Non-thermal, energy efficient hydrodynamic cavitation for food processing, process intensification and extraction of natural bioactives: A review.

Hydrodynamic cavitation (HC) is the process of bubbles formation, expansion, and violent collapse, which results in the generation of high pressures in the order of 100-5000 bar and temperatures in the range of 727-9727 °C for just a fraction of seconds. Increasing consumer demand for high-quality foods with higher nutritive values and fresh-like sensory attributes, food processors, scientists, and process engineers are pushed to develop innovative and effective non-thermal methods as an alternative to conventional heat treatments. Hydrodynamic cavitation can play a significant role in non-thermal food processing as it has the potential to destroy microbes and reduce enzyme activity while retaining essential nutritional and physicochemical properties. As hydrodynamic cavitation occurs in a flowing liquid, there is a decrease in local pressure followed by its recovery; hence it can be used for liquid foods. It can also be used to create stable emulsions and homogenize food constituents. Moreover, this technology can extract food constituents such as polyphenols, essential oils, pigments, etc., via biomass pretreatment, cell disruption for selective enzyme release, waste valorization, and beer brewing. Other applications related to food production include water treatment, biodiesel, and biogas production. The present review discusses the application of HC in the preservation, processing, and quality improvement of food and other related applications. The reviewed examples in this paper demonstrate the potential of hydrodynamic cavitation with further expansion toward the scaling up, which looks at commercialization as a driving force.

One pot clarification and debittering of grapefruit juice using co-immobilized enzymes@chitosanMNPs.

In the present work, enzymes pectinase and naringinase were simultaneously co-immobilized on an eco-friendly chitosan coated magnetic nanoparticles (chitosanMNPs) by cross-linking using chitosan as a macro-molecular cross-linker. The maximum activity recovery of both enzymes in the co-immobilized form was obtained at chitosanMNPs to enzymes ratio of 1:3, 3% cross-linker concentration and 150 min cross-linking time. The synthesized MNPs before and after co-immobilization were characterized using different techniques. The prepared biocatalyst was found spherical with an average size below 200 nm and showed supermagnetic property with saturation magnetization of 38.28 emu/g. The optimum pH and temperature of both enzymes in co-immobilized form was found at 5.5 and 65 °C. The prepared biocatalyst exhibited an improved thermal stability with 1.8-fold increase in the half-life. The secondary structural analysis revealed that, prepared co-immobilized biocatalyst undergone changes in the conformational and structural rigidity due to macro-molecular cross-linker. The co-immobilized biocatalysts were evaluated for one pot clarification and debittering of grapefruit juice and found ~52% reduction in turbidity and ~85% reduction in the naringin content. The co-immobilized enzymes were recycled up to 7th cycle and can be easily stored at room temperature for 30 days retaining up to 64% and 86% residual activities respectively.

Intensification in biological properties of chitosan after γ-irradiation.

Chitosan, a functional biopolymer, was irradiated with 100 kGy gamma irradiation and used to access its physical, antioxidant, plant growth promoting and antimicrobial properties. The molecular weight of chitosan reduced to 82.2 kDa from 337.7 kDa after irradiation. UV-Vis spectroscopy and FTIR results revealed slight changes in chitosan skeleton after irradiation but the degree of acetylation of both chitosan was ~18%. DSC profile indicated a prominent decline in enthalpy and energy for phase transition, TGA indicated shift in decomposition temperature, while XRD analysis showed a reduction in chitosan crystallinity after irradiation. DPPH and ABTS radical scavenging activity of chitosan (2-10 mg/mL) enhanced significantly by 1.25-1.45 and 1.80-3.14 folds after irradiation. There was a considerable improvement in morphological parameters (number of leaves, nodes, height, fresh weight and dry weight) and biochemical parameters (chlorophyll, total soluble sugars and soluble proteins content) of in vitro potato plant in chitosan supplemented medium at 75 mg/L concentration than the control. The minimum inhibitory concentration of normal and irradiated chitosan for Alternaria spp. was 2500 and 2000 mg/L and for Fusarium spp. was 1750 and 1500 mg/L, respectively. IC50 value of normal and irradiated chitosan for Fusarium spp. was 1387.9 ±â€¯9.2 and 954.3 ±â€¯6.1 mg/L, and for Alternaria spp. was 1536.1 ±â€¯24.3 and 1416.8 ±â€¯3.5 mg/L, respectively.

Synergistic effect of ultrasonication and co-immobilized enzymes on tomato peels for lycopene extraction.

In the present work, tomato peels were pre-treated using combination of ultrasound and enzyme co-immobilized amino-functionalized magnetic nanoparticles (AMNPs) for the efficient release of lycopene. To achieve maximum activity of enzymes in the co-immobilized form, optimization of several parameters were carried out. Moreover, the influence of ultrasound and enzyme co-immobilized magnetic nanoparticles on lycopene release was studied. Maximum lycopene release was obtained at 3% (w/w) enzyme co-immobilized AMNPs, pH 5.0, temperature of 50 °C, at 10 W ultrasound power and 20 min incubation time. After enzymatic pre-treatment, lycopene from the pre-treated mixture was extracted and separated using tri-solvent extraction method. Maximum recovery of lycopene using solvent extraction was obtained at 50 °C, 90 min of incubation time and agitation speed of 150 rpm. The presence of lycopene in the extract was confirmed by FT-IR, UV-vis spectroscopy and HPLC analysis. The co-immobilized bio-catalyst showed excellent reusability giving more than 50% lycopene yield even after 6th cycles of reuse.

Optimization of pectinase-assisted and tri-solvent-mediated extraction and recovery of lycopene from waste tomato peels.

In the present work, optimization of pectinase-assisted and tri-solvent-mediated extraction of lycopene from waste tomato peels was carried out. The optimized parameters for enzymatic pre-treatment were 2% pectinase concentration, pH 5.5, 4-h incubation, 45 °C and 150 rpm. Maximum recovery of lycopene from tomato peels using optimized tri-solvent extraction was achieved at 45 °C, 120-min incubation and 200 rpm. The extracted lycopene was confirmed through functional and characteristic peaks in UV-Vis and FTIR spectra and with retention time in HPLC. The radical scavenging activity was 72.30 ± 2.70 and 43.40 ± 2.01 µg ascorbic acid equivalents (AAE)/ml for 1,1-diphenyl-2-picrylhydrzyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals, respectively. The optimized method resulted in 7.38, 4.65 and 1.59 times enhancement in lycopene extraction and recovery in correlation with single solvent, enzyme-treated and tri-solvent extraction methods, respectively.

Macromolecular cross-linked enzyme aggregates (M-CLEAs) of α-amylase.

Macromolecular cross-linked enzyme aggregates (M-CLEAs) of α-amylase were prepared by precipitation and subsequent cross-linking. The non-toxic, biodegradable, biocompatible, renewable polysaccharide based macromolecular cross-linkers viz. agar, chitosan, dextran, and gum arabic were used as a substitute for traditional glutaraldehyde to augment activity recovery toward macromolecular substrate. Macromolecular cross-linkers were prepared by periodate mediated controlled oxidation of polysaccharides. The effects of precipitating agent, concentration and different cross-linkers on activity recovery of α-amylase CLEAs were investigated. α-Amylase aggregated with ammonium sulphate and cross-linked by dextran showed 91% activity recovery, whereas glutaraldehyde CLEAs (G-CLEAs) exhibited 42% activity recovery. M-CLEAs exhibited higher thermal stability in correlation with α-amylase and G-CLEAs. Moreover, dextran and chitosan M-CLEAs showed same affinity for starch hydrolysis as of free α-amylase. The changes in secondary structures revealed the enhancements in structural and conformational rigidity attributed by cross-linkers. Finally, after five consecutive cycles dextran M-CLEAs retained 1.25 times higher initial activity than G-CLEAs.