Development of a tomato–Onion culinary ingredient through infrared-assisted refractance window drying

Herein, a culinary ingredient based on a tomato–onion blend was developed and the effects of drying technologies—refractance window (RW) and RW infrared-assisted (RW+IR) drying—were compared. Their impacts on the drying rate; moisture content; water activity; colour; hygroscopicity; antioxidant activity; total phenolic content, quercetin and lycopene content; and sensory profile of two tomato–onion blends (M1: 50–50 and M2: 70–30 w/w) were assessed. Such parameters of fresh samples were compared to that of freeze-dried (FD) products. Overall, RW, RW+IR, and FD did not significantly affect most variables; however, RW+IR showed the fastest drying time, showing reduced drying time by up to 22 % compared to that of RW. Additionally, RW and RW+IR preserved the quercetin content but increased lycopene concentration by ∼60 % compared with fresh mixtures. The antioxidant activity of the dried samples evaluated by DPPH assay did not differ significantly across drying treatments. The retention of bioactive compounds was affected by the mixtures. The 50–50 blend presented higher levels of quercetin, while the 70–30 blend had a greater lycopene content. Furthermore, the 50–50 blend exhibited the maximum antioxidant activity in the ORAC assay. Thus, it was preferred for sensory evaluation as it did not show any significant differences in sensory attributes compared with the fresh 70–30 blend. These findings suggest that RW+IR can serve as a rapid and efficient drying method by improving bioactive compound retention and sensory quality in tomato and onion condiments. The 50–50 blend is a potential dried culinary ingredient.