Effects and mechanism of tea polyphenols on the quality of oil during frying process

Lipophilic antioxidants in edible oils: Mechanisms, applications and interactions

Essential fatty acids (EFAs) in edible oils are crucial for human nutrition. However, their high unsaturation renders edible oils susceptible to oxidation during storage and processing. The addition of lipophilic antioxidants is an effective strategy to inhibit oxidation and safeguard the nutritional integrity of edible oils. This review focused on the diverse mechanisms and applications of lipophilic antioxidants to inhibit oxidation of edible oils. A range of both synthetic and natural lipophilic antioxidants, including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), propyl gallate (PG), tocopherols, tocopherols, carotenoids, flavonoids, ascorbyl palmitate, and lipophilic phenolic compounds were discussed. Moreover, lipophilic antioxidant extracts, as the mixture of natural lipophilic antioxidants, can significantly inhibit oil oxidation. The interaction mechanisms of natural lipophilic antioxidants were reviewed. However, compared to synthetic lipophilic antioxidants, the mechanisms and interactions of natural lipophilic antioxidants need to be further studied. Additionally, their stability and solubility, the extraction and purification costs, and the impact on the sensory must be considered when applying natural lipophilic antioxidants to edible oils. This review serves as a timely reference for application of natural lipophilic antioxidants in edible oils, contributing to the development of healthier and more sustainable options.

Fractionating the Flavonoids in Lonicerae japonicae Flos and Lonicerae flos via Solvent Extraction Coupled with Automated Solid-Phase Extraction

Due to the structural diversity of flavonoids in functional plant foods and the inherent limitations of existing techniques, it is important to develop a simple and green (environmentally friendly) method of extracting flavonoids from plant foods. In this study, a method involving solvent extraction followed by automated solid-phase extraction was developed for extracting flavonoids from Lonicerae japonicae flos (JYH) and Lonicerae flos (SYH), both of which are widely used functional plant-based foods in Asian countries. For the optimisation of the solvent extraction method, solvent concentration (0.0, 20.0, 40.0, 60.0, 80.0 and 100.0% (v/v) of ethanol-water solution), extraction temperature (40, 60 and 80 °C) and extraction time (15.0, 30.0, 60.0, 90.0 and 120.0 min) were evaluated via design of experiment after screening. For solid-phase extraction, five cartridges (Strata-X, InertSep RP-2, InertSep RP-C18, Bond Elut-ENV, Oasis Prime HLB) were evaluated and different elution steps were optimised to obtain high recoveries (79.69-140.67%) for eight target flavonoids, including rutin, isoquercetin and luteolin. Antioxidant capacity assays revealed that JYH samples demonstrated superior antioxidant potential compared to SYH. The optimised extraction method provides a valuable tool for industrial-scale flavonoid production.

Synthesis of Antibacterial Bioactive Compounds Using Linoleic Acid Extracted from Melon Seeds Oil and Evaluation of Its Waste Meal Ash for Fried Oil Regeneration

This work aimed to use linoleic acid extracted from melon seed oil for the development of biological compounds, and to use the ash of melon seed cake for fried oil treatment. Eight active compounds were developed using linoleic acid and the elucidation of their structure was established according to elemental analysis and spectral data. The developed compounds were tested for their antibacterial activity. The melon seed cake was carbonized for the treatment of fried oils. The melon seed oil was rich in linoleic acid (61.4%) and it contains several fatty acids including lauric, myristic, palmitic, palmitoleic, stearic, oleic, linolenic, arachidic, and paulinic in concentrations of 0.2%, 0.73%, 11.7%, 0.11%, 10.3%, 14.1%, 0.49%, 0.19%, and 0.1%, respectively. The extracted linoleic acid showed a high refractive index (1.471), iodine value (122.3 g I2/100 g), saponification (184.42 mg KOH/g), low peroxide value (3.9 meq/kg oil), polymer content (1.00%), polar contents (1.95%), and moisture content (42 g/kg). The melon seed ash was rich in several metals including magnesium (743.5 mg/kg), calcium (137 mg/kg), sodium (12.95 mg/kg), potassium (1040 mg/kg), chromium, manganese, iron, copper, zinc, cadmium, and mercury in concentrations of 0.072, 40.88, 19.29, 3.334, 8.21, 0.005, 0.005 mg/kg, respectively, as well as arsenic (0.09 mg/kg), lead (0.044 mg/kg), phosphorus (1222 mg/kg) and selenium (0.13 mg/kg) which they improved the physic-chemical properties of fried oils. Linoleic acid was used for the development of 9 compounds with antimicrobial activity against Gram-positive and Gram-negative bacteria. Additionally, the melon seed ash improved the chemical characteristic of used cotton and sunflower oils. Therefore, the linoleic acid extracted from melon seed oil is a promising source for the development of antibacterial agents and the leftover cake is promising for the production of adsorbent material suitable for fried oils treatment.

Graphical Abstract

Health benefits, mechanisms of interaction with food components, and delivery of tea polyphenols: a review

Tea polyphenols (TPs) are the most important active component of tea and have become a research focus among natural products, thanks to their antioxidant, lipid-lowering, liver-protecting, anti-tumor, and other biological activities. Polyphenols can interact with other food components, such as protein, polysaccharides, lipids, and metal ions to further improve the texture, flavor, and sensory quality of food, and are widely used in food fields, such as food preservatives, antibacterial agents and food packaging. However, the instability of TPs under conditions such as light or heat and their low bioavailability in the gastrointestinal environment also hinder their application in food. In this review, we summarized the health benefits of TPs. In order to better use TPs in food, we analyzed the form and mechanism of interaction between TPs and main food components, such as polysaccharides and proteins. Moreover, we reviewed research into optimizing the applications of TPs in food by bio-based delivery systems, such as liposomes, nanoemulsions, and nanoparticles, so as to improve the stability and bioactivity of TPs in food application. As an effective active ingredient, TPs have great potential to be applied in functional food to produce benefits for human health.

Antibacterial Effects of Theaflavins against Staphylococcus aureus and Salmonella paratyphi B: Role of Environmental Factors and Food Matrices

This study aimed to investigate the effects of different environmental factors (temperature, pH, and NaCl) and food matrices (skimmed milk powder, lecithin, and sucrose) on the antibacterial activity of theaflavins (TFs) against Staphylococcus aureus (S. aureus) and Salmonella paratyphi B (S. paratyphi B). TFs showed a larger diameter of inhibition zone (DIZ, 12.58 ± 0.09 mm-16.36 ± 0.12 mm) value against S. aureus than that of S. paratyphi B (12.42 ± 0.43 mm-15.81 ± 0.24 mm) at the same concentration (2-10 mg/mL). When temperatures were 25-121 °C, the DIZ of TFs against both S. aureus and S. paratyphi B was not significantly different. As pH increased from 2 to 10, their DIZ values decreased significantly from 16.78 ± 0.23 mm to 13.43 ± 0.08 mm and 15.63 ± 0.42 mm to 12.18 ± 0.14 mm, respectively. Their DIZ values increased slightly as the NaCl concentration increased from 0.2 mol/L to 0.8 mol/L, while their DIZ values decreased significantly for skimmed milk powder concentrations in the range of 20-120 g/L. Regarding the concentrations of lecithin and sucrose were 2-12 g/L and 10-60 g/L, their DIZ values showed no significant change against S. paratyphi B, but an increased trend for S. aureus. Under the above different environmental factors and food matrices, TFs maintained excellent antibacterial activity against S. aureus and S. paratyphi B, providing a theoretical guidance for applying TFs as novel antibacterial additives in the food industry.

Effects of High-Canolol Phenolic Extracts on Fragrant Rapeseed Oil Quality and Flavor Compounds during Frying

Fragrant rapeseed oil (FRO) is a frying oil widely loved by consumers, but its quality deteriorates with increasing frying time. In this study, the effect of high-canolol phenolic extracts (HCP) on the physicochemical properties and flavor of FRO during frying was investigated. During frying, HCP significantly inhibited the increase in peroxide, acid, p-anisidine, and carbonyl values, as well as total polar compounds and degradation of unsaturated fatty acids. A total of 16 volatile flavor compounds that significantly contributed to the overall flavor of FRO were identified. HCP was effective in reducing the generation of off-flavors (hexanoic acid, nonanoic acid, etc.) and increased the level of pleasant deep-fried flavors (such as (E,E)-2,4-decadienal). Therefore, the application of HCP has a positive effect on protecting the quality and prolonging the usability of FRO.

Polyphenolic compounds from rapeseeds (Brassica napus L.): The major types, biofunctional roles, bioavailability, and the influences of rapeseed oil processing technologies on the content

The rapeseed (Brassica napus L.) are the important oil bearing material worldwide, which contain wide variety of bioactive components with polyphenolic compounds considered the most typical. The rapeseed polyphenols encompass different structural variants, and have been considered to have many bioactive functions, which are beneficial for the human health. Whereas, the rapeseed oil processing technologies affect their content and the biofunctional activities. The present review of the literature highlighted the major types of the rapeseed polyphenols, and summarized their biofunctional roles. The influences of rapeseed oil processing technologies on these polyphenols were also elucidated. Furthermore, the directions of the future studies for producing nutritional rapeseed oils preserved higher level of polyphenols were prospected. The rapeseed polyphenols are divided into the phenolic acids and polyphenolic tannins, both of which contained different subtypes. They are reported to have multiple biofunctional roles, thus showing outstanding health improvement effects. The rapeseed oil processing technologies have significant effects on both of the polyphenol content and activity. Some novel processing technologies, such as aqueous enzymatic extraction (AEE), subcritical or supercritical extraction showed advantages for producing rapeseed oil with higher level of polyphenols. The oil refining process involved heat or strong acid and alkali conditions affected their stability and activity, leading to the loss of polyphenols of the final products. Future efforts are encouraged to provide more clinic evidence for the practical applications of the rapeseed polyphenols, as well as optimizing the processing technologies for the green manufacturing of rapeseed oils.

Oil Penetration of Batter-Breaded Fish Nuggets during Deep-Fat Frying: Effect of Frying Oils

Four frying oils (rapeseed, soybean, rice bran, and palm oils) were employed either as received (fresh) or after preheating at 180 °C for 10 h, and measured for their fatty acid composition, viscosity, and dielectric constant. Batter-breaded fish nuggets (BBFNs) were fried at 180 °C (60 s), and the effect of the oils’ quality on the oil penetration of fried BBFNs were investigated via the analysis of the absorption and the distribution of fat. Preheating increased the viscosity and dielectric constant of the oils. The total fat content using fresh oils was the greatest for palm oil (14.2%), followed by rice bran oil (12.2%), rapeseed oil (12.1%), and soybean oil (11.3%), a trend that was nearly consistent with the penetrated surface oil, except that the penetrated oil for soybean oil (6.8%) was higher than rapeseed oil (6.3%). The BBFNs which were fried using fresh oils possessed a more compact crust and smaller pores for the core and underwent a lower oil penetration compared to the preheated oils. The results suggested that the oils’ quality significantly affected the oil penetration of fried BBFNs.

Two Novel Lipophilic Antioxidants Derivatized from Curcumin

Tert-butyl curcumin (TBC), demethylated tert-butylated curcumin (1E,6E-1,7-bis(3-tert-butyl-4,5-dihydroxyphenyl)hepta-1,6-diene-3,5-dione, DMTC), demethylated curcumin (DMC), and Cur were synthesized from the starting compound, 2-methoxy-4-methylphenol. TBC and DMTC are two novel lipophilic compounds, and Cur and DMC are polar and hydrophilic. The antioxidant activities of Cur, TBC, DMC, and DMTC were evaluated by using the methods of 2,2-diphenyl-1-(2,4,6-trinitro-phenyl)-hydrazinyl (DPPH), deep-frying, and Rancimat. Tert-butylhydroquinone (TBHQ) and Butylated hydroxytoluene (BHT) were used as comparison compounds. Both Rancimat and deep-frying tests demonstrated that DMTC was the strongest antioxidant, and TBC also had stronger antioxidant activity than Cur. In the DPPH assay, DMC showed the highest scavenging activity, followed by DMTC, TBHQ, Cur, and TBC. DMTC and TBC can be potentially used as strong antioxidants in food industry, especially for frying, baking, and other high temperature food processing. DMTC is the strongest antioxidant in oil to our knowledge.

Improving the quality of used frying niger seed oil with adsorbent treatment

High temperature continuous deep fat frying of foods will result in the frying oil and food quality deterioration. Although the quality can be retained by using fresh oil, this approach will increase the production cost. In this study, quality improvement of used niger seed oil using adsorbent treatment was evaluated. Each adsorbent was mixed with 20 h used niger seed oil (15% w/v) at 150 °C and stirred for 30 min. The oil was recovered through centrifugation at 4200 rpm for 15 min. The tested chemical parameters of the oil increased after 20 h of frying (acid value (AV) (2.24-8.31) mg KOH/gm oil, free fatty acid (FFA) (1.13-4.17) %, and peroxide value (PV) (1.00-13.97 mEq oxygen/Kg of oil). The improvement in free fatty acid, peroxide value and oil recovery upon treatment of the fried oil with ash, bentonite, bleaching earth, silca gel and magnesium oxide (MgO) was (61, 57, 80), (66, 43, 88), (56, 21, 85), (61, 50, 70), and (73, 64, 40) % respectively. Ash and MgO effectively improved the physico-chemical characteristics of the used oil. Thus, the two were selected for further optimization of effective concentration and to evaluate their synergetic effect. Treatments with 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0 % of ash reduced the AV of the fried oil by 26, 39, 46, 53, 53 and 60 % respectively (p < 0.05). Also the combination of ash and MgO (1:1) improved the physico-chemical properties of the frying oil to nearly fresh quality.