Study on Effects of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose on the Properties of Gluten-free Bread

 

Due to such advantages as good taste, various kinds and easy to carry, bread has become popular food among consumers. Wheat flour bread contains gluten, and if you have celiac disease, eating gluten will trigger an immune response in the small intestine and then damage the lining of small intestine. At present, one in every 200 people in Europe and one in every 250 people in USA have celiac disease. Although there’s no effective cure for celiac disease, following a strict gluten-free diet can help manage the symptoms.

 

The greatest difficulty in making gluten-free bread is that starch contains no gluten, and that during the process of making no network structure of gluten can be formed to maintain the CO2 gas generated during the fermentation process. But this problem can be solved by adding the binder into starch to to simulate gluten in wheat flour bread, and then the cellular network they have formed can maintain the CO2 gas generated during the fermentation process. Cellulose molecules have macromolecular structures similar to network shape through the formation of crystalline supramolecular structure by intermolecular and intramolecular hydrogen bonds, and the molecular chains of cellulose have the same structural units as those of starch.

Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose are respectively non-ionic and ionic ethers of cellulose, used for food to increase the viscoelasticity, stability, and hygroscopicity. Attempts are made in this paper to study their effects on the specific volume, water loss rate, crust color, hardness, elasticity and sensory characteristics of gluten-free bread by adding different amounts of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose into rice flour and sweet potato starch, and provide a reference for the making process and storage of gluten-free bread.

 

Ingredients

Rice flour, sweet potato flour; white granulated sugar of first grade, salt of first grade; peanut oil; yeast; water; Hydroxypropyl methyl cellulose, Sodium carboxy methyl cellulose (100 mesh): Sidley Chemical Co., ltd., food additives.

 

Making Process of Bread

Mixing of the ingredients in proportion→Preparation of dough→Shaping of bread dough→Proofing→Baking→Finished product

After well mixing the ingredients, use a stand mixer and beat at a rotational speed of 150 r/min for 7 min. Then shape bread in a prepared 10 x 4 x 7 cm model loaf pan. While proofing, the temperature of bread proofer is 30 ℃, the relative humidity 70%, and the proofing time is 45 min. Baking conditions: the top temperature is 205 ℃, the bottom temperature 200 ℃ and the baking time is 28 min. It is finished after the temperature of bread is dropped to 30 ℃ in freezer bags.

 

2.1 Effects on the Specific Volume of Bread

The specific volume of bread has been increased after adding Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose, and larger with the addition of 2% Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose than with 1%. Compared with the blank sample, the increase in the specific volume of bread after adding 2% Sodium carboxy methyl cellulose is the largest, by 22%, while the increase after adding 1% Sodium carboxy methyl cellulose is the smallest, by 6%. The specific volume of bread is determined by two factors. One is the amount of CO2 gas generated during the fermentation process; the second is the amount of CO2 gas maintained in bread. Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose both have the crystalline network structure, can better maintain the CO2 gas, and increase the volume of bread.

 

2.2 Effects on the Water Loss Rate of Bread

After adding Hydroxypropyl methyl cellulose, the water loss rate of bread is basically unchanged; after adding Sodium carboxy methyl cellulose, it is slightly decreased, by 7% with the addition of 1% Sodium carboxy methyl cellulose. Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose have similar chain structures to starch and good compatibility with starch. Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose have viscous nature and water-holding capacity, not only can bond starch granules together and then decrease the fluidity of the starch granules, but also can bond bread crumbs and improve the bonding force, thereby retaining moisture of bread. As an ionic ether, Sodium carboxy methyl cellulose is easy to produce electrostatic interactions with the slat in bread and weaken the effects with water molecules, but the amount of salt is small, resulting in a slight decrease in the water loss rate of bread.

 

2.3 Effects on the Crust Color of Bread

The color of bread can affect consumers’ sensory acceptability, and the yellow index is an important parameter to measure the color of the bread. The larger the yellow index is, the more likely consumers are to accept.

Under the same baking temperature and time, the yellow index of bread after adding Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose is both larger than that of the blank sample. And with the increase of addition amount, the yellow index of bread increases. The increase in the yellow index of bread with the addition of 2% Sodium carboxy methyl cellulose is the largest, by 37%, while the one with the addition of 1% Hydroxypropyl methyl cellulose is the smallest, by 6%.

2.4 Effects on the Hardness and Elasticity of Bread

Hardness and elasticity are the most important parameters to measure the staling rate of bread. From the hardness and elasticity of gluten-free bread by adding different amounts of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose after placed for 2h, 24h, and 48h, it can be seen that adding Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose can significantly reduce the hardness of bread, while increasing the elasticity of bread. With the prolonging of time, the hardness of bread gets increased, while the elasticity gets decreased. Compared with the blank sample, after bread is placed for 24 h and 48 h, the decrease in the hardness change rate of bread is the maximum by adding 1% Sodium carboxy methyl cellulose, respectively 18% and 21%, while the decrease in the elasticity change rate of bread is the maximum by adding 1% Hydroxypropyl methyl cellulose, respectively 18% and 19%.

 

2.5 Effects on the Sensory Characteristics of Bread

By sensory evaluation, for bread with the addition of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose, the crust color, surface texture, chewiness, and taste are all better than the blank sample. The chewiness of bread with the addition of 2% Hydroxypropyl methyl cellulose is the highest, but the taste is not better than the blank sample. This is because the aqueous solution viscosities of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose are large so that the viscosity inside the bread is larger and the taste of bread declines. Since there are differences in the gas-holding capacity of Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose, surface cracking phenomena may occur during the baking process of bread, making the surface texture of bread decline.

 

3. Conclusion

After adding Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose, the quality of gluten-free bread is significantly improved. The specific volume, color, hardness, elasticity of bread after adding Hydroxypropyl methyl cellulose and Sodium carboxy methyl cellulose are all improved compared with the blank sample, and it is more easily acceptable in the senses. But the water loss rate is slightly reduced compared with the blank sample.