In two separate studies, scientists from the University of Illinois found that altering the porosity of food could reduce the amount of oil absorbed by foods during frying and increase the amount of salt that is tasted during chewing, so that less is needed.
According to lead author of the salt study Youngsoo Lee, between 70 to 95% of the salt added to processed foods was not released in our mouths during chewing but rather during digestion, meaning it was superfluous to taste.
Given that up to 75% of salt consumed in industrialised countries comes from processed food, the study said that reducing the amount added to food during processing could have significant health benefits.
“We wanted to alter porosity in processed food, targeting a certain fat–protein emulsion structure, to see if we could get more of the salt released during chewing. Then food manufacturers won’t have to add as much salt as before, but the consumer will taste almost the same amount of saltinesss” said Lee.
Manipulating the porosity of foods also means they are broken down in the mouth differently, thus increasing the surface area and the number of salt molecules that are tasted.
“When foods crumble easily, we further reduce the amount of salt that is needed. Changing the number or size of pores in the food’s surface can help us to accomplish this,” he said.
Meanwhile the second study, published in the Food Research International, used mathematical equations to analyse the interaction between water, oil and gas during frying and the textural changes which result.
According to the scientists, led by Harkirat Bansal also from the University of Illinois, frying food is a complex chemical process involving more than 100 equations with different chemical reactions occurring simultaneously and food polymers changing state.
Co-author Pawan Takhar said that gently fried processed foods such as crackers had an optimal frying time of 40 seconds: “That’s the cracker’s peak texture. Any longer and you’re just allowing more oil to penetrate the food.”
Capillary pressure of food makes the overall pore pressure negative – and it is this negative pressure that creates suction, drawing oil inside the food pores.
Previous research conducted into the science of frying focused on capillary pressure during the oil phase of frying, but Takhar et al. found that pressure during the water phase (the point during frying when water molecules evaporate) could also significantly affect the oil uptake.
The researchers identified at what point the pressure became negative, but noted that food manufacturers must also take into consideration taste and texture to find the optimal point.
“The trick is to stop when pore pressure is still positive (or less negative)—that is, when oil has had less penetration. Of course, other variables such as moisture level, texture, taste, and structure formation, must be monitored as well. It’s an optimization problem.”
Source: Journal of Food Science
First published online ahead of print November 2014, doi: 10.1111/1750-3841.12669.
“Temporal Sodium Release Related to Gel Microstructural Properties—Implications for Sodium Reduction”
Authors: Youngsoo Lee, Wan-Yuan Kuo et al.
Source: Food Research International
First published online ahead of print April 2014, doi.org/10.1016/j.foodres.2014.04.016
“Modeling Multiscale Transport Mechanisms, Phase Changes, and Thermomechanics during Frying”
Authors: Pawan Takhar, Harkirat S. Bansal et al.