Upgrading the quality of Africa's rice: a novel artisanal parboiling technology for rice processors in sub‐Saharan Africa

Abstract

In order to increase the quality of locally produced rice, the artisanal parboiling process in West and Central Africa was reconceptualized. A novel parboiling unit was constructed using stainless steel (Inox 304) and fitted directly on an improved stove made from fired bricks. The heat profile at different locations in the unit, the physicochemical properties, cooking properties of the parboiled rice, and the fuel efficiency of the stove were evaluated and compared with that of the traditional system. The heat flow in the new unit was from the top to the bottom while the reverse occurred in the traditional unit. The percent impurities and heat‐damaged grains, swelling and water uptake ratios, amylose content, stickiness, and cohesiveness were lower for rice produced using the improved technology (IT) compared to the traditional technology (TT). Whole grains (%), lightness (L*), yellowness (b*), cooking time, viscosity were higher for rice produced using the IT compared to the TT. Most of physicochemical and cooking properties of rice produced using the IT were not different from that of premium quality imported rice and this was achieved when steaming time was between 20–25 min. The improved stove recorded a lower time to boil water and specific fuel consumption and a higher burning rate and firepower at the hot‐start high‐power phase compared to the traditional stove. Most end users rated the IT as easy and safe to use compared to the TT. The new technology was code‐named “Grain quality enhancer, Energy‐efficient and durable Material (GEM) parboiling technology.”

Physicochemical and nutritional properties of rice as affected by parboiling steaming time at atmospheric pressure and variety

“…() reported on changes in thiamine and riboflavin content in parboiled rice. However, the maximum steaming time used for that study was 12 min which was lower than what is used by rice processors in the region (Ndindeng et al., ). As it has been demonstrated that, during parboiling, the water‐soluble nutrients diffuse from the husk and outer layer of the rice grain into the endosperm with some authors proposing parboiling as a method of rice fortification (Fukai, Godwin, Rerkasem, & Huang, ; Rerkasem, Cakmak, & Huang, ), it is important to demonstrate how increasing steaming time affects physicochemical and nutritional properties of different rice varieties.…”

“…Several rice varieties have been developed for different rice production systems. In addition, good practices (agronomic and postharvest) including mechanization options are also being developed or adapted to increase the quantity and quality of locally produced rice (Amponsah, Addo, Dzisi, Moreira, & Ndindeng, ; Ndindeng et al., ; Saito et al., ). It is worth noting that most technologies have not reached most end‐users to produce the desired impact.…”

“…Due to parboiling, the physical, chemical, textural, pasting, cooking, and nutritional properties of the milled rice are bound to change. Physical changes include increased head rice yield (Buggenhout et al., ), grain translucency, and decreased chalkiness due to starch pregelatinization (Bhattacharya, , ; Delcour & Hoseney, ; Lamberts, Gormand, Deryck, & Delcour, ; Patindol, Newton, & Wang, ), increased grain hardness, and reduced grain breakage due to swelling of the starchy endosperm during gelatinization, which heals the pre‐existing defects (Ndindeng et al., ; Newton, Wang, & Mauromoustakos, ). Chemical changes include lower glycemic index, high‐resistant starch content, and high contents of B vitamins (Jenkins, Wolever, & Jenkins, ; Manful, Grimm, Gayin, & Coker, ; Newton et al., ; Odenigbo, Ndindeng, Nwankpa, Woin, & Ngadi, ; Zohoun et al., ).…”

“…In addition, parboiling leads to development of some unique aromatic and textural characteristics that are appealing to certain groups of consumers (Demont et al., ; Heinemann, Behrens, & Lanfer‐Marquez, ; Prom‐U‐Thai, Rerkasem, Cakmak, & Huang, ). Some authors have reported on the optimization of soaking temperature and steaming conditions for parboiling, but the response variables were mostly related to the physical and textural properties of the rice (Graham‐Acquaah et al., ; Himmelsbach, Manful, & Coker, ; Ndindeng et al., ). Little information exists on the effect of varying parboiling steaming time under atmospheric pressure on the physicochemical and nutritional properties of milled parboiled rice although this information may be critical in understanding the steaming time that is rewarding for desired physicochemical and nutritional properties.…”

Pourquoi le riz étuvé local est-il peu disponible sur les marchés urbains du Bénin ?

“…Cette qualité « inférieure » du riz blanc local, due aux pratiques post-récolte peu appropriées utilisées par les riziculteurs et les transformateurs, peut être améliorée grâce à l'étuvage. En effet, l'étuvage, qui consiste à ré-humidifier, chauffer et sécher le paddy avant le décorticage, permet d'obtenir un riz de qualité physique, organoleptique et nutritionnelle supérieure à celle du riz blanc (Houssou et al, 2016 ;Ndindeng et al, 2015).…”