title: True density and apparent density during the drying process for vegetables and fruits: a review.
abstract: This review presents the concepts involved in determining the density of foodstuffs, and summarizes the volumetric determination techniques used to calculate true density and apparent density in foodstuffs exposed to the drying process. The behavior of density with respect to moisture content (X) and drying temperature (T) is presented and explained with a basis in changes in structure, conformation, chemical composition, and second-order phase changes that occur in the processes of mass and heat transport, as reported to date in the literature. A review of the empirical and theoretical equations that represent density is presented, and their application in foodstuffs is discussed. This review also addresses cases with nonideal density behavior, including variations in ρ(s)  and ρ(w)  as a function of the inside temperature of the material, depending on drying conditions (X, T). A compilation of studies regarding the density of dehydrated foodstuffs is also presented.
authors.affiliation: Inst. Politécnico Nacional, Centro Interdisciplinario de Investigación para el Desarrollo Integral Regional, Hornos 1003, Sta. Cruz Xoxocotlán, Oaxaca, México, 71230. jrodrigr@hotmail.com
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Ramírez
authors.forename: L
authors.initials: L
authors.lastname: Méndez-Lagunas
authors.forename: A
authors.initials: A
authors.lastname: López-Ortiz
authors.forename: S Sandoval
authors.initials: SS
authors.lastname: Torres
mesh_terms: D003890:Desiccation / Q000379:methods*; D005504:Food Analysis / Q000379:methods*; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D006358:Hot Temperature; D008962:Models, Theoretical; D014675:Vegetables / Q000737:chemistry*; D014867:Water / Q000032:analysis
chemical_list: D014867:Water