Frank Sherkat

Lactulose production from milk concentration permeate using calcium carbonate-based catalysts

Milk concentration permeate (MCP), a low-value by-product of ultrafiltration plants and calcium carbonate-based catalysts were used for lactulose production. The results obtained show the effectiveness of oyster shell powder and limestone for lactose isomerisation as a replacement for egg shell powder. With the reaction conditions of 12mg/ml catalyst loading, reflux time of 120min at 96°C, a maximum yield of 18-21% lactulose was achievable at a cost of <50% of original lactose degradation (measured by HPLC). De-proteination of MCP by acidification prior to isomerisation helped lactulose formation in the earlier stages, but did not significantly increase the yield. The resulting lactulose MCP (40°B) incorporated at the rate of 3-4% was effective in enhancing the growth rate and acid production of Lactobacillus acidophilus (LA-5) in probiotic products.

Combined pH and high hydrostatic pressure effects on Lactococcus starter cultures and Candida spoilage yeasts in a fermented milk test system during cold storage

The combined effects of high pressure processing (HPP) and pH on the glycolytic and proteolytic activities of Lactococcus lactis subsp. lactis, a commonly used cheese starter culture and the outgrowth of spoilage yeasts of Candida species were investigated in a fermented milk test system. To prepare the test system, L. lactis subsp. lactis C10 was grown in UHT skim milk to a final pH of 4.30 and then additional samples for treatment were prepared by dilution of fermented milk with UHT skim milk to pH levels of 5.20 and 6.50. These milk samples (pH 4.30, 5.20 and 6.50) with or without an added mixture of two yeast cultures, Candida zeylanoides and Candida lipolytica (10(5) CFU mL(-1) of each species), were treated at 300 and 600 MPa (≤20°C, 5 min) and stored at 4°C for up to 8 weeks. Continuing acidification by starter cultures, as monitored during storage, was substantially reduced in the milk pressurised at pH 5.20 where the initial titratable acidity (TA) of 0.40% increased by only 0.05% (600 MPa) and 0.10% (300 MPa) at week 8, compared to an increase of 0.30% in untreated controls. No substantial differences were observed in pH or TA between pressure-treated and untreated milk samples at pH 4.30 or 6.50. The rate of proteolysis in milk samples at pH values of 5.20 and 6.50 during storage was significantly reduced by treatment at 600 MPa. Treatment at 600 MPa also reduced the viable counts of both Candida yeast species to below the detection limit (1 CFU mL(-1)) at all pH levels for the entire storage period. However, samples treated at 300 MPa showed recovery of C. lipolytica from week 3 onwards, reaching 10(6)-10(7) CFU mL(-1) by week 8. In contrast, C. zeylanoides did not show any recovery in any of the pressure-treated samples during storage.

Influence of Galactooligosaccharides and Modified Waxy Maize Starch on Some Attributes of Yogurt

This study examined the influence of galactooligosaccharides (GOS) and modified waxy maize starch (MWMS) addition on the growth of starter cultures, and syneresis and firmness of low-fat yogurt during storage for 28 d at 4 °C. The control yogurt (CY) was prepared without any prebiotics. Incorporation of 2.0% (w/v) GOS improved the growth of L. delbrueckii ssp. bulgaricus ATCC 11842 resulting in a shorter fermentation time. There was a significant (P < 0.05) increase in proteolysis in yogurt made with GOS (GOSY) as measured by absorbance value (0.728). Addition of GOS resulted in higher (P < 0.05) concentration of lactic and acetic acids in comparison with that of MWMSY and the CY up to day 14, thereafter, the product showed a decrease in lactic acid content in all 3 batches until the end of storage. The level of syneresis was the lowest (2.14%) in MWMSY as compared with that of GOSY (2.35%) and CY (2.53%). There was no statistically significant (P > 0.05) difference in the firmness among the 3 types of yogurt.

The effect of NaCl substitution with KCl on proteinase activities of cell-free extract and cell-free supernatant at different pH levels and salt concentrations: Lactobacillus acidophilus and Lactobacillus casei

The aim of this study was to investigate the effect of substitution of NaCl with KCl at different pH levels and salt concentrations on proteinase activity of cell-free extract and cell-free supernatant of the probiotics Lactobacillus acidophilus and Lactobacillus casei. de Man, Rogosa, and Sharpe broth aliquots were mixed with 2 pure salts (NaCl and KCl) and 2 salt concentrations at 2 concentration levels (5 and 10%), inoculated with Lactobacillus acidophilus or Lactobacillus casei, and incubated aerobically at 37°C for 22 h. The cultures were then centrifuged at 4,000×g for 30 min, and the collected cell pellets were used to prepare cell-wall proteinases and the supernatants used as a source of supernatant (extracellular) proteinases. The proteolytic activity and protein content of both portions were determined. After incubation of both portions with 3 milk caseins (α-, β-, κ-casein), the supernatants were individually subjected to analysis of angiotensin-converting enzyme (ACE)-inhibitory activity and proteolytic activity using the o-phthalaldehyde method. Significant differences were observed in ACE-inhibitory and proteolytic activities between salt substitution treatments of cell-free extract and cell-free supernatant from both probiotic strains at the same salt concentration and pH level.

Purification of avian biological material to refined keratin fibres

Keratin derived from chicken feather fibres (CFFs) has many potential applications that are constrained by the quality and pathogen content after purification treatment. The pathogen activity after purification has not been evaluated elsewhere. Plucked chicken feathers are prone to impose biological hazards due to accommodating blood-borne pathogens; therefore, establishing an efficient purification process is crucial. Bactericidal performance of surfactants (anionic, non-ionic, and cationic), bleach (ozone and chlorine dioxide), ethanol extraction, and a combination method comprising surfactant-bleach-ethanol extraction on chicken feathers was investigated via (A) standard plate count and enumeration of Escherichia coli, Pseudomonas species, coagulase positive Staphylococcus, aerobic and anaerobic spore-formers and (B) Salmonella and Campylobacter detection tests. Among the purification methods, only ethanol extraction and combination methods eliminated Salmonella from the untreated feathers. Although ethanol extraction exhibited superior bactericidal impact compared to the combination method, the feathers treated through the latter method demonstrated superior morphological and mechanical properties. Scanning electron microscopy-energy dispersive spectroscopy was employed to determine the remaining content of selected purifiers on treated CFFs. Fourier-transform infrared spectroscopy confirmed the successful removal of fatty esters from CFFs using nominated purifiers. Ethanol extraction was found to be the most efficacious single treatment, while combination of surfactant and oxidative sterilizer with ethanol was superior.

Avian keratin fibre-based bio-composites

Purpose This paper aims to use the solvent–casting–evaporation method to prepare new bio-composites with thermoplastic poly(ether urethane) (TPU-polyether) as the polymer matrix and reinforced with natural chicken feather fibre (CFF). Design/methodology/approach To produce the bio-composites, 0 to 60 per cent·w/w of fibres in steps of 30 per cent·w/w were added to the polymer matrix. The uniformity of distribution of the keratin fibres in the polymer matrix was investigated via scanning electron microscopy, and the results suggested compatibility of the TPU-polyether matrix with the CFFs, thereby implying effective fibre–polymer interactions. Findings Addition of natural fibres to the polymer was found to decrease the mass loss of the composites at higher temperatures and decrease the glass transition temperature, as well as the storage and loss modulus, at lower temperatures, while increasing the remaining char ratio, storage modulus and loss modulus at higher temperatures. Originality/value The investigation confirmed that waste keratin CFF can improve the thermo-mechanical properties of composites, simply and cheaply, with potentially large environmental and economic benefits.