Pyrolytic formation of polyaromatic hydrocarbons from steroid hormones

Formation, migration, derivation, and generation mechanism of polycyclic aromatic hydrocarbons during frying

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and lipophilic, which can be found in frying system. This review summarized the formation, migration and derivation for PAHs, hypothesized the possible mechanism for PAHs generation during frying and presented the research prospects. Some factors like high oil consumption, high temperature, long time and oil rich in unsaturated fatty acids promoted the formation of PAHs and the presence of antioxidants inhibited the PAHs formation. The effect of proteins and carbohydrates in foods on the formation of PAHs is inconclusive. The formed PAHs were migrated into food and air. Moreover, some PAHs transformed into more toxic PAHs-derivatives during frying. The generation of PAHs may be related to low-barrier free radical-mediated reaction and the unsaturated hydrocarbons may be precursors of PAHs during frying. In future, the isotope tracer technology and on-line detection may be applied to discover intermediates and provide clues for studying PAHs generation mechanisms.

Polycyclic aromatic hydrocarbons in coffee samples: Enquiry into processes and analytical methods

Polycyclic aromatic hydrocarbons (PAHs) are considered to be potentially genotoxic and carcinogenic in humans. These ubiquitous environmental pollutants may derive from the incomplete combustion and pyrolysis of organic matter. Coffee is an extensively consumed drink, and its PAHs contamination is not only ascribed to environmental pollution, but mainly to the roasting processes. Although no fixed limits have yet been set for residual PAHs in coffee, the present review intends to summarise and discuss the knowledge and recent advances in PAHs formation during roasting. Because coffee origin and brewing operations may affect PAHs content, we thoroughly analysed the literature on extraction and purification procedures, as well as the main analytical chromatographic methods for both coffee powders and brews. With regards to the safety of this appreciated commodity, the control on the entire production chain is desirable, because of coffee beverage could contribute to the daily human intake of PAHs.

Polycyclic aromatic hydrocarbons in edible oils and fatty foods: Occurrence, formation, analysis, change and control

Numerous studies have demonstrated that dozens of polycyclic aromatic hydrocarbons (PAHs) are mutagenic, genotoxic and strongly carcinogenic. PAHs are found to be widely present in foods contaminated through multiple paths. Due to their lipophilic nature, these compounds easily accumulate in edible oils and fatty foods where they can range from no detection to over 2000μg/kg. Compared to precursor PAHs, researchers have seldom studied the presence of PAH derivatives, especially in food matrices. This chapter includes the physical and chemical characteristics of PAHs and their types, occurrence, sample pretreatment and instrumental determination methods, and their formation, change and control in edible oils and fatty foods. The occurrence and formation of PAH derivatives in foods are much less investigated compared to those of their precursor PAHs. Although the removal of matrix effects and accuracy remain difficult for current rapid determination methods, a prospective research direction of PAH analysis for large-scale screening is in demand. To date, physical absorption, chemical oxidation and biodegradation have been widely used in PAH removal techniques. Specific types of bacteria, fungi, and algae have also been used to degrade PAHs into harmless compounds. However, most of them can only degrade a range of LPAHs, such as naphthalene, anthracene and phenanthrene. Their ability to degrade HPAHs requires further study. Moreover, it is still a great challenge to maintain food nutrition and flavor during the PAH removal process using these methods.

Modern Procedures for Removal of Hazardous Compounds From Foods

This chapter deals with interactions between foods or food additives and plastic package materials oriented to elimination of hazardous compounds from foods. As found, polycyclic aromatic hydrocarbons (PAHs) can be effectively eliminated from liquid smoke flavors and smoked meat products by migration of PAHs into low-density polyethylene (LDPE), when the limiting factor of the elimination is diffusion in food matrix. After leaving food bulk, PAHs migrate deeper into LDPE bulk what brings about permanent renewal of material imbalance on LDPE/food matrix interface that maintains the migration process in an intensive regime causing extensive lowering of PAH content in food matrix. To the opposite, polyethylene terephthalate (PET) in contact with vegetable oils is able to absorb only PAHs on active center deposited on its surface without deeper migration into plastic bulk and therefore this type of elimination process is less effective. Overall, migration processes are affected by polarity of food matrix and package materials, presence of compounds able to compete for adsorption center on PET surface, the time of interactions, and, of course, imbalance of PAH chemical potentials in individual systems.

Simultaneous extraction and determination of free and conjugated phytosterols in tobacco

Acid hydrolysis and alkaline saponification were incorporated into a microwave-assisted extraction process for the simultaneous extraction of free and conjugated phytosterols from tobacco. The crude extract of the microwave-assisted extraction was purified by C18 solid-phase extraction and then determined by high-performance liquid chromatography. Phytosterols of cholesterol, ergosterol, stigmasterol, campesterol, and β-sitosterol were determined by chromatographic quantification. The multiple parameters of microwave-assisted extraction were optimized by a uniform design method. The optimal ratio of extraction ethanol solvent to tobacco mass was 30 mL/g. The microwave-assisted extraction acid hydrolysis was carried out in sulfuric acid medium by heating for 10 min at 55°C. The microwave-assisted extraction alkaline saponification was performed after adding excessive sodium hydroxide by heating another 10 min. The repeatability of the proposed method was acceptable with recoveries from 69.68 to 88.17% for the phytosterols. Five target phytosterols were all found in the tobacco samples, and the contents were significantly different in samples from different producing areas.