Evaluation of Soumbara (Parkia biglobosa) Quality During Storage Using Mid-Infrared Spectroscopy and Physicochemical Methods

The fermented seed of néré (Parkia biglobosa), known as Soumbara, is a condiment widely consumed by the population in West Africa and Guinea in particular. The present study aims to use physicochemical, colorimetric methods and mid-infrared (MIR) spectroscopy to evaluate the evolution of the quality of Soumbara during storage (30 days). Thus, 5 kg of Soumbara were taken, subdivided into 7 batches of samples, and analysed every 5 days for 30 days. Physicochemical analyses (water activity, moisture, proteins, and total ash) would show that the storage duration induced a variation during storage; for example, the total ash contents on days 1, 5, 10, 15, 20, 25 and 30 are respectively 3.96 ± 0.25, 3.89 ± 0.43, 3.97 ± 0, 23, 3.99 ± 0.12, 4.54 ± 0.14, 4.57 ± 0.2 and 4.8 ± 0.21%. During the first 15 days of storage, no significant differences (p < 0.05) were observed between samples. The colorimetric measurements showed that the storage duration did not significantly affect the values of a* and b*, except the L* value which decreased significantly (p<0.05) (42.16 ± 0.015 on day 1 to 40.02 ± 0.015 on day 30). Applying statistical methods to mid-infrared spectroscopy allowed a clear distinction between the Soumbara samples during storage for 30 days. The partial least squares regression (PLSR) applied to MIR spectra made it possible to predict water, moisture and protein activity levels, since R2 greater than 0.99 were obtained. The results demonstrated that mid-infrared spectroscopy coupled with chemometric tools could be used as a rapid screening tool to assess and monitor the quality of Soumbara during storage.