Comparative Study between Hot Air and Infrared Drying of Parboiled Rice: Kinetics and Qualities Aspects

Abstract

The objectives of this study were to analyze the effects of drying employing three different heat sources on drying kinetics and to evaluate qualities of parboiled rice after drying. Drying temperature was varied between 60 and 100C. Power of infrared (IR) heat source was fixed at 1,000 and 1,500 W and air flow rate was fixed at 1.0 ± 0.2 m/s. The three drying strategies composed of hot air (HA), IR and combined HA + IR drying. The experimental results were simulated using various equilibrium moisture content models and the mathematical drying model for prediction of drying kinetics and evaluation of effective diffusion coefficient (Deff) followed by Fick's law of diffusion. The results revealed that Deff values of HA and IR drying were in the range of 10−12–10−11 m2/s and relatively depended on temperature. For quality evaluation, conclusions reached that head rice yield using HA + IR drying had the highest value, while yellowness and whiteness of the parboiled rice are significantly affected by drying condition (P > 0.05). Practical Applications These results suggested that combined hot air and infrared (HA + IR) drying offers a great potential for preserving Leb Nok Pattani parboiled rice. Drying kinetics and quality aspects determined that IR drying is more efficient than the other drying method. However, the color degradation in the grain kernel is an issue for quality measurement.

Infrared radiation drying of parboiled rice: Influence of temperature and grain bed depth in quality aspects

“…No variation in cooking time as a function of the drying temperature was observed (Figure 6a). Bualuang et al () reported that the cooking time and water absorption of the parboiled rice dried by IR at temperatures between 60 and 100°C did not change, mainly because it was the same gelatinization temperature between the parboiled rice samples.…”

“…Bualuang et al () studied the drying of parboiled rice with IR (1,000 to 1,500 W) and hot air with a temperature range of 60 to 100°C. These authors reported an increase in the hardness of the rice grains according to the increase of the drying temperature.…”

“…The IR drying can reduce energy consumption 4.6 times during the parboiling process (Bualuang et al, ). Moreover, compared to conventional methods, IR drying promotes whiter rice grains (Ding et al, ) and the head rice yield (HRY) varies from 60 to 70% (Likitrattanaporn & Noomhorm, ).…”

Fundamentals of Infrared Heating and Its Application in Drying of Food Materials: A Review

“…), parboiled rice (Bualuang et al . ), paddy (Das et al . ; Laohavanich and Wongpichet ), pomegranate arils (Alaei and Chayjan ), vegetables (Hebber et al .…”

“…As a result, the combination of IR radiation and other dying methods can be found more efficient and useful to get improved results. Various researchers have carried out IR drying and combined IR-convective drying for food and agriculture products such as onion (Lewicki et al 1998;Wang 2002;Sharma et al 2005), potato Abe 1998, 1999;Tan et al 2001), pineapple (Tan et al 2001), carrot (Togrul 2006;Mihoubi et al 2009;Wu et al 2014;Doymaz 2015), banana (Nimmol et al 2007;Leonard et al 2008;Swasdisevi et al 2009), apple (Nowak and Lewicki 2005; Witrowa-Rajchert and Rzaca 2009), meat products (Sheridan and Shilton 1999), cashew (Hebber and Rastogi 2001), welsh onion (Mongpraneet et al 2002), industrial tomato products (Celma et al 2009a), seedless grapes (Celma et al 2009b), wet olive husk (Celma et al 2008), citrus press cake (Senevirathne et al 2010), barley Markowski et al 2007), parboiled rice (Bualuang et al 2013), paddy (Das et al 2009;Laohavanich and Wongpichet 2009), pomegranate arils (Alaei and Chayjan 2015), vegetables (Hebber et al 2004), cabbage seeds (Zhu et al 1999), potato chips (Supmoon and Noomhorm 2013) and Murta berries (Puente-Díaz et al 2013).…”