Seasonal variations of the acids in birch sap

摘要: Abstract The alterations of acids in birch sap (Betula pendula Roth. and B. pubescens Ehrh.) used for syrup production Finland were observed the flow seasons 1983 1984. pH decreased from over 7·5 to 5·5 during spring. Malic acid increased 100 600 mg litre−1 dropped quickly after bud opening. level phosphoric was about one-tenth that malic showed an analogous trend. concentration succinic progressively 10 300 citric 5 20 litre−1. No differences between contents two species. sugar-acid ratio rapidly first week remained nearly constant (between 25) main period.