Effect of Glycerol and Gluten on Mechanical Properties and 1H NMR Mobility of Cooked Pasta

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.

Starch Retrogradation in Rice Cake: Influences of Sucrose Stearate and Glycerol

Retrogradation properties and kinetics of rice cakes with the addition of glycerol (GLY) and sucrose fatty acid ester (SE) were investigated. In hardness, both rice cakes with glycerol (RGLY) and rice cakes with sucrose fatty acid ester (RSE) showed lower initial hardening compared with the control for up to 5 days. X-ray diffraction (XRD) pattern of RSE showed a B+V-type pattern, and the relative crystallinity showed that GLY and SE lowered the initial and final crystallization of rice cake. Both GLY and SE affected the retrogradation enthalpy, glass transition temperature, and ice melting enthalpy in differential scanning calorimeter (DSC). However, ¹H NMR relaxation time (T₂) of rice cake decreased regardless of additives. From these results, the addition of glycerol and sucrose stearate inhibits the retrogradation process of rice cakes, which will solve industrial problems. Applying the Avrami equation for retrogradation kinetics of rice cake was suitable in XRD and DSC with high coefficient of determination (0.9 < R²). Meanwhile, the other retrogradation index improved the R² when the exponential rise to maximum equation was used. This suggests that there is an alternative of Avrami equation to predict the retrogradation.

Impact of enrichment with egg constituents on water status in gluten-free rice pasta - nuclear magnetic resonance and thermogravimetric approach

Effects of freeze-dried egg white, yolk and whole egg enrichment on water behaviour in fresh pasta dough, dried and cooked rice pasta with respect to control samples were studied by ¹H nuclear magnetic resonance (NMR) relaxometry and thermogravimetric analysis. Enrichments caused lower mobility of water (T₂) localised within the starch-protein matrix in fresh dough as well as dried pasta. Water compartmentalization was also downgraded in cooked products. Water fractions with different T₂ values were linked to temperature peaks at the first derivative of the thermogravimetric (DTG) curve. From the DTG curve strong interaction of water molecules with proteins of egg white was revealed. Egg proteins also influenced viscoelastic properties of dough, and enhanced the firmness and chewiness of cooked pasta. Structural changes induced by various types of enrichment were reflected in the different molecular mobility at the water-matrix interface (T₁). The enrichments also altered the colour and cooking properties.