Protein-stabilized emulsions containing beta-carotene produced by premix membrane emulsification

Protein-stabilized O/W emulsions containing beta-carotene were produced by premix membrane emulsification (ME) using polymeric microfiltration membranes. Bovine serum albumin (BSA) and a whey protein concentrate (WPC) were used as protein emulsifiers while a nonionic small-molecule surfactant, Tween 20, was used both as a control and co-emulsifier. Membrane fouling caused by WPC reduced more significantly transmembrane flux than that by BSA. Mixtures of WPC or BSA with Tween 20 reduced protein membrane fouling and, simultaneously, decreased the mean droplet size. WPC/Tween 20 mixtures enable to produce emulsions with low polydispersion (span < 1) but with a significant membrane fouling while BSA/Tween 20 mixtures led to higher transmembrane fluxes although polydisperse emulsions (span = 7). During storage at 22 and 35 °C, the chemical degradation rate of emulsions with WPC/Tween 20 was slower than those with BSA/Tween 20 whereas Tween 20-stabilized emulsions led to the highest rate of beta-carotene reduction during storage at 35 °C.     

Effect of whey protein concentration on the fouling and cleaning of a heat transfer surface

In the studies of fouling and cleaning of heat exchange surfaces in dairy plants, whey protein deposits and heat induced whey protein gels (HIWPG) are considered as suitable model material to simulate the proteinaceous based type “A” milk fouling. Protein concentration of the fouling solution may significantly influence the formation of milk deposits on heat exchange surfaces, hence affecting the cleaning efficiency. In this study, a laboratory produced heat induced whey protein gels (HIWPG) and a pilot plant heat exchanger fouling/cleaning were used to investigate the effect of protein concentration on formation and cleaning of dairy fouling. Here, HIWPGs made from different protein concentrations were formed in capsules and then dissolved in aqueous sodium hydroxide (0.5 wt%). The dissolution rate calculation based on the UV spectrophotometer analysis. In the pilot-scale plant study, whey protein fouling deposits were formed by recirculating whey protein solutions with different concentrations through the heat exchange section in different runs, respectively. The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt%) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were monitored as indications of cleaning completion. It was found that increasing the protein concentration of the HIWPG significantly increased the gel hardness and the dissolution time. In addition, increasing the protein concentration significantly increased both, the amount of the fouling on the pilot-scale plant and the time required to clean the fouling deposit.     

Experimental study of hydrodynamics in a flat ohmic cell—impact on fouling by dairy products

This study highlights the link between hydrodynamics and fouling phenomena in a continuous rectangular ohmic cell. The hydrodynamic study was carried out using flow visualisation techniques and particle image velocimetry (PIV). The distribution of deposits in the ohmic cell was investigated by heating an aqueous solution of β-lactoglobulin-xanthan gum mixture. Experimental results show that the deposit distribution on the electrode surfaces is directly related to the flow structures in the ohmic cell.     

Fouling behaviour of milk and whey protein isolate solution on doped diamond-like carbon modified surfaces

Doped diamond-like carbon (DLC) coated stainless steel surfaces were studied for their fouling behaviour with milk and whey protein isolate (WPI) solution at both laboratory and pilot-scale. Stainless steel (316 SS 2B) surfaces were modified with three different doped DLC coatings (DLC-1, DLC-2 and DLC-3) using plasma assisted chemical vapour deposition. At the laboratory-scale, the DLC-1 coated surface showed a statistically significant reduction in the mass of milk fouling deposits. However, at the pilot-scale, none of the modified surfaces offered significant benefit in fouling mitigation over the control stainless steel surface. Subsequently, in the laboratory-scale trials with a whey protein isolate (WPI) solution, the mass of fouling deposits for all doped DLC modified surfaces were about 35–40% lower in comparison to their controls when fouled for 120 min. However, these benefits were reduced to less than 15% with longer fouling duration. Thus, the results obtained in this study found no commercial benefit of modified surfaces in fouling mitigation when fouled for longer times with skim milk, whole milk or WPI solution.     

Optimization of modified atmosphere packaging with respect to physicochemical characteristics of Requeijão

The effects of modified atmosphere packaging on physicochemical and sensorial characteristics (contents of free fatty acids, lactose, lactic acid and moisture, as well as pH and rigidity) in Portuguese whey cheese (Requeijão) were studied following a response surface methodology using storage time, storage temperature and fraction of CO₂ in the flushing gas as manipulated variables. Inspection of the sensorial optima in terms of the different parameters indicated that it is convenient to set the storage temperature equal to 4°C because no significant lipolysis takes place, irrespective of overhead atmosphere. Plain CO₂ as flushing gas will in general ensure more constant composition until 15 days and will provide protection against extensive lipolysis. In terms of overall visual aspect, all packaged cheeses were preferred to their unpackaged counterparts; however, in terms of acidic smell, only whey cheeses stored at 4°C exhibited significant differences relative to those stored at higher temperatures.     

Influence of different content of cheese whey and oligofructose on the properties of fermented lactic beverages: Study using response surface methodology

Lactic beverages have been used as an important vehicle for probiotics, and the utilization of cheese whey and oligofructose would contribute even more to the functional properties of this product. However, because of the short lifespan of probiotics, studies have been carried out aiming at the evaluation of the contribution of the prebiotics in the improvement of the viability of these microorganisms. The technological properties (fermentation time, acidity and syneresis index) and the population of probiotic bacteria in fermented lactic beverages manufactured with different content of cheese whey and oligofructose were evaluated. The results showed that oligofructose, at the concentrations evaluated in this study, did not show any significant influence on the response variables, whereas the content of cheese whey only influenced the syneresis index of lactic beverages.     

On-line local thermal pulse analysis sensor to monitor fouling and cleaning: Application to dairy product pasteurisation with an ohmic cell jet heater

In the process industry, fouling is considered as a complex (sometimes partially known and identified) phenomenon. In this paper, a fouling sensor (FS) based on local differential thermal analysis is scrutinized and we report the comparison of two operating modes, steady (STR) and periodic (PTR) thermal regimes. Moreover, the development of alternating technologies like direct Joule effect (ohmic) heating to pasteurise and sterilise liquid food products in a continuous process is of great scientific and industrial interest. Heat treatment by direct Joule effect exhibits numerous advantages because rapid heating kinetics or homogeneous heat treatment is required. However, fouling of electrode surfaces in this kind of apparatus is much more problematic than in conventional heat exchangers. In the present study, a new continuous ohmic heating apparatus (Emmepiemme®, Piacenza, Italy) in which an alternating electrical current is applied directly to a jet falling between two stainless steel electrodes is investigated during pasteurisation of a dairy product. Conventional fouling measurements (pressure drop, heat transfer or electrical parameters) cannot be used in such a heater. Fouling and cleaning phases are monitored with fouling sensor and fouling quantified.     

乳制品与糖尿病的饮食防控

本文综述了乳制品与糖尿病之间关系的研究进展。流行病学研究表明,乳制品对糖尿病的发生风险无不良影响,甚至有一定降低风险的作用。乳制品中的乳糖不会快速升高血糖,其反式脂肪成分并不是糖尿病的风险因子,而其中的乳清蛋白对于糖尿病患者是有利的。因此,乳制品是糖尿病患者饮食的有益组成。     

Preparation of galacto-oligosaccharides using membrane reactor

Galacto-oligosaccharides (GOS) have many biological functions. They are produced from lactose by a glycosyl transfer of one or more d-galactosyl units onto the d-galactose moiety of lactose catalysed by β-galactosidase. This reaction can proceed in batch or in continuous system. Membrane reactor with ultrafiltration ceramic membrane (150 kDa) was used and batch system as well. Lactose in phosphate buffer (197.9 g L⁻¹), recombined whey (197 g L⁻¹) and evaporated ultrafiltration permeate (200.7 g L⁻¹) were used as substrates. The used concentration of enzyme Maxilact LX 5000 was 6 U mL⁻¹. The highest concentration of GOS in buffer was reached after 30 min of batch reaction and it was 25.5 g L⁻¹, for recombined whey it was 31.1 g L⁻¹ and for ultrafiltration permeate it was 32.9 g L⁻¹. For continuous process was obtained 8.8 g L⁻¹ of GOS for buffer and 21.0 g L⁻¹ for recombined whey and 16.7 g L⁻¹ of GOS for ultrafiltration permeate.     

Analysis of the fouling mechanisms during cross-flow ultrafiltration of apple juice

The purpose of this work was to study the fouling mechanisms of a Carbosep^® M8 membrane during the cross-flow ultrafiltration of apple juice. A new fouling model has been developed that simultaneously considers membrane blocking within the pores, at the pore mouths and by cake formation at the membrane surface. Membrane fouling by apple juice was due to internal pore blocking as well as cake formation. When operating ultrafiltration at a transmembrane pressure of 150 kPa and a cross-flow velocity of 7 m/s, fouling was minimal with a gradual decrease of the relative contribution of cake formation; however, transmembrane pressure still exceeds critical pressure. The fouling model predicts no cake formation at a cross-flow velocity of 7.4 m/s and a transmembrane pressure of 150 kPa or at a cross-flow velocity of 7.0 m/s and a transmembrane pressure of 120 kPa. Under these conditions, internal membrane blocking would be the only mechanism responsible for the decrease of permeate flux.     

膜分离技术处理制革污水

制革生产湿操作工序与微滤、超滤、纳滤、反渗透等膜分离技术结合，可便捷的实现各工序污水单独处理，回收未充分利用的化工材料和绝大部分水，回用于制革生产，有效提高化工材料的利用率和水的回用率、减少污水排放量、减轻污水处理负荷。