Vol.:(0123456789) 1 3 Journal of Food Measurement and Characterization https://doi.org/10.1007/s11694-019-00324-z ORIGINAL PAPER Efect of microwave processing on physicothermal properties, antioxidant potential, in vitro protein digestibility and microstructure of durum wheat semolina Dinkar B. Kamble 1  · Rakhi Singh 1  · Barjinder Pal Kaur 1  · Savita Rani 1  · Ashutosh Upadhyay 1 Received: 5 October 2018 / Accepted: 11 November 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract The efect of microwave treatment on the physicothermal properties, antioxidant activity, protein digestibility and structural features of durum wheat semolina was investigated by varying time periods (1, 1.5 and 2 min) in a microwave oven set at 900 W. Results suggested that microwave treatment on durum wheat semolina caused a signifcant improvement in functional properties like water holding capacity (1.91 ± 0.08 to 2.63 ± 0.04 g/g), oil holding capacity (2.25 ± 0.36 to 3.05 ± 0.09 g/g), swelling power (6.08 ± 0.06 to 9.23 ± 1.15 g/100 g) and solubility (0.11 ± 0.01 to 0.13 ± 0.15 g/100 g). Overall colour dif‑ ference (∆E*) increase from 22.63 ± 0.36 (untreated) to 31.14 ± 0.27 (2 min), while signifcant decrease in gelatinization enthalpy (2.49 ± 0.08 to 1.53 ± 0.09 J/g) and peak viscosity (1501 ± 5.29 to 127 ± 3.60 cP) was seen after the treatment. Total phenolic content (free + bound) decreased from 2.61 ± 0.01 to 0.98 ± 0.03 mg GAE/g, while antioxidant activity expressed as inhibitory concentration (IC 50 ) improved (1.60 ± 0.05 to 0.79 ± 0.01 mg/ml) as microwave heating progressed. In vitro protein digestibility decreased signifcantly (71.35 ± 0.05 to 53.64 ± 0.04%) as the duration of microwave heating increased. Microstructure examination revealed small defects and rupturing of starch granules, whereas FTIR spectra of durum wheat semolina did not change by microwave heating. Keywords Microwave treatment · Antioxidant capacity · In vitro protein digestibility · Microstructure · FTIR Introduction Wheat is a major cereal crop which is consumed worldwide as a staple food. It is the third most essential crop beside maize and rice while concerning its total global productions. It is rich in carbohydrate, protein and micronutrients together with minerals and B vitamins and fulflls approximately 20% of the energy intake worldwide [1]. Basically, wheat is pro‑ cessed into intermediate products like semolina, four which further can be used to develop a wide range of food prod‑ ucts. Semolina is the main product (endosperm) of durum wheat milling and can be processed into macaroni and spa‑ ghetti types products. Storage of durum wheat semolina is problematic due to the development of the insect’s infes‑ tation which reduces the shelf life of semolina. Recently, microwave irradiation has been used to reduce insect infes‑ tation in many agricultural products such as rice [2] wheat grain and wheat four [3], mung bean [4], dates [5]. Along with insect infestation, microwave treatment also reduces the increase in free fatty acid value during storage and slows down the rancidity process which further increases the shelf life of wheat four [6]. Microwaves are the electro‑ magnetic radiations, characterized by the frequency range of 300 MHz–300 GHz which could produce the deep heat inside the processed material as a result of rapid variation in the electromagnetic feld takes place at high frequency. Compared with other conventional technology, microwave processing is better in terms of its shorter processing time, high yield as well as superior product quality [7]. For pro‑ moting the microwave processing to industrial level, a lot of research related to its infuences on the physicochemical and structural characteristics of cereals and their starches have been done [8–14]. Roman et al. [10] reported that microwave treatment can be used to alter the starch granules crystallin‑ ity, facilitating swelling as well as the formation of amyl‑ ose–lipid complexes without undergoing the gelatinization * Rakhi Singh rakhi117@gmail.com 1 National Institute of Food Technology Entrepreneurship & Management, Sonipat Kundli‑131028, India