2. Carbohydrates – types, health-promoting forms (sources) and quantities in foods
There are 5 types of carbohydrates that I am concerned with when formulating foods:
- soluble fiber
- insoluble fiber
- sugar alcohols
I will discuss each one of them in the order they are above. As far as human health is concerned, although we can survive without carbs, we need them in our diet, and we function better when they are in our foods. I don’t want to get off-point and dive into discussing the health implications of having or not having carbs in our diet. That’s why I’m going to focus on how I formulate with carbs.
The psychological/physiological impact of all forms of carbs in the human diet are discussed by others in length elsewhere (if you are interested, you can start your search by reading Stephan Guyenet’s Is Sugar Fattening article).
First, as far as the range of total carbohydrates in a serving of food, I try to have at least as much carbs as I have proteins (I discussed the protein in functional foods here) and try not to have more than 3 times the amount of protein. Example: if I have a food that, by design should have 15 g of protein, my total carbs in this food range between 15 g and 45-50g. I almost never go beyond this amount. Most of the time this number even includes the sugar alcohols (I will get to that in a minute).
Starches. These are the flours (in baked goods) and starchy vegetables in cooking (potatoes, cassava root, etc.). In baked goods starches give the structure and the body of the food. Some foods can be formulated without starches for very low carb food design, but most of the time starches are used in the form of different flours and starches, like wheat, rice, sorghum, tapioca/cassava, corn, plantain, potato, oat, bean flours, even algae flour. There are lots more.
I personally do not use wheat flour due to its gluten content (more specifically gliadin content). I’ve come to realize that human nutrition is burdened by prolamins, like gluten. I don’t eat wheat myself, I never used it in my specialty bakery, and I even try to avoid most cereal grains. That doesn’t mean you have to (unless you are convinced that cereal grains do not have a place in our diets). For sure, formulating without wheat/gluten in baking is far more challenging then with it… but certainly possible for pretty much all baking applications.
Sugars. For the purposes of this article sugars include table sugar (sucrose) in all its forms – white, brown, demerara, sucanat, etc. Also, honey, high-fructose corn syrup (HFCS), glucose, fructose, palatinose, etc. If you use any of these in your application you will have to declare it in the Nutrition Facts label under Total Carbohydrates and under Sugars.
When I formulate, I am interested in diminishing the amount of sugar to half or zero per serving. This is mostly for the fact that this way I decrease the total amount of calories of the food but also because added refined sugars are not natural to human nutrition (as opposed to sugars coming from natural sources, like fruit).
Of course it is possible, even if a zero-calorie sweetener is used, for the food to have a certain low amount of sugar. This is due to sugar being percent naturally in some of the other ingredients. For example, coconut flour naturally contains a very low amount of sugar.
Fiber. I am interested in achieving at least 5g of fiber per serving from both soluble and insoluble fiber, which allows me to use the “excellent source of fiber” claim (FDA requires at least 20 percent of the RDI in a single serving, which is 5g). Some fiber may come naturally from the ingredients in the formula (ex. flours, gums, resistant starches). I prefer to add fiber to reach and usually exceed the 5g per serving mark.
My preferred sources of fiber are mostly soluble fiber, like gums, dextrins, resistant starches. The reasons are two. 1) Soluble fibers seem to be more beneficial to human health; 2) Soluble fibers are more undetectable and usually minimally alter the food texturally, visually, as well as the taste.
Some soluble fibers have other properties that are beneficial in cooking and baking in particular. Inulin, for example, is a polyosaccharide that aids in the sweetness of the product as well as moisture and browning (Maillard reactions).
Soluble fibers contain calories in the range 1-3 kcal per gram, depending on how much energy it contributes (digestible carbohydrates like sugars and starches are around 4 kcal/g). Insoluble fibers do not contribute calories to foods. They mainly add bulk in the human digestive tract.
Another thing to keep in mind. Most soluble fibers and all insoluble fibers usually do not alter the viscosity of the batter. However, gums generally do. That’s why gums (xanthan, guar, etc.) are used for other reasons, such as binding, whereas contributing to the fiber pool is a secondary benefit.
Sugar alcohols (polyols). Sugar alcohols are molecularly-altered carbohydrates. They are partially digested or not digested at all. Because of that they provide less calories than regular carbohydrates or none at all.
Sugar alcohols are usually used as sugar replacers. The most common ones used in cooking/baking are xylitol (2.7 kcal/g), erythritol (0.2 kcal/g) and maltitol (2.1 kcal/g). They cause less of a blood sugar spike in comparison with sugar. They also cause digestive problems in most people, and the rule is: the more calories the sugar alcohol provides, the more digestive distress it may cause. The reason for that is simple: most sugar alcohols reach the lower digestive tract to a different degree (and when they do, they are metabolized by bacteria, thus providing calories/energy, just like resistant starches and soluble fiber). Sugar alcohols do not cause tooth decay – they have the potential to kill the bacteria in the mouth rather than feeding it, like sugar does.
Sugar alcohols are used as bulk sweeteners as, in general, they are less sweet than table sugar. In baking they also behave differently. Let’s look at two of them individually.
Xylitol is about 90 percent as sweet as table sugar. It can be used in baked goods as a 1:1 replacer of sugar without the use of high-intensity sweeteners. It has similar properties to sugar in cooking. It is readily absorbed in water at low temperatures. It melts at 95C (203F) – for reference the melting point of table sugar is 186C (367F). So, xylotol becomes a liquid early in the cooking process.
Due to its larger molecule it has the ability to create space between starch and protein molecules thus making the product lighter in texture (sugar does the same thing). It also contributes to the browning (Maillard) process. Xylitol is considered natural. It can be found in some fruits and vegetables. It has a slight cooling effect in the mouth.
Important note: Xylitol is potentially lethal to dogs – they don’t have the enzymes needed to digest it. It causes hypoglycemia and liver toxicity. So, don’t feed your dog baked goods, made with xylitol.
Erythritol is about 70 percent as sweet as table sugar. It can be used on its own as a stand-alone sweetener (challenging) or in combination with sucrose (table sugar) or high-intensity sweeteners, such as Reb-A (stevia extract) or Monk Fruit Extract (Luo Han Guo). It has a very small molecule and it is almost completely absorbed undigested in the upper digestive tract. Very small amount of it reaches the lower intestines. Most of it leaves the system unchanged. That’s the reason why it only provides 0.2 kcal/g. That’s also the reason why baked goods, where erythritol is the main sweetener, usually have denser structure and smaller crumb – it doesn’t create enough space between the starch and/or protein molecules.
Erythritol is not readily dissolved in water at room temperature. That’s why icings made with it have crystalline structure. The melting point of erythritol is 121C (250F) – lower than table sugar, but erythritol tends to return back to its crystalline structure when the final product is cooled down. Muffins or cookies, sweetened with erythritol will have crystals on their tops when completely cooled – even more so when refrigerated.
Erythritol has a well-pronounced cooling effect in the mouth (it’s endothermic). For people that are not used to it it may be distracting. This cooling effect seems to be counteracted well by another sugar alcohol – glycerol, which has heating effect in the mouth. Also, my observations are that Reb-A, although used in very small quantities, has a similar cooling feel-reducing effect.
Erythritol does not contribute much to the browning (Maillard) reactions. Addition of sugar, inulin and or whey protein resolves this problem. Erythritol is considered natural – it’s naturally found in many fruits and fermented foods.
Note on sugar alcohols: By FDA regulations they are classified as carbohydrates and as such sugar alcohols must be included under Total Carbohydrates row regardless of how many calories they contribute to the food. On the Nutrition Facts label they have to be included after Fibers and Sugars as a separate item – Sugar alcohols , if more than one is used, or it’s possible to use only the name of the sugar alcohol, if only one is used in the formula.
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In part 3 I will write about fats (lipids) in cooking/baking and how they affect human health – so we know what fats to formulate with. Again, if there are any inaccuracies or incompleteness, I’d like to know, so I can correct or add the information.