Durum wheat (Triticum turgidum) is used for the production of various ready-to-eat products such as breakfast cereals, puffed grains, and extruded products. Technological processes of grain processing and the addition of different ingredients cause changes in the physical and chemical properties of the product, which give puffed grains a unique porous structure and change their nutritional value. This study aimed to evaluate the effect of coating on the physico-chemical characteristics of puffed wheat grains depending on the coating material. The study revealed that the application of coating increased dry matter and thousand-kernel weight (TKW). Water activity decreased in puffed grain without coating (BZ), and puffed grain with whey powder (MC) compared to wheat grain. The reduction in the moisture content increased the crispiness of product. Application of coating led to a decrease in the hardness of both MC and puffed wheat grain with vanillin and sugar (BV). Applying additives to the product’s surface led to a decrease in the water absorption index (WAI). The water solubility index (WSI) increased in the MC and BV samples. Samples BZ, BV and MC had higher L* (lightness) values than wheat grains because the puffing process expanded the cells, confirmed by scanning electron microscopy, and caused starch gelatinisation. The a* (redness) value of wheat was greater than that of BZ, BV and MC, which may be due to the partial removal of the outer layer of wheat grains. The milled samples of BZ, BV and MC were slightly darker, having lower L* values, compared to unprocessed wheat grain.

Puffed grains made from whole wheat, corn or rice grains are ready-to-eat breakfast cereals that do not require additional preparation. Two recipes for puffed grain coatings were developed in the previous studies. Sunflower oil was used in the coating, which may affect storage stability. Due to lipid hydrolysis, free fatty acids may be released, causing rancid off-flavour. The aim of this study was to determine the changes in the acid value of lipids and sensory attributes of sweet-coated puffed wheat grains ‘Badyrak vanilla’ (BV) and ‘Badyrak with whey’ (MC) depending on temperature during their eight-month storage. The products were packaged in metallised polypropylene pouches, 30 g each. The acid value was studied monthly at different storage temperatures (20 ± 2 °С and 4 ± 2 °С). In puffed wheat grain products, 65% of fatty acids are polyunsaturated, 25% monounsaturated, and 10% saturated. The high proportion of unsaturated fatty acids over saturated makes oil more susceptible to oxidation. Literature studies and sensory evaluation of puffed wheat grains allowed setting a limiting acid value at 4.0 mg KOH gE−1 lipids. The increase in acid value was storage temperature dependent. Thus, the acid value exceeded the established limit in the fifth month for MC and the sixth month for BV when stored at 20 ± 2 °С. At the same time, noticeable changes in puffed wheat grain flavour were observed. The temperature coefficient (Q10) for MC was 2.0, whereas for BV it was 1.5, indicating that the acid value increase in MC was more affected by temperature than that in BV.