Effect of Sugar Replacer (Stevia and Maltitol) on Quality Characteristics of Bread

Bread is one of the most widely consumed bakery products in the world. The technology for bread making is the oldest technique and it is evolving through time with development of new ingredients, equipment and processes. The sensory and nutritional qualities of bread under various ingredients have been studied by many researchers (Tong et al., 2010; Struck et al., 2014). Sweeteners are one of the important ingredients in bakery products. It plays important role in fermentation, appearance, volume, color and texture of the final products, other than providing a sweet taste. The desired appearance and texture can be obtained by varying sweeteners. The sweetener is generally selected based on its function and degree of sweetness (Sun et al., 2014). Major sweetener used in bakery products is the sucrose. It contributes to the sweetness and energy content but it causes dental carries and diet related issues (Zoulias et al., 2002). To overcome this in recent years low calorie sweetener substitutes for sucrose have been researched (Sun et al., 2014). Partially replacing the sucrose with its substitute is one possibility of handling its energy content and preserving its functions in the bakery products. A complete replacement of sucrose is possible if the substitute fulfills the maintenance of desired viscosity of the dough or batter and the texture of the product with the combination of the high intensity sweetener and low-calorie sweeteners (Obiegbuna et al., 2013). The substitute should have sweetness similar to that of sucrose; also, it should be colorless, non-carcinogenic and odorless. The substituting sweeteners should also replace other functions of sucrose in bakery products such as browning, crystallization, the control of starch and protein thermal set temperature, viscosity and structure formation, and moisture control (Luo et al., 2019). The high intensity sweeteners are saccharin, aspartame, sucralose, acesulfame-K, Neotame, Stevia and the polyols are sorbitol, maltitol, mannitol, xylitol, lactitol, erythritol, isomalt.
       
Maltitol (4-O-α-glucopyranosyl-D-sorbitol) is a non-reducing disaccharide polyol or sugar alcohol that consists of glucose and sorbitol with hygroscopicity. The maltitol has sweetness of 70-90% compared with sucrose and has the potential for a substitute for sucrose. Intestines can only digest maltitol partially. (Livesey, 2003; Ghosh and Sudha, 2012). It has techno functional properties like melting point, solubility and hygroscopicity similar to that of sucrose but doesn’t undergo maillard reaction (Struck et al., 2014). When used as a sugar substitute, it also produces functional benefits to the products. Maltitol substituted products helps in the maintenance of blood sugar level and also good oral health (Ghosh and Sudha, 2012). Due to the presence of 9 hydroxyl groups in the molecule, staling in bread and moisture loss can be hindered (Ding et al., 2019).
       
Stevia is a natural sweetener that is up to 300 times sweeter than sucrose with sufficient thermal stability, which can act as a potential substitute for sucrose. In many parts of the world, the stevia is used as non-caloric sweetener (Goyal et al., 2010). In 2011, European union approved the use of steviol glycosides as a replacer, at specific intake conditions is 4 mg/kg body weight and E number is E960 (Ruiz-Ruiz et al., 2015). Several studies revealed that stevioside reduces excess glucose in bloodstream and boots insulin secretion. Due to the presence of phenols it can act also as a potential anti-oxidant. Such studies show that it can be used in the production of functional foods (Salazar et al., 2018). Though it has high sweetness than sucrose it lacks in the bulk characteristics which make the replacement of sucrose with stevia difficult leading to partial replacement. Addition of hydrocolloids, sugar alcohols and plant fibers could make the loss of volume due to sucrose reduction (Struck et al., 2014). In this study, sucrose is replaced by maltitol and stevia to overcome the problem of high calorie content, tooth decay and diet related health issues. The aim of this study is to formulate the bread using sugar replacer (stevia and maltitol) and to analyze the physicochemical properties such as loaf weight, volume and specific volume, fermentation rate, calorific value and the sensory characteristics of bread. 

Materials
 
Flour, sugar, stevia, instant dry yeast, salt and butter were procured from the local supermarkets. Food grade maltitol was purchased from Urban platter, Maharashtra. All the experiments were carried out at Department of Food Technology, Kongu Engineering College, Erode, Tamilnadu during the year 2019.
 
Experimental variable
 
The independent variables were varying amount of maltitol, stevia whereas amount of sugar and other ingredients were fixed variable. The dependent variables were loaf weight, specific volume, fermentation rate, calorific value, sensory characteristics of breads.
 
Preparation of breads
 
Bread samples were prepared using a straight dough method (Tong et al., 2010). The formula containing flour (100 g), sugar (20 g), dry yeast (3 g), butter (5 g), salt (1 g) and water (60 ml) were used for making control sample. The experimental trials were conducted by replacing sugar partially with stevia and maltitol in various proportions as shown in Table 1.
 

 
Loaf weight
 
After cooling of bread to room temperature, the weight of loaf was measured using an analytical weighing balance (Obiegbuna et al., 2013).
 
Specific volume
 
The volume of the bread was determined by rape seed displacement method. The volume of loaf was calculated using the equation (3). Specific volume of bread was calculated using the equation (4) (Ding et al., 2019).
 

                        W_seeds = W_total- W_bread- W_container                                                     (1)
                        V_seeds = W_seeds / ρ_seeds                                                                      (2)
                        V_bread= V_container - V_seeds                                                                    (3)

 
Where, W = weight (g), V = volume (m³), r = density (kg/m³)

                                            (4)

Where,
SV = specific volume of bread (cm³ /g), V = volume of bread (cm³) and M = mass of the bread (g).
 
Fermentation rate
 
Fermentation rate was determined as the difference in height of the dough before proofing and after proofing (Obiegbuna et al., 2013).
 
Calorific value
 
Calorific value was measured using Bomb Calorimeter and energy value calculated according to equation (5) (Bhise and Kaur, 2014).

 
                                                                                                   (5)

where,
T= final temperature, W= water equivalent (2332 cal/°C), C_vt= length of thread x 2.1cal/°C, C_vw= length of nichrome x 2.33 cal/°C.
 
Sensory evaluation
 
Bread was evaluated for sensory properties such as crust color, crust hardness, taste, aroma, uniformity pores, crumb softness and overall acceptability by sensory panelist containing 30 members of 20 – 45 age group. The evaluation was carried out on a nine point hedonic scale [ 9= like extremely, 8= like very much, 7= like moderately, 6= like slightly, 5= neither like nor dislike, 4= dislike slightly, 3= dislike moderately, 2= dislike very much, 1= dislike extremely]  (Morais et al., 2013).
 
Statistical analysis
 
Data analysis was performed using minitab18. All the experiments replicated thrice and mean values were taken for analysis. One-way analysis of variance (ANOVA) was applied to detect significant difference among trials discriminated by Tukey’s test at p < 0.05 (Obiegbuna et al., 2013).

Weight of loaf
 
The quantity of baked bread was determined by loaf weight and carbon dioxide diffused out of the loaf during baking. The mean value of weight of loaf was significantly different (p < 0.05) and increased from 260.17 ± 0.29 to 286.83 ± 0.76 g among trials as shown in Table 2. T6 was slightly equal to control. The minimum score of weight of loaf was found in T3 for equal proportion of maltitol and Stevia and also T8 (completely Stevia) had low weight of loaf because stevia affected weight loss in bread. Similar results were obtained by Choi et al., (2014). He reported that deduction of the weight of baked bread from the initial weight of the dough and that attributed to difference in moisture loss. Fig 1 represents the effect of maltitol and stevia on weight of bread loaves.
 

 

 
Specific volume
 
Specific volume is the volume per unit weight of loaf. It is the integral of weight and volume of the loaf related to the rising power of the loaf during baking. The mean scores of different trials for response of specific volume of bread was significantly different (P < 0.05), as shown in Table 2. The maximum volume was recorded in T4 which is slightly equal to T9 (control) as shown in the Fig 2. The volume of loaf increased with increasing amount of maltitol. Similar results had been obtained by Sun et al., (2014) where xylitol was used to evaluate its effect on bread qualities and they showed improved loaf volume. The samples were suitable in relation to this parameter, because breads with higher specific volume are preferred by consumers (Bhise and Kaur, 2014).
 

  
Fermentation rate
 
There is no significant difference in fermentation rate of bread (p > 0.05) among various trials where the mean values ranges from 0.35± 0.03 to 0.67 ± 0.19. The influence of maltitol and stevia on fermentation rate of bread was presented in Fig 3. Table 2 indicated that bread with maltitol and stevia had an overall slower fermentation rate when compared to the control. It had a retarding effect on dough fermentation and less production of CO₂. Gluten proteins along with starch and other ingredients created viscoelastic film network to entrap gas. Higher viscosity structures produced by a denser gluten network slow gas diffusion and maintain uniformity pores. The fermentation rate indicated the bread texture and volume. As a result, bread with maltitol and stevia had a relatively slow fermentation rate and tended to exhibit a lower specific volume than control. Similar result was obtained by Ding et al., (2019).
 

 
Calorific value
 
The effect of sugar replacers on calorific values were obtained by bomb calorimeter and data were shown in the Table 2. There is significant difference in energy value of bread among treatments (p < 0.05) and it ranges from 2118.28 ± 0.3 to 2587.51 ± 0.46 (Cal/100 g). T8 (stevia) sample had low calorie because stevia has no calorie and glycemic index. The calorific value is increasing with increasing addition of maltitol. Calorie value of control bread was more than sugar replaced bread. Reductions in calorific values of bread using polyols as sugar replacer have been reported by Bhise and Kaur, (2014). The graph (Fig.4) represented the effect of sugar replacer in bread on calorific value.
 

 
Sensory characteristics
 
The 30 panelists rated the following bread samples attributes: crust hardness, crust color, taste, aroma, uniformity pores, crumb softness and overall acceptability results as shown in Fig 5. A 9-point hedonic scale, which ranged from dislike extremely to like extremely, was used to evaluate how much the panelists liked the breads. The overall acceptability of bread had higher scores (T2, T3, T4) than the control. The addition of maltitol resulted in low scores because less sweet taste. Similar results had been reported by Pourfarzad et al., (2011). According to the study, the sensory characteristics of trial T3 bread were slightly equal to control (T9).
 

The physical properties like weight of the loaf and specific volume which is most important attributes with respect to consumer perception. Both the parameters got better results when the amount of sugar replacers increased. The presence of stevia alone lowers the dough fermentation rate and specific volume of bread, whereas increased loaf volume can be obtained in combination with maltitol. The use of stevia as a sugar replacer improves the nutritional value of bread by lowering glycemic index and decreasing energy value of bread. Maltitol provides good bulk characteristics as similar to sucrose for application in bakery products but have occasionally a low relative sweetness that limits their applicability from a sensory point of view. This study concluded that combination of stevia and maltitol gives good physiochemical properties of bread.