Rapid detection of vegetable cooking oils adulterated with inedible used oil using fluorescence quenching method with aqueous CTAB-coated quantum dots

Abstract

a b s t r a c tVegetable cooking oils adulterated with inedible used oils or impure oils have posed a severe food safety problem. Current detection methods cannot meet the needs for rapid detection of adulterated oils on line or in field. Therefore, the objective of this research was to develop a rapid optical sensing method based on fluorescence quenching of CdSe/ZnS quantum dots (QDs) for identification of adulterated vegetable cooking oils. High quality hydrophilic photoluminescent nanoparticles were synthesized by encapsulating hydrophobic QDs into the micellar structure of an amphiphilic surfactant cetyltrimethyl ammonium bromide (CTAB) via phase transfer method. TEM, AFM, and fluorescence spectroscopy were used to characterize the prepared CTAB-coated QDs. Oil samples were first captured into the core of the twolayer-structural micelle and then the fluorescence of CTAB-coated QDs, working as fluorescence probes, was selectively quenched by components of the adulterated oils. Heavy metal ions and free radicals were presumed to be main quenchers. After quenching for 1 min, fluorescence intensity was measured and converted to quenching percentage to determine the adulteration concentration. The results showed that in comparison with oil-soluble QDs, water-soluble CTAB-coated QDs had a greater ability to identify oil adulteration. A good quantitative relationship between quenching percentage and adulteration concentration (y = 5.96x + 14.99; R 2 = 0.94) was obtained. The sensitive, simple and low-cost sensing method did not require sample pretreatment and could detect refined used oils at 0.4% or higher concentrations in soybean oil within 2 min, showing great potentials for rapid screening of used oils and quantitative analysis of used oil adulteration in field.

Study of vegetable oils and their blends using infrared reflectance spectroscopy and refractometry

“…First, changes were observed in weak bands. Similar findings on applying this method are given in papers on other sciences, such as medicine and biology ( Li et al, 2016 , Xu et al, 2014 ).…”

“…In most cases, sunflower, rapeseed, and maize oils are used for blending ( Correa et al, 2019 , Li et al, 2016 ) due to the high concentration of ω-6 fatty acids. At the same time, flaxseed and linseed oils are an alternative source for ω-3 series acids, despite their rather specific taste ( Xu et al, 2014 ).…”

Conversion of Waste Cooking Oil to Rhamnolipid by a Newly Oleophylic Pseudomonas aeruginosa WO2

“…When WCO was used as the sole carbon source in the culture medium, the growth of bacteria and lipase activity decreased compared with rapeseed oil. It is speculated that the toxic substances contained in WCO, such as phenylpyridine and aflatoxin, may inhibit the growth of bacteria [30,39]. When glucose was used as a sole carbon source, strain WO2 produced the highest cell biomass, while a significant decrease in lipase activity was observed.…”

Rapid testing methods for food contaminants and toxicants

“…It is recommended to promote the rapid test of nitrite and nitrate in agriculture industry to lower the risk of over-uses of nitrogenous fertilizers. A rapid optical sensing method based on encapsulated hydrophobic CdSe/ZnS QDs for the identification of adulterated vegetable cooking oil has been reported by Xu et al (2014). In the presence of oil sample, these QDs show quenching of fluorescence emission that leads to a color change from red to blue.…”