APPLICATION OF SPECTROSCOPIC TECHNIQUES AS F AST DETECTION METHODS FOR THE QUALITY OF SOME FOODS

Abstract

Honey and meat products represent important components of human food. Their qualities are of concern to consumers, governmental control authorities and retailers. Nevertheless, meat and honey can be an attractive target for adulteration in many ways. The quality and adulteration of honey and meat were evaluated by classical methods and in parallel with FT-IR and Raman spectroscopes as a fast and easy detection method. Results could be summarized as follows:- Part I: Honey 1- Physicochemical Properties of honey: • Physicochemical 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. • The viscosity of adulterated honey with glucose corn syrup was higher than the viscosity of adulterated honey with sucrose and natural honey. While the viscosity of adulterated honey with sucrose was lower than the viscosity of natural honey. • pH values of authentic honey (control) was 4.49, while pH values of honey samples that adulterated with 25, 50 and 100% glucose were 4.63, 4.01 and 4.53, respectively. Also, pH values of adulterated honey with 25, 50 and 100% sucrose decreased to 3.95, 3.80 and 3.72, respectively. • Color parameters; whiteness (L), redness (a) and yellowness (b) of natural honey were 12, -0.46 and 2.12, respectively. While adulterated honey had a higher whiteness values, where it reached to 13.3 and 17.07 in adulterated honey with 25 and 50% glucose and 12.7 and 12.2 in adulterated honey with 25 and 50% sucrose, 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.

2- Identification and quantification of sugar profiles and HMF in honey by HPLC: • HPLC was used to detect adulteration of honey through determining their sugars content. 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). • Natural honey had the lowest HMF (2.1 mg/100g), followed by 25%, 50% and 100% glucose syrup, where HMF were 2.38, 2.41 and 2.53 mg/100g, respectively. While HMF was maximized to reach 36.65, 76.80 and 148.56 mg/100g in adulterated honey with 25, 50 or 100% sucrose syrup.

3- Evaluation of Honey Quality by Spectroscopic Techniques: • The main FT-IR spectral bands of sucrose, glucose and fructose were identified at different concentration levels. Selected main peaks of sucrose, glucose and fructose provide the best calibration model with correlation coefficient (R2) higher than (0.9). • Adulterated honey samples with glucose syrup were characterized with specific spectral peaks where 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 led to increase in the absorbance of spectral bands which are characterized for sucrose at 1054, 1149 and 987 cm-1 especially in adulterated authentic honey with sucrose (50:50 %). • Adulterated honey with sucrose (100 %) had a definite spectral peaks that attributed to main functional groups in sucrose with a high absorbance at 922, 988, 1051, and 1138 cm-1, while honey with 100% glucose was characterized with spectral bands at 993, 1049, 1078, 1106 and 1152 cm-1 with high absorbance. In mixed adulterated honey with 50 % sucrose plus 50% glucose, it was found that some of characteristic bands were high in their absorbance than sucrose and low in their absorbance than glucose such as 921, 989, 1048, 1078 and 1151 cm-1.

4- Evaluation of some commercial honey by FT-IR and HPLC • FT-IR spectroscopy was applied as a fast detection method to identify the quality of local commercial honey. The honey samples show the same significant features, in which the region 921 - 1189 cm-1 corresponds to the major functional groups of fructose, glucose and sucrose. Honey sample (1) contains characteristic peaks of fructose 1632 and 1057 and another bands of glucose at 1029, 1077, 1105 and 1149 cm-1, honey sample (2) has bands of glucose at 1029, 1078, 1105 and 1149 cm-1 and sucrose at 1078 cm-1, while honey sample (3) contain sucrose at 1077 cm-1 and glucose at 1028 and 1077 cm-1 and honey sample (4) has wavenumbers at 1077 and 1150 cm-1 which indicate to sucrose and glucose respectively. • The same honey commercial samples were evaluated using HPLC to confirm the obtained FT-IR results. The results showed honey samples (1) and (2) were characterized by their higher fructose content, where they reached to 34.675% and 36.08%, respectively. While fructose content of honey samples (3) and (4) decreased to 22.344 and 16.22%, respectively. Also, honey sample (1) and (2) characterized by their higher glucose content than honey sample (4) was 23.201%, where they reached to 29.407 and 28.737%, respectively. On the other hand, the highest sucrose content was found in honey samples (3) and (4) were 14.22 and 15.79%, respectively.

5- Identification and Quantification of Sucrose, Glucose and Fructose by Raman Spectroscopy: • Raman spectroscopy was applied to Identification and Quantification of Sucrose, Glucose and Fructose. Fructose was characterized with its sharpness spectral peaks at 1481, 1276, 1091, and 871 cm-1. Glucose was dominated at 1461, 1357, 1153, 916 and 844 cm-1. Sucrose was assigned with four spectral peaks at 1469, 1373, and 1060 cm-1. • The major and sharp peaks in honey were observed at 782±5, 829 ± 5, 879 ± 5, 917, and 1072 cm-1 that due to bending C1-H & CH2, C-H out of plane deformation of unknown carbohydrate, Bending C(1)H and COH, and Bending C(1)H and COH C-N (protein or amino acids), respectively • Adulterated honey with 25 and 50% sucrose or 25 % glucose corn syrup have specific spectral bands at 1373and 1299cm-1 respectively. Also, there were specific spectral bands at ~1122 and 1072 cm-1 characterized the adulterated honey with sucrose or glucose corn syrup. Moreover, the intensity of specific bands was increased at due to the presence of glucose corn syrup and sucrose syrup.