Q: "I have noticed on a few labels lately the term 'ash' and a measurement in grams. What does this mean? They're not talking about the same stuff that ends up in the bottom of my fireplace, are they?"
A: We asked Caroline Gunn, director of Food Safety Services Ltd in Napier, what 'ash' means on a food label:
"Ash is the term used to describe the non-combustible elements left over when our body burns up the food we eat. During digestion the carbohydrates, proteins, fats and vitamins in the food we eat all 'burn up' as part of metabolism, however the minerals can't be burnt away because they are elements and exist forever just exactly how they are. Similarly, when a body is cremated there is a small amount of ashes left which represent these same minerals in our body that can't be burnt away. They are mainly composed of calcium (from our bones), phosphorus, potassium, sodium, chloride, magnesium and sulphur, with smaller amounts of trace elements such as iron, iodine and zinc etc.
You may have heard foods referred to as acid forming or alkaline. This means that depending on the mineral content of the various foods we eat, the ash residue left after metabolism will be acidic, neutral or alkaline. In general meat, dairy, eggs, processed or refined foods, fruit and sugars are said to be acidifying whereas vegetables are said to be alkalising.
Pet food companies usually put labels regarding ash or specific minerals on their cat and dog food labels because components of the ash (mineral) content in the food may contribute to urinary crystals (particularly magnesium) in susceptible cats or dogs.
So in answer to your question: no, ash is not added to food as an ingredient but it is recorded on the label as an indicator of mineral content. The ash in your fireplace represents the mineral content of the tree from which the wood came and would have a quite different mineral composition to that of a food."