DanYang Ying

Microencapsulated Lactobacillus rhamnosus GG Powders: Relationship of Powder Physical Properties to Probiotic Survival during Storage

Freeze-dried commercial Lactobacillus rhamnosus GG (LGG) were encapsulated in an emulsion-based formulation stabilized by whey protein and resistant starch and either spray-dried or freeze-dried to produce probiotic microcapsules. There was no difference in loss of probiotics viability after spray drying or freeze drying. Particle size, morphology, moisture sorption, and water mobility of the powder microcapsules were examined. Particle size analysis and scanning electron microscopy showed that spray-dried LGG microcapsules (SDMC) were small spherical particles, whereas freeze-dried LGG microcapsules (FDMC) were larger nonspherical particles. Moisture sorption isotherms obtained using dynamic vapor sorption showed a slightly higher water uptake in spray-dried microcapsules. The effect of water mobility, as measured by nuclear magnetic resonance (NMR) spectroscopy, at various water activities (a(w) 0.32, 0.57, and 0.70) and probiotic viability during storage at 25 °C was also examined. Increasing the relative humidity of the environment at which the samples were stored caused an increase in water mobility and the rate of loss in viability. The viability data during storage indicated that SDMC had better storage stability compared to FDMC. Although more water was adsorbed for spray-dried than freeze-dried microcapsules, water mobility was similar for corresponding storage conditions because there was a stronger water-binding energy for spray-dried microcapsule. This possibly accounted for the improved survival of probiotics in spray-dried microcapsules.

Water sorption properties, molecular mobility and probiotic survival in freeze dried protein–carbohydrate matrices

The moisture uptake and molecular mobility of freeze-dried powders containing whey protein isolate-carbohydrate matrices (1WPI:2maltodextrin; 1WPI:1maltodextrin:1d-glucose; and 1WPI:1maltodextrin:1l-glucose) and encapsulated Lactobacillus rhamnosus GG (LGG) in these matrices were investigated at 25 °C and 33% and 70% relative humidity (RH). The inactivation rate constant for probiotics in freeze-dried matrices were positively correlated (R(2) = 0.98) to moisture uptake and molecular mobility measured by NMR relaxometry. The stability of probiotics in glassy protein-carbohydrate matrices was dependent on the composition of the matrix. The partial substitution of maltodextrin with glucose (d- or l-) which improved microbial survival at 33% RH was related to the reduced molecular mobility and lower water uptake of the matrix. This study suggests that moisture uptake properties and molecular mobility of the matrix composition, as opposed to the relative humidity of the environment, are better determinants of probiotic viability during storage. Dynamic vapour sorption and NMR relaxometry are promising tools to assist in the selection of protein-carbohydrate matrices for enhancing probiotic viability during storage.

Tocopherol and Ascorbate Have Contrasting Effects on the Viability of Microencapsulated Lactobacillus rhamnosus GG

The antioxidants, sodium ascorbate and tocopherol, have contrasting effects on the viability of microencapsulated Lactobacillus rhamnosus GG (LGG) spray-dried powders during storage (4 and 25 °C; 32, 57, and 70% relative humidity). The addition of tocopherol improved probiotic viability during storage, while the incorporation of Na-ascorbate alone or in combination with tocopherol had detrimental effects on probiotic survival. The beneficial effect of tocopherol is a consequence of its chemical antioxidative action. The reduced viability in Na-ascorbate containing microcapsule formulations is hypothesized to be due primarily to the production of acetic acids arising from chemical degradation reactions and the catabolism of ascorbate by LGG. This study highlights the importance of considering the detrimental consequences of degradative chemical reactions and the metabolic fate of additives on the viability of probiotics when designing probiotic encapsulant formulations.

Physical characterisation of high amylose maize starch and acylated high amylose maize starches

The particle size, water sorption properties and molecular mobility of high amylose maize starch (HAMS) and high amylose maize starch acylated with acetate (HAMSA), propionate (HAMSP) and butyrate (HAMSB) were investigated. Acylation increased the mean particle size (D(4,3)) and lowered the specific gravity (G) of the starch granules with an inverse relationship between the length of the fatty acid chain and particle size. Acylation of HAMS with fatty acids lowered the monolayer moisture content with the trend being HAMSB<HAMSA<HAMSP<HAMS, showing that the decrease is affected by factors other than the length of the fatty acid chain. Measurement of molecular mobility of the starch granules by NMR spectroscopy with Carr-Purcell-Meiboom-Gill (CMPG) experiments showed that T2 long was reduced in acylated starches and that drying and storage of the starch granules further reduced T2 long. Analysis of the Free Induction Decay (FID) focussing on the short components of T2 (correlated to the solid matrix), indicated that drying and subsequent storage resulted in alterations of starch at 0.33a(w) and that these changes were reduced with acylation. In vitro enzymatic digestibility of heated starch dispersions by bacterial α-amylase was increased by acylation (HAMS<HAMSB<HAMSP≤HAMSA) showing that the trend was not related to the length of the fatty acid chain. Digestibility was enhanced with an increase in particle size, or decrease in G, and inversely proportional to the total T2 signal. It is suggested that both external surface area and an internal network of pores and channels collectively influence the digestibility of starch.

Probiotics and Prebiotics

Probiotic bacteria have long been believed to influence general health and well-being through their association with the gastrointestinal tract (GIT) and its normal microbiota. The microbiotas of humans, animals, and fowl vary considerably with the architecture of their GITs. Species of microorganisms are located at different locations throughout the GIT and include strains that are either harmful or beneficial to the host depending on the circumstances and specific strains involved. Probiotic microorganisms typically designed for delivery in dairy foods are most often members of the Lactobacillus or Bifidobacterium genus. This chapter discusses the effects of probiotics on GIT ecology, and deals with the appropriateness, technological suitability, competitiveness, and performance and functionality, as the criteria for selection of probiotic cultures. Prebiotics stimulate the growth and activity of beneficial bacteria in an individual’s intestinal microbiota. The best-known prebiotics are fructo-oligosaccharides derived from food sources. Production of designer prebiotics can offer multiple activities in retarding undesirable microorganisms, better promoting the native desirable microbiota, or stimulating the growth or activity of synbiotic cultures. Expansion of avenues for incorporation into appropriate food vehicles and improved stimulation of beneficial microfloras are some of the aspects that are good targets for development of prebiotics.

Effect of Drying Methods on Protein and DNA Conformation Changes in Lactobacillus rhamnosus GG Cells by Fourier Transform Infrared Spectroscopy

Microencapsulation protects cells against environmental stress encountered during the production of probiotics, which are used as live microbial food ingredients. Freeze-drying and spray-drying are used in the preparation of powdered microencapsulated probiotics. This study examines the ability of Fourier transform infrared (FTIR) spectroscopy to detect differences in cells exposed to freeze-drying and spray-drying of encapsulated Lactobacillus rhamnosus GG cells. The FTIR analysis clearly demonstrated there were more significant molecular changes in lipid, fatty acid content, protein, and DNA conformation of nonencapsulated compared to encapsulated bacterial cells. The technique was also able to differentiate between spray-dried and freeze-dried cells. The results also revealed the extent of protection from a protein-carbohydrate-based encapsulant matrix on the cells depending on the type drying process. The extent of this protection to the dehydration stress was shown to be less in spray-dried cells than in freeze-dried cells. This suggests that FTIR could be used as a rapid, noninvasive, and real-time measurement technique to detect detrimental drying effects on cells.

Urea Controlled-Release Fertilizer Based on Gelatin Microspheres

Gelatin microsphere, as a sustained release urea carrier, was prepared by an emulsion–cross linking method with glutaraldehyde (GA) as a cross-linking agent. The influence of urea/gelatin ratio, emulsifier, GA concentration, and cross-linking time on the urea loading and encapsulation efficiency was investigated using response surface methodology. It was found that the urea/gelatin ratio had greater impact on urea loading and encapsulation efficiency than other factors. Equilibrium swelling of microspheres were performed in distilled water, and as expected, the water uptake decreased with the increase of GA as well as the reaction time. The cumulative release of urea from the microspheres decreased with the increase of reaction time and urea release presented a Fickian trend, indicating a diffusion controlled urea release mechanism. The insight from this study is useful to the design and process of controlled release urea fertilizers.Graphical Abstract

Physical properties and FTIR analysis of rice-oat flour and maize-oat flour based extruded food products containing olive pomace

Olive pomace, a waste stream from olive oil processing, was fractionated by centrifugation to obtain a supernatant and a flesh-enriched fraction, and freeze dried to obtain a powder. The dried supernatant contained 5.8% moisture, 4.8% protein, 3.5% fat, 3.5% ash, 82.4% carbohydrate (including 17.2% dietary fiber) and polyphenols (2970mg gallic acid equivalents (GAE)/100g). The dried flesh-enriched fraction, contained 5.9% moisture, 13.4% protein, 14.2% fat, 3.5% ash, 63.1% carbohydrate (including 42.7% dietary fiber) and polyphenols (1960mg GAE/100g). The extruded products using rice-oat flour or maize-oat flour mixtures as the base were formulated to contain 5% or 10% olive pomace fractions (dry basis). The extruded products with added olive pomace fractions has higher fiber (2-7g/100g) and polyphenol contents (67-161mg GAE/100g) compared to the corresponding mixtures of rice-oat flour base (0.92g/100g fiber, 20mg GAE/100g) or maize-oat flour base (3.2g/100g fiber, 20mg GAE/100g) without olive pomace fractions. Addition of olive pomace fractions reduced the die pressure and specific mechanical energy during extrusion and resulted in lower radial expansion in the extruded product. The impact of the addition of olive pomace fraction on physical characteristics of the extruded product is higher for rice-oat flour base than maize-oat flour base. The underlining mechanism was explained by FTIR analysis. FTIR showed that there were significant changes in the carbohydrate components and the structure of the proteins on extrusion, with consequent effects on the expansion and density of the extruded product. This study showed the feasibility of preparing fiber and polyphenol enriched extruded products by incorporation of olive pomace. This shows the potential of recovery and diversion of edible components from waste streams of olive oil processing for formulation of extruded products.

Effect of extrusion conditions on the physico-chemical properties and in vitro protein digestibility of canola meal

Canola meal has potential as a high protein food ingredient. The extrusion-induced changes in color, pH, extractable protein and in vitro protein digestibility of canola meal under different extrusion conditions was assessed. The extrusion barrel moisture (24%, 30% or 36%) and screw kneading block length (0, 30 or 60mm) were used as independent process parameters. Extrusion at high barrel moisture (36%) favored protein aggregation resulting in lower extractable protein compared to extrusion at the lowest barrel moisture (24%). At lower barrel moisture contents (24% and 30%), a longer kneading block length increased extractable protein but this was not the case at 36% barrel moisture. Canola protein digestibility was improved upon extrusion at 30% barrel moisture but there was no significant change at lower (24%) or higher (36%) barrel moisture. The kneading block length of the screw had no significant effect on the canola protein digestibility within the same barrel moisture level. The relationship between the physico-chemical parameters and in vitro digestibility was examined. This study highlighted the complex interplay of extrusion processing variables that affect protein degradation and the interaction of components, with consequent effects on protein digestibility.

Comparison of the adsorption behaviour of catechin onto cellulose and pectin

The adsorption behaviour of catechin onto cellulose and pectin was compared. The adsorption of catechin onto the two fibres involved an initial fast adsorption phase followed by a slower adsorption as the sites became saturated and the systems moved towards equilibrium. The adsorption capacity of pectin for catechin (20.71 ± 2.24 mg/g) was significantly greater than that of cellulose (2.41 ± 0.05 mg/g) after equilibration for 24 h at 37 °C. The Langmuir and Freundlich models were applied to obtain the quantitative information about the adsorption of catechins to pectin and cellulose. Thermodynamic data derived from the isothermal adsorption carried out at the temperatures of 27 °C, 32 °C, 37 °C and 42 °C suggested that the adsorption was spontaneous and the binding was driven predominantly by physisorption. Fluorescence experiments confirmed the adsorption of catechins onto cellulose and pectin. The results showed that catechin adsorption capacity and adsorption mechanism were different for pectin and cellulose.