To market, with just the right crisp

WHEN Martin’s Family Fruit Farm decided to turn the fruit of its labour into a snack, Kevin Martin drove from Ontario to North Carolina with boxes of apples in the back of his truck. He dreamed of developing a product from the orchards of the family’s 700-acre farm, and he wanted Buhler Aeroglide’s drying expertise to help bring the idea to market.

The vision of a new product

The Martin family business harvests a variety of apples as one of the largest growers, packers and shippers in Canada, but the idea to develop an apple snack was new. Mr Martin envisioned a healthy snack with the crunchy texture of a potato chip, free of the preservatives and added sugars commonly found in many snack food products. He wanted to use the air drying process to remove as much moisture as possible to create a product as healthy tasting as a natural apple.

“We couldn’t improve nature, but we wanted to package what nature has given us in a healthy way,” Mr Martin said. “It had to taste as fresh as the handpicked apples from our orchards.”

He knew the colour and texture he wanted to achieve, but he needed to define the parameters for drying. He also needed processing technology that would bring the product to fruition.

Results in the technical lab

With pilot scale lab configurations that include dual impingement, through-air and fluidised bed technology, Buhler Aeroglide could offer the processing knowledge and confidential design and testing Mr Martin needed. To obtain the desired results, Buhler Aeroglide recommended multiple drying stages.

Key testing variables included thickness of the apples, time to dry and temperature set points. Experiments started with cored apples sliced in different ways, some with the peel on and some without. The thinnest apple wheels dried faster and remained crisper. They also held the most fruit flavour. Next, they tested the thickness of the first layer. If the apples were stacked too thick, they would stick together. Also important was how much heat to apply initially and for how long. Airflow and temperature adjustments were made. When the product reached a leathery stage, it was time to turn the apples and decrease the temperature.

“We tested many varieties from our orchards, experimenting with drying time at different stages, depths, and thickness,” Mr Martin said. “Then, we’d check the results and make adjustments by shortening the length of drying time and increasing the thickness of the bed.”

The apples were blanched to prevent browning. That’s because keeping the apples as lightly coloured as possible would make the most appealing apple. They tested Crispin, Empire, Idared, Red Delicious, Golden Delicious and apples, and each variety reacted differently to the variables with changing colours and textures. They waited for the apples to develop a fluffy texture with curling edges, which meant it was time to cool. Then, the final test was conducted by dropping the apple wheel onto the lab floor. When the apple broke apart, the desired product characteristics were achieved. A new product was born.

The next step was to optimise the process. Buhler Aeroglide’s application engineers worked with Mr Martin to determine how to make the project feasible. “We simulated the process using four pilot dryers in the lab, moving the product from dryer to dryer to create different drying stages in a continuum,” said Aldo De Tuoni, applications engineer at Buhler Aeroglide.

Every possible variable was measured in order to maximise the capacity of the projected dryer. This included product shrinkage, product bulk density, retention times, temperature, and product load. “When dehydrating a vegetable or a fruit, we process five to six times the mass we want to obtain for the final product,” said Mr De Tuoni. “For example, to obtain 50 lbs. of dried apples, a customer would need to process approximately 250 lbs to 300 lbs of fresh apples. We helped the customer create a processing plan based on the lab measurements.”

In the end, Martin’s Crispy Apple Chips reflected the perfect blend of innovation and product excellence. Buhler Aeroglide created a drying process that met the customer’s requirements, and a multi-stage AeroDry conveyor dryer was manufactured for the processing site.