Ultrafiltration Of Apple Juice Research Articles

Reduction of waste production during juice processing with a simultaneous creation of the new type of added-value products

Abstract The paper presents a new method for the reduction of waste production during juice processing through the reformulation of cloudy juices by ultrafiltration (UF), resulting in simultaneous production of a new type of cloudy juice of reduced sugar content. In contrast to the traditional juice production process, the final product was UF retentate. During UF, sugars were partially removed, while fibre and other macromolecular components present in a cloudy fraction, with health-promoting properties, were retained. Such treatment gives the possibility to reduce waste production during juice processing, because in the traditional approach, the cloudy fraction is usually treated as a waste after the clarification step. After UF in apple cloudy juice, the total content of soluble solids and sugars decreased from the initial values 11.0% and 10.4% to 9.2% and 8.8%, respectively; while in apple-beetroot cloudy juice, it reduced from 11.4% and 8.2% to 8.7% and 5.8%, respectively. At the same time, the cloudy fraction was retained and concentrated. The retention of soluble solids and sugars after the UF of apple juice was 66% and 67%, respectively, that is, 34% of soluble solids and 33% of the sugars were removed to the permeate. In apple-beetroot juice, 68% and 71% of soluble solids and sugars was retained, respectively.

Analysis of flux decline during ultrafiltration of apple juice in a batch cell

In the present work, ultrafiltration of enzyme pre-treated apple juice is studied under batch concentration mode in a stirred batch cell. Response surface methodology (RSM) is used to study the effects of incubation temperature, incubation time and enzyme concentration and their mutual interaction effects on the physical characteristics of apple juice such as alcohol insoluble solid (AIS), viscosity, clarity, total polyphenol, flavonoid and protein during enzyme treatment of apple juice. A central composite design (CCD) is employed to develop the quadratic model and optimizing the operating conditions of the enzyme treatment process for obtaining the desired characteristics of juice. During ultrafiltration enzyme pre-treated apple juice, the flux decline behavior is modeled using Hermia's approach for constant pressure dead-end filtration laws. Two model parameters, namely intermediate pore blocking coefficient and cake filtration coefficient are obtained by minimizing the error involved between calculated and experimental flux data. These parameters along with known operating conditions, membrane permeability and physical properties of feed enable one to predict the transient permeate flux decline. The effect of various operating conditions, such as feed temperature, stirrer speed and transmembrane pressure on the flux decline is demonstrated. Experimental results show that operating conditions have significant effect on the onset of cake formation as well as on the flux decline behavior. The model predictions are in good agreement with the experimental data.

Effects of pretreatment and various operating parameters on permeate flux and quality during ultrafiltration of apple juice

SummaryThe central composite design with a quadratic model was used to investigate the effect of temperature (20–40 °C) and transmembrane pressure (TMP) (100–300 kPa) as well as pretreatment with gelatin and bentonite (0:0–300:1500 mg L−1) on permeate flux and fouling resistance during ultrafiltration of apple juice. The changes in some physicochemical properties were also investigated. Pretreatment of apple juice with gelatin and bentonite and an increase in the temperature and TMP significantly improved the permeate flux. In general, physicochemical properties of apple juice other than polyphenolics were not affected by the applied parameters. Using 150 mg L−1 of gelatin and 750 mg L−1 of bentonite for fining significantly reduced the total phenolic content and so did the fouling resistance. Fouling resistance also decreased with increasing temperature, and increasing pressure increased the fouling resistance.

Contribution of fouling and gel polarization during ultrafiltration of raw apple juice at industrial scale

The flux behavior during the industrial cross-flow ultrafiltration of apple juice in a batch process was modeled using a combination of the fouling and concentration polarization models. It was observed that the major flux reduction was at the beginning and at the end of operation due to fouling and increasing solute concentration in the feed tank, respectively. The fouling phenomenon was analyzed by classical and empirical models and it was shown that the empirical one has the best correlation within less than 0.3% error for each experiment. The most significant advantage of this model is its ability to predict a steady flux, while other models predict zero flux at infinite time, which is contrary to the observation. With continued permeation, the solute concentration in the feed becomes important in which the back diffusion of solute from the membrane surface to the bulk or concentration polarization becomes controlling. Consequently about 4:53 h after starting the operation, corresponding to increase of solute concentration to about 151% of its initial value, the dominant mechanism changes from fouling to concentration polarization. It was confirmed that at every moment of ultrafiltration actual experimental flux follows that model (fouling or concentration polarization) which predicts lower flux.

ASSESSMENT OF AN EXPONENTIAL MODEL FOR ULTRAFILTRATION OF APPLE JUICE

ABSTRACT The clarification of apple juice by ultrafiltration has been commercially used for many years. A common phenomenon in membrane processes is the decline of permeate flux (J) with time (t), called “membrane fouling.” The phenomenon of membrane fouling is very complex and difficult to describe theoretically, and model studies are limited. A number of semiempirical and empirical models have been proposed to explain flux behavior during membrane filtration processes. Using these models, typical t versus J curve observed in membrane filtration applications was examined in two or three periods. However, the boundaries between each period could not be accurately determined and were specific to the system under investigation. Thus, these semiempirical and empirical models are valid only for the system investigated. In this article, the applicability of an exponential model to ultrafiltration of apple juice was studied. The results showed that the exponential model can be successfully applied to analyze the raw filtrate volume V versus t data of ultrafiltration of apple juice, and initial flux J0, membrane resistance Rm and exponential fouling coefficient k values can easily be determined from the raw data.

Effect of pretreatment with gelatin and bentonite on permeate flux and fouling layer resistance during apple juice ultrafiltration

The effects of pretreatment with gelatin and bentonite, pressure (Δ P) and molecular weight cut-off (MWCO) on flux performance of apple juice during ultrafiltration were studied. Filtration data (volume versus time) were satisfactorily fitted to De La Garza and Boulton’s exponential model to find the exponential fouling coefficient ( k) and the membrane resistance ( R m). Increasing the amounts of gelatin and bentonite used for pretreatment of apple juice decreased k values during ultrafiltration which was a clear evidence of flux improvement by means of delaying the membrane fouling. The molecules in apple juice which are responsible for membrane fouling could be successfully retained by the aggregate formed by gelatin and bentonite. Both k and R m values increased as Δ P increased during ultrafiltration of apple juice. A decrease in R m was observed as MWCO of membrane increased. However, the membrane having MWCO of 100 kDa had the highest k value which indicated the increased tendency of this membrane to foul.

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.

Hollow Fibre Ultrafiltration of Apple Juice: Macroscopic Approach

Permeate flux in hollow fibre ultrafiltration of apple juice was modelled using different approaches. The effect of flow velocity (10, 15 and 20 L/min), transmembrane pressure (73.5 and 118 kPa) and molecular weight cut-off (30,000, 50,000 and 100,000) was determined over the 1 to 14 range of volume concentration ratio(VCR). The flux showed an exponential decay behaviour operating at constant VCR and proved to be pressure-independent at a value that increased with flow velocity andVCR. Classical flow-through filtration theory was used to model the flux dependence withVCR. Energy consumption during hollow fibre ultrafiltration of apple juice under different operating conditions was also calculated. It was observed that energy expenses for apple juice ultrafiltrate increased with flow velocity and optimum value should be estimated. Influence in hollow fibre ultrafiltration of different enzymatic treatments was also considered.