicate that GSL degradation significantly affects the volatile odor of RO and tends to produce low-carbon nitriles. Furthermore, the thermal degradation pathways of GSLs were explored according to the structure of individual GSLs and nitriles. These results provide information for the thermal degradation pathways of GSLs and the formation mechanism of nitriles during seed roasting.

Aroma profile and volatile composition of black ripe olives (Manzanilla and Hojiblanca cultivars)

The aroma profile and volatile composition of 8 samples of black ripe olives from Manzanilla and Hojiblanca cultivars were analyzed with the aim to characterize this type of table olive. The aroma of samples was described by a sensory panel using quantitative descriptive analysis (QDA), whereas the volatiles were analyzed by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Eleven odor descriptors (briny, sautéed mushroom, earthy/soil-like, oak barrel, nutty, artificial fruity/floral, natural fruity/floral, vinegary, alcohol, fishy/ocean-like, and cheesy) were evaluated, of which only one descriptor (briny) showed a significant difference between cultivars. A total of 74 volatile compounds were identified in the headspace of samples, of which 12 were identified as significant volatiles contributing to the discrimination between Manzanilla and Hojiblanca black ripe olives. Partial least squares (PLS) regression was able to predict one odor descriptor (nutty) with sufficient accuracy and allowed identifying the volatiles that highly contributed to three odor descriptors of black ripe olives (nutty, natural fruity/floral, and cheesy).

Bioactive Compounds and Stability of a Typical Italian Bakery Products "Taralli" Enriched with Fermented Olive Paste

Olive paste (OP) is a novel by-product of olive mill industry composed of water, olive pulp, and skin. Due to its richness in bioactive compounds, OP exploitation for human consumption has recently been proposed. Starter driven fermented OP is characterized by a well-balanced lipid profile, rich in mono and polyunsaturated fatty acids, and a very good oxidative stability due to the high concentration of fat-soluble antioxidants. These characteristics make OP particularly suitable as a functional ingredient for food/feed industry, as well as for the formulation of nutraceutical products. New types of taralli were produced by adding 20% of fermented OP from black olives (cv Cellina di Nardò and Leccino) to the dough. The levels of bioactive compounds (polyphenols, triterpenic acids, tocochromanols, and carotenoids), as well as the fatty acid profile, were monitored during 180 days of storage and compared with control taralli produced with the same flour without OP supplementation. Taralli enriched with fermented OP showed significantly higher levels of bioactive compounds than conventional ones. Furthermore, enriched taralli maintained a low amount of saturated fatty acids and high levels of polyphenols, triterpenic acids, tocochromanols, and carotenoids, compared to the initial value, up to about 90 days in the usual conditions of retailer shelves.

Application of chemometric tools for the comparison of volatile profile from raw and roasted regional and foreign almond cultivars (Prunus dulcis)

In almonds, volatile compounds are major contributors to flavour, being scarce the current knowledge about their volatile profile. Hence, this work intended to characterize the volatile profile, using headspace solid-phase microextraction and gas chromatography-mass spectrometry, in raw and roasted almond cultivars (regional cvs. Amendoão, Bonita, Casanova, Molar and Pegarinhos and foreign cvs. Ferragnès and Glorieta). Overall, 35 compounds were identified, with major chemical classes being alcohols and aldehydes. In raw fruits, benzaldehyde and 3-methyl-1-butanol were key compounds, with roasting changing volatile profiles, increasing release of compounds, with predominance of hexanal and benzaldehyde. Cultivars Glorieta and Molar didn't show significant increase in aldehyde content after roasting, which may indicate higher resistance to heat-caused oxidation. The use of linear discriminant analysis and principal components analysis permitted the recognition of patterns in the volatile profiles, that can be useful for cultivars identification. This work allowed the characterization and monitoring changes caused by roasting of volatile components of less studied almond cultivars, identifying some that can withstand roasting procedures with reduced formation of compounds associated with off-flavours.

Changes in volatile composition during the processing and storage of black ripe olives

The present study revealed the effects of each step of black ripe olive processing (preservation, darkening, packing + sterilization) and storage on the volatile composition of two olive cultivars (Manzanilla and Hojiblanca). The preservation step enriched the volatile profile of the olives, mainly in ethyl acetate, methyl acetate, and ethanol. The darkening step produced the total or partial elimination of 55-65% of the volatiles identified before this step. Around 70% of the volatiles in the final products corresponded to compounds that were formed or increased significantly as a result of the sterilization treatment at 121 °C. Although differences in the volatile compositions and contents between Manzanilla and Hojiblanca were found, the dominant volatiles in both cultivars were benzaldehyde, dimethyl sulfide and ethyl acetate. Storage for 8 months had little influence on their volatile profiles, although the stability of individual volatiles in Manzanilla was better than that in the Hojiblanca cultivar.

Comprehensive profiling of lipid oxidation volatile compounds during storage of mayonnaise

Lipid oxidation is a primary cause of quality deterioration in mayonnaise that leads to a decrease in the nutritional and sensorial value. The evolution of volatile oxidation compounds in sunflower oil mayonnaise stored at varying temperatures for 92 days and the antioxidative effect of butylated hydroxyanisole were investigated by static headspace extraction and separation by two dimensional gas chromatography/time-of-flight mass spectrometry. Considerable differences in the headspace composition of samples stored at 4, 25 and 38 °C were found due to the different oxidation levels reached. The content of hexanal in mayonnaise at 1-5 days of storage at 38 °C could be used to predict the corresponding compound in mayonnaise at 1-62 days of storage at 25 °C. The 10 most important discriminating volatile compounds during lipid oxidation of mayonnaise (at 38 °C for 92 days) are 3-hexenal, pentanal, 2-heptenal, 2-ethylfuran, hexanal, benzeneacetaldehyde, 2-pentylfuran, 3-methylhexane, 1-pentanol and 2,4-heptadienal. More than half of these compounds have a close relationship with the initial content of linoleic acid that agrees with the fatty acid profile of sunflower oil (~ 70% linoleic acid). These volatiles could be used as additional markers of oxidation in sunflower oil mayonnaise.

Characterization of Key Aroma Compounds in Beijing Roasted Duck by Gas Chromatography-Olfactometry-Mass Spectrometry, Odor-Activity Values, and Aroma-Recombination Experiments

The dominant aroma compounds in the breast skin and breast muscle of Beijing roasted duck were investigated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS), odor-activity values, and aroma recombination. The results demonstrated that a total of 42 aroma compounds were identified in Beijing roasted duck, including aldehydes, ketones, alcohols, acids, phenols, sulfur-containing compounds, and nitrogen-containing compounds. Among the 42 aroma compounds, 18 were identified as important odorants with odor-activity values (OAVs) greater than 1. Aroma-recombination-omission experiments and sensory evaluation demonstrated that nine aroma compounds significantly contributed to the characteristic aroma of Beijing roasted duck. These nine key aroma compounds were 2-furfurylthiol, dimethyl trisulfide, hexanal, heptanal, octanal, nonanal, methional, 1-octen-3-ol, and ( E, E)-2,4-decadienal. Among these, 2-furfurylthiol (3620 ≤ OAV ≤ 31 606) and dimethyl trisulfide (2515 ≤ OAV ≤ 23 470) significantly contributed to the aroma of roasted duck ( p < 0.01). Sensory evaluation of the recombination model with the nine aroma compounds scored 4.5 out of 5 points. The major aroma profile of Beijing roasted duck included strong fatty, roasty, and meaty aromas. The key aroma compounds of Beijing roasted duck were concluded to be 2-furfurylthiol, dimethyl trisulfide, hexanal, heptanal, octanal, nonanal, methional, 1-octen-3-ol, and ( E, E)-2,4-decadienal.

Higher Straight-Chain Aliphatic Aldehydes: Importance as Odor-Active Volatiles in Human Foods and Issues for Future Research

Owing to their apparent lack of health significance, higher straight-chain aliphatic aldehydes, i.e., those having alkyl chains with more than six carbon atoms, have been largely neglected in food and nutraceutical research. However, they are an important class of odor-active volatiles in human foods. Indeed, certain aldehydes, such as hexanal, E-2-nonenal, and E, E-2,4-decadienal, serve as key odorants in a range of our foods and drinks. This perspective describes the significance of higher straight-chain aliphatic aldehydes as food odorants, focusing on several representative ones, and raises the issues regarding these aldehydes to be addressed in the future.