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

A comprehensive investigation of the use of freeze concentration appro aches for the concentration of fish protein hydrolysates

Fish protein hydrolysates (FPH) are inherently unstable in their liquid form, necessitating either freezing or dewatering for stabilization. Gentle methods such as freeze concentration can be used to remove water, this can be achieved by freezing water in solution by decreasing the bulk temperature below freezing point and separating pure ice crystals from concentrated solution. This approach serves as an alternative to techniques like evaporation and reverse osmosis for concentrating solutions that have high water content, significant nutritional value, and thermolabile compounds. This is crucial as many bioactive compounds degrade when exposed to elevated temperatures. Another notable advantage of this technology is its potential to reduce energy consumption by up to 40% when integrated into the FPH drying process. Although this technology is currently industrialized primarily for juices, it can achieve concentrations of up to 60°Brix and manage viscosities up to 400 mPa.s. Numerous studies have been dedicated to enhancing design and processes, leading to a 35% reduction in the system's capital cost and a 20% reduction in energy consumption. Moreover, freeze concentration can synergize with other concentration techniques, creating more efficient hybrid processes. This review aims to introduce freeze concentration as a superior option for preserving fish protein hydrolysates, enhancing their stability, and maintaining their nutritional and bioactive qualities.

An opportunity for acerola pulp (Malpighia emarginata DC) valorization evaluating its performance during the block cryoconcentration by physicochemical, bioactive compounds, HPLC-ESI-MS/MS, and multi-elemental profile analysis

The present study evaluated the effect of cryoconcentration of pulp blocks of acerola (Malpighia emarginata DC). The study evaluated cryoconcentration in three stages. The cryoconcentrated samples, the ice fractions, and the initial pulp were evaluated for physicochemical composition, bioactive composition, and multielement profile. The cryoconcentrated sample obtained in the third stage of cryoconcentration showed the best results for the concentration factor, process efficiency, total soluble solids content, red color intensity, and increasing of the macro and micronutrients: Cu, Ca, S, Sr, K, Mn, Na, P, Mg, Fe. All stages presented good performance in the total soluble solids content, increase in the titratable acidity of the concentrates, and progressive increase in the intensity of the red color. Generally, higher levels of total phenolic and antioxidant activity were found for the 2nd and 3rd concentrates. The phenolic activity showed an increase of 166.90% in the 3rd stage concentrate compared to fresh pulp, and the antioxidant activity was 112.10% by the ABTS method and 131.60% by the DPPH method, both in the 3rd stage concentrate. The major individual polyphenols were Ferulic acid, Protocatechuic acid, and Taxifolin, with significant increases in the concentration of the compounds in the 2nd and 3rd stage concentrates. In addition, the contents of potentially toxic metals were below detection limits. During the cryoconcentration process, there was a decrease in the values ​​of vitamin C content, moisture content, density, and elements Cu, Sr, and Zn.

Treatment of compressed leachate from refuse transfer stations by freeze-melt method

A small amount of leachate with complex composition will be produced during the compressing of municipal solid waste in refuse transfer stations. In this study, the freeze-melt method, a green and efficient wastewater treatment technology, was used to treat the compressed leachate. The effects of freezing temperature, freezing duration, and ice melting method on the removal rates of contaminants were investigated. The results showed that the freeze-melt method was not selective for the removal of chemical oxygen demand (COD), total organic carbon (TOC), ammonia-nitrogen (NH₃-N) and total phosphorus (TP). The removal rate of contaminants was positively correlated with freezing temperature and negatively correlated with freezing duration, and the slower the growth rate of ice, the higher the purity of ice. When the compressed leachate was frozen at -15 °C for 42 h, the removal rates of COD, TOC, NH₃-N and TP were 60.00%, 58.40%, 56.89% and 55.34%, respectively. Contaminants trapped in ice were removed during the melting process, especially in the early stages of melting. The divided melting method was more beneficial than the natural melting method in removing contaminants during the initial stage of melting, which contributes to the reduction of produced water losses. This study provides a new idea for the treatment of small amounts of highly concentrated leachate generated by compression facilities distributed in various corners of the city.

Vacuum-Assisted Block Freeze Concentration Studies in Cheese Whey and Its Potential in Lactose Recovery

Block freeze concentration (BFC) is considered an emerging technology which allows the acquiring of high quality organoleptic products, due to the low temperatures employed. In this study we have outlined how the vacuum-assisted BFC of whey was investigated. The effects of vacuum time, vacuum pressure, and the initial solids concentration in whey were studied. The results obtained show that the three variables significantly affect each of the following parameters analysed: solute yield (Y) and concentration index (CI). The best Y results were obtained at a pressure of 10 kPa, 7.5 °Bx, and 60 min. For CI parameter, the highest values were given at 10 kPa, 7.5 °Bx, and 20 min, respectively. In a second phase, by applying the conditions that provide higher solute yield to three different types of dairy whey, Y values of 70% or higher are reached in a single step, while that the CI of lactose are higher than those of soluble solids. Therefore, it is possible to recover, in a single step, at least 70% of the lactose contained in the initial whey samples. This suggests that vacuum-assisted BFC technology may be an interesting alternative for the recovery of lactose contained in whey.

Plant-based pecan nut cake beverage enrichment of phytochemicals and antioxidant properties using multi-stage block freeze concentration

Pecan nut (Carya illinoinensis) processing to obtain oil generates circa 37% of press cake, which is currently underutilized and primarily employed as animal feed. Due to its nutritional- and bioactive-rich composition, pecan nut cake (PNC) can be used as raw material for plant-based beverages, whose properties may be enhanced using a non-thermal technology based on block freeze concentration (BFC). The effect of five-stage BFC on total solids content (TSC), pH, color parameters, retention of phytochemicals, and the antioxidant activity (AA) of a pecan nut cake beverage (PNB) was assessed in this work. BFC afforded 98% (w/w) solids retention after three stages and 85% efficiency after four stages. The process also provided a 254% concentration factor in stage 5. In the last step, approximately a 64% increase in TSC and a slight decrease (7.3%) in pH compared to the control PNB was observed. In addition, total phenolic compounds, condensed tannins, total flavonols, and AA were significantly (P < 0.05) improved after the BFC, resulting in a 2.6-10.2- and 1.9-5.8-fold increase in phytochemicals and antioxidants, respectively. On the other hand, BFC caused the darkening of concentrates due to TSC and bioactive compounds retention. The processing strategy evaluated herein indicated a great potential of PNC as a raw material for obtaining high-quality ingredients for the food industry, which may reduce agro-industrial waste production and add value to a coproduct rich in nutrients and biocompounds with potential biological activity.

Graphical Abstract

Distribution of florfenicol and norfloxacin in ice during water freezing process: Dual effects by fluorine substituents

Distribution in ice is regarded as one of important transport modes for pollutants in seasonal freeze-up waters in cold regions. However, the distribution characteristics and mechanisms of fluorinated antibiotics as emerging contaminants during the water freezing process remain unclear. Here, florfenicol and norfloxacin were selected as model fluorinated antibiotics to investigate their ice-water distribution. Effects of antibiotic molecular structure on the distribution were explored through comparative studies with their non-fluorinated structural analogs. Results showed that phase changes during the ice growth process redistributed the antibiotics, with antibiotic concentrations in water 3.0-6.4 times higher than those in ice. The solute-rich boundary layer with a concentration gradient was presented at the ice-water interface and controlled by constitutional supercooling during the freezing process. The ice-water distribution coefficient (K_IW) values of antibiotics increased by 34.8%-38.0% with a doubling of the cooling area. The solute distribution coefficient (K_bs) values of antibiotics at -20 °C were 65.6%-70.3% higher than at -10 °C. The K_IW and K_bs values of all antibiotics were negatively correlated with their water solubilities. The fluorine substituents influenced the binding energies between antibiotics and ice, resulting in a 1.1-fold increase in the binding energy of norfloxacin on the ice surface relative to its structural analog pipemidic acid. The results provide a new insight into the transport behaviors of fluorinated pharmaceuticals in ice-water systems.

Optimization of Encapsulation by Ionic Gelation Technique of Cryoconcentrated Solution: A Response Surface Methodology and Evaluation of Physicochemical Characteristics Study

The objective of this study was to evaluate the optimal conditions to encapsulate cryoconcentrate solutions via ionic gelation technique. Hydrogel beads were prepared using alginate (1%, 2% and 3% (w/w)) and cornstarch (0.5%, 1% and 2% (w/w)). Later, a sucrose/acid gallic solution was concentrated through block freeze concentration (BFC) at three cycles. Thus, each solution was a mixture with the respective combination of alginate/cornstarch. The final solution was added drop-wise on a CaCl₂ solution, allowing the formation of calcium alginate-cornstarch hydrogel beads filled with sucrose/acid gallic solution or cryoconcentrated solution. The results showed that alginate at 2% (w/w) and cornstarch at 2% (w/w) had the best efficiency to encapsulate any solution, with values close to 63.3%, 90.2%, 97.7%, and 75.1%, and particle sizes of approximately 3.09, 2.82, 2.73, and 2.64 mm, for initial solution, cycle 1, cycle 2, and cycle 3, respectively. Moreover, all the samples presented spherical shape. Therefore, the appropriate content of alginate and cornstarch allows for increasing the amount of model cryoconcentrated solution inside of the hydrogel beads. Furthermore, the physicochemical and morphological characteristics of hydrogel beads can be focused for future food and/or pharmaceutical applications, utilizing juice or extract concentrated by BFC as the solution encapsulated.

Effect of Cryoconcentration Assisted by Centrifugation-Filtration on Bioactive Compounds and Microbiological Quality of Aqueous Maqui (Aristotelia chilensis (Mol.) Stuntz) and Calafate (Berberis microphylla G. Forst) Extracts Pretreated with High-Pressure Homogenization

The objective of this study was to evaluate the effect of cryoconcentration assisted by centrifugation-filtration on the bioactive compounds and the microbiological quality of aqueous maqui (Aristotelia chilensis (Mol.) Stuntz) and calafate (Berberis microphylla G. Forst) extracts pretreated with high-pressure homogenization (HPH). Aqueous extracts were prepared from fresh fruits which were treated with HPH (predefined pressure and number of passes). The best pretreatment was determined by aerobic mesophilic, fungal, and yeast counts. Treated extracts were frozen at −30 °C in special tubes and centrifuged at 4000 rpm for 10 min to obtain the cryoconcentrated product. The optimal pretreatment conditions for HPH were 200 MPa and one pass in which the extracts exhibited no microorganism counts. Cryoconcentration by freezing and subsequent centrifugation-filtration in a single cycle showed high process efficiency (>95%) in both soluble solids and bioactive compounds (total polyphenols and anthocyanins) and antioxidant capacity of the fresh fruits and extracts. The HPH treatment and subsequent cryoconcentration assisted by centrifugation-filtration is an efficient technology to obtain concentrates with good microbiological quality and a high content of bioactive compounds.

Effect of Freeze Crystallization on Quality Properties of Two Endemic Patagonian Berries Juices: Murta (Ugni molinae) and Arrayan (Luma apiculata)

This work studied the effects of centrifugal block freeze crystallization (CBFC) on physicochemical parameters, total phenolic compound content (TPCC), antioxidant activity (AA), and process parameters applied to fresh murta and arrayan juices. In the last cycle, for fresh murta and arrayan juices, the total soluble solids (TSS) showed values close to 48 and 54 Brix, and TPCC exhibited values of approximately 20 and 66 mg gallic acid equivalents/100 grams dry matter (d.m.) for total polyphenol content, 13 and 25 mg cyanidin-3-glucoside equivalents/100 grams d.m. for total anthocyanin content, and 9 and 17 mg quercetin equivalents/100 grams d.m. for total flavonoid content, respectively. Moreover, the TPCC retention indicated values over 78% for murta juice, and 82% for arrayan juice. Similarly, the AA presented an increase over 2.1 times in relation to the correspondent initial AA value. Thus, the process parameters values were between 69% and 85% for efficiency, 70% and 88% for percentage of concentrate, and 0.72% and 0.88 (kg solutes/kg initial solutes) for solute yield. Therefore, this work provides insight about CBFC on valuable properties in fresh Patagonian berries juices, for future applications in health and industrial scale.

Influence of Cryoconcentration on Quality Attributes of Apple Juice (Malus Domestica cv. Red Fuji)

Apple juice was subjected to centrifugal block cryoconcentration (CBCC) for three cycles and their effect on the physicochemical properties, bioactive compounds, antioxidant activity, volatile profile, and sensory analysis was investigated. In the final cycle, the solutes were approximately four-fold of the initial condition (≈14 °Brix) and the color (ΔE* ≈ 25.0) was darker than the fresh juice, with bioactive compound concentration values close to 819 mg GAE/100 g d.m., 248 and 345 mg CEQ/100 g d.m. for total polyphenol, flavonoid, and flavanol content, respectively, equivalent to a retention of over 60%. DPPH and FRAP assays presented high antioxidant activities, with values of approximately 1803 μmol TE/100 g d.m. and 2936 μmol TE/100 g d.m, respectively. The cryoconcentrate showed a similar aromatic profile to the fresh juice, with 29 and 28 volatile compounds identified, respectively. The centrifugal force allowed to obtain excellent process parameters, with 73%, 0.87 (kg/kg), and 85% for efficiency, solute yield, and percentage of concentrate, respectively. Sensory evaluation shows that the odor, aroma, and flavor of fresh sample were remained in the reconstituted cryoconcentrate sample, with good qualifications (four points in a five-score hedonic scale) by trained panelists. Therefore, CBCC can preserve important quality attributes from apple juice.

Effect of cryoconcentration process on phenolic compounds and antioxidant activity in apple juice

BACKGROUND

Freeze concentration is an alternative process where bioactive compounds are preserved during the processing of juice concentrates. This study proposed a simple and cheaper cryoconcentration process assisted by centrifugation in apple juice.

RESULTS

The levels of phenolics increased significantly (P < 0.05) with each freeze concentration cycle that was performed. Furthermore, the process resulted in an average increase in the concentration of phenolics of 1.9, 2.9 and 3.8 times for the first, second and third steps of the concentration, respectively. In relation to phenolics, the antioxidant potential, which was evaluated by radical scavenging activity and reduction power, also increased with the cryoconcentration steps. The influence of the phenolics on the in vitro antioxidant activity was confirmed by a significant correlation between the antioxidant assays and total phenolics, flavonoids, flavan-3-ols, and flavonols (r > 0.70).

CONCLUSION

The increase in antioxidant activity may have been attributed to the increase in the phenolic compounds in the apple juices because of the cryoconcentration process. Therefore, this could be an excellent natural product to supplement and enrich blends, juices, ciders, smoothies, and jams in order to improve the sensorial, nutritional and antioxidant properties. © 2018 Society of Chemical Industry.

Retention of Ascorbic Acid and Solid Concentration via Centrifugal Freeze Concentration of Orange Juice

Freeze concentration of liquid foods produces high-quality concentrates while retaining the heat-labile compounds found in fresh samples. Centrifugal freeze concentration is a cryoconcentration method assisted by an external force, centrifugation, to enhance the separation of concentrate from the ice. When applying centrifugal freeze concentration to orange juice, after the third cryoconcentration cycle, the ascorbic acid content in the concentrate showed retention close to 70% of the initial value. After the third cycle, the solutes in the concentrate increased 4 times the initial value of the fresh sample with 70% efficiency. The color evaluation showed that the final concentrated fraction was darker than the fresh juice. The centrifugal freeze concentration in orange juice was effective for obtaining a high-quality concentrate with a higher concentration of solids and ascorbic acid retention.