Abstract: Freeze dried crude bacteriocin was encapsulated within an acid-soluble coating material, Eudragit EPO, using a surface modification technique through a hybridization system. The pH and titratable acidity of control yoghurt were 3.92 and 1.56%, respectively, after 24 hr of fermentation at 42 degrees C, whereas yoghurt containing 500 AU/mL encapsulated bacteriocin exhibited a higher pH (4.37) and lower titratable acidity (1.2%). Yoghurt containing encapsulated bacteriocin had significantly lower titratable acidity when the duration of fermentation (to pH 4.5) and subsequent refrigerated storage (4 degrees C) was longer than 20 days. There were no significant differences in the viability of lactic acid bacteria after 15 hr of fermentation. This suggests that microencapsulated bacteriocin has the potential to control the excessive growth of yoghurt starters caused by temperature abuse or post-acidification.
Abstract: The effects of 6 mo of freezing and refrigeration on organic acid profiles of 2 types of goat milk cheese [ plain soft ( PS) and Monterey Jack (MJ)] were studied in comparison with those of a nonfrozen control (NFC). Three lots of commercial PS cheeses were purchased, and 3 lots of MJ cheeses were manufactured at the University dairy plant. Each lot of the 2 types of cheeses was subdivided into 4 equal portions, and one subsample of each cheese was immediately stored at 4 degrees C as the NFC for 0, 14, and 28 d. The other 3 were immediately frozen (-20 degrees C) for 0, 3, and 6 mo (0MF, 3MF, and 6MF) and subsequently thawed the next day at 4 degrees C. The samples were then stored at 4 degrees C for 0, 14, and 28 d. Organic acids were quantified using an HPLC. The PS had no pyruvic acid, and MJ contained no isotartaric acid; however, several unknown large peaks appeared between propionic and butyric acids. Differences in organic acid contents between PS and MJ cheeses were significant for all acids except citric and lactic acid. Lot effect was significant for most of the known acids, indicating that variations existed in milk composition and manufacturing parameters. Effects of storage treatments (NFC, 0MF, 3MF, and 6MF) were significant for most organic acids, except for orotic and a few unidentified acids. Aging at 4 degrees C for 4 wk had little influence on all organic acids, except butyric acid. Concentrations of butyric, lactic, propionic, tartaric, and uric acids were significantly elevated as the frozen storage period advanced. At the initial stage, there were no differences in pH and acid degree values between NFC and frozen-stored groups of both cheeses. However, acid degree values gradually increased as the refrigerated storage extended up to 4 wk, indicating that lipolysis increased as the refrigeration storage at 4 degrees C advanced. Although levels of several organic acids were changed in the goat cheeses, the prolonged frozen storage, up to 6 mo, was apparently feasible for extending storage.
Abstract: Calcium-alginate coated microspheres consisting of whey proteins and a model sensitive core, paprika oleoresin, were prepared using an all-aqueous process. Core-in-wall emulsions containing 20% or 25% whey protein isolate and 15% to 50% (wt/wt) core were investigated. Retention of proteins and core during the process ranged from 84.9% to 95.6% and from 91.4% to 95.7%, respectively. Results indicated that microspheres were water-insoluble and the encapsulated sensitive core was effectively protected against oxidative deterioration. This protection could be attributed to the protein-based layer adsorbed at the oil/water interface. The matrix of the microspheres exhibited microstructural features of an interactive composite-type material. Results suggested the potential suitability of the microspheres as delivery systems for controlled core release in food applications.
Abstract: An 'all aqueous' encapsulation process followed by a heat treatment was used to prepare calcium-alginate-coated, whey protein-based, water insoluble microspheres containing micronized calcium carbonate as a model core. Results obtained with this process were compared to those obtained with a similar process in which chemical cross-linking was utilized. At an initial core load of 25 or 50% (w/w), core retention ranged from 84.2-95.12% and was not significantly affected by the initial core load or by the cross-linking method. Regardless of the cross-linking method, protein retention during the process was high and ranged from 78.2-87.5%. Outer topography of the microspheres was not influenced by the cross-linking method, however, at a given composition, the inner structure of heat treated microspheres differed from that obtained with chemically-cross-linked microspheres. Swelling properties of denovo microspheres were affected by pH. Results indicated that the micronized calcium carbonate could be used as a porogenic core. Removal of the core, by an acid treatment, allowed preparing microporous delivery devices. In addition to offer opportunities for encapsulation and delivery of crystalline core, the investigated process can provide means to prepare 'ghost' microporous delivery systems that can, in potential, be loaded, following their preparation, with sensitive core materials at conditions that favour the stability and functionality of this core.
Abstract: The effects of heat treatment and homogenization of whole milk on chemical changes in the milk fat globule membrane (MFGM) were investigated. Heating at 80 C for 3-18 min caused an incorporation of whey proteins, especially beta-lactoglobulin (beta-lg), into MFGM, thus increasing the protein content of the membrane and decreasing the lipid. SDS-PAGE showed that membrane glycoproteins, such as PAS-6 and PAS-7, had disappeared or were weakly stained in the gel due to heating of the milk. Heating also decreased free sulphydryl (SH) groups in the MFGM and increased disulphide (SS) groups, suggesting that incorporation of beta-lg might be due to association with membrane proteins via disulphide bonds. In contrast, homogenization caused an adsorption of caseins to the MFGM but no binding of whey proteins to the MFGM without heating. Binding of caseins and whey proteins and loss of membrane proteins were not significantly different between milk samples that were homogenized before and after heating. Viscosity of whole milk was increased when milk was treated with both homogenization and heating.
Abstract: Theophylline was microencapsulated in composite whey protein-based wall systems containing different proportions of dispersed apolar filler, anhydrous milkfat. Wall emulsions exhibited uni-modal particle size distribution and had a mean particle size of 0.36-0.38 mum. Microcapsules were cross-linked by glutaraldehyde-saturated toluene via an organic phase. Spherical microcapsules ranging in diameter from 150 to larger than 700 mum were obtained and exhibited some surface cracks that could be attributed to the fragile nature of a peripheral, highly cross-linked 'shell' layer around the capsules. Core content ranged from 46.9-56.6% (w/w) and filler content ranged from 12.0-33.4% (w/w). Core and filler retention during microencapsulation ranged from 84.9-96.9% and from 85.1-89.6%, respectively. Core retention was proportionally related to the proportion of filler embedded in the wall matrix. Core release into SGF and SIF was affected by microcapsule size, type of dissolution medium and wall composition. Rate of core release was inversely proportional to filler content of the wall matrix. This could be attributed to effects of filler content on diffusion through the wall matrix and probably on swelling properties of microcapsules. Results indicated that incorporation of apolar filler in wall matrix of whey protein-based capsules provided the means to enhance retention of a water-soluble core during the microencapsulation process and to decrease the rate of core release into aqueous dissolution media.
Abstract: A method, consisting of double emulsification and chemical cross-linking with glutaraldehyde was used to prepare whey protein-based microcapsules containing anhydrous milk fat as a model core. Effects of emulsion composition and pH on core retention, microstructure, and water-solubility of microcapsules were investigated. In all cases, core retention higher than 88% was accomplished and, in most cases, was not significantly affected by emulsion composition. In all cases, spherical microcapsules, 10-80 mu m in diameter, were obtained. Outer topography and the inner structure of microcapsules were significantly affected by the pH of the emulsion. In all cases, microcapsules were practically water-insoluble. Microcapsules similar to the developed prototype may be suitable for controlled core release in application fields where chemical cross-linking is acceptable.
Abstract: Whey protein-based microcapsules containing a model apolar core, anhydrous milkfat, were prepared using a process consisting Of double emulsification and subsequent heat gelation. Wall solids concentration and core load ranged from 15 to 30 g/100 g and from 25 to 50 g/100 g ton dry basis), respectively. In all cases, spherical microcapsules, 10-100 mum in diameter; were obtained and their outer. topography and inner structure was affected by the pH of the core-in-wall emulsion. Microcapsules prepared from pH 7.2 core-in-wall emulsions exhibited smooth, dent-fee surfaces. Surface porosity of microcapsules prepared from pH 4.5, 5.5 and 5.5 core-in-wall emulsions was inversely related to pH. Core retention during microencapsulation was higher than 90% and core losses could be attributed mainly to removal of core droplets from the outer surface and to some core extraction from inner parts of microcapsules by the solvents used to wash the microcapsules. Water solubility of microcapsules prepared fr om pH 4.5 ol pH 7.2 core-in-wall emulsions was very limited and ranged from 0.2 to 6.3%, was inversely related to the pH of core-in-wall emulsion and Ic ns affected by incubation conditions. Results suggested that the microencapsulation process might be used to prepare whey protein-bused microcapsules for controlled core-release applications in food systems.
Abstract: Effects of core-to-wall ratio ranging from 1:1.5 to 5:1.5 on formation, properties and core release from whey protein-based microcapsules containing theophylline were investigated. Microcapsules were cross-linked by glutaraldehyde-saturated toluene (GAST) in an organic phase. Size distribution of microcapsules, core content and core retention were affected by core-to-wall ratio. Proportion of small capsules was inversely related to core-to-wall ratio. Core content in microcapsules ranged from 6.7 to 65.7% (w/w) and core retention ranged from 16.8 to 85.4%. Outer topography and inner structure of microcapsules were influenced by core-to-wall ratio. Core release into simulated intestinal- and gastric-fiuids was influenced by a combined effect of type of dissolution medium and core-to-wall ratio, through its influence on size, core content and structure of microcapsules. Results indicated that in order to attain a desired core content and release profile, the ratio of core-to-wall components, in suspensions consisting of whey proteins and theophylline, has to be carefully considered and adjusted.
Abstract: Whey protein-based microcapsules containing a model drug, theophylline, were prepared in organic phase, using glutaraldehyde-saturated toluene. In all cases, spherical microcapsules, ranging from <400 to 1000 mu m in diameter, were obtained. Results indicated that core crystals were embedded throughout the wall matrix. In all cases, retention efficiency of theophylline was higher than 74% and was not affected by cross-linking conditions. Results of theophylline release in simulated intestinal and gastric fluids at 37 degrees C indicated that the diffusion-governed core release was significantly affected by size of microcapsules, cross-linking conditions, and by type of dissolution medium. In all cases, core release in simulated intestinal fluid was faster than in simulated gastric fluid.
Abstract: Near-infrared reflectance spectroscopy (NIRS) equations were developed for rapid analysis of curds during Cheddar cheese making. The coefficients of determination (R(2)) for NIRS and chemical analysis were: moisture (0.982), protein (0.965), fat (0.951), and lactose (0.909). When validation samples were compared by NIPS and chemical analysis, the R(2)s were moisture (0.984), protein (0.964), fat (0.957), and lactose (0.982). These results suggest that NIRS is applicable for rapidly monitoring chemical changes in curds.
