EFFECT OF WATER ACTIVITY ON TEXTURE PROFILE PARAMETERS OF APPLE FLESH

ABSTRACT Fresh apple with a water activity of approximately 0.99 was partially dehydrated, then equilibrated to nine water activity levels down to Aw 0.01. The water desorption isotherm, for apple is given. Instrumental texture profile analysis was performed at each Aw level. As the Aw decreased, hardness increased slowly, then rapidly at Aw 0.12 then decreased again at Aw 0.01; deformation first increased sharply then steadily decreased; springiness increased to Aw 0.33 then decreased; cohesiveness increased down to Aw 0.65, held steady to Aw 0.33 then decreased; gumminess and chewiness increased down to Aw 0.12 then decreased. Fracturability was present only at the extremes (Aw 0.99 and 0.01) and was absent at all other water activity, levels. Complex changes in textural properties occur as apple is dehydrated and most of these changes occur most rapidly near the BET monolayer level of water activity.