Molecular Interactions Between Xanthan Gum, Psyllium, Milk Proteins and Starches, and Their Implications on Gluten-Free Bakery Products

Abstract

Gluten in bread can cause severe health problems in patients with celiac disease. However, gluten-free substitutions often show impaired quality characteristic like a liquid dough because of a missing gluten-network or accelerated staling due to the high amount of gluten-free starch. Therefore, hydrocolloids are considered to improve gluten-free bread quality characteristics. The idea of this
degree project was to understand the interactions between xanthan gum and specific bread ingredients on a molecular basis with subsequent analysis of xanthan gum’s function in gluten-free dough and bread. The molecular interactions between xanthan gum, psyllium, starches and milk powder were tested as model systems in water-salt solutions and analysed by rheological measurements, i.e. amplitude sweep, temperature sweep and apparent viscosity profile. Based on these analyses, two types of gluten-free doughs and breads were prepared, one of which contained 1.2% xanthan gum and the other not. The doughs were analysed using rheometry, moisture analysis, texture analysis and kneading behaviour. Moisture analysis as well as texture analysis was performed after baking bread loafs of both types of dough. The analysis of molecular interactions showed that the addition of xanthan gum increased the overall rigidity and viscosity when mixed
with starches and psyllium. Also, the combination of xanthan gum with starches resulted in a lower pasting temperature compared to starches without xanthan gum probably due to enhanced starch granule swelling. In contrast to that, the behaviour of the xanthan gum and milk powder
formulation seemed to be xanthan-gum driven. The derived effects on gluten-free dough and bread based on the molecular interactions in solution could be partially confirmed in the analysis of dough and bread. For example, the incorporation of xanthan gum to gluten-free dough resulted in a more rigid dough with less moisture release during moisture analysis compared to the gluten-free dough without xanthan gum. The different properties of both tested gluten-free breads showed the thickening effect of xanthan gum, which led to lower baking loss and higher loaf weight with a firmer bread texture in comparison. Also, the observed lower moisture content in the crust of the bread with xanthan gum could probably delay retrogradation and bread staling. From these results it can be concluded that xanthan gum can act as a moisturizer and thickener for gluten-free bread and affects the molecular behaviour of gluten-free starches and psyllium.

Popular Abstract

An approach to understand molecular interactions of xanthan gum and effects on gluten-free products.

Many people associate bread mainly with carbohydrates and starch, although it is the unique protein gluten that gives bread its springy structure with a fine-pored bread crumb by forming a molecular network. However, gluten can cause health problems like diarrhea or malabsorption of vitamins in people suffering from celiac disease. This requires affected individuals to abstain from products with gluten such as wheat bread. On this account, the food industry is increasingly focusing on gluten-free alternatives which is reflected in the global market and the increasing offer of gluten-free products.

However, the unique characteristic of gluten in wheat flour cannot be easily substituted. The lack of a gluten-network often leads to a more liquid dough which can affect processing and bread quality characteristics. Since bread texture is one of the most important factors for consumer acceptance it is important to find an adequate substitution for gluten. Research has shown that hydrocolloids are commonly used in gluten-free bakery products. Hydrocolloids like xanthan gum are molecules that can easily bind water which can lead to a thicker dough and influences final bread quality characteristics. Although xanthan gum could be used in gluten-free bread, attention must be paid to whether and how it can interact with other ingredients for example starches and milk proteins or further hydrocolloids like psyllium, and what effects xanthan gum generally could have on the gluten-free doughs and breads.

The results of this degree project show that xanthan gum had a great effect on starch gelatinization and on psyllium whereas no influence of xanthan gum has been observed in combination with milk powder proteins. The analysis of the dough and bread revealed that xanthan gum mainly increased the dough stiffness and crumb firmness and decreased the moisture release. Especially the latter can be seen as positive influence on bread hardening by decreasing the moisture migration to the crust and subsequent loss of moisture. These results are mainly based on rheological measurements which measure the flow and deformation behaviour of a sample based on which the molecular interaction can be derived. This understanding was then used to predict possible gluten-free dough/bread properties. The effect of xanthan gum on gluten-free doughs and breads was analysed by comparing a gluten-free dough/bread with xanthan gum to a gluten-free dough/bread without xanthan gum regarding. This was performed by rheometry, kneading behaviour, moisture and texture analysis for the doughs and by moisture and texture analysis for the breads.

Overall, the results can be important for dough processing and manufacturing regarding dough handling. Especially, when considered in product development, the incorporation of xanthan gum has the potential to increase consumer acceptance of gluten-free bakery products like bread.

• author: Bischoff, Carolin
• supervisor: Jeanette Purhagen
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM01 20212
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Rheology, Xanthan gum, Gluten-Free, Food Technology
• language: English
• id: 9069198
• date added to LUP: 2022-06-07 16:32:32
• date last changed: 2022-06-07 16:32:32