Texture of Gluten-Free Tortillas and the Effect of Buckwheat Addition, Baking Time and Aging

Louise Rolander (1)
(1) Diploma work at Finax AB, Helsingborg, Sweden

Abstract

Taco is a popular dish in Swedish homes, but for people who are intolerant to gluten the choice of tortilla bread is limited. The purpose of this study was to compare the texture of gluten-free tortillas baked with different amounts of guar gum, buckwheat flour and baking time. The tortillas were also compared to a wheat flour based tortilla and two gluten-free tortilla breads available in stores.
The results showed that the tortilla bread with buckwheat flour was softer than the bread without buckwheat when they were stored for 1–8 days at room temperature. The baking time affected the hardness of the bread. A long baking time resulted in bread with higher hardness. However, the elasticity was not affected by the baking time. Compared to the tortillas based on wheat flour, the gluten-free tortillas baked and analysed in this study were less hard and less elastic. To make a gluten-free tortilla similar to the wheat flour tortillas further improvements need to be made.

Key words: gluten-free tortilla, buckwheat, guar gum, baking time

Introduction

Coeliac disease is an autoimmune disorder with a prevalence of 1 in 100 people in northern and western Europe and in northern America. Intake of gluten causes immune-mediated damage to the small bowel’s mucosa. The only known treatment to normalize the mucosa and to avoid future complications is a strict gluten-free diet. All food containing wheat, rye, barley and sometimes oats have to be excluded from the diet (Dubé et al., 2005). Products like bread, pasta and pizza are staple foods in many countries and are often based on products containing gluten. Therefore people with coeliac disease have to find alternatives. Products are especially manufactured to be gluten free and the market for gluten-free food is growing.

When this project started there were not many gluten-free tortilla breads on the Swedish market. Tortillas are traditionally made of corn, but the tortillas sold in Sweden are mainly based on wheat flour. The corn tortillas available in Swedish stores also contain wheat flour, which excludes them from a gluten-free diet. The purpose of this study was therefore to develop soft gluten-free tortillas for Finax AB, a company producing gluten-free products since 1983 (Finax, 2014).

Methods

To find an optimal recipe, breads with different flours and proportions were baked. From those trials a standard tortilla was found. To improve the tortilla further, different amounts of buckwheat flour were added, and the amount of guar gum was altered as well as the baking time. To examine the storage capability, the tortillas were stored at room temperature and measured after 1–8 days. This article focuses on the texture analyses (for further reading see my thesis ’Produktutveckling av glutenfria tortillabröd – hur påverkas bröden av ingrediensval och gräddningstid’, Rolander, 2015).

Tortilla production
The tortillas were produced using the following ingredients: water, wheat starch, rice flour, rape seed oil, sugar, psyllium husk, salt, yeast, baking powder. Guar gum and buckwheat were added according to Table 1. All ingredients were mixed in a mixer (Hobart N50), 2 min. at low speed and 4 min. at middle speed. The dough was allowed to rest at room temperature (20–23 °C) for 30 min., dough balls of 140 g were formed and sheeted. Using a mold, tortillas with diameter 230 mm were formed from the dough. The tortillas were baked at 225°C (Elektrolux co 5940) according to Table 1. The tortillas were cooled at room temperature and then placed in plastic bags and stored at room temperature (20–23°C) until they were analyzed.

Evaluation of tortilla properties
An objective way to measure the texture of tortillas is to undertake a texture analysis. In this study, a texture analyzer TVT-6700 (Perten Instruments, Sweden) was used to measure the stretchability by penetration of the tortilla and also to measure the extensibility by tension. To notice change in texture when aging, the tortillas were measured after 1, 3 or 6 and 8 days. For each batch 1–4 tortillas were measured.

The penetration test was done according to method 08-05.01 (Perten Instruments), see Table 2 for set values. A cylindrical probe (diameter 18 mm) punctured the tortilla that was placed on a platform with a 50 mm large hole. For this analysis tortillas with similar shape and size were used to get a representative value. In this test the force (g) and distance (mm) was recorded. The force was the maximal force required to rupture the tortilla, the hardness of the bread. The elasticity and stretchability of the tortillas were measured by distance to peak force, the longer distance the more elastic tortilla.

Table 1 Levels of buckwheat, guar gum and the baking time.

Trial

Buckwheat level Guar level Baking time (min.)

bg-

0

Low

4

bg+

0

Low

5

Bg-

High

Low

4

Bg+

High

Low

5

bG-

0

High

4

bG+

0

High

5

 BG-

 High

 High

 4

 BG+

 High

 High

 5

 Middle

 Middle

 Middle

 4.5

 Table 2. Set values for puncture test.

Single cycle compression

Sample height

3.0 mm

Headroom above object

8.0 mm

Compression distance

30.00 mm

Pre-test speed

6.0 mm/s

Test speed

1.7 mm/s

Post-test speed

10.00 mm/s

Trigger force

 20 g

 Data rate

200 pps

 Load cell

7 kg

The extensibility test was made according to method 08-06.01, see Table 3. A sample of the tortilla (30 x 100 mm) was attached to two clamps. One clamp was attached to the base and one to a moving arm. As the arm moved the tortilla was stretched. The measurements stopped when the tortilla bread was ruptured or after it had been stretched 15 mm. In the extensibility test, force (g) and distance (mm) were recorded. The force needed to stretch the sample, extension resistance force, corresponds to the peak force, while the distance it could be stretched corresponds to the extensibility and elasticity of the tortilla.

Table 3. Set values for extensibility test.

Single cycle tensile

Sample height

40.0 mm

Extension distance

15.0 mm

Pre-test speed

1.0 mm/s

 Test speed

 1.7 mm/s

Post-test speed

10.0 mm/s

Trigger force

5 g

Data rate

333 pps

Load cell

 7 kg

Statistical analysis

The study design full factorial trial with three variables on three levels and replicates in the centrum was chosen to see the effects of different ingredients. All trials were done in duplicate, except the middle level which was made in triplicate. The duplicates were baked on two different days. Three tortilla breads on the Swedish market, of which two were gluten free, were used as control tortilla. One of the tortilla breads was based on wheat. Analysis of variance (ANOVA – general linear model) was performed using Minitab® version 16. Samples with p<0.05 were counted as significantly different. Only the highest and lowest level of the parameters were analyzed with the general linear model. To see if the relationship was linear, ANOVA (mail effect plot) was used for all three levels.

Results

Texture affects the consumer’s opinion of the tortilla’s freshness. In the puncture test the tortillas were significantly harder the longer the baking time and as they aged. On the other hand, the tortillas were significantly softer if a large amount of buckwheat was added to the recipe. There was a relationship between age and buckwheat, Figure 1. Breads with buckwheat, a large amount or middle amount, did not increase in hardness as they aged. Bread with no buckwheat almost reached a doubled hardness value.

Figure 1. Tortilla hardness during storage. Control tortillas are also shown as GF1, GF2 and wheat.

In the extensibility test the distance the bread could be stretched corresponded to the elasticity of the tortilla. All tortillas were more elastic at first measurement (day 1) and loosened elasticity as they aged. Addition of buckwheat made the tortillas significantly less elastic. Tortillas without buckwheat could be stretched a longer distance. The elasticity was not affected by the baking time. The reference tortilla containing wheat flour was the most elastic.

Discussion

The buckwheat made the bread become less hard; this is in line with a study made by Wronkowska et al. (2013) in which buckwheat was added to gluten-free bread mixes. In that study the bread with buckwheat was less hard than bread based on starch only. As the bread aged 1–8 days, the bread without buckwheat increased in hardness, while the bread with a high level of buckwheat only increased a little. In the study by Wranowska et al (2013) an addition of 10–40% of buckwheat increased the hardness of the bread significantly during the first 24 hours. After that the increase in hardness stopped. The more buckwheat added, the less the hardness increased. In this study, there was no difference between tortillas with a middle amount and a large amount of buckwheat.

Mariotti et al. (2013) concluded that the addition of buckwheat to a gluten-free bread mix based on different starches, made the bread increase in hardness only 5.4 times compared to 20 times when no buckwheat was added. In another gluten-free bread mix containing psyllium husk and guar gum, an addition of buckwheat made the bread harder after only 3 hours. (Mariotti et al., 2013) It seems that the choice of ingredients in a gluten-free bread influences how the addition of buckwheat affects the bread.

As this project was a baking project, there are sources of errors such as different days for baking the tortilla (for further reading see the author’s thesis Rolander, (2015)).

Conclusions

Compared to the tortillas based on wheat flour, the gluten-free tortillas in this study were less hard and less elastic. To make a gluten-free tortilla more like the wheat-flour tortillas, further improvements need to be made.

References

Dubé, C., Rostom A., Sy, R., Cranney, A., Saloojee, N., Garritty, C., Sampson, M., Zhang, L., Yazdi, F., Mamaladze, V., Pan, I., Macneil, J., Mack, D., Patel, D. & Moher, D. (2005) The prevalence of celiac disease in average-risk and at-risk western European populations: A systematic review, Gastroenterology 128: 57–67.

Finax (2014). Glutenfritt som smakar och gör gott. http://se.finax.com/product_category/glutenfritt-2/ [2014-05-06]

Mariotti, M., Ambrogina Pagani, M. & Lucisano, M. (2013) The role of buckwheat and HPMC on the breadmaking properties of some commercial gluten-free bread mixtures, Food Hydrocolloids 30: 393–400.

Rolander, L. (2015) Produktutveckling av glutenfria tortillabröd – hur påverkas bröden av ingrediensval och gräddningstid? Finax AB, Helsingborg http://www.finax.se/en/contact/ 

Wronkowska, M., Haros, M. & Soral-Smietana M. (2013) Effect of starch substitution by buckwheat flour on gluten-free bread quality, Food Bioprocess Technology 6: 1820–1827.