What are the effects of xanthan gum on the texture of protein bars?

Xanthan gum is a kind of water-soluble biopolysaccharide, which is produced by the fermentation of Xanthomonas campestris. It has good rheological properties, can be quickly dissolved in water and miscible with a variety of salt solutions, good salt resistance, and good stability to heat acid and alkali, and these properties make it have a special role to improve the texture and taste, improve stability, increase the water retention, and prolong the shelf-life in food.
Protein bars are a class of protein-rich food bars, containing plant proteins and animal proteins synergistically complementing each other, which can effectively supplement high-quality proteins, and have a certain effect on relieving fatigue and restoring physical strength.

In food characterization, texture is usually used to represent the organization, structure, texture and taste of food. Textureprofileanalysis (TPA), also known as the 2-chew test, is a mechanical test developed to mimic the sensory evaluation of food texture. The Physical Property Analyzer is capable of performing TPA test on samples, mainly by imitating the oral chewing action to objectively reflect the texture properties of food such as hardness, elasticity, adhesion, cohesion and chewability, and at the same time, the texture characteristic curve of the samples can be obtained through the connected microcomputer.
In this paper, different amounts of xanthan gum were added to the protein bars, and a physical property analyzer was used to analyze the texture of the protein bars to study the effect of xanthan gum on the texture of the protein bars and to provide technical support for the processing and production of protein bars.
Sensory evaluation of protein bars
Sensory evaluation is to make an objective evaluation of the quality of food through the senses of sight, smell, touch, taste and hearing. In this paper, the color, appearance, hardness, chewiness, viscosity and cohesiveness of the protein bar samples were examined.
The results of the sensory evaluation of protein bars are shown in Table 2.

As can be seen from Table 2, the total scores of protein bars with xanthan gum added were higher than those of the blank control group, among which the protein bars with 0.3% xanthan gum added had the highest scores.
Compared with the blank control, there was no significant difference in the color and appearance of the protein bars after the addition of xanthan gum. Through visual observation, the surface of the protein bars was coated with chocolate, and the thickness of the coating was consistent and complete; the products were complete in block type, with smooth surface, neat edges, no cracks, no missing corners, and no obvious deformation.
Compared with the blank control, the hardness, cohesion and viscosity of the protein bars were improved after the addition of xanthan gum; the protein bars of the blank control group were the hardest, and the addition of xanthan gum could reduce the hardness of the protein bars, and the hardness of the protein bars of the group with the addition of 0.3% xanthan gum was moderate; the addition of xanthan gum could improve the cohesion of the protein bars, and the appearance of the protein bars of the group with the addition of 0.3% xanthan gum was the most intact, and the most resistant to the formation of crumbs; The protein bars in the 0.4% xanthan gum group were slightly sticky to the teeth, while the protein bars in the 0.2% xanthan gum and 0.3% xanthan gum groups had a good texture and the stickiness was appropriately reduced.

The combined scores of the sensory evaluation showed that the addition of 0.3% xanthan gum had the best effect on improving the texture of the protein bars.
Textural characterization curves of protein bars
Szczesniak et al. have done a lot of research in food texture, the first proposed that the texture of food can be measured by instrumentation, and the use of TPA to reflect the mechanical properties of food texture, the mechanical properties of food texture in accordance with the order of eating is divided into primary and secondary characteristics.
The primary properties include hardness, brittleness, cohesiveness, elasticity and adhesion, and the words used in daily descriptions include softness, hardness, crispness, crunchiness, elasticity, and stickiness, which are the initial sensations people have on the food population. The TPA textural characterization profile of protein bars was obtained by 2 downward presses of the detection probe using a physical property analyzer. The TPA texture characterization curves of protein bars are shown in Fig. 1.

As can be seen from Fig. 1, the TPA texture profile of the protein bar in the first compression cycle is relatively smooth with no obvious brittleness peaks, which indicates that the texture characteristics of the protein bar are homogeneous. With the downward compression of the probe, the force gradually increases, and the sample shows resistance to the external force, and the maximum peak force it can reach is the hardness of the protein bar.
Elasticity is the extent to which the sample is able to recover after the first compression, expressed as the ratio of the time in the two compression cycles, and the test results show that the structure of the protein bar does not undergo serious breakage after compression, but the extent of recovery decreases. Adhesion is the resistance to upward travel of the probe and is expressed as the negative area under the curve between the time the 1st compression curve reaches zero and the start of the 2nd compression curve.
Cohesion is the ratio of the 2nd compression area to the 1st compression area in the TPA curve. Chewability is the product of hardness, cohesiveness and elasticity.
The effect of xanthan gum on the hardness of protein bars
Hardness is the force required to make the protein bar reach a certain deformation, which is the peak pressure when the sample is compressed for the 1st time during the TPA test, and it is the main index for evaluating the texture of the protein bar. The effect of xanthan gum on the hardness of protein bars is shown in Figure 2.

From Figure 2, it can be seen that the addition of xanthan gum can lead to the reduction of the hardness of protein bars, and the more xanthan gum added, the lower the hardness of protein bars.
Combined with the sensory evaluation, it was found that the hardness of the protein bars in the group with 0.3% xanthan gum was moderate and had a good texture. Xanthan gum has good hydrophilicity and stability, and its addition to protein bars can form a weak gel structure inside the bars and maintain good water-holding capacity, thus reducing the hardness of the protein bar samples and improving the texture.
Effect of xanthan gum on the adhesion of protein bars
In the TPA texture characteristic curve, the adhesion can be expressed by the negative area under the curve between the 1st compression curve reaching zero point and the beginning of the 2nd compression curve, which corresponds to the negative value, the negative sign represents the direction, and the vertical coordinate represents the magnitude of the adhesion value. The effect of xanthan gum on the adhesion of protein bars is shown in Figure 3.

As can be seen from Figure 3, the addition of xanthan gum can cause a significant reduction in the adhesion of protein bars. Against the blank sample, the addition of 0.3% xanthan gum had the greatest reduction in the stickiness of the protein bar, reflecting that when chewing this protein bar, the stickiness of the protein bar to the tongue, teeth, palate and other contact surfaces was small. Adhesion is usually said to be sticky teeth feeling, combined with sensory evaluation found that the addition of xanthan gum can appropriately reduce the stickiness of protein bars, the quality of protein bars is favorable.

As can be seen from Figure 4, the addition of xanthan gum can increase the cohesion of protein bars compared with the samples of the blank group, and the cohesion values of protein bars with different xanthan gum additions were 0.3% xanthan gum group, 0.2% xanthan gum group, and 0.4% xanthan gum group, in descending order.
The largest cohesion value was found in the 0.3% xanthan gum group, reflecting that the internal organization of the protein bar had the greatest binding force, and the protein bar resisted damage and was tightly connected when chewing the protein bar, so that the integrity of the protein bar was maintained the strongest.
Sensory evaluation showed that protein bars with xanthan gum maintained a good colloidal morphology and were less prone to crumb formation, resulting in a relatively delicate taste when tasted. The effect of xanthan gum on the elasticity of protein bars
Elasticity is the degree to which a sample can recover after the first compression. The effect of xanthan gum on the elasticity of protein bars is shown in Figure 5.

As can be seen from Figure 5, compared with the blank group samples, xanthan gum has a certain increase in the elasticity of the protein bar, the addition of xanthan gum can improve the structure of the protein bar, which may be due to the molecular weight of the xanthan gum is fully stretched, and with the combination of soy protein, whey protein and other protein bars in the protein bar adhesion occurs, so that the protein bar to form a soft and elastic colloidal form.
However, the elasticity of the three groups of protein bar samples with 0.2%, 0.3% and 0.4% xanthan gum added respectively did not change much, which indicates that the amount of xanthan gum added does not have much effect on the elasticity of protein bars.
The effect of xanthan gum on the chewability of protein bars
Chewability reflects the continuous resistance of protein bars to chewing. The effect of xanthan gum on the chewability of protein bars is shown in Figure 6.

As can be seen from Figure 6, the addition of xanthan gum can cause a reduction in the chewability of the protein bar, and the more xanthan gum is added, the lower the chewability of the protein bar, the easier it is to be chewed, which is consistent with the change rule of the hardness of the protein bar. The addition of xanthan gum can reduce the work needed to be done when the protein bar is chewed.
The chewiness of protein bars with 0.3% xanthan gum is moderate, and the taste of protein bars with 0.3% xanthan gum is better than those with 0.3% xanthan gum, according to the sensory evaluation.