Nanofiltration of lactic acid whey prior to spray drying: Scaling up to a semi-industrial scale
Introduction
Acid whey is the by-product of the cheese and caseinate industries. Its high mineralization, ranging from 12 to 20 g/100 g of dry matter (DM) according to Pearce (1992), makes its further processing difficult and limited. For example, lactic acid whey (LAW) decreases the performance of vacuum evaporators due to the increase in mineral fouling and overall heat transfer resistance. On the other hand, the kinetics of lactose crystallization in the LAW concentrates obtained by vacuum evaporation are slower than for sweet whey concentrates, with an increase in the crystal size dispersion and a decrease in the final crystallization rate (Modler & Lefkovitch, 1986). These LAW concentrates are therefore more difficult and complex to spray dry than other whey types because of the increased risk of stickiness and caking due to the high hygroscopicity of the LAW powder (Alais, 1984). Moreover, their use in human nutrition is limited by their nutritional imbalance (Batchelder, 1987). The low market price of lactic acid whey compared to sweet whey has made it necessary to circumvent these limitations by demineralization prior to drying, either by ion exchange resins (Hoppe & Higgins, 1992) or by electrodialysis, although Chen, Eschbach, Weeks, Gras, and Kentish (2016) revealed that the energy cost of a 90% demineralization of acid whey is comparable to a demineralization of a sweet whey. These two techniques are widely used at the industrial scale but generate high investment and cleaning costs due to the high volume of effluent that needs to be treated in a wastewater treatment plant (Pearce & Marshall, 1991). Whey demineralization by nanofiltration (NF) makes it possible to sidestep many of these disadvantages (Eriksson, 1988). The NF process allows concentration (up to 20–22 g/100 g of DM) and demineralization of the whey in one step (between 25 and 60% or 90% with diafiltration) (Gregory, 1987, Kelly et al., 1992, Kelly and Kelly, 1995), with lactose losses ranging between 1 and 6%. This technique could be used on milk protein concentrate in the powder state to improve storage stability (Cao et al., 2016). The benefits of an NF processing step in the production of spray-dried demineralized acid casein whey powder have already been reported by Jeantet, Schuck, Famelart, and Maubois (1996). Moreover, the removal of lactic acid in whey promotes lactose crystallization by increasing the glass transition temperature (Safari & Langrish, 2014) and decreasing the risk of thickness of the lactic acid whey concentrate (Mimouni, Bouhallab, Famelart, Naegele, & Schuck, 2007). Consequently, there is a great deal of information in the literature about the benefits of using NF on whey, but a semi-industrial scale-up of all these results has not yet been demonstrated. Some authors have used model solutions, small nanofiltration, evaporators and spray dryer pilot plants on the lab scale alone (low membrane surface, low water evaporation capacity, etc.), but they are not sufficiently representative of the dairy industry scale (Chandrapala et al., 2016a, Chandrapala et al., 2016b, Safari and Langrish, 2014; ). The aim of this study was therefore to take account of the abundant literature available in order to evaluate the feasibility of a semi-industrial scale-up in view of the ability of NF to improve the dryability of NF concentrate and the quality of the LAW powder. Dryability, composition and the physical properties of the LAW and NF LAW powders were particularly emphasized, as was the energy consumption involved in both processing schemes.
Section snippets
Lactic acid whey
Liquid lactic acid whey (LAW) at 5.9 g/100 g DM and pre-concentrated lactic acid whey at 33 g/100 g DM were provided by a French factory specialized in the processing of fresh dairy foods (cheeses and yogurts). The pre-concentrate was prepared in the industrial production plant using a falling-film evaporator (FFE) (Fig. 1). The composition of the liquid LAW is given in Table 1 and was in accordance with classical LAW. The product was stable, stored at 4 °C and no bacterial growth was detected
Results
The chemical composition of LAW and NF LAW is presented in Table 1. The nanofiltration step at a volume reduction factor of 3 made it possible to concentrate the liquid LAW at 17.1% DM before vacuum evaporation and spray drying. The results showed that lactic acid, ash, potassium, sodium and chloride content was reduced by 30, 27, 53, 60 and 53%, respectively, in the NF LAW retentate compared to the liquid LAW. Similarly, the reductions in lactic acid, ash, potassium, sodium and chloride
Discussion
The results shown in Table 1 demonstrated that NF allowed 50–60% selective demineralization of the monovalent cations (sodium and potassium) and monovalent anions (chloride), while maintaining the divalent cation (calcium, magnesium) and anion (phosphate) content almost constant. These results are in agreement with the demineralization range reported by Chandrapala et al., 2016a, Chandrapala et al., 2016b, Gernigon et al., 2011 and Jeantet, Maubois, and Boyaval (1996), and . Similar lactic acid
Conclusion
As expected from the literature, the use of NF to remove some of the monovalent ions and lactic acid in lactic acid whey following semi-industrial concentration by vacuum evaporation and spray drying improved the dryability of the concentrate and the hygroscopicity of the resulting LAW powder without affecting the particle size distribution at a semi-industrial scale. Moreover, NF decreased the overall industrial energy cost of the LAW powder production process compared to a standard process.
References (28)
- et al.
Removal of lactate from acid whey using nanofiltration
Journal of Food Engineering
(2016) - et al.
Nanofiltration and nanodiafiltration of acid whey as a function of pH and temperature
Separation and Purification Technology
(2016) - et al.
Removal of lactic acid from acid whey using electrodialysis
Separation and Purification Technology
(2016) - et al.
Whey processing demineralization
- et al.
Semi-continuous production of lactic acid in a bioreactor coupled with nanofiltration membranes
Enzyme and Microbial Technology
(1996) - et al.
The formation of calcium lactate crystals is responsible for concentrated acid whey thickening
Journal of Dairy Science
(2007) - Alais C.. (1984). Les produits laitiers: Problèmes techniques et problèmes alimentaires. In Science du lait, Sepaic,...
Electrodialysis applications in whey processing
Bulletin lnternational of Dairy Federation
(1987)- et al.
Heat balance of a multistage spray-dryer: Principles and example of application
Lait
(2002) - et al.
Étude de la teneur en éléments minéraux des produits obtenus lors de l'ultrafiltration du lait sur membrane
Lait
(1974)