Fifty shades of peanut butter

Light spectroscopy gives quick clues on peanut quality for theoretically best peanut butter.
Peanuts very considerably in their properties, which influences the peanut butter. Photo Hongwei Yu and Simeng Zhao

Peanuts come in many shapes and sizes. The quality of peanuts can be very variable, and so can the resulting peanut butter. Hongwei Yu designed a method to quickly assess nutrient composition of peanuts by light reflection, and identify the best peanuts for different types of peanut butter.

Worldwide there are about forty thousand genetic resources of peanut (Arachis hypogaea). Depending on the variety, soil, and climate, the peanut quality can be very different. This can be a problem to make peanut butter of consistent quality. Hongwei Yu (Food Quality and Design) developed a quick method to assess peanuts, based on their reflection of light.

Quick and easy

The so-called near-infrared spectroscopy results in light spectrum data of the peanut. Yu related these data of Chinese peanut varieties with chemical data via models. Through chemometrics and machine learning, the models could predict the nutrient composition based on the spectroscopy data. ‘This method makes quality assessment much quicker than the traditional methods of chemical analysis in the lab,’ says Yu. ‘Besides, it is easy for people to learn how to use the technique.’

The best peanut butter

The researcher linked these peanut properties to the quality of resulting peanut butters. He found that peanuts with high sucrose and low fat content produce peanut butters with good texture, rheology and pyrazine content. Rheology is the ease with which you can spread peanut butter on a sandwich. To measure this, Yu used a rheometer, a special machine that rolls a plate on peanut butter. Pyrazine gives the typical smell of peanut butter after peanut roasting.

With this information, Yu identified a group of peanut varieties to make peanut butter with the highest pyrazine content and best texture and rheology. Did he make the best peanut butter? ‘Theoretically yes, but sensory research is needed to find out what people think of it.’

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