Development of an improved extraction and HPLC method for the measurement of ascorbic acid in cows' milk from processing plants and retail outlets

• Published in: International journal of food science & technology Vol. 49; no. 3; pp. 679 - 688
• Main Authors: Chotyakul, Nattaporn, Pateiro-Moure, Miriam, Martínez-Carballo, Elena, Saraiva, Jorge Alexandre, Torres, José Antonio, Pérez-Lamela, Concepción
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01-03-2014; Wiley Subscription Services, Inc
• Subjects: Ascorbic acid; Chromatography; cow milk; Food science; HPLC-DAD; Milk; vitamin analysis
• ISSN: 0950-5423; 1365-2621
• DOI: 10.1111/ijfs.12350

Summary
An improved extraction (2.5% HPO3, 5 mm dithiothreitol) and HPLC quantification methodology using a C–18 column at 35 °C and 0.1 m acetic acid (98%) and acetonitrile (2%) mobile phase was developed to quantify total ascorbic acid (AA) in commercial whole/semi‐skim/skim raw/pasteurised/UHT milk packaged in opaque bags, transparent plastic, cardboard and Tetra Brik™. AA content ranged from 0.21 to 10 and from 3.4 to 16 mg L−1 in milk from retail outlets and processing plants, respectively, and was higher in organic milk. For same processor/lot samples, pasteurised milk showed higher AA content than UHT milk. This was not true for retail outlets samples. AA content was similar for whole/semi‐skim and semi‐skim/skim milk, but not for whole/skim comparisons. Among UHT samples, the AA content trend was whole<semi‐skim<skim and lower for UHT milk in opaque plastic and Tetra Brik™ container. After 14 days at 4 °C in the dark, AA losses ranged 35–83% depending on milk type and preservation method with a higher AA retention in unopened containers.