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.

Groundwater depletion is an important problem driven by population growth, land use and land cover (LULC) change, climate change, and other factors. Groundwater depletion generates water stress and encourages unstainable resource use. The aim of this study is to determine how population growth, LULC change, and climate change relate to groundwater depletion in the Alto Atoyac sub-basin, Oaxaca, Mexico. Twenty-five years of dry season water table data from 1984 to 2009 are analyzed to examine annual groundwater depletion. Kriging is used to interpolate the region’s groundwater levels in a geographic information system (GIS) from mapped point measurements. An analysis of remotely sensed data revealed patterns of LULC change during a 34-year (1986–2018) period, using a supervised, machine-learning classification algorithm to calculate the changes in LULC. This analysis is shown to have an 85% accuracy. A global circulation model (GFDL-CM3) and the RCP4.5 and RCP8.5 scenarios were used to estimate the effects of climate change on the region’s groundwater. Estimates of evapotranspiration (using HELP3.5 code) and runoff (USDA-SCS-CN), were calculated. Since 1984, the region’s mean annual temperature has increased 1.79 °C and urban areas have increased at a rate of 2.3 km²/year. Population growth has increased water consumption by 97.93 × 10⁶ m³/year. The volume of groundwater is shrinking at a rate of 284.34 × 10⁶ m³/year, reflecting the extreme pressure on groundwater supply in the region. This research reveals the nature of the direct impacts that climate change, changing LULCs, and population growth have in the process of groundwater depletion.