Soy-based meat substitutes rate highly for nutrition: Study

Soy is known to provide a good source of protein when supplied as a nutritional supplement, but soy protein in the form of meat analogue has become more popular in recent years, as the protein’s palatability is improved with the high-moisture extrusion process. However, the researchers behind this latest study claim that there has been no systematic evaluation of the nutritional quality of soy processed in this manner, although soy products extruded under low- to moderate-moisture conditions have previously been evaluated.

To this end, they assessed the overall body weight, organ weights, muscle and bone growth, intestinal tract measures and bone strength of mice fed a one of two different experimental diets over a 90-day period – either including extruded soy protein isolate (ESP), or with unextruded soy protein isolate.

The researchers found: “Minor differences in some parameters were observed; however, these tended to be small and within the expected normal range. It may be concluded that ESP is a high-quality protein that provides adequate nutrition in this animal model.”​

Nevertheless, they added that longer-term feeding trials may be necessary to better define the nutritional qualities of the protein.

Simulating chicken​

One of the authors of the USDA-funded research, Fu-Hung Hsieh, a professor of biological engineering and food science at the University of Missouri, has been working for a number of years to produce a soy product that simulates the fibrous qualities of a chicken breast, rather than one that simply adds flavour and colour to soy protein. He claims that the best process is one with a very high moisture content of up to 75 per cent.

Hsieh said: “Early tests provided some of the fibrous texture to the final product, but it tasted more like turkey. In order to produce a more realistic product, we had to tweak the process and add extra fibre to give the soy a stringy feeling that tears into irregular, coarse fibres similar to chicken."​

He added that it is the high moisture content that gives soy a similar texture and appearance to chicken.

Apart from its protein content, soy has received attention for its hypolipidaemic and hypocholesterolaemic properties, as well as its ability to lower blood pressure, improve arterial compliance and endothelial function, insulin resistance and weight loss in obesity.

Source: Journal of Agriculture and Food Chemistry​

2009, Vol. 57, pp. 3550–3555

“Soy Protein Isolate Extruded with High Moisture Retains High Nutritional Quality”​

Authors: Ruth S. MacDonald, Joseph Pryzbyszewski and Fu-Hung Hsieh.