Development of a device and method for the time-course estimation of low water fluxes and mean surface water activity of food products during ripening and storage

Evaluation of dehydrated marolo (Annona crassiflora) flour and carpels by freeze-drying and convective hot-air drying

“…Almost all deterioration processes that occur in food are influenced by the mobility and concentration of water (Le Page, Mirade, & Daudin, 2010), so it is necessary to control the moisture and the Aw of food to their increase shelf life. In this study, the dehydrated products had moisture levels lower than 10 g/100 g and Aw values lower than 0.60 (Table 1), which according to Troller (1980), prevents microorganisms, xerophilic molds and osmophilic yeasts from growing because they typically grow between 0.60 and 0.65 Aw.…”

Time-course estimation of evaporated water fluxes together with mean surface water activity in uncooked pressed cheeses during ripening using a purpose-built micro-bioreactor

“…Preliminary trials were performed to test the ability of the purpose-built MBRA to estimate q evap and a w,s in simple situations: first, a pure water tub 4 cm in height and 10 cm in diameter subjected to air ventilation at 11.2 C, 3.5 cm s À1 and 98% RH, for four days; and second, three tubs filled with various sodium chloride solutions in order to set a w at 0.87, 0.90 or 0.95, respectively, and subjected to air ventilation at 19 C, at either 3 or 5 cm s À1 and at an air RH ranging from 62% to 84%. The results highlighted that estimations of mean water flux q evap and a w,surf were accurate, with discrepancies less than 2% and 0.01 a w units, respectively, over the entire drying period (Le Page et al, 2010).…”

“…where k is the mass transfer coefficient (kg Pa À1 m À2 s À1 ), which was determined as a function of air velocity by psychrometry from independent experiments (Le Page et al, 2010); S ch is the cheese surface (m 2 ); P air is the partial water vapour pressure in the air (Pa) around the cheese, derived from the ripening cell air temperature and water content; and P sat(Tsurf) is the saturated water vapour pressure (Pa) at cheese surface temperature. Preliminary trials were performed to test the ability of the purpose-built MBRA to estimate q evap and a w,s in simple situations: first, a pure water tub 4 cm in height and 10 cm in diameter subjected to air ventilation at 11.2 C, 3.5 cm s À1 and 98% RH, for four days; and second, three tubs filled with various sodium chloride solutions in order to set a w at 0.87, 0.90 or 0.95, respectively, and subjected to air ventilation at 19 C, at either 3 or 5 cm s À1 and at an air RH ranging from 62% to 84%.…”

“…On the other hand, results from experimental studies conducted in small 1 m 3 in-lab ripening cells (Leclercq-Perlat, Picque, Riahi, & Corrieu, 2006;, which clearly show effects of the atmosphere around cheeses on microbial and biochemical development of the cheese, are hard to interpret as the low air velocity around the cheeses is not accurately measured. Accordingly, we decided to purpose-build a micro-bioreactor (MBRA) to study the ripening of a single cheese subjected to controlled high-humidity and low-velocity airflow, with the objective of non-destructively estimating both surface-evaporated water fluxes as low as 10 À7 kg s À1 over short periods of time, and mean cheese a w,s evolution (Le Page, Mirade, & Daudin, 2010). As listed earlier, there are many accurate methods available, but none of them are able to non-destructively track the time-course of mean a w,s in wetted food products undergoing transient water transport.…”

“…1). Complete information on the development and precise description of how the purpose-built MBRA runs can be found in Le Page et al (2010).…”