Current Analytical Techniques for Food Lipids

Thee analysis of food lipids presents significant challenges due to the wide variety of sample matrices, large range of total fat contents, and complex compositions of fatty acids. This is chapter reviews conventional analytical techniques for the quantification of total fat and fatty acids in foods and food ingredients, including the gravimetric determination of total fat, the calculation of fat and fatty acids using gas chromatography (GC), and the analysis of proximates content (i.e., fat, protein, carbohydrate, moisture, and ash) by Fourier transform infrared (FTIR) spectroscopy. Current official methods of analysis are evaluated and the use of certified reference materials and spike-recovery experiments for verifying method performance is discussed. Recent advances in automated and semi-automated sample preparation systems and rapid and portable spectroscopic devices are highlighted for their potential to significantly improve the speed by which accurate determinations of total fat and fatty acids may be achieved

Rapid Turbidimetric Detection of Milk Powder Adulteration with Plant Proteins

Development of assays to screen milk for economically motivated adulteration with foreign proteins has been stalled since 2008 due to strong international reactions to the melamine poisoning incident in China and the surveillance emphasis placed on low molecular weight nitrogen-rich adulterants. New screening assays are still needed to detect high molecular weight foreign protein adulterants and characterize this understudied potential risk. A rapid turbidimetric method was developed to screen milk powder for adulteration with insoluble plant proteins. Milk powder samples spiked with 0.03–3% by weight of soy, pea, rice, and wheat protein isolates were extracted in 96-well plates, and resuspended pellet solution absorbance was measured. Limits of detection ranged from 100 to 200 μg, or 0.1–0.2% of the sample weight, and adulterant pellets were visually apparent even at ∼0.1%. Extraction recoveries ranged from 25 to 100%. Assay sensitivity and simplicity indicate that it would be ideally suitable to rapidly screen milk samples in resource poor environments where adulteration with plant protein is suspected

Accelerating Bacterial Identification by Infrared Spectroscopy by Employing Microarray Deposition of Microorganisms

ABSTRACT A microarray method for the deposition of bacteria onto an agar slide was developed to accelerate the formation of microcolonies. Representative microarrays each consisting of 40 micro-spots of five replicates of eight foodborne bacteria (Yersinia enterocolitica, Staphylococcus aureus, Salmonella typhimurium, Listeria monocytogenes, Enterobacter cloacae, Citrobacter freundii, Klebsiella pneumoniae, and Escherichia coli) were printed on a Brain Heart Infusion (BHI) agar slide using a contact micro-spotting robotic system. Within 3 h, sufficient bacterial cells were obtained to allow accurate identification of the microorganism by infrared spectroscopy. This approach allows a "complete-in-a-single-day" analysis of a large array of samples. 17