Sanghoon Ko

Very high gravity (VHG) ethanolic brewing and fermentation: a research update.

There have been numerous developments in ethanol fermentation technology since the beginning of the new millennium as ethanol has become an immediate viable alternative to fast-depleting crude reserves as well as increasing concerns over environmental pollution. Nowadays, although most research efforts are focused on the conversion of cheap cellulosic substrates to ethanol, methods that are cost-competitive with gasoline production are still lacking. At the same time, the ethanol industry has engaged in implementing potential energy-saving, productivity and efficiency-maximizing technologies in existing production methods to become more viable. Very high gravity (VHG) fermentation is an emerging, versatile one among such technologies offering great savings in process water and energy requirements through fermentation of higher concentrations of sugar substrate and, therefore, increased final ethanol concentration in the medium. The technology also allows increased fermentation efficiency, without major alterations to existing facilities, by efficient utilization of fermentor space and elimination of known losses. This comprehensive research update on VHG technology is presented in two main sections, namely VHG brewing, wherein the effects of nutrients supplementation, yeast pitching rate, flavour compound synthesis and foam stability under increased wort gravities are discussed; and VHG bioethanol fermentation studies. In the latter section, aspects related to the role of osmoprotectants and nutrients in yeast stress reduction, substrates utilized/tested so far, including saccharide (glucose, sucrose, molasses, etc.) and starchy materials (wheat, corn, barley, oats, etc.), and mash viscosity issues in VHG bioethanol production are detailed. Thereafter, topics common to both areas such as process optimization studies, mutants and gene level studies, immobilized yeast applications, temperature effect, reserve carbohydrates profile in yeast, and economic aspects are discussed and future prospects are summarized.

Curcumin and Genistein Coloaded Nanostructured Lipid Carriers: in Vitro Digestion and Antiprostate Cancer Activity

To increase the oral bioavailability of curcumin and genistein, we fabricated nanostructured lipid carriers (NLCs), and the impact of these carriers on bioaccessibility of curcumin and genistein was studied. Entrapment efficiency was more than 75% for curcumin and/or genistein-loaded NLCs. Solubility of curcumin and/or genistein in simulated intestinal medium (SIM) was >75% after encapsulating within NLCs which otherwise was <20%. Both curcumin and genistein have shown good stability (≥85%) in SIM and simulated gastric medium (SGM) up to 6 h. Coloading of curcumin and genistein had no adverse effect on solubility and stability of each molecule. Instead, coloading increased loading efficiency and the cell growth inhibition in prostate cancer cells. Collectively, these results have shown that coloaded lipid based carriers are promising vehicles for oral delivery of poorly bioaccessible molecules like curcumin and genistein.

Preparation of sub-100-nm β-lactoglobulin (BLG) nanoparticles

Sub-100-nm nanoparticles were prepared from β-lactoglobulin (BLG) with a narrow size distribution by a desolvation method using glutaraldehyde for cross-linking. With pre-heating of the BLG solution to 60°C and subsequent pH readjustment to 9.0, nanoparticles of 59 ± 5 nm were obtained with improved uniformity. Bovine serum albumin (BSA) nanoparticles, prepared under similar conditions for comparison, were larger and less uniform. The half-width of 80% particle distribution was used to compare the uniformity of particle size distribution. The stability of the nanoparticles was investigated by degradation tests at neutral and acidic pHs with and without proteolytic enzymes, trypsin and pepsin. The degradation time, determined by a graphical approach, was used to compare the relative stabilities of BLG and BSA nanoparticles. The particles of BLG were more stable than those of BSA in acidic and neutral media with and without added enzymes.

Environmentally friendly preparation of pectins from agricultural byproducts and their structural/rheological characterization

Apple pomace which is the main waste of fruit juice industry was utilized to extract pectins in an environmentally friendly way, which was then compared with chemically-extracted pectins. The water-based extraction with combined physical and enzymatic treatments produced pectins with 693.2 mg g(-1) galacturonic acid and 4.6% yield, which were less than those of chemically-extracted pectins. Chemically-extracted pectins exhibited lower degree of esterification (58%) than the pectin samples obtained by physical/enzymatic treatments (69%), which were also confirmed by FT-IR analysis. When subjected to steady-shear rheological conditions, both pectin solutions were shown to have shear-thinning properties. However, decreased viscosity was observed in the pectins extracted by combined physical/enzymatic methods which could be mainly attributed to the presence of more methyl esters, thus limiting polymer chain interactions. Moreover, the pectins which were extracted by combined physical/enzymatic treatments, showed less elastic properties under high shear rate conditions, compared to the chemically-extracted pectins.

Co-delivery of hydrophobic curcumin and hydrophilic catechin by a water-in-oil-in-water double emulsion

Curcumin and catechin are naturally occurring phytochemicals with extreme sensitivity to oxidation and low bioavailability. We fabricated a water-in-oil-in-water (W/O/W) double emulsion encapsulating hydrophilic catechin and hydrophobic curcumin simultaneously. The co-loaded emulsion was fabricated using a two-step emulsification method, and its physicochemical properties were characterised. Volume-weighted mean size (d43) of emulsion droplets was ≈3.88 μm for blank emulsions, whereas it decreased to ≈2.8-3.0 μm for curcumin and/or catechin-loaded emulsions, which was attributed to their capacity to act as emulsifiers. High entrapment efficiency was observed for curcumin and/or catechin-loaded emulsions (88-97%). Encapsulation of catechin and curcumin within an emulsion increased their stability significantly in simulated gastrointestinal fluid, which resulted in a four-fold augmentation in their bioaccessibility compared to that of freely suspended curcumin and catechin solutions. Co-loading of curcumin and catechin did not have adverse effects on either compounds stability or bioaccessibility.

Scaling and fractal analysis of viscoelastic properties of heat-induced protein gels

Abstract The scaling of viscoelastic properties of heat-induced gels prepared from egg white was investigated at five pH values (pH 3–11) and various protein concentrations (5–20%) using small-deformation oscillatory rheological measurements. Protein gels were formed by heating samples at 80 °C for 1 h followed by cooling to 25 °C. Storage modulus, G′ and critical strain, γ0 of the gels exhibited pH-dependent power-law relationships with protein concentration. Based on the power-law exponent values, fractal dimension, df of heat-induced protein gels was estimated using scaling models from the literature. Low df values (1.9–2.1) were obtained for gels prepared at acidic and neutral pHs (3–7) whereas higher df values (2.2–2.4) were obtained for gels formed under basic pH conditions. These df values lied well within the range of fractal dimension values (1.5–2.8) reported for protein gels. However, they slightly differed from df for diffusion-limited and reaction-limited cluster–cluster aggregation processes, which made it difficult to justify an assumption regarding the nature of the aggregation process of these protein systems.

Rat pancreatitis produced by 13-week administration of zinc oxide nanoparticles: biopersistence of nanoparticles and possible solutions

Zinc oxide (ZnO) nanoparticles (NPs) are used in diverse applications ranging from paints and cosmetics to biomedicine and food. Although micron‐sized ZnO is a traditional food supplement, ZnO NPs are an unknown public health risk because of their unique physicochemical properties. Herein, we studied the 13‐week subchronic toxicity of ZnO NPs administered via the oral route according to Organization for Economic Cooperation and Development (OECD) test guideline 408. Well‐dispersed ZnO NPs were administered to Sprague–Dawley (SD) rats (11/sex/group) at doses of 67.1, 134.2, 268.4 or 536.8 mg kg–1 per body weight over a 13‐week period. The mean body weight gain in males given 536.8 mg kg–1 ZnO NPs was significantly lower than that of control male rats, whereas no significant differences were observed between the other treatment groups and the controls. Male and female rats dosed at 536.8 mg kg–1 ZnO NPs had significant changes in anemia‐related hematologic parameters. Mild to moderate pancreatitis also developed in both sexes dosed at 536.8 mg kg–1, whereas no histological changes were observed in the other treatment groups. To evaluate the mechanism of toxicity, we performed a bio‐persistence study and evaluated the effects of the ZnO NPs on cell proliferation. The treatment of a human gastric adenocarcinoma cell line with ZnO NPs resulted in a significant inhibition of cellular proliferation. The anti‐proliferative effect of ZnO NPs or Zn2+ was effectively blocked by treatment with chelators. These results indicate that the bio‐persistence of ZnO NPs after ingestion is key to their toxicity; the no‐observed‐adverse effect level (NOAEL) of ZnO NPs was found to be 268.4 mg kg–1 per day for both sexes. Copyright

Antioxidant activity and bioaccessibility of size-different nanoemulsions for lycopene-enriched tomato extract

Lycopene nanoemulsions were prepared to protect the antioxidant activity and improve the bioaccessibility of lycopene-enriched tomato extract (containing 6% of lycopene) by an emulsification-evaporation method. Lycopene nanoemulsions, with droplet sizes between 100 and 200 nm, exhibited higher anti-radical efficiency and antioxidant activity, than did those smaller than 100 nm. Strong protectability of lycopene in droplets smaller than 100 nm was associated with relatively slower rates of DPPH and ABTS reactions. In vitro bioaccessibility values of lycopene-enriched tomato extract, lycopene nanoemulsions with droplets larger than 100 nm (approximately 150 nm on average), and lycopene nanoemulsions with droplets smaller than 100 nm (69 nm on average) were 0.01, 0.53, and 0.77, respectively. Interestingly, nanoemulsions with droplets smaller than 100 nm showed the highest in vitro bioaccessibility, which could be interpreted as evidence of nanoemulsification enhancing the in vitro bioaccessibility of lycopene.

Physicochemical properties of whey protein, lactoferrin and Tween 20 stabilised nanoemulsions: Effect of temperature, pH and salt

Oil-in-water nanoemulsions were prepared by emulsification and solvent evaporation using whey protein isolate (WPI), lactoferrin and Tween 20 as emulsifiers. Protein-stabilised nanoemulsions showed a decrease in particle size with increasing protein concentration from 0.25% to 1% (w/w) level with Z-average diameter between 70 and 90 nm. However, larger droplets were produced by Tween 20 (120-450 nm) especially at concentration above 0.75% (w/w). The stability of nanoemulsions to temperature (30-90°C), pH (2-10) and ionic strength (0-500 mM NaCl or 0-90 mM CaCl2) was also tested. Tween 20 nanoemulsions were unstable to heat treatment at 90°C for 15 min. WPI-stabilised nanoemulsions exhibited droplet aggregation near the isoelectric point at pH 4.5 and 5 and they were also unstable at salt concentration above 30 mM CaCl2. These results indicated that stable nanoemulsions can be prepared by careful selection of emulsifiers.

Physiochemical properties and prolonged release behaviours of chitosan-denatured β-lactoglobulin microcapsules for potential food applications.

Chitosan (CS) and β-lactoglobulin (βlg) double-wall coating was designed as a shell structure to achieve prolonged release of core material in the gastrointestinal tract (GI) for potential food applications. A model core material, brilliant blue (BB) dye, was incorporated into CS as the primary wall material, and subsequently, denatured βlg, a secondary wall material, was used to coat the outer layer. The strongest interaction occurred between 0.5% (w/v) βlg and 0.5% (w/v) CS at pH 5.5 ± 0.1, where the opposite charges of CS and βlg formed a complex, which is especially favourable in acidic beverage systems. Under simulated stomach conditions, a denatured-βlg coat resisted acid conditions and pepsin hydrolysis for 2h. While mimicking small intestine conditions, βlg was degraded by pancreatin, causing the release of BB-loaded CS to the intestinal fluid at a constant rate. The sustained release of core material later in the GI tract provided an optimal absorption rate in the small intestine.