Getting The Brown Rice Mix
Tuesday, September 12th, 2017
Fermentation can reduce the negative effects of bran on final cereal products. In fulfilling gluten free requirements, fermented brown rice flor has shown great promise as a functional ingredient that can improve the quality of rice products. By Muna Ilowefah, Chiemela Chinma, Jamilah Bakar, Hasanah M. Ghazali, Kharidah Muhammad and Mohammad Makeri, Universiti Putra Malaysia
The past two decades have seen a rapid increase in consumer demand for healthy foods, which has prompted recent research to find methods for production of healthy and functional foods.
The usage of whole grain cereal instead of milled cereals is one such trend for production of healthy and functional foods, as consumption of whole grain foods has shown a reduction in the risk of several diseases, such as cardiovascular diseases, obesity, diabetes and some types of cancers.
One of the most significant components in the whole-cereal grains that play a significant part in its health properties is dietary fibre and phenolics, which are mainly concentrated in the outer layers of the cereal grain.
Production of whole grain foods is a complicated task for the food industry due to the mechanical negative effects of the bran on protein network formation and consequently on the sensory properties of the end product. Accordingly, the most common forms of cereals composition are milled products, such as white wheat flour or white rice.
Rice is a unique crop due to its colourless, soft taste, low sodium levels, easy digestible carbohydrates and hypoallergenic properties. Therefore, its flour is an attractive food material to be used for making gluten free foods.
Steamed bread is a traditional product made from white rice and is known as Apam in Malaysia. It is very popular in this part of the world and consumed at breakfast. It is formulated with white rice flour, sugar, salt, water and yeast. This kind of product is an example of gluten free foods.
Gluten free materials such as white rice flour do not have the required characteristics for production of leavened foods, since their proteins have no ability to develop a viscoelastic network such as gluten. In addition, lack of nutritional value has existed as a health problem of gluten free products specifically produced from white rice flour.
Consequently, in recent years, there has been an increasing interest in using different food materials such as, gums, hydrocolloids and starches to enable developing a similar gluten network. Moreover, whole grain flour such as millet, brown rice and sorghum were used to enrich gluten free foods. Accordingly, using whole grain cereals flour could be promising for the development of healthy and acceptable gluten free foods.
Modification of whole-cereal flour prior to its usage by using simple food processing, such as fermentation, could eliminate the negative effects of the bran. Pre-fermentation of the whole-flour might increase fibre solubility due to enzyme reactions on the cell wall structure.
The addition of pre-fermented wheat bran to wheat dough caused an increase in the bread volume of high fibre wheat bread. The addition of yeast-fermented peeled bran to wheat bread increased its volume by 10–15 percent and softened the crumb structure by 25–35 percent compared to its unfermented bran. Also, the addition of pre-fermented flour positively affected the texture, shelf life, aroma and nutritional value of gluten free foods, most probably because of metabolic activities of the microbes.
The positive effects associated with fermentation are the partial degradation of fibre and softening of bran particles. The acidification rate of the dough is also an important property to achieve appropriate crumb structure and higher bread volume, since it affects the enzyme activities.
Recently, fermentation became a trend for production of healthy foods from whole grain cereals. Industrial application of the biotechnology of fermentation for the production of gluten free baked products is a promising innovation in the health foods industry.
Fermented Brown Rice Flour
A study was recently conducted to evaluate assess the possibility of using fermented brown rice flour (FBRF) as a functional ingredient. The results show that with addition of FMRF, the peak viscosity increased significantly. However, breakdown, final viscosity and setback were significantly reduced.
The breakdown is associated with the ability of starch granules to be more resistant to being broken during heating and shearing. The results of this study indicated that the breakdown value was significantly reduced with the addition of FBRF.
This result may be explained by the fact that, with an increase in protein content, some rice proteins could protect starch granules from being broken and increase pasting viscosity, as FBRF had a higher protein content after fermentation.
In addition, the increase of peak viscosity and the decrease in breakdown values might indicate higher resistance to deformation and higher stability of the paste during baking. Moreover, the findings of the study are consistent with those of earlier research which reported that final viscosity of rice paste decreased at low pH (4.10) and, in this study, the acidity of the rice batter with FBRF was higher than that of the control (data not shown).
Another important finding was that the retrogradation phenomena could be significantly reduced in the final product, where setback—which is an indication of retrogradation phenomena—declined after addition of FBRF.
The viscoelastic properties of the white rice batter (WRB) and WRB containing 40 percent FBRF were studied using a dynamic oscillatory test.
The mechanical spectra of the WRB sample indicated that both elastic (G′) and viscos module (G′′) values were higher than that of WRB with FBRF at all the tested frequency ranges. In addition, G′ and G′′ of WRB containing FBRF, independent of the frequency, compared to the reference sample.
This suggested that the structure of WRB containing FBRF became softer and stronger than the control. It is reported that addition of acid to wheat dough reduced its extensibility and increased its resistance to extension.
The steamed white rice bread (SWRB) containing 40 percent FBRF gained higher volume (80 cubic cm) and specific volume (2.46 cubic cm/g) in comparison to the reference sample (70 cubic cm and 2.06 cubic cm/g, respectively).
The reduction in the pH during dough fermentation activates some enzymes such as α-amylase and protease. During addition of pre-fermented flour to wheat dough the acidity performs on the gluten network, which could improve extensibility and softness of the dough that helped to retain higher amount of carbon dioxide produced during fermentation, consequently increase the loaf volume.
However, high rate of acidity might increase hydrolysation of the protein network, resulting in less elastic and softer dough that lead in a reduction in the bread volume, and elevate staling rate and bread firmness, as indicated by the addition of sourdough with high acidity to wheat dough.
The moderate decrease in the pH (5–6) of the dough because of microbial fermentation positively influences its structure specifically in high fibre breads, where addition of cereal fibre causes detrimental effects on the dough and bread structure. Also, the increase in bread volume of SWRB containing FBRF could be linked with the reduction in the loss and storage moduli of its batter and the reduction in breakdown of starch granules, which make the structure of the batter softer, stronger and more stable during steaming.
The results indicated that the addition of FBRF softened the bread by recording less hardness value in comparison to the control. The SWRB containing FBRF had higher values of chewiness, cohesiveness and resilience, but a lower springiness value that indicated FBRF significantly improved the texture properties of SWRB.
The values of hardness and resilience of breads with fermented wheat germ were lower than those of the control, which means bread containing fermented germ was softer than its counterparts. The addition of pre-fermented wheat bran to wheat bread supplemented with bran improved the crumb texture properties, specifically the elasticity.
In addition, it improved the bread volume and its shelf life. It is reported that adding pre-fermented bran with yeast and lactic acid bacteria improved the carbon dioxide retention during dough proofing, and as a result increased the bread volume and the crumb softness.
Addition of fermented brown rice flour to steamed white rice bread significantly improved rheological and textural properties as well as volume of the bread as indicated in this study. Currently, investigation of the effect of fermented brown rice flour on the nutritional value of steamed white rice bread is under way.
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