Nondestructive Quantification of Betalain Secondary Metabolites in Red Beet (Beta vulgaris) Powder Using Near- and Mid-Infrared Spectroscopy

Abstract

Betacyanin and betaxanthin are well-known secondary metabolites of betalains in red beet (Beta vulgaris), which contribute to the natural red–purple and yellow–orange color. Various analytical techniques, such as chromatography and nuclear magnetic resonance spectroscopy, are currently available and have been performed to quantify the betalain content. However, evidence shows that these methods remain arguable because of their disadvantages, such as being time-consuming, labor-intensive, destructive, and producing chemical wastes. This study aimed to encompass the spectroscopic techniques through near-infrared (NIR) and mid-infrared (MIR) spectroscopy coupled with partial least squares regression PLSR analysis for rapid and nondestructive measurements of red beet powder betalain content. This study evaluated full and effective wavebands to determine the optimum model for predicting betacyanin and betaxanthin in red beet powder. The finding of effective wavebands was done by employing a variable important in projection (VIP) technique. This study demonstrated that betacyanin and betaxanthin were optimally predicted using NIR, with an R² of 0.92 and a RMSEP of 0.07 mg/g for betacyanin and R² of 0.83 with RMSEP of 0.04 mg/g for betaxanthin. This optimum model was achieved through the effective wavebands via VIP method. Thus, the proposed model is applicable for predicting betalain content in red beet powder nondestructively.