CHICAGO The term “alternative flour” implies a foodstuff other than traditional milled cereal or seed that has been ground into a fine consistency. Among reasons a product developer may use such flours is to eliminate gluten-containing grains, namely wheat, from formulations. Other motives include replacing nutrient-void flours such as those from rice and tapioca with flours that contain protein, fiber, heart-healthy fats and other nutrients.

Sometimes an alternative flour may be made from traditional grains that already have been used, also known as spent in the brewing world. They are upcycled and given a second chance to be consumed.

And while all these sources of “flour” are technically plants, flagging legume-, nut- and vegetable-based flours on snack foods appeals to consumers following plant-based diets.

When Katlin Smith founded Chicago-based Simple Mills in 2012, the clean label movement was in its infancy. The 26-year-old entrepreneur had recently “cleaned up her diet” and was on a mission to bring cleaner options to store shelves, starting in the bakery mixes category and over time progressing into savory crackers, sweet baked goods, snack bars and more.

“When I founded Simple Mills, all the mixes I found on grocery store shelves had a ton of sugar, a lot of highly processed ingredients, things I couldn’t even pronounce,” Ms. Smith said. “I wanted to offer products that would eliminate refined sugar, high-glycemic flours, gluten and genetically-modified ingredients.”

Almond flour is the predominant ingredient in the Simple Mills bakery mixes, as well as most of the snack products. Coconut flour also is used often. Her first savory snack cracker line debuted in 2016 and is made with a proprietary flour blend of almonds, sunflower seeds and flax seeds.

“This combination yields a higher vitamin and mineral content than many competitive products, as well as a lower carbohydrate count and glycemic impact,” Ms. Smith said. “Most other crackers include ingredients like rice flour, potato starch, xanthan gum, soy lecithin, ammonium bicarbonate and maltodextrin with little or no nutritional value.”

One of the brand’s newest concepts is Seed and Nut Flour Sweet Thins in chocolate brownie, honey cinnamon and mint chocolate varieties. They are made from a diverse mix of nutrient-dense ingredients, with the flour blend based on watermelon, flax and sunflower seeds, and cashews.

“We chose watermelon seed flour as the leading ingredient in our flour blend because it helps create a deliciously light and crispy texture and brings protein, good fats and micronutrients,” Ms. Smith said. “If that wasn’t enough, watermelon seed introduces greater crop diversity, which is a key principle of regenerative agriculture.”

Building on the company’s commitment to people and planetary health, Sweet Thins are sweetened with coconut sugar from farmers that use regenerative practices such as agroforestry, perennial cropping and composting. Another sustainable ingredient the company is exploring is chestnut flour. It is the first ingredient in the new Simple Mills No Added Sugar Pancake & Waffle Mix.

Chestnuts are a largely forgotten crop that was big business in the United States before devastating blight killed billions of trees in the early 1900s. While chestnut flour is a niche product, its versatility and nutritive value as a gluten-free flour is attracting bakers, with some suppliers expecting US-grown chestnuts to go mainstream over the next decade, replacing the mostly imported coconut flour.

Chestnuts are referred to as “the grain that grows on trees” in Italy, where dried chestnuts have long been made into a tannish, sweet-flavored flour that is used in everything from crepes to cakes. Chestnuts do not have a high fat content like most other nuts; rather, they contain mostly carbohydrates. As a result, the flour made from chestnuts has similar properties to wheat flour, just without the gluten.

Reducing food waste

Many of the up-and-coming alternative flours are focusing on reducing food waste by using edible byproducts of food production, such as watermelon seeds, and turning them into products for human consumption. While munching on watermelon seeds is likely not something most consumers want to do, when these seeds that are loaded with iron, magnesium, zinc and heart-healthy omega-3 fatty acids get pulverized into a flour, the possibilities are numerous.

Here’s another example of turning waste into a nutritious, delicious ingredient. This one comes from the acorns produced by oak trees. Squirrels may enjoy acorns, but most humans consider them a nuisance.

Acorns — the nuts with caps and shells removed — are high in protein, potassium, magnesium, calcium and vitamin B6. They are naturally gluten-free and loaded with fiber. More than 400 species of oak trees are grown around the world, and the acorns they produce vary in color, flavor and size. They naturally contain tannic acid, a water-soluble bitter substance that leaches out during processing, allowing their natural sweetness to come forward.

Acorn flour is still a specialty ingredient; however, it is gaining traction on local levels. On Kea Island in Greece, Marcie Mayer, a California native, heads up the Oakmeal Acorn Initiative, which is a multifaceted project to help farmers rekindle the collection of acorn caps for exportation to tanneries, as well as establishing acorn flour-based products in the local cuisine. Ms. Mayer produces and markets a line of acorn cookies and acorn pasta.

“Acorn flour behaves very differently than wheat flour,” she said. “It has a darker color and much richer aroma. It is typically blended with wheat flour.”

Thousand Oaks Acorn Co., Thousand Oaks, Calif., produces four varieties of the gluten-free AcornBar. While oats are the first ingredient, locally harvested and milled acorn flour is the marketing proposition. Varieties are coconut-ginger-apricot, coffee-chocolate-cinnamon, chocolate-orange-ginger and cranberry-orange-coconut.

Don Guerra’s passion for baking and his commitment to community is showcased in every loaf baked at Barrio Bread, Tucson, Ariz. Local-grown and milled grains are a pillar of his business. His ingredients include alternative flours sourced from some unexpected places.

One alternative flour that Mr. Guerra uses comes from the mesquite tree (Prosopis glandulosa), which is widespread in southern Arizona. The pods are considered a nuisance by landscapers, but when they are dried and ground into a reddish flour, they are the secret ingredient in many locally produced foods.

The fleshy part of the pod provides carbohydrates, including soluble and insoluble fibers, while the seeds are a concentrated source of protein, including the essential amino acid lysine, which often is limited in plant-based proteins. All told, mesquite flour is a nutritional powerhouse, as it’s also loaded with calcium, iron, magnesium, potassium and zinc. The flour has a malty, nutty, smoky, sweet flavor profile often described as having hints of cocoa, maple, molasses and hazelnut.

Legumes also may be dried and ground into alternative flours. Chickpea flour, for example, often is used to increase the protein content of crackers and baked snacks. It has almost double the fat content of whole wheat flour and is about 25% higher in protein. The flour tends to be denser and stickier than regular wheat flour, and recipes need to be adjusted.

Legume flours are made from cooked beans that have been dehydrated and milled to specification. This includes grit, meal and powder forms.

Banana flour is an emerging industrial alternative flour yet to gain traction in the United States. It is made from green bananas that may never ripen and often become waste. The green varieties feature high levels of RS2-type resistant starch, which is a prebiotic dietary fiber shown to provide a range of health benefits. Green banana flour also may function like a hydrocolloid. The flour provides bulk and replaces sugar in baked foods, in particular bars, as well as snack foods. The flour has a beige color with a bland, earthy flavor.

Circle of life

San Francisco-based Renewal Mill converts the pulpy leftovers of soy and oat milk production into versatile, gluten-free flours that boost the fiber and protein content in a variety of consumer packaged goods. The upcycled soy ingredient is referred to as okara flour. It has a neutral flavor, which is described as slightly milky or nutty. It has a light color, allowing it to blend easily into most flour-based products, said Claire Schlemme, chief executive officer.

“Okara flour has a number of functional benefits, including having high water- and oil-binding abilities,” Ms. Schlemme said. “This improves moisture retention and can lengthen shelf life of bakery products.”

ReGrained, San Francisco, developed a patented technology to repurpose spent grains produced by beer brewers and process them in a way that makes them stable as a food ingredient. Its first certified upcycled ingredient is ReGrained SuperGrain. It has a toasted appearance, flavor and aroma. The flour provides a minimum of three-and-a-half times the dietary fiber and double the plant protein of whole grain flour, as well as prebiotics, according to the company.