Influences of Superheated Steam Roasting and Water Activity Control as Oxidation Mitigation Methods on Physicochemical Properties, Lipid Oxidation, and Free Fatty Acids Compositions of Roasted Rice

Abstract

The feasibility of using superheated steam roasting and wetting to control the water activity in an optimal range to mitigate oxidation of roasted rice was evaluated. Changes in the bed temperature as well as rice kernel moisture content, water activity, and color were monitored during fluidized bed roasting with superheated steam and hot air at 170, 190, and 210 °C. Air-roasted rice was rewetted to raise its water activity to 0.30 to 0.35. All the samples were analyzed for the total oil content, peroxide value (PV), thiobarbituric acid (TBA) value, and free fatty acids (FFA) content and compositions. Higher roasting temperatures, especially at 210 °C, led to a significant increase (P ≤ 0.05) in the total oil content of the roasted rice. Wetting led to a significant (P ≤ 0.05) decrease in the TBA value of the air-roasted rice, although the total FFA content significantly (P ≤ 0.05) increased. Rice roasted in superheated steam at 210 °C exhibited significantly (P ≤ 0.05) lower PV and TBA value; their total FFA content also tended to decrease, which is desirable for a longer shelf life.

Improvement in Physicochemical, Microbial, and Sensory Properties of Common Squid (Todarodes pacificus Steenstrup) by Superheated Steam Roasting in Combination with Smoking Treatment

“…is was in accordance with a study on rainbow trout which showed lower TBARS values in essential oil-treated rainbow trout compared with the control group [37]. Lower TBARS values in rice samples roasted by superheated steam than the hot air were reported by Yodkaew et al [40]. Another experiment that compared superheated steam treatment and conventional pan-frying treatment on pork bundle conducted by Huang et al [41] showed suppressed content of peroxide values (POV), TBARS, and volatile compounds.…”

Roasting Kinetics and Chemical Composition Changes of Robusta Coffee Beans During Hot Air and Superheated Steam Roasting

“…For more information on the fluidized bed roasting system set‐up, the reader is referred to Yodkaew et al. ().…”

“…Because of the limitations of hot air as the roasting medium, superheated steam has been proposed as an alternative roasting medium and has been applied to a variety of products, including cocoa beans, peanut, and rice (Idrus & Yang, ; Yodkaew, Chindapan, & Devahastin, ; Zzaman & Yang, ). In the case of coffee beans, superheated steam roasting at appropriate conditions has shown to help increase the extraction efficiency, decrease the losses of dry solids and desirable aroma compounds as well as remove the naturally occurring undesirable flavor (that is, cereal and musty flavor) of Robusta beans (Maki & Haruyama, ).…”

“…This is probably because of the higher heating rate during superheated steam roasting in comparison with that during conventional hot air roasting. This leads in turn to the shorter required roasting time, and hence lower losses of those heat sensitive compounds (Idrus & Yang, ; Yodkaew et al., ; Zzaman & Yang, ). Because of the lack of oxygen, superheated steam roasting has also noted to help decrease the content of unsaturated aldehydes, which are formed by lipid oxidation, that contribute to the undesirable woody, cardboard‐like flavor of Robusta beans (Maki & Haruyama, ).…”

Dietary oxidised lipids, health consequences and novel food technologies that thwart food lipid oxidation: an update

“…Germination, another food processing technique of whole grains, increases healthy functional components, but, results in an unsavoury flavour profile. Further, another study showed that when water activity is not controlled during superheated steaming, a technique that can be utilised to roast rice, there is a significant increase in peroxide value and TBA of rice (Yodkaew et al, 2017). Fortification of cereal products can also reduce their antioxidant components.…”