Article pubs.acs.org/IECR
Concentration of Milk Proteins for Producing Cheese Using a ShearEnhanced Ultrafiltration Technique Luhui Ding,‡,⊥ Wenxiang Zhang,*,†,⊥ Aissa Ould-Dris,‡ Michel Y. Jaffrin,§ and Bing Tang† †
School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, People’s Republic of China ‡ EA 4297 TIMR, University of Technology of Compiegne, 60205 Compiegne Cedex, France § UMR 7338, Technological University of Compiegne, 60205 Compiegne Cedex, France S Supporting Information *
ABSTRACT: A shear-enhanced filtration process with ultrafiltration (UF) for the concentration of milk was investigated to recycle nutrients and produce cheese. Full recycling experiments were utilized to study the influence of operation conditions (rotating speed, transmembrane pressure (TMP), and membrane types) on separation performance, flux behavior, energy cost, and permeability recovery in membrane cleaning. Then, extreme hydraulic conditions (2500 rpm, 6 bar, and a 10 kDa P010P membrane) were selected to concentrate skim milk, whole milk, and dairy factory whole milk. Four Hermia blocking models were utilized to explain the membrane fouling mechanism and estimate the degree of pore blocking. The retentate solution of dairy factory whole milk was utilized for lactic fermentation and making cheese by adding two kinds of fermentation agents FD-DVS YF-L903 and yogurt. However, these cheeses had a lower nutritional value than traditional cheeses due to a long concentration time, high operating temperature, and low concentration. Other strategies should be used to enhance flux behavior, reduce membrane fouling, and shorten concentration time.
1. INTRODUCTION Cheese, as an important food, is produced by milk protein coagulation. The cheese production efficiency depends on the separation and concentration of protein from milk.1 As a promising separation technology, ultrafiltration (UF) can separate organic matters, according to their different sizes.2 During the last decades, UF has grown in industrial development due to its lower cost, easy combination with other processes, and good acceptability for the environment. Therefore, it is extensively applied in the biotechnological industry, especially for the separation of fermentation products.3 Due to its high efficiency in separating proteins, UF has become a promising approach for protein recovery and preconcentration of skim and whole milk in ice cream and cheese production.4,5 In 1969, a French patent was the first to propose using UF to treat milk for making cheese.6 The milk was concentrated by UF, and cream and partially fermented or unfermented retentate were combined to produce precheese.7 Traditional cheese making usually uses heat-treatment and diafiltration to concentrate milk, which may damage proteins and substances.8 The advantage of UF is that it concentrates milk in an economic and efficient way by rejecting proteins into the cheese and enhances the productivity at a suitable temperature.9−11 Moreover, UF has a low energy cost and a high stability. In UF, as an inherent phenomenon, membrane fouling limits the wide application of it in the food industry.12,13 During © XXXX American Chemical Society
separation of proteins and milk concentration by UF, casein and whey are the most important foulants, affecting flux behavior, separation efficiency, and productivity.14,15 Inorganic fouling is negligible in the UF process of skim milk.16 After filtration, a 5 μm thick organic−inorganic precipitate layer, including proteins, silica, and calcium carbonate, was observed on the membrane surface or in the pores.17 In order to control flux decline and reduce fouling, a number of control strategies were studied.12 Jin et al.17 used ultrasound to enhance the filtration performance in cross-flow UF of skim milk because excessive ultrasound operation may cause membrane damage and require higher energy cost. Arunkumar et al.18 concluded that an increase of tangential flow could prevent fouling but resulted in high energy cost. Khider et al.19 applied Algerian clay to help UF in treating milk effluent and got low fouling behavior and excellent rejection; however, the operation cost was high and the process unstable. Rahimpour et al.20 claimed that a modification of the membrane surface could improve antifouling performance for UF of milk, but this effect was unstable and of short duration. Therefore, there are many strategies for retarding flux decline and controlling fouling, but they were not optimal or nonpractical, which limits their application. Received: July 18, 2016 Revised: September 21, 2016 Accepted: October 3, 2016
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DOI: 10.1021/acs.iecr.6b02738 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research
Figure 1. Schematic diagram of the (a) rotating disk membrane module and (b) dynamic shear-enhanced membrane filtration process.
Dynamic shear-enhanced membrane filtration with high shear rates on the membrane21,22 not only enhances the flux substantially but increases the concentration factor and membrane selectivity, which allows high water recovery during wastewater filtration and very viscous concentrations in the food industry.23 In our previous studies,4,24 on the basis of dynamic shear-enhanced filtration, UF was used to recover proteins from milk, and then, nanofiltration (NF) or reverse osmosis (RO) was utilized to recover lactose from UF permeate. During these processes, the high shear stress produced by rotating disk/membrane or vibration systems reduced concentration polarization and membrane fouling and improved membrane selectivity and clarification.24 However, most investigations were limited to diluted milk or to recirculation of highly concentrated milk.25 In the actual food industry, milk processing is very crucial. At the same time, a high protein concentration causes a serious flux decline. Therefore, the study of separation efficiency, flux behavior, and fouling control in milk concentration is very important. There are two main novelties in this study: (1) the shearenhanced UF module is first used to filtrate nondiluted milks
(skim milk, whole milk, and company whole milk) and concentrate milk protein, and (2) the concentrated milk by UF is utilized to first directly produce cheese, and then the cheese performance (appearance, texture, and taste) is evaluated and compared with other commercial cheeses. For the first novelty, nondiluted milk is totally different than dairy wastewater (diluted milk) due to its much higher foulant (protein and lipid) concentration. Its flux behavior, fouling mechanism, and fouling model are totally different. As far as we know, there is no study about the shear-enhanced UF membrane of nondiluted milk. This study first systematically looks at the filtration performance of shear-enhanced UF modules for filtrating nondiluted milk. For the second novelty, in previous studies of cheese production, no researcher used concentrated milk by UF to directly produce cheese. This article utilizes a shear-enhanced UF module to concentrate nondiluted milk, and the concentrated milk is used to produce cheese; it then evaluates the cheese performance (appearance, texture, and taste) and compares with other commercial cheeses. In this paper, the aim was to concentrate commercial milks for making cheese. The effects of the transmembrane pressure B
DOI: 10.1021/acs.iecr.6b02738 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research (TMP), rotating speed, and membrane type on separation efficiency, flux behavior, energy cost, and membrane permeability recovery by cleaning using full recycling tests were studied. Then, three kinds of milks were concentrated for making cheese, and their fouling mechanisms were evaluated by four Hermia blocking models. Hot water rinsing and chemical cleaning, assisted by high shear stress, were applied to clean fouled membranes and recover their permeability. After that, the retentate of commercial milk was utilized for lactic fermentation and making cheese using two kinds of fermentation agents, FD-DVS YF-L903 and yogurt.
Table 3. Main Characteristics of Dairy Factory Whole Milk
2. MATERIALS AND METHODS 2.1. Experimental Apparatus and Membranes. A rotating disk module (RDM), shown in Figure 1, was used for milk filtration, and detailed information was introduced in previous studies.4,26 Three MICRODYN-NADIR UF membranes were used, and their properties are shown in Table 1.
surface materiala
molecular weight cutoff (kD)
water permeabilityb (Lm−2 h−1 bar−1)
UP005P P010P PES20
PES PESH PES
5 10 20
15−16 24−35 30−40
a
PES, polyethersulphone; PESH, permanently hydrophilic polyethersulphone. bOwn measurement at 25 °C and 0.1−0.8 MPa.
2.2. Test Fluid. Ultrahigh temperature (UHT) skim milk and UHT whole milk were provided from commercial milk (Mountain milk, Carrefour, France). Dairy factory whole milk was provided by a French company. Their mean compositions and characteristics are described in Tables 2 and 3. Table 2. Main Characteristics of Skim Milk and Whole Milk index
skim milk
whole milk
casein (g L−1) whey protein (g L−1) lactose (g L−1) calcium (g L−1) sodium (g L−1) lipid (g L−1) conductivity (μs cm−1) pH dry mass (g L−1) °Brix ash (g L−1)
25.5 6.3 45.9 1.2 0.51 skim
