Thermal Treatment Effect on Free Amino Acids in Honey Samples

Abstract

Free amino acids are minor constituents in honey which are responsible for the determination of botanical origin of honey. However, the composition of free amino acids was likely to be altered upon thermal treatment. Therefore, this study was conducted to investigate the profile of free amino acids before and after thermal treatment at 90°C for 30 minutes. This study revealed that phenylalanine (101.84-139.74 mg/kg), tyrosine (28.71-138.36 mg/kg) and proline (23.93-83.21 mg/kg) were found abundantly in all honey samples such as Tualang, Gelam and Acacia honey samples. After the honey were heated, it was found that proline and threonine were significantly reduced, while tyrosine, valine and lysine were increased in all honey samples. The proteolytic digestion was responsible for the increase of tyrosine, valine and lysine concentration after thermal treatment. The decrease could be attributed to the denaturation of proline and threonine themselves, apart from the reaction between the carbonyl group of reducing sugar and the amino acids upon thermal treatment.

Physicochemical and Antioxidant Properties of Honey: Effect of Heat and Storage

“…The results regarding the increase of the HMF content with increasing temperature from 40 to 100 C (Figure 1b) were concordant with the results obtained by other researchers [14,35,36]. On the other hand, it was observed that different thermal treatments resulted in a decrease in proline content, which is usually associated with denaturation of protein [12]. Compared to the different treatments, oven heating caused a marked decrease in the proline content.…”

“…Many researchers have reported that the quality or certain nutritional properties of honey can be degraded during processing, thermal treatment and storage [11][12][13]. During processing honey is heated at temperatures ranging from 30 to 140 C to reduce crystallisation and water content in order to increase its shelf life [14,15].…”