Complementary tools to interpret the role of water as related to structure and functionality of cereal food products

BUERA, MARÍA DEL PILAR; ROLANDELLI, GUIDO; ABEL EDUARDO FARRONI; MARIO CUETO; SILVIO DAVID RODRIGUEZ

New Orleans

Simposio; 255th ACS National Meeting: Water in foods Symposium in honor of Louise Slade & Harry Levine; 2018

The objective of this work is to present how several complementary tools can be combined in order to interpret the impact of water and its interactions with solids, useful to define processing and storage conditions in order to obtain desired cereal products. Maize flours and formulations containing milled chia or quinoa seeds were prepared for producing cereal breakfast by hydrothermal/flaking treatment or by extrusion. Thermal transitions were analyzed by differential scanning calorimetry, water sorption isotherms were obtained at 25 ° C and transversal relaxation times of proton magnetization (T2), obtained by 1 H-NMR were studied after a single pulse of 90 ° or after Hahn and CPMG pulse-sequences. The distributions of relaxation times were also determined. Spectral changes of the different systems were evaluated employing FTIR and cluster analysis. Starch crystallinity was analyzed by XRD analysis. By means of the analysis of the relaxation times T2, the presence of populations of protons of different mobility was verified, which allowed to define clearly the different stages of sorption and to explain the characteristics of the product in relation to the water content. Spectral analysis employing multivariate techniques was helpful to select the IR frequencies which allowed a rapid and non-destructive discrimination between sample processing and compositional aspects. Correlations between the textural behavior, physical properties and the proposed FTIR indexes were obtained, which were useful to track changes promoted by extrusion both at molecular and macroscopic levels. Starch crystallinity loss after extrusion averaged 50 %, showing evidence of amylose-lipid complexes and XRD analysis data correlated with FTIR selected variables. The changes related to formulation or processing conditions were reflected in the microstructure of the products and in their dynamic modifications, including the kinetics of deterioration reactions, color changes or loss of functional ingredients. The complementary techniques employed provided data of motions at the molecular level that could facilitate interpreting thermal and mechanical properties, based on supramolecular interactions. These aspects depend on the presence and quantity of water and are relevant in assessing the quality of cereal products, playing a decisive role in the design of innovative products with defined characteristics.