Yogurt Fortified with Date Fiber

Abstract

Yogurt is an important dairy product, particularly for consumers with lactose intolerance. Yogurt is considered a healthy food because it contains viable bacteria that are considered probiotics. Milk and dairy products do not contain fiber. Fiber is found in the cell wall of fruits, vegetables, and cereals [1, 2]. Fiber of different sources is added to products to increase cooking yield and water-holding capacity, reduce lipid retention, improve textural properties and structure, or reduce caloric content by acting as a bulking agent [3]. Consumption of foods containing fiber may prevent or decrease gastrointestinal disorders [4], hypertension, hypercholesterolemia, obesity [5], diabetes [6–8], coronary heart disease [9, 10], and cancer [11, 12]. Several researchers have studied the effect of dietary fiber on yogurt quality. Addition of 1.32 % oat fiber improved the body and texture of unsweetened yogurt and decreased the overall flavor quality [13]. The effect of wheat bran (natural and toasted) and flavor (pineapple and pia colada) on yogurt quality were studied [14]. The pH increased and syneresis decreased with increasing fiber (1.5, 3.0, and 4.5 % by weight). Natural bran had a greater effect on consistency than did toasted bran, and yogurt flavored with pia colada had higher viscosity than yogurt flavored with pineapple [14]. The effects of commercial fibers from apple, wheat, bamboo, or inulin on sensory and rheological properties of yogurt were studied [15]. Although some rheological characteristics were modified, the supplemented yogurts were acceptable to consumers. Yogurt fortified with apple fiber had a different color compared with unfortified yogurt. The reported findings showed that yogurt containing 1 % orange fiber had a lighter, more red and more yellow color [lower lightness (L*), higher redness (a*) and yellowness (b*) values] in addition to having lower syneresis than control and yogurt containing 0.6 and 0.8 % orange fiber [16]. Fermented milk enriched with citrus fiber (orange and lemon) had good acceptability [17]. Addition of 0.5 % barley β-glucan or inulin and guar gum (>2 %) were effective in improving serum retention and viscoelastic properties of low-fat yogurt [18]. Incorporation of fiber obtained from asparagus shoots increased yogurt consistency and imparted a yellow-greenish color to the yogurt [19]. Dates are a good source of dietary fiber [20–22]. The dietary fiber content of dates ranges from 4.4 to 11.4 % depending on date variety and ripening stage [23–26]. A serving of dates (5–6 fruits) can provide 14 % of the recommended daily intake of dietary fiber [23]. The United Arab Emirates (UAE) is the fourth leading country worldwide for date production, producing 755,000 tons of dates annually, representing 12 % of the world’s production [27]. The dates, one of the most important fruit crops in the UAE, are processed to produce date syrup. Date fiber, a by-product remaining after date syrup extraction, contains 51.57 % total dietary fiber [28]. Incorporation of date fiber into yogurt without affecting sensory quality and acceptability was investigated. The quality of fresh yogurt fortified with date fiber (acidity, pH, color, texture profile, sensory properties, and consumer acceptance) was studied [29].