Sugar, d ‐pinitol, volatile composition, and antioxidant activity of carob powder roasted by microwave, hot air, and combined microwave/hot air

Abstract

The effects of hot air, microwave, and combined microwave/hot air roasting on physical and chemical properties of carob powder were determined. The comparison of different roasting processes was evaluated whether the combined microwave/hot air roasting could be an alternative to other roasting methods or not. The moisture content (2.86%–5.03%), water activity (0.20–0.35), and pH (4.94–5.12) values of the carob powder decreased by increasing microwave power and roasting time; whereas total phenolic content (10.13–13.74 mg/g dm), total antioxidant activity (0.69–1.53 g/mg DPPH), browning index (23.57–70.30), and UV absorbance (427.41–701.05) increased. Hunter L (41.54–55.28) and b (16.45–20.91) values of the carob powder decreased after roasting while color value a (8.88–20.91) increased. The main sugar was sucrose (317.54–347.68 mg/kg), followed by fructose (80.98–90.11 mg/kg), and glucose (45.16–62.19 mg/kg). Roasting process reduced the sugar content while increased the d‐pinitol (62.41–76.71 mg/kg) content. The main volatile was isobutyric acid (acidic/butter odor). Hot air and the combined microwave/hot air roasted samples showed similar volatile and sensorial profile. According to the results, the combined microwave/hot air roasting consumed 50% less energy than the hot air roasting and got the best sensory scores. Practical applications The effects of microwave, hot air, and the combined microwave/hot air roasting processes on the properties of carob powder were first investigated. d‐pinitol content of carob was increased by roasting processes. Different roasting processes increased organoleptic properties of carob powder. Total phenolic content and antioxidant activity of carob powder increased by roasting. The combined microwave/hot air roasting consumed 50% less energy than the hot air roasting and it is recommended to produce carob powder with preferable product quality.

Application of a neural network mathematical model in the development of hot air roasting process technology for Chironji (Buchanania lanzan) kernels

“…WA of 0.0021 ± 0.0070 was found to be minimum for the kernels roasted at a temperature of 160°C for 50 min, whereas maximum WA of 0.6235 ± 0.0017 was recorded for the raw kernels. Similar trend of reduction in WA with the increase in temperature and time was reported for carob powder (Gunel et al., 2020), and Robusta coffee beans (Herawati et al., 2019).…”

“…The maximum BI of 80.08 ± 0.18 was recorded for the kernels roasted at 160°C for 50 min. A similar trend of increase in BI with the increase in temperature and time was reported for sesame seeds (Kahyaoglu & Kaya, 2006), carob powder (Gunel et al., 2020), and date seeds brew (Fikry et al., 2019). The increase in BI after roasting maybe because of the formation of brown pigment due to the Maillard reaction (Sharanagat et al., 2019).…”

“…The maximum a * value of 11.37 ± 0.11 was measured for the kernels roasted at 160°C for 50 min, whereas the minimum was found to be 9.78 ± 0.06 for raw kernels. During the roasting process, the occurrence of nonenzymatic browning reactions may be the cause of a decrease in L *, b * values, and an increase in a * value (Gunel et al., 2020). A similar trend of decrease in L * and b * values while an increase in a * value after roasting was reported for peanuts (Shi, Sandeep, Davis, Sanders, & Dean, 2017) and carob powder (Gunel et al., 2020).…”

“…The maximum a* value of 11.37 ± 0.11 was measured for the kernels roasted at 160°C for 50 min, whereas the minimum was found to be 9.78 ± 0.06 for raw kernels. During the roasting process, the occurrence of nonenzymatic browning reactions may be the cause of a decrease in L*, b* values, and an increase in a* value (Gunel et al, 2020).…”

“…Different roasting methods like hot air roasting, microwave roasting, sand roasting, and pan‐roasting have been used for roasting of several food products (Gujral, Sharma, & Rachna, 2011; Kahyaoglu, 2008; Kaur, Singh, & Sodhi, 2005). It has been reported that for roasting of carob powder, the combined microwave‐hot air technique consumed 50% less energy than hot air technique and led to a roasted product with better sensory properties than the microwave and hot air roasted samples (Gunel, Torun, & Sahin‐Nadeem, 2020). Other novel techniques like hot air‐assisted radio frequency roasting (HA‐RF) for almonds have been reported in the literature, where the HA‐RF roasted and conventional oven‐roasted almonds had comparable overall quality (Xu, Liao, Wang, & Jiao, 2020).…”