Suspension Freeze Concentration Research Articles

Separation methods in the food industry: An exploration of reverse osmosis, evaporation and freeze concentration applications

Separation method is broadly used in various industries, mainly in the food industry. Some of the applications include retaining the nutrients and concentrating fruit juices, liquid foods, and milk products. Fundamentally, the concentrated liquid product is achieved by these separation methods. Technology advances daily, impacting food quality characteristics such as flavour, colour, and texture. Production and commercialisation processes are key considerations, from conventional to modern approaches. Hence, this study aims to review the various types of separation methods with their application in food industries which are evaporation, reverse osmosis, and freeze concentration that is separated into two: suspension freeze concentration and progressive freeze concentration

Freeze concentration of aqueous pyrolysis oil extract and levoglucosan recovery by cooling crystallization

In this work, pyrolysis oil produced by the slow pyrolysis of pinewood was the feed solution for a freeze concentration study and cooling crystallization recovery of levoglucosan. Liquid-liquid extraction of water-soluble compounds was performed by adding water to the original pyrolysis oil with ratios of 1:1 and 1:5 water: pyrolysis oil (wt%), respectively. A two-step suspension freeze concentration was then performed with the 1:1 and 1:5 aqueous pyrolysis oils (AqPO) to concentrate the solutions. The efficiency of water removal from AqPO was assessed by measuring the ice yield and distribution coefficient of ice impurities. Levoglucosan recovery from a supersaturated 1:1 AqPO-water mixture was performed for 37.5 min and 60 min by cooling crystallization with an aging time of 60 min. The average recovery rate of levoglucosan was 24 wt% with mean levoglucosan crystal size of 831 μm.

Laboratory suspension freeze concentration (Lab SFC) followed by a simple centrifugal procedure for separation

Suspension freeze concentration (SFC) is a low temperature technology which has a promising prospect in food and bioproducts industry. In SFC, the dispersed ice crystals are made in aqueous fluid and become bigger in sizes after ripening, are then separated from the mother liquor to achieve ice removal. A laboratory device of 2 L capacity integrating ice nucleation and ripening in one pot has been investigated in this study. Centrifugation is then applied to the whole slurry (in contrast to a tightly packed ice phase in previous studies) to separate the liquid out, which simplifies greatly the SFC process. This procedure was successfully used to concentrate sucrose solution from 10oBrix (wt%) to 17.6oBrix (wt%). For the first time, Scanning Electron Microscopy (SEM) was used to look at the microscopic distribution of sucrose attached and partly included in the ice particles. The solute loss (sucrose inclusion in the ice phase) was further reduced to only 0.6oBrix (wt%) by partially melting the particle phase. The yield of solute reached to about 97% in one go of about 2 hours. Agitation, partial ice melting, etc., were also examined in the current work. Similarly, the solid contents of orange juice, skim milk and the red wine can be concentrated to similar levels in runs of about 1.5 hours. This work has shown that this laboratory scale device is nice and simple for concentrating small amounts of practical aqueous liquids. The centrifuge as it is adopted here is also simple to operate and the whole procedure shows great promise for practical applications.

Integrated and intelligently controlled unit for suspension freeze concentration: design and experimental verification

Suspension freeze concentration (SFC) can avoid denaturation while concentrating thermal-sensitive aqueous solutions. However, the complex treatment process and high capital cost severely limit its application in large-scale production. In this paper, a compact and integrated unit is devised to overcome these shortcomings and improve the operability of SFC. The unit is in a vertical layout and supports multistage treatment to successively condense the solution. Several innovative designs are made for the key components, including the helical blades in the scraped surface heat exchanger and a dual-use column for recrystallization and washing. The former helps to establish the circulation of solution and impose forces to compress the ice column, while the latter enables seamless switch between different processes. As the whole process of SFC is well known to be time-consuming and labor-intensive, an intelligent controlling system is installed on the unit to realize on-site and/or remote monitoring and adjustment of the treatment. A concentration experiment using apple juice was conducted to verify the design and demonstrate the advantages. The results show that high-quality solutions were obtained with this unit. The recovery yields of the soluble solids and nutrients components are over 98.5% and 80.0%, respectively. Based on the work principles of the freezing and washing process in this design, the mechanism behind the superior recovery yields is analyzed. This study opens up a potential route for scaling up SFC and is expected to stimulate further work to achieve industrial application.

Freeze concentration of apple juice followed by centrifugation of ice packed bed

Based on the porous morphological characteristics of the packed ice bed produced by suspension freeze concentration (FC), this study describes the introduction of a full-bed centrifugal filtration step to separate concentrated apple juice from the ice bed. After FC and centrifugal filtration, the recovery yield of soluble solids in the concentrated juice was 93.6%, with the other 6.4% solute lost due to the separation process. The permeability and permeability coefficient of the ice cake in the centrifugal filtration mathematical model were 4 × 10 −8 m 2 and 0.16 m s −1 , respectively. The specific resistance of the ice cake was 4.10 × 10 4 m kg −1 , which was at least one order of magnitude lower than that obtained from block FC. We believe that this strategy offers a viable alternative to the conventional wash column for the separation and purification of ice crystals and concentrate. • A process of freeze concentration of apple Juice followed by full-bed centrifugation of packed ice bed was presented. • The rotating speed of the centrifugal filter is 3000 rpm with a centrifuging factor of 503. • The recovery yield of soluble solids is 93.6% when the juice concentration achieved 40.3°Bx. • The permeability and permeability coefficient of the ice bed were 4 × 10 −8 m 2 and 0.16 m s −1 , respectively. • The specific resistance of the ice cake was 4.10 × 10 4 m kg −1 , less than one tenth of that of the ice block produced by block freeze concentration.

Heat and mass transfer of scraped surface heat exchanger used for suspension freeze concentration

Freeze concentration (FC) by suspension crystallization is a complex process due to the combination of a scraped-surface heat exchanger, crystallizer, and wash column. Following the study of a three-in-one structure of a multi-pass FC published earlier this year, modeling and experiments of the heat and mass transfer of this freeze concentrator are presented in this paper. The experimental assessment of the system performance, including the measured values of the heat transfer coefficient, ice production rate, and energy efficiency as well as their correlation with the concentration ratio and partition coefficient are presented in this article.

Progressive Freeze Concentration of Coconut Water and Use of Partial Ice Melting Method for Yield Improvement.

Coconut water is a highly nutritious liquid food which is a by-product of the desiccated coconut industry. Freeze concentration is the most suitable concentration method for coconut water since the low-temperature operation for concentration does not deteriorate the original quality of coconut water. Suspension freeze concentration (SFC) and progressive freeze concentration (PFC) are the available FC methods, and SFC is a complex and expensive method compared with PFC. PFC is a novel freeze concentration technique to concentrate liquid food by using a simple system. The limitation of PFC is the lower product yield than SFC, and to overcome the problem, the partial ice-melting technique can be used. A simple cylindrical apparatus was used for PFC which consists of a sample vessel, agitator system, and a cooling bath (at −23°C ± 2°C temperature). The final concentration of the liquid product was directly affected by the apparatus agitator speed and sample vessel dipping speed. PFC agitator speed of 290 rpm and dipping speed of 1.3 cm h−1 were reported as the optimum operating conditions to achieve the highest concentration for the PFC apparatus used in this study. Using optimized agitation speed and dipping speed, coconut water was concentrated up to Brix 8.5° from the initial concentration of Brix 3.5°. PFC coconut water achieved 73.56% of total yield, 2.42 of concentration ratio, 0.7° of ice phase concentration, and 0.08 of effective partition coefficient. The partial melting technique was successfully explored by recovering initial ice fractions with high solute concentrations, and the total yield was improved up to 80%.

Progressive Freeze Concentration of Coconut Water: Effect of Circulation Flowrate and Circulation Time

Progressive freeze concentration integrated with a coil crystallizer was applied to concentrate coconut water in order to increase its sugar content. In progressive freeze concentration system, only a single ice is formed as a layer on cooled surface. It is introduced as an alternative in compensating the disadvantages of conventional method of freeze concentration, called suspension freeze concentration. In this research, the efficiency of the progressive freeze concentration system was determined through effective partition constant (K) value and percent increment of sugar content. Hence, the effect of circulation flowrate ranging from 2000 to 2800 ml/min and circulation time from 10 to 18 minutes on those two variables was then investigated through experiments designated using one factor at a time. From the experimental work, it was found that higher efficiency results at higher circulation flowrate of 2800 ml/min based on lower K and high percentage of sugar increment achieved. It was also found that the percentage of the sugar increment is high when the period given for circulating the solution is increased and the most suitable circulation time is 14 minutes.

Performance Investigation on a New Design for Progressive Freeze Concentration System

Freeze concentration freezes or crystallizes water component in a solution out as ice crystals and leaves behind a highly concentrated solution. Conventional Suspension Freeze Concentration (SFC) system has to deal with difficult separation of ice formed in a suspension of the mother liquor, which leads to a high cost of operation. Scraped surface heat exchanger used to form seed ice to ensure production of large ice crystals also hiked up the capital cost involved. Progressive Freeze Concentration (PFC) is believed to be able to reduce the capital and operation cost by eliminating some unit operations used. In PFC, ice crystals were formed progressively as a single block of ice, on the surface where cooling is supplied. In this particular study, a new helical structured copper Crystallization Chamber (CC) was designed and fabricated. Three operating parameters which affect the performance of the system were investigated namely the circulation period, circulation flow rate and coolant temperature. Effective partition constant, K was used as an indication of the system efficiency and to assess its performance, calculated from the volume and concentration of the solid and liquid phase. Circulation period was found to produce a constant value of K at each period tested with the CC. It was also discovered that higher flowrate resulted in a lower K, which translated into high efficiency. The efficiency is the highest at 1000 mL min-1. The process also gives the highest efficiency at a coolant temperature of -6°C.

Review. Freeze Concentration in the Fruit Juices Industry

In conventional processes, such as evaporation, higher levels of concentration can be reached compared with freeze concentration or membrane techniques. However, the advantage of the freeze concentration technique is based on the quality of the product obtained due to the low temperatures used in the process, which makes it a very suitable technology for the processing of fruit juices. There are two basic methods for concentrating solutions by freezing: suspension and film freeze concentration. Suspension freeze concentration systems (FCS) already have operating equipment in the food industry, while film FCSs, also called layer crystallization, is still at an experimental stage. This review summarizes the most important studies relating to the suspension and film freeze concentration in fruit juices and sugar solutions, illustrating the different possibilities that freeze concentration has in the fruit juices industry; it also presents trends and suggests improvements for the future development of this technology. It is noted that most recent publications refer to the film FCS. The technology used to design, build and maintain layer crystallization equipment is simple and it can be available to any operator in the food industry, layer systems will be used in the future if their results can be improved in terms of ice purity and degree of fluid concentration.

Freeze concentration for enrichment of nutrients in yellow water from no-mix toilets

Separately collected urine ("yellow water") can be utilized as fertilizer. In order to decrease storage volumes and energy consumption for yellow water transport to fields, enrichment of nutrients in yellow water has to be considered. Laboratory-scale batch freeze concentration of yellow water has been tested in ice-front freezing apparatus: a stirred vessel and a falling film freeze concentrator (coolant temperatures: -6 to -16 degrees C). With progressing enrichment of the liquid concentrate, the frozen ice was increasingly contaminated with yellow water constituents (ammonia, total nitrogen, total phosphorus, TOC, and salts determined as conductivity). The higher the initial salinity of the yellow water and the lower the mechanical agitation of the liquid phase contacting the growing ice front, the more the frozen ice was contaminated. The results indicate, that in ice-front freezing devices multistage processes are necessary, i.e. the melted ice phase has to be purified (and the concentrates must be further enriched) in a second or even in a third stage. Energy consumption of this process is very high. However, technical scale suspension freeze concentration is reasonable in centralized ecological sanitation schemes if the population exceeds 0.5 million and distance of yellow water transportation to fields is more than 80 km.