Edumania-An International Multidisciplinary Journal

Sensory Evaluation of Value-added Snack Bars

Sensory evaluation is essential in ascertaining the acceptability and overall quality of food products. In the current investigation, a sensory assessment was conducted on waffles, snack bars, biscuits, and cupcakes that were formulated with varying levels of orange peel and orange pomace powder incorporation, specifically at 5, 10, 15, and 20 percent. This evaluation provided insights into consumer preferences and the impact of the incorporation of citrus by-products on product quality. Essential sensory attributes including taste, aroma, texture, appearance, and colour were meticulously examined, as these factors exert a significant influence on consumer perception and acceptance.

A panel consisting of 12 trained and semi-trained evaluators was established for the sensory evaluation. Prior to the evaluation process, the panelists were thoroughly acquainted with the evaluation methodology and scoring criteria to ensure consistency in judgment and to mitigate potential biases during the assessment. Based on the outcomes of the sensory evaluation, the formulation that attained the highest overall acceptability score was selected for further analysis, and its proximate composition, dietary fibre, and mineral content were analyzed.

Estimation of Proximate Composition, Dietary Fibre, and Mineral Content of Control and Most Acceptable Value-added Snack Bar

The proximate analysis of the selected snack bar formulation was performed utilizing standard analytical methodologies as described by AOAC (2000). The carbohydrate composition was ascertained employing the difference method, which involves subtracting the cumulative percentage of moisture, ash, protein, fat, and crude fibre from a total of 100 (Ani and Abel, 2018). The total dietary fibre was assessed utilizing the enzymatic–gravimetric technique as specified by Kumar et al. (2014). The calcium concentration was evaluated through the standard titrimetric approach as stipulated by AOAC (2000). The potassium concentration was ascertained subsequent to the acid digestion of the sample, in accordance with the methodology detailed by Allen (1989).

2.6.1 Moisture 

The evaluation of moisture levels was performed by employing the standard analytical method as specified by the AOAC (2000).

Procedure: A sample weighing ten grams was precisely measured in a petri dish and subjected to drying in an oven maintained at a temperature of 105°C for a duration of six hours or until a consistent weight was achieved. The sample was subsequently weighed following its cooling in desiccators.

Moisture (%)= Loss in weight (in grams)Weight of the sample (in grams)×100

2.6.2 Crude Protein

The total nitrogen concentration was assessed using a standardized approach as outlined by AOAC (2000). The estimation of crude protein was performed employing a conversion factor of 6.25.

Reagents: 

1. Hydrochloric acid (N/100) 

2. Boric acid (4%) 

3. Sodium hydroxide (40%) 

4. Digestion mixture: 10 grams of K2SO4, 0.5 grams of CuSO4·5H2O, and 2 grams of FeSO4. 

5. Mixed indicator solution: A solution was prepared by dissolving 0.1 grams of methyl red and 0.5 grams of bromocresol green in 100 ml of 95% ethanol, subsequently adjusting the solution to a bluish-purple hue with the addition of dilute NaOH.

Procedure: A sample weighing two hundred milligrams was subjected to digestion with 20 ml of concentrated H2SO4 along with a small quantity of the digestion mixture. The nitrogen, in the form of ammonium salt, was subsequently diluted with 40 percent NaOH within a Micro Kjeldahl apparatus. The liberated ammonia was absorbed in a 10 ml boric acid solution containing several drops of the mixed indicator and was then titrated against standard HCl (N/100). The endpoint of the titration was signified by a colour change from bluish-green to pink.

Crude Protein %=0.00014×V×(S-B)×100V1×W×F

Where, 

W = Weight (g) of the sample taken

V = Volume (mL) made 

V1 = Volume (mL) of aliquot taken for distillation 

S = Volume (mL) of HCl (N/100) used in titration for blank 

B = Volume (mL) of HCl (N/100) used in titration for blank 0.00014 = 10 mL of 0.1 N HCl neutralize 0.00014 grams of nitrogen 

F = Factor for converting N to protein (6.25)

2.6.3 Crude Fat

Procedure: The quantification of crude fat was conducted in accordance with the established protocol outlined by AOAC (2000), employing the Soxhlet extraction apparatus. 5 grams of the ground sample was meticulously weighed and placed into an extraction thimble, which was subsequently covered with cotton wool. The thimble was then positioned within the Soxhlet extractor, and the fat was extracted into a pre-weighed flask over a duration of 6 hours utilizing petroleum ether (B.P. 40˚C – 60˚C). Following the extraction process, the solvent was removed through evaporation, the flask was allowed to cool within a desiccator, and its weight was recorded. The crude fat content was subsequently calculated and expressed as a percentage relative to the dry matter content of the sample.

Crude Fat %=Weight of the flask with sample-Weight of flaskWeight of dry sample×100

2.6.4 Ash Content 

Procedure: The ash content of the sample was determined using the AOAC (2000).  5.0 grams of the sample was meticulously measured and subsequently placed into pre-dried crucibles. The specimens were then subjected to ashing in a muffle furnace at a temperature of 550˚C for a duration of 6 hours. The ashed specimens were allowed to cool within a desiccator until they reached ambient temperature, after which they were weighed. The ash content was calculated as:

Ash content %=Weight of crucible+Ash-Weight of crucibleWeight of sample×100

2.6.5 Crude Fibre

The measurement of crude fibre in the sample was performed using the standardized analytical protocol as specified by the Association of Official Analytical Chemists (AOAC, 2000). 

Reagents:

1. Hydrochloric acid (%) v/v 

2. Sulfuric acid stock solution (10% v/v): A dilution was prepared by combining 55 milliliters of concentrated sulfuric acid with 1 liter of distilled water. 

3. Sulfuric acid working solution (1.25%): This solution was prepared by diluting 125 milliliters of the stock solution to a final volume of 1 liter.

4. Sodium hydroxide stock solution (10% w/v): This was achieved by dissolving 100 grams of sodium hydroxide in distilled water and adjusting the volume to 1 liter. 

5. Sodium hydroxide working solution (1.25%): A dilution was prepared by mixing 125 milliliters of the stock solution with distilled water to a final volume of 1 liter. 

6. Antifoam (2%): This was composed of silicone in carbon tetrachloride. 

Procedure: A two-gram of fat-free dried sample was placed into a 1-liter tall beaker, to which 200 milliliters of 1.25 percent sulfuric acid and several drops of antifoam were added. The resultant solution was subjected to boiling for a duration of 30 minutes under a bulb condenser. The beaker was intermittently rotated to ensure thorough mixing of the contents and to dislodge any particles adhering to the sides. The contents were subsequently filtered into the beaker utilizing a Buchner funnel. The sample was then reintroduced into the beaker with 200 milliliters of 1.25 percent sodium hydroxide and was boiled again for precisely 30 minutes. The entire insoluble residue was transferred to a crucible (designated as G-1) using boiling distilled water until it was confirmed to be acid-free. The residue was washed twice with alcohol and thrice with acetone, followed by drying at 100 degrees Celsius until a constant weight was achieved. The dried sample was ashed in a muffle furnace at a temperature of 550 degrees Celsius for one hour. The crucible was subsequently cooled in a desiccator and weighed.

Crude fibre %=W2-W3W1×100

Where, 

W1= weight (g) of the sample

W2 = weight (g) of insoluble material (weight of crucible-insoluble matter – weight of crucible)

W3 = Weight (g) of ash (crucible + ash – weight of crucible)

2.6.6Carbohydrate

The carbohydrate content was quantified employing the difference method. The cumulative percentage of moisture, ash, protein, fat, and crude fibre was deducted from 100 (Ani and Abel, 2018).

Carbohydarte %=100-(% moisture+% ash+% protein+% fat+% crude fibre)

2.6.7 Estimation of Total Dietary Fibre, Insoluble Dietary Fibre, and Soluble Dietary Fibre 

The quantification of dietary fibre was conducted in accordance with the methodology outlined by Kumar et al. (2014). For the determination of dietary fibre, a sample weighing 1 g was placed in an Erlenmeyer flask, to which 25 mL of 0.1 M sodium phosphate buffer (pH 6.0) was added and mixed thoroughly. Subsequently, 100 mg of Termamyl was introduced and the mixture was incubated in a boiling water bath for a duration of 15 minutes, after which it was cooled and 20 mL of distilled water was added, followed by adjustment of the pH to 1.5 using 4 N HCl (hydrochloric acid). An additional 100 mg of pepsin was incorporated, and the mixture was incubated at 40°C with agitation for 60 minutes, after which it was cooled, 20 mL of water was added, and the pH was adjusted to 6.8 using 4 N sodium hydroxide. Following this, 100 mg of pancreatin enzyme was introduced, and the mixture was incubated at 40°C with agitation for 60 minutes, subsequently cooled, and the pH was adjusted to 4.5 with 4 N HCl. The processed sample was then filtered through dry Celite, serving as the filtration aid. 

Insoluble fibre: The residue was subjected to washing with two aliquots of 10 mL of 95% alcohol and acetone, dried at 105 ± 2°C until a constant weight was achieved, and the weight of the crucibles was recorded (D1), followed by incineration at 550°C for 5 hours. After cooling, the weight of the crucibles was recorded (I1). 

Soluble fibre: The volume of the filtrate was adjusted to 100 mL, followed by the addition of 400 mL of warm 95% alcohol, which was allowed to stand for 1 hour to facilitate precipitation, after which it was filtered through dried and weighed crucibles (D2), and rinsed with two aliquots of 10 mL of alcohol and acetone, subsequently dried at 105 ± 2°C overnight. The samples were incinerated at 550 ± 10°C for a duration of 5 hours, cooled, and the weights of the crucibles were recorded (I2). 

Blank samples (B) for both insoluble and soluble fractions were prepared without the inclusion of the sample, adhering to the identical procedural framework.

Insoluble dietary fibre %= D1-I1-BW×100

Soluble dietary fibre %= D2-I2-BW×100

Total dietary fibre (%)=Insoluble dietary fibre+Soluble dietary fibre

Where, 

W = weight of the sample

2.6.8 Calcium 

The standard Titrimetric method of analysis was used to measure the amount of calcium in the sample (AOAC, 2000).

Reagents: 

1. A saturated solution of ammonium oxalate. 

2. A dilute solution of hydrochloric acid (1-part HCl + 4 parts water). 

3. Methyl red indicator (0.5% in absolute alcohol). 

4. A 0.1 N solution of potassium permanganate. 

5. A dilute solution of ammonium hydroxide (1-part NH4OH + 1 part water). 

6. A 10% solution of sulphuric acid. 

7. A 0.1 N solution of oxalic acid: Sodium oxalate is subjected to drying in an oven at a temperature of 100 degrees Celsius for a duration of 12 hours. Precisely 6.7 grams is subsequently dissolved in distilled water, after which 5 ml of concentrated H2SO4 is incorporated, and the solution is adjusted to a total volume of 1L post-cooling.

Standardization of the potassium permanganate solution: A volume of 10 ml of 0.1 N oxalic acid solution is transferred into a conical flask. An addition of 1 ml of concentrated H2SO4 is made, and the mixture is heated to approximately 70 degrees Celsius before being titrated against the KMnO4 solution until a persistent faint pink hue is observed.

Procedure: A clear sample filtrate, measuring 50 ml and derived from ash, is placed into a beaker. Ten ml of saturated ammonium oxalate solution is introduced. The mixture is then boiled, followed by the addition of two drops of methyl red indicator. The solution is neutralized with dilute ammonium hydroxide and reboiled to facilitate the formation of a coarse crystalline precipitate. A few drops of dilute hydrochloric acid are incorporated until the colour is adjusted to a faint pink. The solution is permitted to stand overnight. The precipitates are subsequently filtered through Whatman filter paper and thoroughly washed with hot distilled water until they are devoid of oxalates. The precipitate along with the filter paper is returned to the original beaker and dissolved in 20 ml of 10% sulphuric acid. The contents are then heated to approximately 70 degrees Celsius and titrated against the 0.1 N potassium permanganate solution until a faint pink colour is achieved. A blank is also executed employing a similar procedure. Calculations: The volume of 1 ml of 0.1 N KMnO4 consumed corresponds to 0.002 grams of Calcium.

Calcium=ml pf 0.1N KMnO4 used ×0.002×ABWeight of sample in grams×100

2.6.9 Potassium 

For the purpose of potassium mineral estimation, the sample underwent digestion in accordance with Allen’s methodology (Allen, 1989). 

Preparation of the digestion mixture: 0.42 g of selenium powder was combined with 14 g of lithium sulphate monohydrate in 350 mL of hydrogen peroxide, ensuring thorough mixing. Subsequently, 420 mL of concentrated sulfuric acid (H2SO4) was introduced to this solution while it was maintained in an ice bath for cooling. The resulting mixture was preserved at a temperature of 2˚C and exhibited stability for a duration of four weeks. 

Digestion method: 0.3 g of each sample was precisely weighed in digestion tubes, followed by the addition of 4.4 mL of the digestion mixture. The digestion apparatus was sustained at a controlled temperature of 360 ˚C for a period of two hours to ensure the complete digestion of the samples. 

Reagents:

Potassium Standards

The stock solution (1000 ppm) was prepared by dissolving 1.9068 g of dry potassium chloride in distilled water and adjusting the final volume to 1 L. 

The working standard was subsequently prepared by further diluting the stock solution to obtain concentrations of 100, 70, 50, 30, 10, and 1 ppm. 

Procedure

The procedure for total potassium determination involved the utilization of the flame photometric method. Standard solutions ranging from 0 to 100 ppm were analyzed in the flame photometer employing the K filter following the requisite settings and calibration of the instrument. Post-calibration, the samples were analyzed, and the concentrations displayed on the digital screen were recorded based on the established standard curve. Following calibration, the samples were processed, and the concentrations were computed with reference to the prepared standard curve. The percentage of potassium was determined utilizing the equation.

Potassium=C (ppm)×0.125Weight of the sample

Where, 

C= Corrected Concentration of sample solution (concentration of sample-concentration of blank). 

2.7 Statistical Analysis 

Data acquired through sensory evaluation was subjected to sensory analysis. Mean values alongside standard deviations were computed for all parameters to evaluate central tendency and variability. Statistical analysis was executed employing Microsoft Excel, and findings were articulated as mean ± standard deviation to facilitate precise interpretation of the data.

Results and Discussion 

3.1Sensory Evaluation of Value-Added Snack Bars

In the present study, rice flakes flour was partially substituted with a 1:1 blend of orange peel and pomace powder at levels of 5, 10, 15, and 20 percent, while a control sample without substitution was used for comparison. The control and all experimental snack bar formulations are shown in Figure 2, highlighting the visual changes associated with increasing levels of citrus by-product incorporation.

The mean sensory scores of the developed snack bars are presented in Table 3 and illustrated in Figure 3. The control sample exhibited good acceptability, with overall acceptability scored at 7.95 ± 0.60, indicating that the base formulation was well received by the panelists. Sample 1 (5% substitution) showed sensory scores comparable to the control across all attributes, with an overall acceptability score of 7.86 ± 0.69, suggesting that low-level incorporation of orange peel and pomace powder did not adversely affect sensory quality.

Sample 2 (10% substitution) recorded comparatively lower scores for all sensory parameters, including taste (7.50 ± 0.79), texture (7.33 ± 0.88), and overall acceptability (7.56 ± 0.66). This decline may be attributed to a slight imbalance in flavor or textural changes at this level of substitution, as perceived by the panelists. However, the scores remained within the acceptable range on the nine-point Hedonic scale.

In contrast, Sample 3 (15% substitution) demonstrated improved sensory performance, with scores for taste (8.08 ± 0.51), aroma (8.00 ± 0.42), and overall acceptability (8.00 ± 0.31) slightly exceeding those of the control. This indicates that moderate incorporation of citrus by-products enhanced sensory appeal without introducing negative attributes. The highest sensory scores were observed for Sample 4 (20% substitution), which achieved an overall acceptability score of 8.25 ± 0.55. This formulation received the highest ratings for taste, appearance, aroma, and colour, highlighting its strong consumer preference.

A comparable study by Negrete (2022) explored the development of gluten-free oat-based snack bars containing varying concentrations (14%, 17%, 20%, 23%, and 26%) of orange peel derived from the Citrus sinensis (Valencia) variety. Orange peel was used in both powder and zest forms. Sensory evaluation using a 9-point hedonic scale revealed that bars containing 17% and 20% orange peel were most acceptable, with overall liking scores of 6.05 ± 1.65 and 6.04 ± 1.84, respectively. However, a decline in acceptability was observed at 23% (5.54 ± 1.74), attributed to increased bitterness from limonin, a compound present in citrus peel. Moreover, findings also showed that orange flavor became excessive at higher levels, with 48.5% of consumers rating it as “too much” at 23%, compared to 33.98% at 17%. Furthermore, a rejection tolerance threshold (RTT) analysis in the second part of study determined that overall consumer rejection began beyond 18.16% orange peel concentration. In contrast, the present study demonstrated high acceptability even at 20% incorporation, likely due to the combined use of orange pomace, which may have diluted bitterness, balanced flavor, and improved textural attributes.  Overall, the results indicate that orange peel and pomace powder can be successfully incorporated into rice flake-based snack bars at levels up to 20% without compromising sensory quality. Among the formulations tested, the snack bar containing 20% substitution emerged as the most preferred, supporting its selection for further nutritional evaluation and reinforcing the potential of citrus by-products as functional ingredients in value-added snack formulations.