4-HYDROXY-2,5-DIMETHYL-3(2H)-FURANONE FORMATION IN BUFFERS AND MODEL SOLUTIONS OF CITRUS JUICE

4-Hydroxy-2,5-dimethyl-3(2H)-furanone (DMHF, furaneol) is formed in st ored citrus juice and has been reported to reduce juice quality. The s ource and pathways by which DMHF is formed in citrus products have not been delineated. In model orange juice solutions, DMHF was formed onl y when rhamnose (6-deoxyhexose) was present. Arginine was the major am ino acid to react with rhamnose via the Maillard reaction. In buffer s olutions, the formation of DMHF was affected by pH, temperature, and t ime of storage. Under acidic conditions, DMHF is formed only from argi nine and rhamnose, whereas at pH 6-8, DMHF was also formed (as verifie d by GC-RIS) from glucose and fructose, albeit in smaller amounts. The formation of DMHF from hexoses required a reducing step, which was ap parently contributed by Maillard-producing reductones. It is concluded that the accumulation of DMHF to above taste-threshold levels, which occurs under the acidic conditions of citrus juices, is related, at le ast in part, to the reportedly small. amounts of rhamnose interacting with arginine via the Maillard reaction.