Removal of HMF in High-Fructose Corn Syrup by Activated Carbon
Hydroxymethylfurfural (HMF) is a chemical that may be produced during the production of high-fructose corn syrup (HFCS). It has been reported that HMF is harmful and potentially carcinogenic to humans. And it is limited to 75 mg/kg in HFCS according to ISBT, 40 mg/kg (non-tropical origins) and 80 mg/kg (tropical origins) in honey, 20 mg/kg in juices for children according to EU.
The effects of factors on HMF generation
By testing the effects of temperature, dry matter content, pH, time on the formation of HMF, and the method of using granular activated carbon to remove HMF, a final high-fructose corn syrup product with HMF content lower than 20 mg/kg is obtained. HFCS 42 samples with a concentration of 70% are used in the test.
Temperature: HMF is a degradation product of fructose or glucose at high temperatures. It is generally believed that monosaccharide is the substrate. But a report proposes that it is caused by reactive fructofuranosyl cation from sucrose. The test result shows that the higher the temperature, the easier it is to generate HMF. The generation rate of HMF is relatively slow at 30 – 50 °C. When the temperature is higher than 50 °C, it increases significantly. Based on this, the temperature is suggested to be controlled under 50 °C during the production process.
pH: When the pH of HFCS 42 samples is lower than 4.5, the content of HMF decreases significantly with the increase of pH value. The HMF content has little change from pH 4.5 to 7.5. So low pH value should be avoided during production.
Storage time: The longer the storage time is, the higher the HMF content is, but in a relatively short time, the HMF content does not change significantly.
From the test results, the temperature factor has the most significant effect on HMF generation, followed by time, dry matter content, pH.
The removal of HMF by activated carbon
The required amount of activated carbon used to remove 95% of HMF will reduce if the contact time increases, which is 77.96, 34.65, 29.24, 27.11 kg/T (on dry basis) with contact time 0.5h, 1h, 1.5h, 2h, respectively. For the suitable contact time and production efficiency, the breakthrough curve should be considered.
The optimum adsorption temperature of granular activated carbon is 60 – 70 °C, and the carbon also has a good adsorption performance in the range of 50 – 80 °C. Generally, the feed temperature is 60 °C.
For granular activated carbon columns with a certain volume, and under a certain flow rate, the concentration of HFCS has a large influence on the treatment of the feed liquid. When the dry matter concentration of the feed liquid is lower than 50%, the adsorption capacity of GAC columns has no obvious change. But if the concentration is too low, it will slow down the GAC adsorption rate. When the concentration is higher than 50%, the HMF will not be fully adsorbed by activated carbon. Therefore, it is suggested to control the concentration at about 50%.
In the range of 4-8, the pH of HFCS has little effect on the HMF adsorption performance of activated carbon according to the test results.