FOURIER TRANSFORM INFRARED SPECTROSCOPY TECHNIQUE FOR DETECTION OF HONEY AUTHENTICATION

Physico-chemical properties of honey and honey samples adulterated with glucose or sucrose were determined. Total soluble solids (TSS), pH and electrical conductivity of honey and its adulterated samples ranged between (84.10-84.50%), (3.80-4.63) and (11.73 – 232.32µS), respectively. Sensory properties of honey and its adulterated samples showed that, no differences in the sensorial properties were found in authentic honey and honey adulterated with 25% sucrose or 25% glucose. Increasing adulteration ratio to 50% glucose decreased taste, flavor, color and general appearance, while adulterated honey with 50% sucrose caused significant decrease in taste and general appearance. The possibility of using HPLC to detect adulteration of honey through determining their sugars content was evaluated. The obtained results indicated that, authentic honey was characterized with its higher fructose/glucose ratio (1.21) compared to adulterated honey samples (ranged between 0.35 - 0.94). FT-IR spectroscopic technique was used to evaluate honey quality. Reliability FT-IR for quantitative and qualitative analysis of sucrose, glucose and fructose were evaluated.  The main FT-IR spectral bands of sucrose, glucose and fructose were identified at different concentration levels. The relationship between sugars concentration (sucrose, glucose and fructose) and its spectral bands absorbance (peak height) were evaluated to prepare sugars standard curves and their linear equations. Selected main peaks of sucrose, glucose and fructose provide the best calibration model with correlation coefficient (r2) higher than (0.9). Honey samples adulterated with glucose were characterized with specific spectral peaks, in which the absorbance was increased by increasing the ratio of adulteration with glucose at 1087, 1105, 1189 and 984 cm-1, while the adulteration with sucrose lead to increase in the absorbance of spectral bands of sucrose as 1054, 1149 and 984 cm-1 especially in honey adulterated with 50 % sucrose.