More information about the ingredients in the baking mixes and what they do.
1. Wheat starch.
This is also know as "corn flour" or "wheaten corn flour" in Australia. It has around 0.3g of protein per 100g. At this level, we would expect it to have 15mg of phenylalanine per 100g (based on the general assumption that 1g of protein = 50mg phenylalanine), but it is a third less at around 4-5mg - a negligible amount.
2. Tapioca flour.
This comes from the cassava root, which is a tuberous plant that is naturally very low in protein, usually around 0.1g per 100g. It is processed into a fine powder that has a neutral taste. It gives bread a "chewiness" and improves the texture.
3. Potato starch
Neutral flavoured starch from potatoes. Improves the texture of breads.
4. Sodium bicarbonate, Bicarbonate of soda or Baking soda (e500)
This is a salt with the chemical formula NaHCO3. It is used in baking a leavening agent that reacts with acids to produce carbon dioxide. Acids that induce this reaction include cream of tartar, lemon juice, vinegar, yoghurt, buttermilk and cocoa. It is also activated by heat. It has a salty/alkaline taste and if the wrong amount of sodium bicarbonate or acid is used not all of the bicarb is converted to carbon dioxide, leaving a salty taste to the baked goods.
Baking powder is sodium bicarbonate and cream of tartare. It has the acid needed to make the sodium bicarbonate activate within it.
5. Psyillium husk
The husk from the seeds of the plant Platago ovata. When mixed with a liquid they swell and become mucilaginous (like jelly). This adds structure to low protein baked goods, acting like the gluten in bread. They are indigestible and contain mostly fibre, and are used medically to treat constipation. Metamucil contains psyllium husk and sugar (but flavoured versions can contain Aspartame).
6. Glucono Delta Lactone (e575) or GDL
This is used as a rising agent. It is an acid and activates bicarbonate soda in a very efficient way, using around 2:1 of GDL to bicarb. This allows baked goods to rise and its addition in the bread mix creates rise and reduces the amount of yeast needed, thus reducing the protein content of the final loaf by around 1.3g.
7. Xanthan gum (e415)
This is a polysaccharide, a gum, produced by the bacteria Xanthomonas campestris. It is the slimy substance that forms on your cabbage and lettuce when left in the fridge too long! The processing of this varies and this affects how much of the bacteria is removed and how pure the xanthan gum is that is left. This in turn affects the protein content and I have seen amounts from 0g/100 to 9g/100. I sourced xanthan gum with 0g protein/100g for these mixes. Xanthan gum increases the viscosity of substances it is mixed with. It is used in these mixes to replace gluten, giving the batters and doughs a "stickiness" and providing structure.
8. Hydroxypropylmethylcellulose (e464)
This is the ingredient in Loprofin's Egg White Replacer. There are many versions of this cellulose, the brand I used was Wellence. It is derived from plant cellulose. It is a fine white powder and functions in a similar way to xanthan gum. It adds viscosity and structure, allowing the air bubbles formed from yeast and other rising agents to be trapped, allowing the bread and baked goods to rise.