Determinação de resíduos de lactose em manteiga clarificada

Abstract

Two novel lactose analysis in butter methods were proposed, developed and tested in this study. The first one of them using paper spray ionization mass spectrometry and the second one using gas chromatography coupled with a mass spectrometer detector. This study’s goal was to evaluate the clarification process efficiency on removing lactose from butter, and also discover if the final product would be suitable for consumption by lactose intolerants. Paper spray was used as a screening method on the identification of lactose presence before and after the clarification process. Analysis were conducted without the need of previous sample preparation steps, applying the butter directly to the chromatographic paper and using methanol as solvent. By evaluating the mass spectra obtained from the butter samples and lactose standard analysis, lactose’s sodium and potassium adducts, m/z 365 and m/z 381, respectively, were identified. A significant decrease on this ions signals were shown after the clarification process, evidencing a lactose removal. Lactose quantification was performed by gas chromatography-mass spectrometry. Samples were prepared by extracting lactose from butter using water and Carrez solutions, followed by vacuum drying. The residue was resuspended in pyridine and then derivatized with a trimethylsilyl imidazole and trimethylchlorosilane mixture. The silliated lactose was then extracted with heptane and the organic solution was injected into the gas chromatograph. Lactose content of regular butter, clarified butter and commercial lactose-free butter were measured using a matrix-matched calibration curve. Lactose content ranged from 486 to 111 mg/100 g of regular butter, whereas it was approximately 4 mg/100 g of commercial lactose-free butter, and ranged from 8 to 21 mg/100 g of clarified butter. A nearly 95% lactose content decrease was observed on butter undergone clarification. Local legislation states that food with less than 100 mg of lactose on 100 g or mL of product can be labelled as “lactose-free”, which means clarified butter can be classified as a lactose-free product. Therefore, the homemade butter clarification process can remove lactose from butter satisfactorily, and consequently the clarified butter can be consumed as a lactose-free product.