Determination of 18O/16O ratio of glycerol of triglyceride in fat using GC/P/IRMS after saponification
Zhong, Q. D., Wang, D. B., Li, G. H.
Abstract:
Small changes in the 18O/18O ratio can provide a fingerprint that provides a unique identifier for the origin of particular compounds within a food, which has been proved be a valuable tool for fighting against fraud food. As the backbone of triglyceride in fat, glycerol contains three non-exchangeable oxygen, which could be used to reveal the biosynthetic origin of corresponding fat. However, the need for highly pure glycerol using tedious procedures for off-line IRMS methods or GC-IRMS analysis limited the researches and applications of glycerol 18O/16O ratio in edible oil authenticity control. In this paper, a new method, with time and cost-saving procedures, is introduced for reliable, rapid, and accurate determination of the 18O/16O ratio of glycerol orginated from triglyceride in fat: By saponification in 20 volumes of KOH methanol solution, the glycerides from different origin were converted to free glycerol and to fatty acid methyl esters (FAMES); 2,2,4-Trimethylpentane were added and the upper layer were removed after shook several times; molecular sieve was added to trap the microscale water; the 18O/16O ratio was measured using GC-Py-IRMS systems. Using standard correction procedures, the method above for δ18O determination was assessed, good precision that better than 0.4‰ was obtained, the reproducibility of δ18O values from triglyceride was better than ±0.7‰. The validation of the method was carried out by measuring the intimate triglyceride samples that mixed with glycerol with known δ18O value, and a very good agreement between the measured values and the predicted data. In addition, 3 animal fats and 10 edible oil were analyzed, the mean δ18O value of glycerol samples from animal fat was approximately 16.2‰ which close to the peanut oil, δ18O value of the edible oils that from crop plant were higher than animal fat but lower than that from woody plant.
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IMEKO-TC23-2017-118.pdf
DOI:
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Event details
IMEKO TC:
TC23
Event name:
3rd IMEKOFOODS Conference
Title:

Metrology Promoting Standardization and Harmonization in Food and Nutrition

Place:
Thessaloniki, GREECE
Time:
01 October 2017 - 04 October 2017
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