Removal of lactic acid from acid whey using electrodialysis

Abstract

The processing of acid whey, a by-product of cream cheese making, casein production and strained yogurt manufacture, has been a challenge in the dairy industry. The high lactic acid concentration causes operational problems in downstream spray drying operations due to increased powder stickiness. In this work, electrodialysis, a well proven demineralisation technology is used to remove the lactate ions from acid whey. If the ratio of lactic acid to lactose is to be reduced to the same level found in sweet whey, 80% of the lactate ions must be removed. For both laboratory prepared solutions and acid whey samples, the lactate ions were removed at a slower rate compared to other anions present in the system. Increasing the pH (from pH 4.6 to pH 6) of the feed solution led to a small enhancement in the rate of lactate ions removal at 5°C. No impact was observed, however, at 30 and 45°C where membrane resistance and solution viscosity is lower. To achieve the same level of lactate ion removal, the processing time in a batch process was three times shorter at 45°C, compared to that at 5°C. This means that significantly less membrane area is required in a continuous industrial electrodialysis operation. The energy consumption (~0.014 kWh/kg whey processed) for achieving 90% demineralization of the acid whey was comparable to the energy requirement reported for sweet whey demineralization in a typical commercial electrodialysis unit, illustrating the feasibility of this approach.

Fouling and in-situ cleaning of ion-exchange membranes during the electrodialysis of fresh acid and sweet whey

“…FuMA-Tech GmbH (Germany) as described in our earlier work (Chen et al, 2016). Cation 111 exchange membranes (Neosepta CMB) and anion exchange membranes (Neosepta AHA) were 112 purchased from Astom Co., Ltd., Japan.…”

“…These membranes are well known for their wide pH 113 tolerance and thermal stability. Information on the membrane characteristics can be found 114 elsewhere (Chen et al, 2016). All membranes were pre-conditioned by soaking in 3% NaCl 115 solution to allow for membrane hydration and expansion.…”

“…Furthermore, the low pH promotes protein precipitation (Jelen, 2011), which reduces 43 the protein content to almost half of the amount found in sweet whey. In our recent publication 44 (Chen et al, 2016), we proposed that acid whey processing could be enhanced by partial removal 45 of minerals and lactic acid using electrodialysis (ED) equipped with ion-exchange membranes 46 (IEMs). 47…”

“…The 170 samples were filtered to remove proteins but were not diluted. Information on the operating 171 parameters of the ICP-OES and HPLC can be found elsewhere (Chen et al, 2016). resistance as a function of time was much greater for acid whey (Figure 1), which might be related 240 to a greater extent of mineral fouling due to the higher concentrations of calcium and phosphate in 241 these samples.…”

The Application of Membrane Separation Technology in the Dairy Industry

“…This is much better than their previous study (30-40% demineralization rate) [68]. Chen et al [69] also successfully applied electrodialysis to remove the lactate ions from acid whey in order to solve operational problems in downstream spray drying operations. Alternatively, electrodialysis has been successfully demonstrated to recover lactic acid from fermentation broths [70,71], as well as to demineralize sweet whey prior to whey powder production [72,73].…”