Functional Properties of Snack Bars

3.1 Snack bar production process

The simplified flowcharts of snack bar production processes are shown in Figure 2. For the baked bar products, dry and wet raw materials are mixed together. This mixture is portioned and subjected to baking.

The baking parameters (time and temperature) differ according to the specific characteristics of the finished product. For cold-formed bar production, the ingredients are also mixed together, and the resulting mixture is portioned in the desired shape without a baking step. For both types of snacks, there may also be additional operations, e.g., filling, coating with various glazes, drying bars, etc. Despite the bar type obtained, the final operation in the technological chart is packing.

3.2 Formulation and physicochemical evaluation of snack bar ingredients

The bars are often made using a base of cereals such as oats, rice, corn, or proteins (milk dairy proteins, soy, or whey) and fortified with vitamins, minerals, and other nutrient- or energy-rich ingredients [9, 10]. Snack bars are not just popular for their portability but also for the health implications associated with their consumption. Trends in health and wellness in food and beverages have increased more and more in recent years, as consumers are turning to less processed and more natural alternatives than regular products. Furthermore, nutritional snacks are suitable products that can provide energy and micronutrients to both healthy people and people from areas affected by famine of the world [10].

Cereal bars are very adaptable products made from processed cereals mixed with a variety of ingredients depending on the target population group [7]. Wheat and/or soy snack bars were designed as nutritional bars to provide the nutrients to consumers on the run [10]. Walnuts were successfully used in the manufacture of snack bars with good nutritional (significant amount of raw fibers and lipids) and sensory quality [11].

In recent years, the demand for high-protein snack bars has grown significantly by the people engaged in sports activities and dieting and as meal substitutes. These snack bars provide a healthy alternative to conventional snacks due to its high content of protein (15–35%, w/w) and other nutritionally beneficial ingredients [12]. In Table 1, different formulations for snack bars are shown.

The tendency to eat more nutritious foods instead of sweet products has led to the development of different snack bar types. Since cereal consumption extends beyond breakfast at any time of the day, these products have become an excellent vehicle for delivering ingredients to functional foods on the market. Cereals have an increasingly important role in modern lifestyle due to the convenient forms they can use such as ready-to-eat food products, snack bars, and energy bars [14].

People who are interested in getting healthier foods and maintaining good body fitness have changed their eating habits, which have promoted growth in the cereal bar market of 20% per year [18]. Therefore, snack bars can be considered as a reliable source of high-quality proteins, fibers, vitamins, and minerals. The nutritive composition of selected snack bars is presented in Table 2.

From the data presented in Table 2, the chemical composition of the snack bars varies greatly depending on their destination. The variation of snack bar composition gives the consumers the possibility to select the proper bar to purchase. Therefore, corn flake crust with fruit breakfast bar is a good source of vitamin A, thiamine, riboflavin, niacin, and vitamin B6, while formulated bar (power bar with chocolate) is a good source of protein, vitamin E (alpha-tocopherol), calcium (covers 50% of the recommended daily dose), iron, magnesium, phosphorus, zinc, and copper. Moreover, the power bar is a very good source of vitamin C (covers 154% of the recommended daily dose), thiamine (covers 537% of the recommended daily value), riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, and manganese [19].

Also, formulated bar, marathon protein performance bar and caramel nut rush, is a good source of protein (covers 50% of the recommended daily dose), calcium, iron, magnesium, zinc, copper, and manganese and a very good source of vitamin C, vitamin E (alpha-tocopherol), thiamine, riboflavin, niacin, vitamin B6, folate, vitamin B12, and pantothenic acid [19], while snack bar with soy can be considered as a good source of high-quality proteins, fibers, and B-complex vitamins [10].

Researchers reported that snack bars with a high ratio of protein/carbohydrate can improve post meal and diurnal glucose profiles in patients with type 2 diabetes and insulin resistance [20]. In addition, proteins can have a very positive effect on the human body, helping to control blood pressure, and the effect has been dependent on the type of protein [18]. Champ et al. [21] reported that the demand to increase dietary fiber content in the daily diet is justified by the positive role of fibers in health and disease prevention, especially in digestive health, energy balance, cancer, and heart and diabetes problems. According to the data presented in Table 2, some formulated snack bars contain higher amounts of minerals and vitamins. Micronutrients are necessary compounds for a proper physiological state of the body that can be administered orally in the diet, and it is necessary to maintain an adequate balance [21, 22]. Minerals must be supplied from foods because they cannot be synthesized, and given the global deficiencies in different minerals, it is worthy to offer convenient food with sufficient amounts of minerals [23].

4.1 Proteins

The importance of dietary protein, as a bioactive factor, is determined deficit terms, by decreasing of metabolic capacity, reduction of energy metabolism, inhibition of biosynthesis processes, diminution of immunity, and the body resistance to external agent’s actions. Proteins are necessary to support growth, tissue repair, and protection [24]. Usually, the protein necessary is influenced by the gender, age, activity level, body health, or physiological states [25, 26]. The conventional protein sources are plants and animals, e.g., meat, milk, whey egg, fish, soy, etc. [26]. In general, protein-based snack bars contain the following proportion of ingredients: soy or dairy proteins (20–40%), carbohydrates as sugar syrups (10–50%), and fats (10–15%) [27, 28]. Protein bars in addition to basic ingredients may contain other components such as flavors and stabilizers [29].

4.2 Fat and fatty acids

In addition to their role as a source of high calories, as a biomembrane construction material, or as a vehicle of fat-soluble vitamins, lipids are important by their intake in polyunsaturated fatty acids, phosphatide, and substances physiologically active, such as prostaglandin, prostacyclin, etc. [30]. The omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids are essential for human health and are obtained exclusively from the nutrition [31]. In recent years, emphasis has been placed on obtaining functional foods supplemented with n − 3 fatty acids. At present, there is a wide range of omega-3-enriched food products such as bakery products, dairy products, juices and soft drinks, meat products, etc. [32]. Usually, the natural sources of n-3 fatty acids are seed and fish oils [31, 33]. Snack bars with a high content of essential fatty acids are generally those that contain crop seeds and vegetable oils (canola, soybeans, corn, and sunflower oils); these are the major sources of linoleic acid (LA, C18: 2) but with a low proportion of α-linolenic acid (ALA, C18: 3) [34]. ALA sources are chia and flaxseed [34, 35]. The flaxseeds have a high antioxidant potential and omega-3 α-linolenic acid content [36, 37]. The addition of milled flaxseed in snack products, such as bars, is explained by their preventive and functional properties, such as vascular function improvement [38], anti-arrhythmic, anti-atherogenic, and anti-inflammatory functions [38, 39, 40].

4.3 Minerals

Mineral elements have a biological key role because they participate in all the vital processes of the body. Mineral substances can have different roles in vitamins and enzyme functionality, having either an activating role (calcium, magnesium, etc.) or an inhibitor (copper), and can be a part of enzyme structure as specific (sulfur, iron, copper, zinc, etc.) or unspecific (magnesium, zinc, cobalt, etc.) elements [41]. The commercial snack bars usually contain the following minerals in different intakes (Table 2): calcium, iron, magnesium, phosphorus, potassium, sodium, and zinc.

4.4 Vitamins

Vitamins are biologically active compounds of organic nature, with variable and complex structure. Vitamins are needed in very small quantities for the normal development of many metabolic processes, including assimilation and the use of nutrients brought by food, growth, and tissue restoration.

Usually, snack bars commercialized on the market are rich in vitamins such as vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B5 (pantothenic acid), vitamin B3 (niacin), vitamin B6 (pyridoxine, pyridoxal, pyridoxamine), folic acid (pteroylglutamic acid, vitamin B9), vitamin B12, vitamin C, vitamin A, and vitamin E (alpha-tocopherol).

Vitamin B1 is found in the outer layers and germ of cereals, nuts, whole grains, brewer’s yeast, etc. Vitamin B1 exhibits several functions within the body, such as essential for maintaining appetite and normal digestion and necessary for growth, fertility, and lactation [42], as well as for the normal functioning of the nervous tissue [43]. According to the nutrition data [19], the bars with the highest content in thiamine are formulated bar, power bar, chocolate (8 mg/100 g), and formulated bar, marathon types: honey nut oat bar; energy bar, all flavors; chewy chocolate peanut bar; and multigrain crunch bar (~3 mg/100 g), with high daily values for adults between 197 and 537%.

Vitamin B2 is widely found in food products. Sources rich in B2 are beer and bakery yeast, meat, eggs, fish, and dairy products. In the body, vitamin B2 fulfills certain metabolic functions, as phosphorus esters are part of the flavin enzyme structure involved in biological oxidation–reduction reactions [44]and together with pyridoxine is involved in the conversion of tryptophan to nicotinic acid.

Vitamin B5, in the form of coenzyme A, is vital in the metabolism of lipids, carbohydrates, and nitrogen compounds [44]. Sources rich in pantothenic acid that are used in snack bar composition are wheat germ, mushrooms, broccoli, cauliflower, oats, dried peas, soybean, etc.

Vitamin B6 is found in large quantities in beer and bakery yeast and raw cereals. Fruits and vegetables have a lower content of vitamin B6. Pyridoxal phosphate and pyridoxamine phosphate are coenzymes involved in transamination, decarboxylation, deamination, etc. [45].

In the body, folic acid as a coenzyme is involved in accepting and transferring one carbon, from a metabolite to another [46], interfering with the synthesis of purines and pyrimidines necessary for nucleic acid formation [47]. Folic acid is mainly found in green leaves, whole grains, soybeans, wheat germ, soybeans, oranges, avocado, etc. [47, 48].

Vitamins E performs several functions in the body such as Krebs cycle regulator, a regulator of nucleic acid metabolism with implications for cell maturation and differentiation, a regulator of porphyrin and heme biosynthesis, a regulator of protein and amino acid metabolism, etc. The main nutritional function is a biological antioxidant for oxidizable vitamins and lipids [44]. Tocopherols are found in almost all foods, the richest sources usually used for bar production being vegetable oils (corn germ oil, wheat germ oil), cereal products, and eggs.

Vitamin C is acting as biochemical antioxidant and as enzyme cosubstrate [44], interfering with numerous processes, including formation of stromal proteins (collagen, elastin), maintaining capillary integrity, etc. Sources rich in vitamin C are rosehips, white sea buckthorn, citrus fruits, tomatoes and tomato juice, cabbage, parsley, nettle, spinach, cauliflower, red and green pepper, red cabbage, eggplant, broccoli, strawberries, etc. [45, 49]. In a study conducted by Sung et al. [50], a cereal bar with welsh onion extracts was obtained, rich in vitamins C, B2, B3, and B9 and with high-protein content. The study also demonstrated the nutraceutical potential of the bars for the obesity and metabolic disorder’s control.

USDA Food Composition Databases [51] provides the selection of snack bars according to deficiency in one or more vitamins or any nutrient that must be reintroduced into the diet. As an example, a selection of the snack bar products according to the content of thiamine, riboflavin, and vitamin C is shown in Table 3.

4.5 Food fiber

In the food industry, fiber plays a significant role in preventing obesity, diabetes, and cardiovascular disease [52]. Fiber is incorporated into different foods for both nutritional benefits and functional properties, as well as low-cost and noncaloric partial replacements for fat and/or sugar flour [52, 53]. Cereals contain quantities of insoluble fiber, except for oats, whereas fruit and, in particular, citrus fruit and apples contain substantial amounts of soluble fiber. Lentils are also used in snack bar development, especially for their dietary fiber and the essential amino acid contents and for the folic acid and iron addition [54].

Lately, emphasis has been placed on the use of resistant starch (RS) in products as a potential functional ingredient. RS may increase the dietary fiber content [55] and promote the probiotic bacteria activity [56]. Aigster et al. [57] studied the addition of RS in granola and cereal bars, to determine the RS health significance and also the consumer acceptability. The study concluded the increasing of dietary fiber intake by the addition of RS.