doughLAB tests for the effects of flour additives on dough quality

Mark L. Bason (1), Jennifer M.C. Dang (1) and Corinne Charrié (2)

(1) Perten Instruments of Australia Pty Ltd, 1/2 Apollo Street, Warriewood NSW 2102, Australia
(2) Perten Instruments AB, PO Box 5101 SE-141 05 Huddinge, Sweden

This article is adapted from the paper ‘Optimised methods for detecting the effect of flour additives in the doughLAB: IV – Effect of improvers: enzymes’ presented at ICC Jubilee Conference, 4–7 July 2005, Vienna

Flour additives play an important role in the modern bakery, including imparting tolerance to variation in raw materials and process conditions, and improving dough handling properties, loaf volume, taste, texture, nutrition and shelf life.

The effects of several additives on dough quality were examined on the doughLAB, a z-arm dough mixer that tests the quality and characteristics of doughs. Using AACC Method 54-21 (30°C, 63 rpm), untreated flour was tested to determine the optimum water absorption (WA).

Using the optimum WA for the hard flour, the effect of fungal a-amylase on dough quality was tested at several enzyme concentrations (25, 50, and 100 ppm) and temperatures (30°C and 50°C). At both temperatures, a-amylase caused a reduction in dough strength by breaking down starch in the flour, observed as a reduction in stability and dough development times (Figure 1). The effect of the amylase is greater at 50°C (greater reduction in torque and stability than at 30°C), as the higher temperature was closer to the optimum temperature of the enzyme, and also possibly due to the greater mobility of molecules at higher temperatures. Testing at the higher temperature of 50°C therefore produces more rapid results (< 5min) than testing at the standard 30°C (~ 8 min). However at 50°C, the effect of the enzyme appears to be more sensitive at low dosage, with a large effect observed using low concentration, while the higher concentrations show similar effects on dough weakening (Figure 1)Figure 1. doughLAB curves showing the effect of a-amylase on dough quality when mixing at 30°C and 50°C.

Hemicellulases (HCs) break down the non-starch polysaccharides (NSPs) hemicellulose. These enzymes are used as an improving agent affecting dough tolerance, loaf volume, and crumb texture. However, HC causes the dough to become ‘sticky’. In some countries, a combination of glucose oxidase and HC is marketed as a substitute for ascorbic acid. Adding the right amount of glucose oxidase restores dryness to the dough (Sluimer, 2005).

The effects of HC on dough quality from hard and wholemeal flours was tested on the doughLAB. For both flours, the HC strengthened the dough by increasing stability and delaying softening (Figure 2). As for a-amylase, the action of HC was more pronounced at higher temperature (for hard flour), where a greater and earlier (< 5 min) difference between the curves was observed. Flours containing NSPs tend to have higher WAs due to the high hydration capacity of the NSPs (Lineback and Rasper, 1988). The addition of HC caused a reduction in hemicellulose, and therefore a reduction in the WA for both hard and wholemeal flours. Again, the effect of the enzyme on WA was more pronounced at high temperature. 

Figure 2. doughLAB curves showing the effect of hemicellulase (HC) on dough quality of hard flour (30°C and 50°C) and wholemeal flour (30°C).

Similar experiments have been trialed and results achieved for other additives, such as salt, sugar, lipid, oxidising and reducing agents, emulsifiers (DATEM, mono- and diglycerides), and hydrocolloids. Work is continuing on optimising the sensitivity and speed of these tests by altering mixing speed and temperature regimes, to suit both the product/process in question and the properties of the additive.

References

American Association of Cereal Chemists (AACC) (1995). Farinograph method for flour. AACC Method 54-21, Approved Methods of Analysis, 9th Edition, AACC, St. Paul, MN.
 
Lineback, D.R. and Rasper, V.F. (1988). Wheat carbohydrates. In Y. Pomeranz, (ed.), Wheat: Chemistry and Technology Volume I, AACC, St Paul, MN, pp.277–372.

Sluimer, P. (2005). Principles of Breadmaking, AACC, St. Paul, MN.