Original article Viability of Lactobacillus acidophilus in rice bran-enriched stirred yoghurt and the physicochemical and sensory characteristics of product during refrigerated storage Saber Hasani, 1 Iraj Khodadadi 2 & Ali Heshmati 3,4 * 1 Laboratory of Food and Drug Analysis, Hamadan University of Medical Sciences and Health Services, PO Box 6517659947, Hamadan, Iran 2 Department of Biochemistry, Medicine Faculty, Hamadan University of Medical Sciences and Health Services, PO Box 6517659947, Hamadan, Iran 3 Nutrition Health Research Center, Hamadan University of Medical Sciences and Health Services, PO Box 6517659947, Hamadan, Iran 4 Department of Nutrition, Medicine Faculty, Hamadan University of Medical Sciences and Health Services, PO Box 6517659947, Hamadan, Iran (Received 14 May 2016; Accepted in revised form 17 July 2016) Summary This study was aimed at investigating the fortification of probiotic yoghurt with rice bran to increase nutritional properties of the product. The different levels of rice bran (0.3%, 0.6%, 0.9% and 1.2%) were incorporated into milk. The yoghurt samples were produced after pasteurisation, addition of starter cul- ture and 1% Lactobacillus acidophilus suspension (6 9 10 8 CFU mL À1 ) and incubation. During sample storage in refrigerator, the viability of L. acidophilus, viscosity and physicochemical and sensory proper- ties of product were investigated. Rice bran significantly increased the viability of L. acidophilus (P < 0.05). In addition, all probiotic yoghurts incorporating rice bran indicated higher viscosity and acid- ity and lower pH and syneresis compared to plain yoghurts. Furthermore, increments in rice bran incor- poration levels resulted in a reduction in consumers’ sample preferences. In general, the addition of rice bran at a suitable level could increase L. acidophilus viability and improve quality attributes of yoghurt. Keywords Lactobacillus acidophilus, microbial survival, prebiotic, probiotic, yoghurt. Introduction In recent years, there has been an increasing tendency for development of functional foods and their applica- tion in consumers’ diets (Barbosa et al., 2015). Probi- otic dairy products are one of the most important groups of functional foods containing enough count of live microorganisms and influencing host health (Batista et al., 2015; Dantas et al., 2016; Felicio et al., 2016; Pereira et al., 2016a,b). Products comprised of probiotic bacteria have therapeutic benefits such as response improvement of the immune system, reduc- tion in cholesterol, reduction in lactose intolerance, faster treatment of diarrhoea and lower risk of colon cancers (Karlton-Senaye et al., 2015). In order to have a beneficial effect of probiotics on the gut, the recom- mended count of viable cells should be 10 8 –10 10 CFU per day, which corresponds to 10 6 –10 8 CFU g À1 in the product at the time of consumption (Albadran et al., 2015). Yoghurt is one of the most important fermented dairy products commonly applied as food vehicle to deliver probiotic to the consumers (Montaseri et al., 2014). Probiotic bacteria incorporated into yoghurt grow poorly compared to common starter culture, that is Streptococcus thermophilus and Lactobacillus del- brueckii ssp. bulgaricus (Batista et al., 2015; Perina et al., 2015). The production of probiotic yoghurt has faced specific problems, because probiotic bacteria are subjected to unsuitable conditions such as pH decrease and increment in concentration of organic acids during cold storage; therefore, probiotic strains could not completely sustain their vitality in the final yoghurt product or may even alter taste of yoghurt (Karlton- Senaye et al., 2015). To date, an increase in the development of symbi- otic products (combination of probiotics and prebi- otics) has been observed due to the prebiotic impact on the viability increase in probiotics in food and gut (Tripathi & Giri, 2014). Prebiotics are naturally nondi- gestible food compounds found in plant sources that selectively stimulate the growth and multiplication of the probiotic microorganism (Al-Sheraji et al., 2013; *Correspondent: Fax: +98 81 38381822; e-mail: a.heshmati@umsha. ac.ir International Journal of Food Science and Technology 2016, 51, 2485–2492 doi:10.1111/ijfs.13230 © 2016 Institute of Food Science and Technology 2485