1. Introduction
Obesity is an important health problem in Mexico and worldwide. Among current dietary trends, consumption of food products with reduced content of digestible carbohydrates has gained in popularity. Dietary fiber (DF) is a food ingredient that is neither digestible nor absorbed in the small intestine of the human. The development of new products with substantial DF contents is a strategic area for the food industry. Consumers are demanding foods that show two main properties: the first one refers to the traditional nutritional aspects of the food, whereas, as a second feature, additional health benefits are expected from its regular ingestion. Foods complying with these requisites are often called functional or nutraceutical foods.
In a rapidly changing world, with altered food habits and stressful life styles, it is more and more recognized that a healthy digestive system is essential for the overall quality of life [
1]. DF plays an important role in decreasing the risks of many disorders such as intestinal constipation, diabetes, cardiovascular diseases, diverticulosis and obesity [
2]. Also, DF may reduce insulin secretion by slowing the rate of nutrient absorption following a meal, a property that is particularly associated to the soluble fraction of fiber. Experimentally, insulin sensitivity tends to increase and body weight decreases on high-fiber diets [
3].
Most fractions (cellulose, lignin, hemicellulose, pectins, gums and mucilages) of DF are the major constituents of plant cell walls [
4]. Although some authors recommend dropping the terms “soluble” and “insoluble” fiber, the physiological effects of this indigestible component of foods is being increasingly recognized [
5].
Among good sources of fiber cereal grains, legumes, fruits (tropical), vegetables, nuts and seeds are of importance. These sources include citrus, as it exhibits 25–70% fiber content [
6]. Approximately 50% of the orange fruit is juice, while the other 50% is the rind, albedo, sacs and seeds, which contain varying amount of fiber [
7]. The fruits and their by-products can be dried for preservation and further use, which enables the exploit of features of interest,
i.e., low in fat and digestible carbohydrates, high in fiber and low calorie content [
8]. Thus, one important source of citrus dietary fiber is the residue from the orange juice industry. Fiber from citrus can be obtained from edible parts [
9,
10] and attracts, binds, and manages high levels of water (up to 12 times its weight) in baked goods, meat and poultry products, and sauces. Additionally, citrus peel is a rich source of fiber and antioxidant, but the high levels of astringent compounds make it unsuitable for human consumption [
11]; however, there is a commercial product, CitraFiber
™ by Natural Citrus Products (LaBelle, FL) that is used in bakery products.
Fibers traditionally used for food processing are derived from cereals. Diverse studies have been conducted to obtain and assess the composition of dietary fiber-rich products obtained from by-products of diverse vegetable sources such as passion fruit, apples, pears, oranges, peaches, artichokes, asparagus, lemon, black currant, pear, cherry and carrot [
12–
14].
Starch is the major digestible carbohydrate in human diet [
15], representing most of the “available” or “glycemic” carbohydrates, defined as those digested by human digestive enzymes in the gastrointestinal tract and absorbed into the bloodstream as glucose [
16]. However, carbohydrates that restrict access of digestive enzymes to the starch substrate, such as certain dietary fiber types, produce a slow release of glucose from the food matrix, prolonging the digestion process [
17].
The rate at which starch and other carbohydrates are digested and absorbed in the small intestine, has received great interest because of its association with the glycemic response and postprandial metabolism. Most baked goods contain free sugars and gelatinized starch, which have a readily dispersible in the food matrix. Starch digestibility can be affected
in vitro and
in vivo by the macro-food properties (e.g., plant tissues containing intracellular starch granules and the starch-gluten matrix in white bread), the presence of other dietary compounds as fiber and lipids, as well as anti-nutrients (protein inhibitors of α-amylase; polyphenols). Also the structure and physicochemical properties of native (raw) starch granules (granule size, amylose-amylopectin ratio and type of crystallinity) may influence the kinetics and extent of the polymer digestion [
18].
It has been observed that co-ingestion of starch and soluble fibers results in slowered gastric emptying, which may also contribute to reduced postprandial blood glucose and insulin levels and thus influence satiety [
19].
Since and increased intake of DF is generally believed to be an effective way for prevention of chronic diseases, this ingredient is used in a variety of foods such as bars, cookies, soups, beverages, confectionery, snacks, in which has. Over the years, various fibers sources have fallen into and out of acceptance by the food industry and consumers alike. However, the use of fiber foods has continued to grow and expand, with ever-incrementing numbers of available applications [
6].
In view of the nutritional and technological relevance of dietary fiber, and the considerable volume of sweet orange bagasse disposal by the juice industry, the objective of this study was to obtain and characterize a dietary fiber-rich product from orange bagasse. The product was used to elaborate composite muffins whose chemical composition, starch digestibility, predicted glycemic index and sensory characteristics were assessed.