Impact of Swell-Drying Process on Water Activity and Drying Kinetics of Moroccan Pepper (Capsicum annum)

Abstract

The impacts of total hot air drying (THD) and the swell-drying process (SD), which is hot air drying coupled with an instant controlled pressure drop DIC process, on the drying kinetics and adsorption isotherm behavior, were determined in the case of Moroccan peppers. Drying kinetics were studied through a model that takes into account the starting accessibility and the internal diffusion model with Fick's law. Adsorption experimental data were obtained by using the gravimetric method at 25, 40, and 50 C. Data were fitted to the GAB, Halsey, and Oswin models. Studied responses were: effective diffusivity (D eff ), starting accessibility (dW s ), monolayer moisture content (X m ), specific surface area (r), internal porosity (e), and microstructure. Mean relative percentage deviation (E) and root mean square (RMS) were used to evaluate the fitting of models. Results showed that: pepper adsorption isotherms followed the type II isotherm curve;the equilibrium moisture content (X eq ) depended on the temperature and the drying method; the GAB and Halsey models fitted well the experimental data; at selected conditions of the DIC treatment (0.35 MPa and 5 s), the monolayer moisture content (X m ), the specific surface area (r), and the internal porosity values were higher than those of THD samples; the DIC process intensified the drying operation, by increasing the effective diffusivity and the starting accessibility. Although the DIC process improves the drying kinetics, this behavior could be ignored related to a higher a w . This study shows that, thanks to the new expanded structure obtained by the DIC process (higher porosity), the adsorption capacities of products are improved (a w is reduced). Thus, the SD process improves both the drying operation and the stability of dried pepper products.

Hot air drying and freeze drying pre-treatments coupled to explosion puffing drying in terms of quality attributes of mango, pitaya, and papaya fruit chips

“…Meanwhile, the expanding gas should be produced from materials other than water. Researchers (Payne et al, ; Tellez‐Perez, Sobolik, Gerardo, Abdulla, & Allaf, ) thought that the moisture contents for the explosion puffing of fruits and vegetable products should be ranged between 14 g/100 g to 35 g/100 g dry matter (d.b.). In other words, the key of EPD processing is to pre‐dry fresh fruits and vegetables to reach the required moisture content and it is not viable to use the EPD processing alone to dry fresh fruits and vegetable.…”

“…Meanwhile, the expanding gas should be produced from materials other than water. Researchers (Payne et al, 1989;Tellez-Perez, Sobolik, Gerardo, Abdulla, & Allaf, 2015) thought that the moisture contents for the explosion puffing of fruits and vegetable products should be ranged between 14 g/100 g to 35 g/100 g dry matter (d.b. ).…”

Flour from 'fruits and vegetables' waste with addition of a South‐American pepper (Capsicum baccatum) proposed as food ingredient

“…The hydration limits ( X m , or ‘monolayer values’) obtained by the GAB equation for PF was in the range of those obtained for different pepper varieties (Seid & Hensel, ). As higher is the GAB constant C , greater is the water‐binding force at the monolayer (Téllez‐Pérez et al ., ). For the analysed systems, GAB constant values, k < 1 and C > 2, were obtained for all studied samples (Table ), which is also typical of type II isotherms.…”

“…The BET, GAB and GDW models employed provided adequate description of the experimental data (Table ), with determination coefficients ( R 2 ) higher than 0.99, and % E less than 10% (Téllez‐Pérez et al ., ), being the BET model limited to a w values lower than 0.5 (Furmaniak et al ., ).…”

“…The adsorption isotherms were adjusted with BET, GAB and GDW (D'Arcy ‐Watt) models, using GraphPad Prism 6 software. The coefficient of determination ( R 2 ), relative mean deviation (% E ), eqn 1 and mean square error (RMS), eqn 2, were calculated to verify the degree of fit of the studied models (Téllez‐Pérez et al ., ).…”