Evaluation of CIE-lab colour parameters during the clarification of a sugar syrup from Mesquite pods (Prosopis Pallida L.)

There are several commercial sugar syrups obtained from the Mesquite pods, however their dark-brown colour limits their use in the food industry. In t his work we clarified sugar syrups from Mesquite pods by a two-step procedu re: (1) lime-milk treatment with the addition of different amounts of calci um hydroxide and aluminium sulphate, and (2) ion-exchange treatment using A -400 anionic and/or C-100 cationic resins. Samples were evaluated for colou r using the Hunter Lab colorimeter (Hunter Associates Laboratory Inc, Resto n, VA, USA) (L*, a*, b*,) and for sensory acceptability during the clarific ation process. The results showed that with the addition of 7.5% calcium hy droxide and 8.0% aluminium sulphate, followed by treatment with the anionic resin A-400, a syrup with a high degree of purity (92.3%) and a lighter-br own colour than other commercial samples could be obtained. The colour valu es, as measured by the Hunter meter were; a lightness of L* = 6.17 and a ye llow colour of 0.74 expressed as a a/b* ratio. A negative correlation was o btained between the total polyphenol content (TP) in the sugar extract and the lightness values (L*); L* = 15.50-0.00511 TP (mg kg(-1)). The A-400 res in retained the greatest amount of polyphenols (92.9%). CIE-Lab parameters are proposed as a good means for objective colour comparison with other stu dies on the clarification of sugar syrups.