DIN EN ISO 11816-2:2016-12

This part of ISO 11816/IDF 155 specifies a fluorimetric method for the determination of alkaline phosphatase (ALP, EC 3.1.3.1) activity in cheese. This method is applicable to soft cheeses, semi-hard and hard cheeses provided that the mould is only on the surface of the cheese and not also in the inner part (for example, blue veined cheeses). If the activity of the supernatant is higher than 7 000 mU/l, then dilute the supernatant with the cheese extraction buffer (4.6) so as to obtain a measurement not higher than 7 000 mU/l. The instrument can read activities in the supernatant up to 7 000 milliunits per litre (mU/l). The alkaline phosphatase activity of the sample is measured by a continuous fluorimetric direct kinetic assay. A non-fluorescent aromatic monophosphoric ester substrate, 2′-[2-benzothiazolyl]-6′-hydroxybenzothiazole phosphate, in the presence of any alkaline phosphatase derived from the sample, undergoes hydrolysis of its phosphate radical, producing a highly fluorescent product. Fluorimetric measurement of alkaline phosphatase (ALP) activity is measured at 38 °C over a 3 min period. This includes pre-incubation of substrate and sample, followed by multiple kinetic readings of the reaction rate. This standard supersedes DIN EN ISO 11816-2:2003-06. The standard has been technically revised and brought in line with the current rules of presentation. This document has been prepared by Subcommittee SC 5 "Milk and milk products" (secretariat: NEN, The Netherlands) of Technical Committee ISO/TC 34 "Food products" (secretariat: AFNOR, France) in collaboration with Technical Committee CEN/TC 302 "Milk and milk products - Methods of sampling and analysis", the secretariat of which is held by NEN (The Netherlands). The responsible committee is NA 057-05-13 AA "Milch und Milchprodukte - Probenahme- und Untersuchungsverfahren" ("Milk and milk products - Methods of sampling and analysis") at DIN Standards Committee Food and Agricultural Products (NAL).