The food industry also focuses on the use of by-products from food processing. Wheat bran is a valuable by-product of the wheat milling process, which is rich in dietary fiber. In addition to nutritional value, dietary fiber has a functional potential in the production of novel foods. Pre-treatment of the dietary fiber using different methods can change its functional properties. The objective of this study was to evaluate the effect of stabilization process on physico-chemical parameters and functional properties of wheat bran. Wheat bran from two wheat variety was treated using microwave and hot air heating. It was observed that wheat bran included more than 45% of total dietary fiber. Results suggested that treatment of bran using both method increased total dietary fiber content. Thermal treatment process decreased the anti-nutritional agent in bran samples. Phytic acid content diminishing of 44% and 49% was observed in microwave treated bran samples. Moreover, treatment of bran using a hot air heating improved the hydration properties (water holding, water retention and swelling capacity), while oil holding capacity was not significantly altered. Treatment decreased the antioxidant activity of treated bran samples. It was observed that thermal treatment modified the color parameters of bran (lightness, yellowness and hue angle decreased and redness and Chroma increased).
With growing interest in health-promoting functional foods, the demand for natural bioactive additives has increased and the exploration for new sources is ongoing. The food processing industry in most countries generates large quantities of byproducts every year, which are frequently abandoned as wastes. However, many of these byproducts are dietary, functional, and potentially novel sources of nutrition. Of the many materials obtained, dietary fibers are particularly promising ingredients that has attracted considerable interest over the past few decades. The reason for this is their significant availability in most food byproducts, low costs, and positive effects for the prevention and treatment of a diverse range of diseases (
Dietary fiber is the edible part of plants or analogous carbohydrates; it consists of polysaccharides that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Total dietary fiber (TDF) is the sum of insoluble (IDF) and soluble dietary fiber (SDF) (
There are various sources of dietary fiber. The most common source in bakery products is cereal bran, especially wheat bran (
This work evaluated the effect of different treatment process (hot air heating and microwave heating) on the physico-chemical parameters and functional properties of treated wheat bran.
Wheat bran from the variety PS Bertold (BB) and PS 215 (WB) were observed from Research and Breeding Station, Vígľaš Pstruša, Slovakia and Research Institute of Plant Production Piešťany, Slovakia. Wheat bran samples were treated using hot-air and microwave heating acording to method described by
Chemical composition of wheat bran included determination of: moisture (AACC Method 44-19.01), ash (AACC Method 08-01.01), protein (AACC Method 46-13.01) and crude fat (AACC Method 30-25.01) (
TDF, IDF and SDF content was determined by enzymatic-gravimetric method (
Phytic acid content was measured using colorimetric method according to McKie and McCleary (
Antioxidant activity of wheat bran was determined according to the method of Cai et al. (
Swelling capacity, water absorption and water retention capacity were determined according to method described by Lauková et al. (2018). Oil holding capacity was evaluated using method presented by Mora et al. (
Solvent retention capacity (SRC) tests were performed according to the method from authors Xiao et al. (
The color parameters
All determinations were carried out in triplicate unless otherwise state. The results were expressed as mean ± standard deviation. The significant differences between mean values of raw and treated bran were establish using a Student`s test at
Composition of wheat bran is purely based on the variety, cultivation conditions and the methods employed for its separation, which determines the amount of starch attached to the aleurone layer after the separation (
Chemical composition of wheat bran.
Moisture (%) | Protein (%) | Ash (%) | Fat (%) | TDF (%) | SDF (%) | IDF (%) | |
---|---|---|---|---|---|---|---|
|
|||||||
7.92 ±0.09 | 15.92 ±0.11 | 2.89 ±0.07 | 2.91 ±0.03 | 46.35 ±0.03 | 1.42 ±0.01 | 44.93 ±0.03 | |
8.37 ±0.06 | 15.46 ±0.09 | 2.90 ±0.03 | 2.39 ±0.02 | 45.99 ±0.08 | 1.37 ±0.06 | 44.62 ±0.03 | |
3.18 ±0.06 |
16.19 ±0.06 |
3.30 ±0.01 | 2.10 ±0.02 | 49.74 ±0.05 |
2.68 ±0.06 |
47.06 ±0.02 |
|
2.84 ±0.06 |
16.36 ±0.11 |
2.84 ±0.11 | 2.19 ±0.03 | 47.80 ±0.06 |
2.06 ±0.01 |
45.74 ±0.05 |
|
3.51 ±0.04 |
17.20 ±0.12 |
3.19 ±0.08 | 2.02 ±0.02 | 48.44 ±0.03 |
1.56 ±0.01 | 46.88 ±0.02 |
|
4.50 ±0.10 |
16.56 ±0.09 |
3.01 ±0.03 | 2.99 ±0.07 | 46.52 ±0.10 |
1.40 ±0.02 | 45.12 ±0.06 |
Note: IDF – insoluble dietary fiber, SDF, soluble dietary fiber, TDF total dietary fiber, * denotes statistically significant difference at
Wheat bran contains more than 15% high quality proteins, but most of them are enclosed within a matrix of cell wall polysaccharides and so they are poorly digested. Wheat bran proteins have also been explored as a source of amino acids and bioactive peptides or as inhibitors of enzymes of industrial interest (Balandrán-Quintana, Mercado-Ruiz and Mendoza-Wilson, 2015). From the results concluded that protein content of raw bran varies from 15.46% (WB) to 15.92% (BB). These results were in agreement with those obtained by
Wheat bran appears as an important dietary fiber source (
Bran also contains phytic acid which is the major phosphorus storage component and comprises 80% of total phosphorus in cereal grains (
Phytic acid content in raw and treated wheat bran.
The antioxidant activity of wheat bran measured using DPPH is illustrated in Figure
Discoloration of DPPH in raw and treated bran.
The technological interest and physiological effects of dietary fibre are related to their functional properties. The hydration properties of dietary fibres determine their optimal usage levels in foods because a desirable texture should be retained (
Functional properties of wheat bran.
WAC (g.g-1) | WRC (g.g-1) | SC (cm3.g-1) | OAC (g.g-1) | LA-SRC (%) | SU-SRC (%) | Na-SRC (%) | |
---|---|---|---|---|---|---|---|
|
|||||||
2.46 ±0.03 | 1.74 ±0.01 | 4.21 ±0.03 | 1.49 ±0.02 | 141.98 ±4.21 | 183.50 ±1.65 | 182.41 ±3.15 | |
2.57 ±0.01 | 2.16 ±0.01 | 4.40 ±0.02 | 1.33 ±0.00 | 142.79 ±3.47 | 161.52 ±2.54 | 176.17 ±2.31 | |
2.99 ±0.00 |
2.38 ±0.00 |
5.22 ±0.06 |
1.48 ±0.02 | 174.44 ±4.06 |
199.74 ±3.02 |
177.84 ±3.01 |
|
3.19 ±0.04 |
2.63 ±0.01 |
5.41 ±0.01 |
1.39 ±0.01 | 198.11 ±1.86 |
214.54 ±1.09 |
163.54 ±2.65 |
|
2.54 ±0.01 | 1.97 ±0.00 | 5.66 ±0.03 |
1.57 ±0.01 | 154.44 ±2.71 |
195.70 ±2.57 |
164.52 ±4.16 |
|
3.13 ±0.02 |
2.34 ±0.01 | 5.75 ±0.02 |
1.39 ±0.00 | 172.12 ±2.48 |
224.56 ±3.63 |
167.88 ±2.45 |
Note: OAC – oil absorption capacity, SC – swelling capacity, LA-SRC – lactic acid retention capacity, Na-SRC – sodium carbonate retention capacity, SU-SRC – sucrose retention capacity, WAC – water absorption capacity, WRC – water retention capacity, * denotes statistically significant difference at
WHC is related to the porous matrix structure formed by polysaccharide chains which can hold large amounts of water through hydrogen bonding (Du, Zhu and Xu, 2014). The WHC of raw bran samples were 2.46 g.g-1 (BB) and 2.57 g.g-1 (WB), which was similar to those described by Cai et al. (
WRC is one of the major key parameter which has been studied in functional food. Most significant changes that happen during baking i.e. gelatinization of starch, denaturation of protein, flavor and color formation are due to water contents (
SC indicates how much the fiber matrix swells as water is absorbed, including loosely associated water. It is a consequence of the macromolecule relaxation during hydration, which leads to an increment in the occupied volume by the fiber product. The greater capacity to swell is the most desirable parameter for the physiological functionality of DF (
OAC is the capability of dietary fiber to adsorb fat. During food processing, the reduction of cholesterol level in blood is linked with higher value of OAC (
The SRC method has been conceived to produce a combined pattern of the four SRC values to establish a practical flour quality/functionality profile. It is clear that fibre functionality in food formulations derived from its interaction and spatial arrangement within the biopolymers system (Rosell, Santos and Collar, 2009). Wheat bran is increasingly added to mostly cereal-based food products (bread, cookies, breakfast cereals, pasta, snacks, cakes, and more) (
Color is an important visual quality (attribute) of food products (
Color parameters of wheat bran.
|
|
|
|
|
|
---|---|---|---|---|---|
|
|||||
63.33 ±0.62 | 8.57 ±0.14 | 13.50 ±0.22 | 14.58 ±0.26 | 57.59 ±0.06 | |
65.84 ±0.02 | 8.41 ±0.06 | 14.53 ±0.07 | 16.44 ±0.09 | 59.25 ±0.22 | |
59.87 ±0.04 |
8.61 ±0.05 | 12.62 ±0.07 |
14.95 ±0.45 | 55.68 ±0.05 |
|
58.60 ±0.62 |
9.25 ±0.10 |
14.16 ±0.30 |
17.17 ±0.22 |
57.38 ±0.21 |
|
61.79 ±0.76 |
8.63 ±0.19 | 13.24 ±0.31 | 15.74 ±0.36 | 57.19 ±0.14 |
|
64.39 ±0.70 | 8.90 ±0.05 |
14.46 ±0.21 | 17.40 ±0.28 |
59.23 ±0.51 |
Note: * denotes statistically significant difference at
Wheat bran is the main source of dietary fiber in bakery products. The results showed that microwave and hot air heating altered the soluble and insoluble dietary fiber content. Hot air treatment significantly increased the total dietary fiber content up to 49.74%. The loss of phytic acid content was more than 44 % after microwave heating. The thermal treatment modified the functional properties of wheat bran, which are important in food processing. Wheat bran treated using hot air had higher water absorption and water retention capacity compared to wheat bran treated using microwave heating. Hot air heating significantly altered the color parameters of treated bran. From this study resulted that treatment of wheat bran using hot air heating significantly improved the wheat bran functional and physico-chemical properties.
This work was supported by grant VEGA No. 1/0583/20.