Block freeze-concentration of coffee extract: Effect of freezing and thawing stages on solute recovery and bioactive compounds

Coffee extract was freeze-concentrated using the total block technique. The effects of four parameters were evaluated: the initial coffee mass fraction (5 and 15% w/w), the cooling temperature ( 10 and 20 C), the heating temperature (20 and 40 C) and the freezing direction (parallel and counter-flow to the thawing direction). The solid concentration was measured during the thawing stage to quantify the solute recovery and the concentration index for one stage of freeze concentration. The coffee mass fraction, the freezing direction and the cooling temperature significantly influenced the solute recovery. A concentration index between 1 and 2.3 was obtained in one cycle. The effect of block freeze concentration on the bioactive compound concentration and the antioxidant activity was measured. The coffee bioactive compounds were distributed in proportion to the total solid content in the ice and liquid. Therefore, block freeze concentration is an effective technique to preserve functional properties of coffee extracts.Postprint (published version

Extracció amb CO2 supercrític. I. Una alternativa als dissolvents per a l'obtenció d'extractes naturals dels aliments

La tècnica d'extracció amb fluids supercrítics a la indústria alimentària i amb CO2 com a dissolvent està plenament establerta, sobretot en processos de descafeïnat de cafè i te, extracció de llúpol, extracció d'aromes i sabors d'espècies i herbes aromàtiques i separació del colesterol de la mantega, la carn i el rovell de l'ou. L'ESC és una tècnica de separació respectuosa amb el medi ambient i pot substituir progressivament molts dels processos d'extracció duts a terme amb uns dissolvents orgànics, que són en general potencialment tòxics, inflamables i tenen un preu elevat. L'ESC presenta un futur encoratjador en processos d'extracció i separació de principis actius de productes naturals pels seus avantatges. Aquesta primera part correspon a les bases teòriques de la nova tècnica d'extracció. En una segona part es presentaran les aplicacions industrials. Aquest article correspon a un resum adaptat d'un treball més complet que ha estat publicat en un review al Food Science and Technology International (octubre 2002), i constitueix el capítol 5 del llibre sobre tecnologies emergents (gener 2003).The extraction technique in the food industry by using supercritical fluids, and with CO2 as solvent, is widely established, especially in caffeine removing from coffee and tea, in the extraction of hops, flavours and fragrances from spices and aromatic herbs, as well as in the separation of cholesterol from butter, meat and egg-yolk. The ESC is an environmental friendly technique and is able to substitute progressively a lot of extraction processes based on organic solvents, which are usually potentially toxic, flammable and expensive.Due to their advantages, ESC shows an encouraging future in the processes of extraction and separation of the active substances in natural products. The present article is an abstracts from the complete job that has been published as a review in FSTI (October 2002) and corresponds to chapter 5 of the book on emergent technologies (January 2003)

Extracció amb CO2 supercrític: II. Aplicacions a la indústria alimentària

La tècnica d'extracció amb fluids supercrítics (ESC) a la indústria alimentària i amb CO2 com a dissolvent està plenament establerta, sobretot en processos de descafeïnat de cafè i te, extracció de llúpol, extracció d'aromes i sabors d'espècies i herbes aromàtiques i separació del colesterol de la mantega, la carn i el rovell de l'ou. L'ESC és una tècnica de separació respectuosa amb el medi ambient i pot substituir progressivament molts dels processos d'extracció realitzats amb dissolvents orgànics, que són en general potencialment tòxics, inflamables i tenen un preu elevat. L'ESC presenta un futur encoratjador en processos d'extracció i separació de principis actius en productes naturals pels seus avantatges. El present article correspon a un resum adaptat del treball complet que ha estat publicat en una revisió al Food Science and Technology International (FSTI) (octubre 2002) i constitueix el capítol 5 del llibre sobre tecnologies emergents (gener 2003).The extraction technique with supercritical fluids at food industries, and with CO2 as a solvent, is fully established, mainly in processes for caffeine extraction in coffee and tea, hops extraction, flavours and fragrances extraction from spices and aromatic herbs, as for cholesterol separation from butter, fats, meat and egg yolk. The SCE is a separation technique that is environmental friendly and can substitute progressively many of the extraction processes that use organic potentially toxic and flammable solvents and have a high cost. SCE shows a pretty good future due to its advantage for extraction and separation processes of active components in natural products. This article corresponds to an adaptation of the original that has been published in a Review at Food Science and Technology International (FSTI) (2002, October) and is the 5th chapter of the book about Emergent Technologies (2003, January)

Ice morphology modification and solute recovery improvement by heating and annealing during block freeze-concentration of coffee extracts

Several treatments on ice blocks can be applied during block freeze-concentration to increase the solute recovery from the ice. In the present study, the changes in the ice block’s temperature and the application of annealing during the block freeze-concentration of aqueous coffee extracts were studied. The ice block was subjected to heating and annealing prior to the thawing stage. The effect of coolant temperature during ice block heating (T = -10 and -5 °C) and the application of annealing (+, -) on solute recovery and ice structure morphology was evaluated. The use of annealing during block freeze-concentration modified the ice crystal morphology and increased the solute recovery only when it is applied at the highest temperature. In general, the annealing process increased the size and circularity of the ice crystals, consequently improving the solute recovery. Thus, annealing can be used to increase the solute recovery during block freeze-concentration.Postprint (published version

Effect of process parameters on progressive freeze concentration of sucrose solutions

The progressive freeze concentration of sucrose solutions was tested. The effect of the initial concentration of the solution (C0), the temperature of the refrigerant (T) and the stirring speed (¿) on the final concentration of the solution was determined. The effects were significant on the freeze concentration, for both individual and combined effects. The maximum concentration achieved in the progressive freeze concentration was 53º Brix, when the initial concentration was 35º Brix, at a speed of 800 rpm and a temperature of refrigerant of -20°C. The best values of the concentration index are obtained at low concentrations, high stirring speed and low temperature. The average distribution coefficient increased with the initial concentration of the solution. The average yield parameter at different initial concentrations is around 0.6 kg ice·kg sol-1·h-1.Postprint (author's final draft

Freeze desalination by the integration of falling film and block freeze concentration techniques

Block and falling film freeze concentration are two technologies that separate water by freezing,with the potential to desalinate seawater. In this study, the integration of two freeze concentration techniques as an alternative to obtain potable water was analysed. Water with 0.5%–8% NaCl was freeze-concentrated by the falling film technique. The ice from each stage was fractionally thawed to recover the solids retained inPostprint (updated version

Progressive freeze concentration of skim milk in an agitated vessel: effect of the coolant temperature and stirring rate on the process performance

The aim of this study was to investigate the freeze-concentration of skimmed milk by a progressive freeze concentration process. The progressive freeze concentration procedure was performed at three different temperatures (5, 10, and 15 C) and stirring rates (0, 500, and 1000 r/min).Postprint (published version

Progressive stirred freeze-concentration of ethanol-water solutions

© 2017 Progressive freeze-concentration is a technology to separate water from solutions by freezing. In the present investigation, ethanol-water solutions were freeze-concentrated by the progressive stirred technique. The freezing stage was carried out in a stirring vessel. Solute recovery by the fractionated thawing of ice was also studied. The effects of stirring speed (500, 1000, and 2000 rpm), initial concentration of the solution (3%, 5%, and 8% ethanol), and temperature of the thawing stage (0, 10, and 20 °C) on the solute yield and average distribution coefficient were determined using response surface analysis. The ethanol concentration was found to have increased by 1.3 and 2.1 times at the end of the freeze concentration process. It was found that the initial concentration had a significant effect on the distribution coefficient. In addition, the average yield was increased by 28% by fractionated thawing. Subsequently, a non-dimensional analysis of the distribution coefficient was developed to yield a model to predict the distribution coefficient as a function of the Reynolds number, the relationship between the average ice growth rate and the stirring speed, the agitator diameter, and the liquid fraction. This technique proved to be valid with respect to the concentration of ethanol-water solutions, with better yields being obtained at low initial concentrations. This model is the first of its kind to describe the ethanol-water interaction in agitated freeze-concentration systems.Postprint (author's final draft