What’s inside a “Metato”? The Case Study of Chestnut Flour Obtained by a Traditional Drying Method: Chemical, Aromatic, and Sensory Properties.

Chestnuts are traditionally dried and processed into flour, which is gluten-free and rich in starch and micronutrients. Over the past decade, demand for chestnut flour has steadily increased, driven by consumer perception of its associated health benefits. As the market for chestnut flour expanded from small-scale to large-scale production, alternative methods were developed to replace traditional processes. However, these innovations often result in a loss of product identity, particularly in terms of sensory attributes and typicity. Despite this shift, traditional production methods remain active in Italy, as evidenced by the certification of 15 chestnut-based products, including two PDO chestnut flours.

This study aimed at evaluating the quality of traditional chestnut flour produced through firewood drying in structures known as “metati”, in terms of sensory and chemical features. For this purpose, two producers of traditional chestnut flour were selected and the processing conditions of their metato were monitored.

The impact on flour was assessed through the analysis of water activity, dry matter, lipid content, starch, glucose, fructose, sucrose, ascorbic acid, total phenolic content, and antioxidant activity. Colorimetry, volatile organic compound (VOC) profiles, and descriptive sensory analysis were also performed.

Although the traditional process typically reduces the content of antioxidant compounds compared to more standardized industrial systems, sensory analysis and VOC profiling revealed that traditional process imparts a distinctive aromatic profile, primarily due to smoke exposure during drying. In contrast, commercially produced chestnut flours generally exhibit a flatter sensory profile, lacking in typicity and recognizable aromatic traits.

However, a weakness of this type of process lies in the poorly controlled conditions within the drying facilities, which can lead to inconsistent drying and affect the final product quality. To address this issue, control methodologies could be developed to improve product quality and simplify process management for producers, in order to reduce the manufacturing costs.