Short communication: Rapid detection of milk fat adulteration with vegetable oil by fluorescence spectroscopy

Abstract

This study assessed the potential application of fluorescence spectroscopy in detecting adulteration of milk fat with vegetable oil and characterizing the samples according to the source of the fat. Pure butterfat was adulterated with different vegetable oils at various concentrations (0, 5, 10, 15, 20, 30, and 40%). Nonfat and reduced-fat milk were also adulterated with vegetable oils to simulate full-fat milk (3.2%). The 2- and 3-dimensional front-face fluorescence spectroscopy and gas chromatography were used to obtain the fluorescence spectra and fatty acid profile, respectively. Principal component analysis and 3-way partial least squares regression analysis were applied to analyze the data. The pure and adulterated samples were discriminated based on the total concentration of saturated fatty acids and unsaturated fatty acids, and also on the 3 major fluorophores: tryptophan, tocopherols, and riboflavin. Fluorescence spectroscopy was able to detect up to 5% of adulteration of vegetable oil into the butterfat. The saturated fatty acids showed higher predictability than the unsaturated fatty acids (R(2) = 0.73-0.92 vs. 0.20-0.65, respectively). The study demonstrated the high potential of fluorescence spectroscopy to rapidly detect adulteration of milk fat with vegetable oil, and discriminate commercial butter and milk according to the source of the fat.

Common milk adulteration and their detection techniques

“…It has also been possible to detect multiple adulterants including ammonium sulfate, dicyandiamide, melamine and urea in milk powder using Raman chemical imaging (Qin et al 2013). Milk fat adulteration is also a very common concern, however, several techniques have been developed to detect the adulteration based on Butyro Refractometer (Arora et al 1996), fluorescence spectroscopy (Ntakatsane, Liu, & Zhou, 2013), derivative spectroscopy (Jirankalgikar & De, 2014) and Raman spectroscopy (Uysal, Boyaci, Genis, & Tamer, 2013).…”

Milk Preservatives and Adulterants: Processing, Regulatory and Safety Issues

“…(110) Vegetable oil Due to higher price and increased demand, milk fat has been a target of the fraudulent practices, such as replacement with cheaper or more readily available non-milk fats of plant and animal origin. (111) Vegetable oils (VO) are commonly used for this purpose. Also, VO is used as a chief source of fat in synthetic milk.…”

“…Therefore, the adulteration of the VO can easily be detected by analyzing the fatty acid profile by gas chromatography. (111) Adulteration of milk with VO, also increases its Butyro Refracto meter reading, which is also a suitable measure for detection. (64) In India, Hydrogenated vegetable oil (HVO) is a common adulterant in milk fat.…”

“…(107) Though soya milk with similar characteristics is on sale, still the replacement of milk fat with fat from other sources is not only an economic fraud, but may also pose a risk to human health. (111) Polyunsaturated fatty acids in VO auto-oxidize during processing, when exposed to oxygen and or ultraviolet radiations; resulting in generation of inflammatory peroxides and hydroperoxides which cause inflammation of cells, digestive diseases and eventually cancer. (112) Urea In India, urea [CO(NH 2 ) 2 ] is commonly used as an adulterant for milk because it is a relatively cheap compound, easily available and rich in nitrogen, but it decreases the nutritive value of the milk.…”

Development of a method employing reversed‐phase thin‐layer chromatography for establishing milk fat purity with respect to adulteration with vegetable oils

“…Direct analysis in real time (DART) ionisation coupled with high resolution mass spectrometry (DART-HRMS) was used by Hrbek et al (2014) to detect the presence of vegetable oils added to soft cheese which involves the use of costly DART-HRMS systems. The study conducted by Ntakatsane et al (2013) revealed that vegetable oils can be detected up to 5% level using fluorescence spectroscopy. There, thus, remains a need for a simple, quick, economic and reliable method for the detection of most of the vegetable oils even at lower levels in milk fat.…”