Miller Magazine Issue: 152 August 2022

79 ARTICLE MILLER / AUGUST 2022 bricks are, the debris will be larger. On the other hand, if the cement does not set the bricks well, the wall is likely to break more easily, releasing the bricks without breaking them. This principle was used to develop the original method for measuring wheat hardness called the Particle Size Index or “PSI.” This test consists of 3 steps: 1. Grinding the grain with a calibrated tool 2. A sieving process for a fixed time 3. A weighing process of product that has passed through the sieve. If there are fine particles passing through the sieve, it means the grain is more “resistant” to crushing, or “harder.” But what does wheat hardness have to do with starch damage? At equivalent an equivalent milling process, a “hard” wheat will produce flour with more damaged starch than a “soft” wheat. This extra damage will in- fluence the quality of flours, most notably their hydra- tion potential, the stickiness of dough, the fermenta- tion, volume, and several other noticeable qualities on finished products. HOW WHEAT IS PREPARED FOR MILLING The preparation of wheat (or conditioning) consists of mixing the wheat with a specific amount of water and then letting it rest. This process makes it easier for the endosperm and the outer layers of the grain (bran) to be parted during milling. The goal is to obtain the maximum amount of flour while minimizing ash content, and thus, the amount of bran in the flour. Water softens the endosperm, mak- ing it easier for the starch to be separated from the protein matrix. This results in less damaged starch. Starch Damage Begins at the Mill All milling, whether industrial or performed in a laboratory, will inevitably produce a certain amount of damaged starch. It occurs when wheat passes through two rollers, which are designed to crush the particles. The narrower of the gap between the roll- ers, the more likely the starch will be damaged. When we look at the behavior of a damaged starch granule compared to that of a native granule, we see that: • Its water absorption capacity has been multiplied by nearly 10 • It is much more susceptible to hydrolysis by am- ylase (an enzyme with the capacity to break down glucose chains that make up starch) The physical modification of the starch granule has very significant repercussion for the baking industry. The initial effect is fairly positive. It increases the water absorption potential of flours, sometimes by several percentage points. The economic impact may also be significant, and can be looked at in two ways: For our example, lets say we have a flour sample with an absorption potential that goes from 64% to 68%. Possibility 1: More Bread can be Produced from the Same Quantity of Flour • 1,000 kg of 64% flour leads to 1,640 kg of dough. This translates to 6,560 loaves weighing 250 g each • 1,000 kg of 68% flour leads to 1,680 kg of dough. This translates to 6,720 loaves weighing 250 g each • That’s 160 extra loaves that cost only the price of 40 liters of water! Possibility 2: Less Flour can be Used to Produce a Set Amount of Bread • 6,500 loaves made from 64% flour requires 1,625 Relative Hardness Scale Category Particle Size Index (PSI%) Extra Hard Up to 7 Very Hard 8-12 Hard 13-16 MediumHard 17-20 MediumSo� 21-25 So� 26-30 Very So� 31-35 Extra Sot Over 35 Figure 2. Type of wheat according to the Particle Size Index obtained.¹