Photooxidation of phytochemicals in food and control: a review

Abstract

Phytochemicals are widely present in food and have been confirmed to be bioactive, thereby contributing to human health. However, some phytochemicals are sensitive to light owing to their structures and may suffer from photodegradation, especially when sensitizers exist, resulting in sensory quality change, nutrient loss in food, and even the formation of toxic compounds. The photooxidation of phytochemicals occurs through three different mechanisms: (1) by directly absorbing luminous energy, (2) with triplet-excited state sensitizers through electron transfer or proton transfer (type I photooxidation), and (3) with singlet oxygen produced by O (type II photooxidation). On the basis of these mechanisms, adequate antioxidants can be added to quench the triple-excited state sensitizers or singlet oxygen to protect against the photooxidation of phytochemicals in food. Here, we summarize and discuss the possible pathways and products of the photooxidation of phytochemicals that have been reported and the relationships between structures and photooxidation. We also propose some control measures, with special attention paid to the potential abilities of phytochemicals in the prevention of food photooxidation.

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

“…The efficiency of each reaction type mainly depends on the relative concentrations of oxygen and substrate. Given that oxygen is more soluble in nonpolar lipids than in water, the formation of COPs in soybean oil containing chlorophyll mainly depends on the type II reaction, while the photo‐oxidation of cholesterol in water‐based foods such as milk mainly depends on Type I reaction (Lu & Zhao, 2017; Min & Boff, 2002). Generally speaking, the formation of COPs under light exposure depends largely on the exposure time and light energy.…”

Phytosterols in Seaweeds: An Overview on Biosynthesis to Biomedical Applications

“…However, a myriad of research studies on phytosterol have inevitably proved that intake of phytosterol has potential health benefits, hence it is suggested that phytosterols-rich foods such as seaweed can be used as functional foods [ 159 ]. Phytosterols are sensitive to oxidation-like cholesterol, resulting in the formation of phytosterol oxidation products by enzymatic or non-enzymatic mechanisms during heat processing, storage, and human metabolism [ 160 , 161 ]. Despite the low concentration of cholesterol oxidation products in food, they have been demonstrated to cause cytotoxicity and genotoxicity.…”

Analytical Strategies to Analyze the Oxidation Products of Phytosterols, and Formulation-Based Approaches to Reduce Their Generation

“…Analytical methods for the qualitative and quantitative analysis of phytosterols and cholesterol oxidation products (COPs) are prevalent [32][33][34][35][36] and may serve as a starting Figure 2. Auto-oxidation and photo-oxidation of phytosterols forming various polar and non-polar phytosterol oxidation products (POPs) [17,18].…”

“…Similar to cholesterol oxidation products, POPs are generated by auto-oxidation and photo-oxidation mechanisms ( Figure 2) [17,18]. Primarily, POPs are formed by the oxidation of the steroid ring of phytosterol.…”

“…This is probably due to the fact that side chain oxidation of phytosterols is mediated by enzymatic reactions in vivo rather than by auto-oxidation [24]. Auto-oxidation and photo-oxidation of phytosterols forming various polar and non-polar phytosterol oxidation products (POPs) [17,18].…”