Frito-Lay's method uses fruit purées blended with cereal ingredients to form the snack which is then vacuum cooked.
The company said there was a need to develop healthy snack alternatives and cater to a new interest in snacks containing fruit matter with a high nutritional content, especially in light of widespread government schemes to drive increased fruit and vegetable consumption.
However, the snack titan said whole fruit in snacks proved inconvenient to eat and created shorter shelf life. Current products on the market also had limited appeal due to added sugars, flavors, chewy texture and unappealing visual appearances, it said.
“Specifically, whole or sliced dried or dehydrated fruit are disadvantaged by the fact consumers may find them polarizing in flavor, texture or appearance and therefore they have limited consumer appeal,” it wrote in its patent filing.
Developing ambient shelf stable snack foods always threw up textural challenges in terms of crunch and mouthfeel, Frito-Lay said.
Temperature-sensitive materials like fruit were also difficult to process, it said, since standard oven drying techniques at high temperatures were not suitable because they could char the fruit or cause poor flavor and nutrient loss.
Alternative methods like vacuum frying or freeze drying also had their pitfalls, predominantly around texture, it said. Snacks containing fruits made using a vacuum frying process, for example, contained high fat levels and were chewy, it said, and freeze drying was very expensive and resulted in a powdery finished texture.
However, it said its patent-pending method ensured a crunchy texture and melt-in-mouth properties by vacuum cooking a mix of whole fruit-based solids and binder solids with ideal moisture content levels.
Solving the problem with unique microstructures
Frito-Lay’s method used a fruit paste and binder material (at least one cereal-based ingredient) to create a mix that was then cooked in a vacuum-controlled atmosphere. For example, an apple purée could be mixed with oat flour, starch material, egg, soy, nut seeds or even pulses. Fruit options included strawberry, blackcurrant, banana, apple, pear, orange, lemon, and cherry, among others.
“This characteristic texture is a function of the unique microstructure of the snack food product,” it explained, because the fruit purée and cereal ingredient were mixed into a rigid matrix. This resulted in a “substantially homogeneous cooked mixture of at least one fruit material and at least one binder material”, it added.
The fruit used could be fresh purée, juice, pomace, paste or concentrated versions with fresh, frozen, diced or shredded fruit added in. Fruit could also be added in whole form, Frito-Lay said, for example as fresh or grated fruit. “The addition of whole fruit increases the residual solids in the mouth after dissolution of the majority of the matrix in the mouth, and the snack food has a chewier texture because of the whole fruit cell structure.”
A dairy material could also be added, such as fresh yogurt, kefir, milk, cream or whey to enhance the creaminess of the snack, Frito-Lay said. Sugars, flavorants or additives could also be incorporated into the mix, but moisture content was critical, it warned.
A moisture content of between 49 and 75 wt% (weight percent) based on the weight of the mixture was vital in creating the correct rheology characteristics which in turn enabled the correct type of bubble formation and matrix structure creation upon drying, it said. Too little water meant bubbles were difficult to create and too much water produced a mixture too low in surface tension, it said.
Critical vacuum step
Mixture and cooking conditions also had to be carefully controlled to ensure bubbles of steam formed in the mixture. If starting viscosity and mixture characteristics were correct, non-spherical bubbles remained in the product – much larger than those typically found in freeze-dried products, creating thicker cell walls which created a unique texture, it said.
“…Without being bound by any theory, it is believed that the structure of the final matrix is primarily influenced by the viscosity and surface tension of the material whilst the product is boiling.”
It also noted that the non-spherical bubbles were typically orientated in line with the length of the chip, improving texture compared to known fruit-containing snack food products.