The influence of extruded flour on water content and retrogradation process in muffins during storage: NMR relaxation st

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The influence of extruded flour on water content and retrogradation process in muffins during storage: NMR relaxation study Andrey Sergeev1 • Srinivas Mettu2,3



Victoria Zaborova4,5

Revised: 22 October 2020 / Accepted: 18 November 2020 Ó Association of Food Scientists & Technologists (India) 2020

Abstract A comparative study of the moisture content, mobility of water protons and retrogradation process in muffin samples with the addition of extruded (ME) flour (10%) during storage (14 days) was carried out and compared to control samples without the addition (MO). A significant increase in water content during swelling of the extruded flour was found. The proton magnetic relaxation signal for both ME and MO showed a two-component character for the fast-decay region (free induction decay, FID experiment) and a three-component character for the slow-decay (CPMG experiment) one. The relaxation times T2 characterizing the protons of both water and nonaqueous fraction decreased during the experiment except for the protons of the fat fraction. The values of relaxation times T2 for ME exceeded the values for MO, which reflects the increased water content in ME. The amplitude & Srinivas Mettu [email protected] Andrey Sergeev [email protected] 1

Semenov Institute of Chemical Physics RAS, Kosygin street 4, Moscow, Russia 119991

2

School of Chemistry, The University of Melbourne, Parkville, VIC 3010, Australia

3

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia

4

Department of Sports Medicine and Medical Rehabilitation, Institute of Clinical Medicine, Sechenov First Moscow State Medical University (Sechenov University), Trubetskaya Street, Moscow, Russia 119991

5

Sports Adaptology Laboratory, Moscow Institute of Physics and Technology (National Research University), Institutskiy pereulok 9, Dolgoprudniy, Moscow Region, Russia 141700

of the signal of water protons (two components of CPMG) decreased for ME more slowly (by about 3–5 days), which can serve as a characterization the shelf life of the muffins. Estimation of the retrogradation rate according to the Avrami model showed a lower value of the rate for ME compared to MO, which may reflect the increased moisture content in ME. Keywords Proton mobility  shelf life of extruded flour  NMR relaxation

Introduction Extruded wheat flour is obtained by intensive action of high temperature, pressure, and shear stress on wheat grain, which leads to various changes of wheat components is widely used in the production of bread and bakery products. When storing bakery products, including cupcakes and muffins, numerous physical and chemical processes occur. As pointed out by several bread staling models (Zobel and Kulp 1996) the starch recrystallization (retrogradation), water loss and redistribution and storage conditions are the most important aspects that characterize the staling. The transition of up to 30% of starch polysaccharides in bread from an amorphous to a crystalline state du