Abstract
The change in the concentration of sodium and calcium ions in the olive flesh and in the lye during the debittering process was quantified. The average concentration of Na increased from 0.0045 to 0,395 meq Na/g of olive flesh and the concentration of Ca increased from 0.018 to 0.0252 meq Ca/g of olive flesh. The firmness of the olives decreased almost linearly from 375 gf to 235 gf during the alkali treatment. The olives also suffered a 25.9% loss in their initial content of reducing sugars. A hypothetical simplified description of the dynamic of ionic charge changes and unwinding of the pectinic structure during the debittering process of green olives has been proposed. In addition, the effective diffusion coefficients were calculated for sodium and calcium using a diffusion model for a composite flat plate and constant diffusion coefficients. The coefficients for both solutes were in the order of 10 –12 m 2 /s for the skin and 10 –10 m 2 /s for the flesh. In both cases, the diffusion coefficients of Na were larger than the diffusion coefficients of Ca.
Highlights
The diffusion of solutes in food products plays an important role in many food processes, such as drying, chemical peeling, etc., as well as in the processing of fermented green olives
The content of calcium was determined with a flame atomic absorption spectrometer (FAAS) Perkin Elmer (Uberlingen, Germany) model 2380, employing the same solutions used to quantify sodium, after the addition of 5% (v/v) of a 10% (w/v) solution of strontium chloride in each sample to avoid interference from other elements
At the beginning of the lye treatment, as the NaOH comes into contact with the skin surface, it takes some time before the lye removes the epicuticular wax and facilitates the diffusion of NaOH into the flesh
Summary
The diffusion of solutes in food products plays an important role in many food processes, such as drying, chemical peeling, etc., as well as in the processing of fermented green olives. The simultaneous and individual diffusion of citric and ascorbic acid have been studied in potato tissue, cut into spheres of various diameters for different immersion times and agitation conditions. In this work the researchers determined effective diffusion coefficients for the acids diffusing individually and used multi-component analysis to evaluate interaction coefficients for the mixture of the two acids (Lombardi and Zaritzky, 1997). The effect of sodium hydroxide on the structure of pimiento peppers during peeling was evaluated using electron microscopy. The authors remarked the importance of controlling the lye concentration and exposure time in order to avoid structural damage of the tissue (Floros et al, 1987)
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