Development and Assessment of Duplex and Triplex Laminated Edible Films Using Whey Protein Isolate, Gelatin and Sodium Alginate.

The objective of this study was to assess the ability of producing laminated edible films manufactured using the following proteins; gelatin (G), whey protein isolate (WPI) and polysaccharide sodium alginate (SA), and to evaluate their physical properties. Additionally, films' preparation employing these ingredients was optimized through the addition of corn oil (O). Overall, 8-types of laminated films (G-SA, G-WPI, SA-WPI, SA-G-WPI, GO-SAO, GO-WPIO, SAO-WPIO and SAO-GO-WPIO) were developed in this study. The properties of the prepared films were characterized through the measurement of tensile strength (TS), elongation at break point (EB), puncture resistance (PR), tear strength (TT), water vapour permeability (WVP) and oxygen permeability (OP). The microstructure of cross-sections of laminated films was investigated by scanning electron microscopy (SEM). Mechanical properties of films were dramatically enhanced through the addition of film layers. GO-SAO laminate showed the best barrier properties to water vapour (22.6 ± 4.04 g mm/kPa d m2) and oxygen (18.2 ± 8.70 cm3 mm/kPa d m2). SAO-GO-WPIO laminate film was the strongest of all laminated films tested, having the highest TS of 55.77 MPa, PR of 41.36 N and TT of 27.32 N. SA-G-WPI film possessed the highest elasticity with an EB value of 17.4%.

Optimization of textural and technological parameters using response surface methodology for the development of beef products for older consumers.

Red meat has a tougher texture compared with many other food products, therefore consumption is often reduced among older adults. Acidic treatments had a positive effect on WBSF values (reduced the WBSF values from 23.35 N for control to 14.83 N), and texture parameters and a combination with apple fiber and rice starch may improve the health profile of a meat product with benefits for consumers, particularly for older population. A novel meat product with a softer texture (apple fiber 0.15%, rice starch 0.30% and citric acid 0.16 M) was optimized and successfully validated in this study. The results obtained for the objective measurements of tenderness were confirmed by consumers' tenderness results (p < .05) moreover texture-optimized beef samples were found to be more acceptable by older consumers compared with control. Meat processors have an important role in increasing the availability of suitable meat products for older consumers, by developing products that will meet their nutritional and textural needs. In this study, a novel meat product with a softer texture was developed, successfully validated and the product was found to be acceptable by older consumers. Meat processors could consider using rice starch, apple fiber, and citric acid as feasible alternative to traditional ingredients used for beef injection, in order to obtain a softer product, that appeal to older consumers with difficulties in mastication.

Water sorption and hydration in spray-dried milk protein powders: Selected physicochemical properties.

Low and high protein dairy powders are prone to caking and sticking and can also be highly insoluble; with powder storage conditions an important factor responsible for such issues. The aim of this study focused on the bulk and surface properties of anhydrous and humidified spray-dried milk protein concentrate (MPC) powders (protein content ~40, 50, 60, 70 or 80%, w/w). Water sorption isotherms, polarized light and scanning electron micrographs showed crystallized lactose in low protein powders at high water activities. High protein systems demonstrated increased bulk diffusion coefficients compared to low protein systems. Glass transition temperatures, α-relaxation temperatures and structural strength significantly decreased with water uptake. CLSM measurements showed that humidified systems have slower real time water diffusion compared to anhydrous systems. Overall, the rate of water diffusion was higher for low protein powders but high protein powders absorbed higher levels of water under high humidity conditions.

Phytosterol crystallisation within bulk and dispersed triacylglycerol matrices as influenced by oil droplet size and low molecular weight surfactant addition.

Phytosterols can lower LDL-cholesterol and are frequently used by the functional food industry. However, little is known regarding how phytosterol crystallisation can be controlled, despite solubilised phytosterols having improved bioaccessibility. This study investigates phytosterol crystallisation in bulk milk fat and in model dairy emulsion systems at two average droplet sizes, 1.0 and 0.2 µm. The effect of lecithin and monoacylglycerol addition on phytosterol crystallisation for both emulsion and bulk systems was also evaluated. Results demonstrated that lecithin and monoacylglycerols enrichment into the bulk system minimised phytosterol crystallisation. However, in emulsions, phytosterol crystallisation was mainly influenced by decreasing the droplet size. Smaller emulsion droplets containing lecithin showed the greatest potential for decreasing phytosterol crystallisation and had improved physicochemical stability. This information can be employed by the functional food industry to minimise phytosterol crystallisation and possibly improve bioaccessibility.

Possibilities for developing texture-modified beef steaks suitable for older consumers using fruit-derived proteolytic enzymes.

Meat intakes in the older population are commonly reduced because the relatively tough texture of meat can impair mastication. Fruit-derived proteolytic enzymes have been reported to have beneficial effects on tenderness, by causing significant degradation of myofibrillar proteins and collagen. Three treatments including: papain, bromelain, and a 50:50 mixture of papain/bromelain, alongside one control were applied to beef M. semitendinosus steaks. Effects on Warner-Bratzler shear force, texture parameters, color, and cook loss were determined. Both enzymatic treatments that included papain significantly reduced Warner-Bratzler shear force values (p < .05) and increased cook loss. Beef steaks tenderized with papain and papain/bromelain offer potential for inclusion in older consumers' diets, but improvement in tenderization may be associated with a reduction in processing yield. PRACTICAL APPLICATIONS: Meat processors have a role to play in enhancing the availability of appropriate foodstuffs for older people, through developing targeted products that will meet the specialized nutritional and chemosensory needs of this cohort. Meat intakes in the older population are commonly reduced because the relatively tough texture of meat can impair mastication. In this study, beef steaks tenderized with papain and papain: bromelain (50:50) were demonstrated to produce more tender meat products, with a lower cook loss compared with tenderization with bromelain alone, which has relevance to the development of texture-optimized meat products that appeal to older adults with difficulty in mastication. This information could help meat processors to develop strategies for optimization of texture-modified beef products within their own businesses.

Effects of depleting ionic strength on 31P nuclear magnetic resonance spectra of micellar casein during membrane separation and diafiltration of skim milk.

Membrane separation processes used in the concentration and isolation of micellar casein-based milk proteins from skim milk rely on extensive permeation of its soluble serum constituents, especially lactose and minerals. Whereas extensive literature exists on how these processes influence the gross composition of milk proteins, we have little understanding of the effects of such ionic depletion on the core structural unit of micellar casein [i.e., the casein phosphate nanocluster (CPN)]. The 31P nuclear magnetic resonance (NMR) is an analytical technique that is capable of identifying soluble and organic forms of phosphate in milk. Thus, our objective was to investigate changes to the 31P NMR spectra of skim milk during microfiltration (MF) and diafiltration (DF) by tracking movements in different species of phosphate. In particular, we examined the peak at 1.11 ppm corresponding to inorganic phosphate in the serum, as well as the low-intensity broad signal between 1.5 and 3.0 ppm attributed to casein-associated phosphate in the retentate. The MF concentration and DF using water caused a shift in the relevant 31P NMR peak that could be minimized if orthophosphate was added to the DF water. However, this did not resolve the simultaneous change in retentate pH and increased solubilization of micellar casein protein. The addition of calcium in combination with orthophosphate prevented micellar casein solubilization and simultaneously contributed to preservation of the CPN structure, except for overcorrection of retentate pH in the acidic direction. A more complex DF solution, involving a combination of phosphate, calcium, and citrate, succeeded in both CPN and micellar casein structure preservation while maintaining retentate pH in the region of the original milk pH. The combination of 31P NMR as an analytical technique and experimental probe during MF/DF processes provided useful insights into changes occurring to CPN while retaining the micellar state of casein.

Effect of Phytosterols on the Crystallization Behavior of Oil-in-Water Milk Fat Emulsions.

Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.

Addition of an Enzymatic Hydrolysate of Bovine Globulins to Bread and Determination of Hypotensive Effects in Spontaneously Hypertensive Rats.

The aim of this study was to develop bread containing a papain hydrolysate of bovine α- and ß-globulins (GPH) with in vitro and in vivo antihypertensive activities. The physical characteristics of the formulated bread were assessed over a six day period and results suggested that the overall quality and acceptance of bread was not affected by the inclusion of GPH at a concentration of 4% (w/w). Bright field light microscopy and confocal scanning laser microscopy images were used to visualize the main ingredients of the bread. In addition, the antihypertensive activity of the bread was assessed in spontaneously hypertensive rats (SHRs) over a 24 h period where a maximum significant decrease in systolic blood pressure of 36.2 ± 1.9 mmHg was observed 8 h after oral administration. Results demonstrate that the antihypertensive activity of GPH was resistant to the baking process and shows potential for use as a functional antihypertensive ingredient.

Transport of a Prolyl Endopeptidase Inhibitory Peptide across the Blood-Brain Barrier Demonstrated Using the hCMEC/D3 Cell Line Transcytosis Assay.

The blood-brain barrier (BBB) remains a significant hurdle for treatment of central nervous system (CNS) and mental health disorders. A prolyl endopeptidase (PEP) inhibitory peptide with the amino acid sequence proline-proline-leucine (PPL) was chemically synthesized labeled with 5-FAM and assessed using a transcytosis assay for its ability to cross the BBB. Transport of this peptide across the BBB was determined using an in vitro model of the human BBB, which utilizes the human cerebral microvascular endothelial cell line (hCMEC/D3). Uptake and transport of 5-FAM-PPL across the hCMEC/D3 cell model was determined using confocal microscopy and mass spectrometry. This is an important parameter in determining whether peptides may reach the target organ (i.e., the brain and central nervous system).This work assessed, for the first time, the ability of a food-derived PEP inhibitory peptide to cross the BBB without the use of animal models.

Improving thermal stability of hydrolysed whey protein-based infant formula emulsions by protein-carbohydrate conjugation.

Whey protein hydrolysate (WPH) ingredients are commonly used in the manufacture of partially-hydrolysed infant formulae. The heat stability of these emulsion-based formulae is often poor, compared with those made using intact whey protein. The objective of this study was to improve the heat stability of WPH-based emulsions by conjugation of WPH with maltodextrin (MD) through wet heating. Emulsions stabilised by different protein ingredients, whey protein isolate (WPIE), whey protein hydrolysate (WPHE), heated WPH (WPH-HE), and WPH conjugated with MD (WPH-CE) were prepared and heat treated at 75°C, 95°C or 100°C for 15min. Changes in viscosity, fat globule size distribution (FGSD) and microstructure, evaluated using confocal laser scanning microscopy (CLSM), were used to monitor the effects of hydrolysis, pre-heating and conjugation on the heat stability of the emulsions. Heat stability increased in the order WPHE

Measurement of pH micro-heterogeneity in natural cheese matrices by fluorescence lifetime imaging.

Cheese, a product of microbial fermentation may be defined as a protein matrix entrapping fat, moisture, minerals and solutes as well as dispersed bacterial colonies. The growth and physiology of bacterial cells in these colonies may be influenced by the microenvironment around the colony, or alternatively the cells within the colony may modify the microenvironment (e.g., pH, redox potential) due to their metabolic activity. While cheese pH may be measured at macro level there remains a significant knowledge gap relating to the degree of micro-heterogeneity of pH within the cheese matrix and its relationship with microbial, enzymatic and physiochemical parameters and ultimately with cheese quality, consistency and ripening patterns. The pH of cheese samples was monitored both at macroscopic scale and at microscopic scale, using a non-destructive microscopic technique employing C-SNARF-4 and Oregon Green 488 fluorescent probes. The objectives of this work were to evaluate the suitability of these dyes for microscale pH measurements in natural cheese matrices and to enhance the sensitivity and extend the useful pH range of these probes using fluorescence lifetime imaging (FLIM). In particular, fluorescence lifetime of Oregon Green 488 proved to be sensitive probe to map pH micro heterogeneity within cheese matrices. Good agreement was observed between macroscopic scale pH measurement by FLIM and by traditional pH methods, but in addition considerable localized microheterogeneity in pH was evident within the curd matrix with pH range between 4.0 and 5.5. This technique provides significant potential to further investigate the relationship between cheese matrix physico-chemistry and bacterial metabolism during cheese manufacture and ripening.

Growth and location of bacterial colonies within dairy foods using microscopy techniques: a review.

The growth, location, and distribution of bacterial colonies in dairy products are important factors for the ripening and flavor development of cheeses, yogurts, and soured creams. Starter, non-starter, spoilage, and pathogenic bacteria all become entrapped in the developing casein matrix of dairy foods. In order to visualize these bacterial colonies and the environments surrounding them, microscopy techniques are used. The use of various microscopy methods allow for the rapid detection, enumeration, and distribution of starter, non-starter and pathogenic bacteria in dairy foods. Confocal laser scanning microscopy is extensively utilized to identify bacteria location via the use of fluorescent dyes. Further study is needed in relation to the development of micro- gradients and localized ripening parameters in dairy products due to the location of bacteria at the protein-fat interface. Development in the area of bacterial discrimination using microscopy techniques and fluorescent dyes/tags is needed as the benefits of rapidly identifying spoilage/pathogenic bacteria early in product manufacture would be of huge benefit in relation to both safety and financial concerns.

Characterization of beta-lactoglobulin fibrillar assembly using atomic force microscopy, polyacrylamide gel electrophoresis, and in situ fourier transform infrared spectroscopy.

The aggregation process of beta-lactoglobulin (beta-lg) from 0 min to 20 h was studied using atomic force microscopy (AFM), scanning transmission electron microscopy (STEM), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Fibril assembly was monitored in real time using AFM up to 20 h. From 0 to 85 min, beta-lg monomers deformed and expanded with some aggregation. After 85 min, fibrillar structures were formed, exceeding 10 mum in length. Fibrillar structures were confirmed by STEM. Secondary structural changes occurring during fibril formation were monitored by ATR-FTIR at 80 degrees C and indicated a decrease in alpha-helix content and an increase in beta-sheet content. SDS-PAGE indicated that fibrils were composed of polypeptides and not intact monomers. In this study, beta-lg and whey protein isolate (WPI)-derived fibrils, including some double helices, in water were observed by AFM under ambient conditions and in their native aqueous environment.

The manufacture of miniature Cheddar-type cheeses from milks with different fat globule size distributions.

A novel 2-stage gravity separation scheme was developed for fractionation of raw, whole bovine milk into fractions enriched in small (SFG) or large (LFG) fat globules. The volume mean diameter of fat globules in SFG, LFG or control (CTRL) milk was 3.45, 4.68 and 3.58 microm, respectively. The maximum in storage modulus (index of firmness) decreased with increasing fat globule size for rennet-induced gels formed from SFG, LFG or CTRL milks. Miniature (20 g) Cheddar cheeses were manufactured using each of the 3 milks. There were no significant (P > 0.05) differences in the pH, moisture and fat in dry matter levels between cheeses made using any of the 3 milks, however, the fat content of the cheese made using SFG milk was approximately 1% lower than that of cheese made using LFG or CTRL milk in each of the 2 trials. Image analysis of confocal scanning laser micrographs of the cheeses illustrated that the star volume of fat globules in the cheeses decreased significantly (P < or = 0.05) as the size of fat globules in the milks used for cheesemaking was reduced. This indicates that it is possible to manipulate the size distribution of fat globules in Cheddar cheese by adjusting the fat globule size distribution of the milk used for cheese-making. The concentration of free fatty acids (FFA) increased in all cheeses during ripening. At 120 d of ripening, the concentration of FFA varied significantly (P < or = 0.05 and P < or = 0.001 for trials 1 and 2, respectively) with fat globule size, with cheeses made in trial 2 from LFG, SFG or CTRL milks having total FFA levels of 3391, 2820 and 2612 mg/kg cheese, respectively.