LACTULOSE

Lactulose (4-O-p-D-gaIactopyranosyl-D-fmctose) (Figure 3.5B) is a non- digestible and synthetic prebiotic disaccharide with wide applications in food and pharmaceutical industries mainly as a multi-functional prebiotic food ingredient for the treatment of chronic constipation and hepatic encephalopathy (Nooshkam and Madadlou, 2016a; Schuster-Wolff-Biilmng, Fischer, and Hinrichs, 2010). The sugar has a low caloric value (2.0 kcal g-1), the empirical fonnula of С H О , the molecular weight of 342.3 g L'1, the melting point of 168.5-170°C and 0.6-0.8 sweetness than that of sucrose disaccharide (Schumann, 2002). Unlike other prebiotics, lactulose is not observed in nature, but it is synthesized from lactose during thermal processing of milk (due to the Maillard reaction) and can be detected in very small amounts in heat-processed dairy products (Olano and Corzo, 2009). Lactulose is synthesized from lactose through chemical and enzymatic techniques and the former leads to higher lactulose yields and is used for lactulose synthesis at industrial levels by the Lobry de Bruyn-Alberda van Ekenstein (LA) rearrangement under alkaline conditions (Nooshkam and Madadlou, 2016b).

In the phannaceutical sector, lactulose is used to reduce the risk of colon cancer, stimulate the absoiption of mineral salts, lower the amounts of blood ammonia and serum lipids, prevent the tumor growth, the formation of endotoxin and gallstone and the growth of pathogenic bacteria, and is also used as an anti-diabetic sugar (lowering the blood glucose level) (Schumann, 2002; Schuster-Wolff-Buhring et al., 2010; Panesar and Kumari, 2011). In the food industry, it is mainly used as a bifidus factor and as a functional prebiotic ingredient for regulating the gut microbiota (Wang et al., 2013). Lactulose, in contrast to its substrates (e.g., lactose) cannot be degraded by human intestinal enzymes. It is able to pass the small intestine and reach to the colon and then fermented by probiotic bacteria, i.e., Bifidobacteria, and Lactobacilli to lower molecular weight compounds like SCFAs, thereby lowering the intestinal pH and increasing the osmotic pressure, which in turn leads to relieve chronic constipation (Schumann, 2002). This sugar can be used as an anti-diabetic drug for diabetics, as a sucrose replacer in infant milk powder, yogurts, daily desserts, confectionary products, and beverages and also as a prebiotic earner for probiotic strains in some dairy products (Panesar and Kumari, 2011).

BETA-GLUCAN

In recent years, the use of beta-glucan (p-glucan) in dairy products has increased due to its documented physiological features and health benefits, p-glucan [(1 —► 3)(1 —► 4)-p-D-glucan] (Figure 3.5C) is mainly found in barley and oat as the main functional soluble substance of cereal fibers and in vitro studies and animal experiments have proved its potentially prebiotic activity for health-promoting intestinal bacteria (Johansson, 2006; Mitsou et al., 2010). This bioactive compound is bonded to the endosperm cell walls along with other non-starch polysaccharides, which does not has a simple extraction and recovery method and three steps are generally used for extracting p-glucan from cereal grains, as shown in Figure 3.6 (Brennan and Cleary, 2005).

Food and Drug Administration (FDA) recommends the daily intake of 3.0 g p-glucan per day for achieving its beneficial health effects (Sahan et al., 2008). It has some functionality such as reducing the risk of colorectal cancer, laxative activity (relief of constipation), lowering serum cholesterol level (hypocholesterolemic activity) and bowel transit time, decreasing the insulin response and postprandial blood glucose (hypoglycemic effect), producing SCFAs and promoting the growth of gut microbiota (Brennan and Cleary, 2005). Most of these beneficial health features are mainly due to its rheological behavior, which is able to entrap free water followed by forming high viscous solutions (Ningtyas et al., 2017). p-glucan dispersions show the Newtonian region and shear-thinning behavior at low and high shear rates, respectively. In addition, it has been observed that under dynamic rheological measurements and at lower frequencies, the loss modulus (G") is greater than the storage one (G'), while an opposite trend is obtained at higher frequencies (G'> G") (Lazaridou and Biliaderis, 2007). The ability of bioactive p-glucan to form a weak gel network has led to an increase in its application in continuous low-fat

p-glucan extraction steps (Brennan and Cleary, 2005)

FIGURE 3.6 p-glucan extraction steps (Brennan and Cleary, 2005).

spreads, yogurt, and cream cheese, p-glucan has also been used to entrap free water and modify products’ texture and appearance and also as a fat substitute in many dairy-based food products, which will be briefly discussed in the applications section of dairy-based functional foods (Ningtyas et al., 2017).

MISCELLANEOUS BIOACTIVE CARBOHYDRATES

In the last decades, many researchers have focused on the extraction of biologically active carbohydrates from different plants sources including fenugreek seed (Rahnama et al., 2017), sage seed (Razavi et al., 2014), basil seed (Khazaei, Esmaiili, Djomeh, Ghasemlou, and Jouki, 2014), wild almond trees (Abbasi and Mohammadi, 2013; Mohammadi-Gouraji et al., 2017) and, etc., which have potential applications as a fat or sugar substitute, together with positive roles in modifying the textural, physicochemical, and sensoiy characteristics of different food products. In this chapter, we mainly focus on the gums extracted from basil seed and wild almond trees, which are native to Iran and currently have received lots of attention due to their potential applications in pharmaceutical and food sections (Khazaei et al., 2014; Hosseini-Parvar et al., 2015, 2016; Javidi et al., 2016; Dabestani et al., 2017). Basil seed gum has anti-diabetic activity and also it can be used as a disintegrant in tablet formulations, a suspending agent in suspensions, cryoprotectant in ice-cream, and fat replacer in dairy products such as yogurt, ice-cream, and processed/imitation cheese (Naji-Tabasi and Razavi, 2017). Persian gum (also known as Zedo, Angum, Shirazi, Jedo, Zed, and Ozdu gum) is a naturally transparent/semi-cloudy odorless polysaccharide extracted from wild almond trees having emulsifying and stabilizing effects in many food products. It has also been used in traditional medicine as a poultice for swollen joints, anti-cough, and parasite agents, an appetizer, a useful drug for toothache relief, and surprisingly as a hair conditioner and a skin glazing agent (Dabestani et al., 2017).

 
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