Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt Survival of probiotics in soyoghurt plus mulberry (c.v. Chiang Mai 60) leaf extract during refrigerated storage and their ability to tolerate gastrointestinal transit Varongsiri Kemsawasd a , Pittaya Chaikham b,* a Institute of Nutrition, Mahidol University, Nakorn Pathom Campus, Nakorn Pathom 73170, Thailand b Division of Food Science and Technology, Faculty of Science and Technology, Phranakhon Si Ayutthaya Rajabhat University, Phranakhon Si Ayutthaya 13000, Thailand ARTICLE INFO Keywords: Lactobacillus casei 01 Lactobacillus acidophilus LA5 Mulberry leaves Soyoghurt In vitro digestive system ABSTRACT This study aimed to examine the influence of mulberry leaf extract (MLE) on viability of Lactobacillus casei 01 and Lactobacillus acidophilus LA5 in soyoghurt during refrigerated storage (4 °C) for 30 days. Changes of phy- siochemical characteristics and sensory attributes of probiotic-soyoghurts supplemented with MLE were in- vestigated. The findings revealed increased antioxidative effects of probiotic-soyoghurts and minimized pro- biotic cell loss over prolonged storage upon supplementation with MLE, while increased levels of acidity and syneresis were observed. On sensory attributes, all samples showed similar scores for all sensory attributes regardless MLE or probiotic strains. However, overall likeability slightly reduced in the products after 30 days of storage. Based on the study under in vitro gastrointestinal conditions, comparing between soyoghurts with and without MLE addition, both probiotics showed no significant difference in their survivals of tolerance to gastric and bile fluids. Soyoghurt containing L. casei 01 and MLE demonstrated the greatest antioxidative properties and highest level of probiotic survivors throughout refrigerated storage. This study contributes to the future de- velopment and applications of the mulberry leaf extract as a potential ingredient in novel probiotic foods with enhanced consumer health benefits. 1. Introduction In the present day, probiotics are incorporated into a wide range of functional food products due to their impartment of beneficial effects towards human metabolism and immunological health. Some of their major roles include gut pathogen inhibition, prevention of antibiotic- associated diarrhea and diarrhea-related diseases, maintenance of bowel health, and treatment of lactose intolerance (Liong, 2007; Vasiljevic & Shah, 2008). Many species of lactobacilli, such as Lacto- bacillus casei and Lactobacillus acidophilus, predominate in the gastro- intestinal tract of healthy humans and have prominent roles in reg- ulating the digestive tract (Chaikham, Apichartsrangkoon, George, & Jirarattanarangsri, 2013a; Chaikham et al., 2013b; Finegold et al., 1977; Sanders et al., 2013). Therefore, those strains are some of the most common probiotics available in functional food industry (Shanahan, 2002). Probiotic commercially applied in dairy food pro- ducts, viz. fermented milk, ice cream, cheese and cheese-incorporated products, baby food, milk powder, sour cream and as frozen dairy- based desserts (Mohammadi & Mortazavian, 2011). L. casei 01 and L. acidophilus LA5 strains are most common probiotic strains applied in fermented dairy, milk, and functional food products, to proclaim re- lated health benefits (Saxelin, Korpela, & Mayra-Makinen, 2003; Shah, 2007). According to Shah (2007) and El-Dieb, Rabo, Badran, El-Fattah, and Elshaghabee (2010), these two strains also exhibited anti- mutagenic, antibacterial, and anticarcinogenic effects, and have been shown to reduce serum cholesterol levels and boost the immune system following consumption. Greater prevalence of lactose intolerance in various communities throughout the world has led to development of numerous probiotic soy-based food products over the recent years (Chen & Mustapha, 2012; Granato, Branco, Cruz, Faria, & Nazzaro, 2010; Gupta & Abu-Ghannam, 2012; Ng, Lye, Easa, & Liong, 2008). Soy-based foods are renowned for having good nutritional attributes due to being excellent sources of protein, amino acids, dietary fiber, vitamins, and trace minerals, alto- gether in the absence of cholesterol and lactose (Naganagouda & Mulimani, 2006; Slavin, Martini, Jacobs, & Marquart, 1999; Wang, Yu, & Chou, 2002). Donkor, Henriksson, Vasiljevic, and Shah (2005) re- ported that soy proteins stimulate growth and metabolism of L. acid- ophilus and L. casei. The metabolism of lactobacilli includes liberation of proteinases, which enable hydrolysis of long oligopeptides in soy-based https://doi.org/10.1016/j.lwt.2018.03.027 Received 27 September 2017; Received in revised form 5 March 2018; Accepted 12 March 2018 * Corresponding author. E-mail address: pittaya.chaikham@gmail.com (P. Chaikham). LWT - Food Science and Technology 93 (2018) 94–101 Available online 12 March 2018 0023-6438/ © 2018 Elsevier Ltd. All rights reserved. T