Determination of Moisture Sorption Characteristics of Oat Flour by Static and Dynamic Techniques with and Without Thymol as an Antimicrobial Agent

Abstract

The effectiveness of thymol as an antimicrobial agent during the determination of equilibrium moisture sorption data at high-water activities (0.50-0.98) was studied at 5, 23, and 45°C in oat flour. The static gravimetric (SG) method (with and without added thymol) and the dynamic vapor sorption technique (DVS) were used. Microbial growth in samples conditioned in these environments at temperatures of 5 and 45°C was null indicating no need for the use of thymol at these temperatures. However, samples confined in environments kept at 23°C, when the SG method was used, needed addition of thymol since mold growth took place in its absence. The statistical comparison between experimental equilibrium moisture content (EMC) mean values showed that, at 45°C, EMC values obtained using the SG technique with added thymol were significantly higher than those obtained without thymol by both SG and DVS techniques. This could indicate an interaction of thymol with food components or absorption by lipids present. Therefore, caution must be exerted when using thymol as an antimicrobial agent at elevated temperatures and high equilibrium relative humidity. Moisture adsorption isotherms for oat flour were determined using a DVS technique and no isotherm crossover with temperature, as previously reported for this product using thymol as an antimicrobial agent, was exhibited. Moisture sorption data obtained in this work by DVS can be considered more accurate than those previously reported for oat flour, since no external agent was involved during isotherm determinations.

Sorption isotherms and isosteric heat estimation of purple cactus pear (Opuntia stricta) juice embedded in gelatin–maltodextrin matrix

“…For instance, León‐Martínez et al () also observed Type III behavior for components rich in sugar and carbohydrates in cactus mucilage. Starch‐rich products also have similar sigmoidal behavior to that one obtained in this study, as presented by Oyelade, Tunde‐Akintunde, Igbeka, Oke, and Raji () and Sandoval, Guilarte, Barreiro, Lucci, and Müller () for maize and oat flour, respectively; where isotherms Type II were obtained, characteristic for products with high water solubility. It is important to note that sorption behavior of spray‐dried products is a function of the wall materials used for microencapsulation (Beristain, Azuara, & Vernon‐Carter, ).…”

“…The initial moisture content of the microencapsulated juice after spray drying was 2.26 AE 0.005% (g water/100 g dry basis). Figure 1 (2008) and Sandoval, Guilarte, Barreiro, Lucci, and Müller (2011) for maize and oat flour, respectively; where isotherms Type II were obtained, characteristic for products with high water solubility. It is important to note that sorption behavior of spray-dried products is a function of the wall materials used for microencapsulation (Beristain, Azuara, & Vernon-Carter, 2002).…”

“…In contrast, the isosteric heat of microencapsulated juice was higher than reported by Goula, Karapantsios, Achilias, and Adamopoulos (2008) with enthalpy around 3-4 kJ/mol for tomato juice processed by spray drying at the same equilibrium moisture of our study. Sandoval et al (2011) reported a maximum heat of~10 kJ/mol at 6% moisture for oatmeal powder. Furthermore, a maximum isosteric heat of close to 20 kJ/mol at 15% moisture was reported on dried leaves of bitter orange; similar result was obtained in this study, but there are differences in moisture (Mohamed et al, 2005).…”

Antimicrobial effects of volatiles produced by two antagonistic Bacillus strains on the anthracnose pathogen in postharvest mangos

“…It is noteworthy that these compounds have been widely used in fields for such use as flavor additives and pharmaceuticals for human consumption. For example, 2-nonanone is naturally produced in volatiles which are released by red raspberries and strawberries (Vaughn et al, 1993) and thymol has been used in oat flour as an antimicrobial agent (Sandoval et al, 2011). As a result of the widespread use of these volatiles in the food industry, they have come to be considered a safe alternative to control mango anthracnose disease.…”

Sorption characteristics of peeled beans and shells of fermented and dry Trinitario cocoa beans (Theobroma cacao L.)

“…The following salts and the corresponding water activities at 25 °C in parenthesis were used [13]: KOH (0.082), LiCl (0.113), KCH 3 CO 2 (0.225), MgCl 2 (0.328), K 2 CO 3 (0.432), Mg(NO 3 ) 2 (0.529), CoCl 2 (0.649), NaCl (0.753), (NH 4 ) 2 SO 4 (0.810), KNO 3 (0.936) and K 2 SO 4 (0.973). Thymol was used as antifungal agent in the desiccators with ambient with relative humidity above 81% to avoid alterations by mold growth that could affect the results of the experiments [14]. The static gravimetric (SG.…”