Adsorption behavior at interface of oil-in-water emulsions prepared with mixtures of milk fat globule membrane proteins and polar lipids

The milk fat globule membrane (MFGM) contains proteins and polar lipids making this complex mixture a good emulsifier. In this study, MFGM material was isolated from reconstituted buttermilk using microfiltration and further separated into MFGM protein concentrate and polar lipid concentrate using solvent fractionation. The emulsifying properties of those two emulsifier fractions, separately or in combination, at various concentrations of proteins (0.3; 1.3 and 2.3 w%) and polar lipids (0.3; 1.3 and 2.3 w%), were investigated. The results showed that at low emulsifier concentrations (< 2.3%), the combination of both proteins and polar lipids resulting in the formation of emulsions with a small droplets size and low apparent viscosity. The addition of polar lipids did not replace the adsorbed proteins. Between the two emulsifier fractions, MFGM protein concentrate had greater emulsifying properties compared to the polar lipid concentrate.

Effect of milk fat globule membrane materials on the crystallization behaviour in dairy recombined cream

Milk fat globule membrane (MFGM) fragments were isolated from reconstituted buttermilk (BM-MFGM) and from buttermilk whey (whey-MFGM) and used to make recombined cream. Besides, the commercial dairy ingredient, Lacprodan® PL20, a material rich in milk polar lipids and proteins, was used as another MFGM source. Recombined cream was prepared by homogenizing 35% (w/w) anhydrous milk fat into an aqueous phase containing individual BM-MFGM, Whey-MFGM, Lacprodan® PL20, or buttermilk powder (BMP) or a mixture of MFGM materials and BMP (4:6, w/w). The effect of MFGM on the fat crystallization behaviour, shear-induced partial coalescence was investigated and compared to those of natural cream and recombined cream made with BMP. It was found that the physicochemical properties of recombined cream were strongly affected by the MFGM source. Shear-induced partial coalescence of WheyMFGM40 was slower compared to that of natural cream. Amongst the four emulsifier materials used in this study, Whey-MFGM showed a similar crystallization behaviour to natural cream.

Calculation procedure for formulating lauric and palmitic fat blends based on the grouping of triacylglycerol melting points

A calculation procedure for formulating lauric and palmitic fat blends has been developed based on grouping TAG melting points. This procedure offered more flexibility in choosing the initial fats and oils and eventually gave deeper insight into the existing chemical compositions and better prediction on the physicochemical properties and microstructure of the fat blends. The amount of high, medium and low melting TAGs could be adjusted using the given calculation procedure to obtain the desired functional properties in the fat blends. Solid fat contents and melting behavior of formulated fat blends showed particular patterns with respect to ratio adjustments of the melting TAG groups. These outcomes also suggested that both TAG species and their quantity had a significant influence on the crystallization behavior of the fat blends. Palmitic fat blends, in general, were found to exhibit higher SFC values than those of Lauric fat blends. Instead of the similarity in crystal microstructure, lauric fat blends were stabilized at β polymorph while palmitic fat blends were stabilized at β’ polymorph.

Compatibility of selected plant-based shortening as lard substitute: microstructure, polymorphic forms and textural properties

A study was carried out to determine the compatibility of three plant-based shortening mixtures to lard shortening (LD) in terms of microstructure, polymorphic forms, and textural properties. The shortenings of binary, ternary, and quaternary fat mixtures were prepared according to a standard procedure by blending mee fat (MF) with palm stearin (PS) in a 99:1 (w/w) ratio; avocado fat (Avo) with PS and cocoa butter (CB) in a 84:7:9 (w/w) ratio; palm oil (PO) with PS, soybean oil (SBO) and CB in a 38:5:52:5 (w/w) ratio, respectively. The triacylglycerol composition, polymorphic forms, crystal morphology, and textural properties of the shortening were evaluated. This study found that all three plant-based shortenings and LD shortening were similar with respect to their consistency, hardness and compression and adhesiveness values. However, all plant-based shortening was found to be dissimilar to LD shortening with respect to microstructure.

Fumed silica-based organogels and ‘aqueous-organic’ bigels

We report the use of fumed silica as a structurant for creating an organogel with a triglyceride solvent (vegetable oil) as the continuous phase. The organogel was further used to prepare aqueous-organic bigels.

Stability of milk fat globule membrane proteins toward human enzymatic gastrointestinal digestion

The milk fat globule membrane (MFGM) fraction refers to the thin film of polar lipids and membrane proteins that surrounds fat globules in milk. It is its unique biochemical composition that renders MFGM with some beneficial biological activities, such as anti-adhesive effects toward pathogens. However, a prerequisite for the putative bioactivity of MFGM is its stability during gastrointestinal digestion. We, therefore, subjected MFGM material, isolated from raw milk, to an in vitro enzymatic gastrointestinal digestion. Sodium dodecyl sulfate PAGE, in combination with 2 staining methods, Coomassie Blue and periodic acid Schiff staining, was used to evaluate polypeptide patterns of the digest, whereas mass spectrometry was used to confirm the presence of specific MFGM proteins. Generally, it was observed that glycoproteins showed higher resistance to endogenous proteases compared with non-glycosylated proteins. Mucin 1 displayed the highest resistance to digestion and a considerable part of this protein was still detected at its original molecular weight after gastric and small intestine digestion. Cluster of differentiation 36 was also quite resistant to pepsin. A significant part of periodic acid Schiff 6/7 survived the gastric digestion, provided that the lipid moiety was not removed from the MFGM material. Overall, MFGM glycoproteins are generally more resistant to gastrointestinal digestion than serum milk proteins and the presence of lipids, besides glycosylation, may protect MFGM glycoproteins from gastrointestinal digestion. This gastrointestinal stability makes MFGM glycoproteins amenable to further studies in which their putative health-promoting effects can be explored.

Influence of NaCl reduction and replacement on the growth of Lactobacillus sakei in broth, cooked ham and white sauce

The growth inhibiting effects of NaCl and selected simple salt replacers (CaCl(2), MgCl(2), KCl and MgSO(4)) on the growth of Lactobacillus sakei were studied in de Man Rogosa Sharpe broth at 7 degrees C over a water phase concentration of 0 to 6.4%. The divalent chloride salts (CaCl(2) in particular) generally had the largest antimicrobial activities at equivalent water phase concentrations, molalities or water activity (a(w)) values. MgSO(4) had not only the least antimicrobial activity but also the smallest a(w) depressing capacity. The results also showed that the antimicrobial effects of CaCl(2) were not fully accounted for by its a(w) depressing effects. Challenge tests performed on cooked ham and white sauce showed that reduction of NaCl levels by 28 and 33%, respectively, had no influence on the microbial stability of these products to L. sakei. Ultimately the study concluded that the microbiological consequences of the full or partial replacement of NaCl on the growth of L. sakei largely depend on the initial level of NaCl, the level of replacement and the nature of the salt replacer used. Altered stability to L. sakei is most likely given a high initial NaCl level, combined with a large level of partial replacement with either CaCl(2) (increased stability) or MgSO(4) (reduced stability) as the replacer.

Release of short chain fatty acids from cream lipids by commercial lipases and esterases

Lipases and esterases are frequently used in dairy production processes to enhance the buttery flavour of the end product. Short chain fatty acids, and especially butanoic acid, play a key role in this and different enzymes with specificity towards short chain fatty acids are commercially available as potent flavouring tools. We have compared six lipases/esterases associated with buttery flavour production. Although specificity to short chain fatty acids was ascribed to each enzyme, clear differences in free fatty acid profiles were found when these enzymes were applied on cream. Candida cylindraceae lipase was the most useful enzyme for buttery flavour production in cream with the highest yield of free fatty acids (57 g oleic acid 100 g(-1) fat), no release of long chain fatty acids and specificity towards butanoic acid.

Thermocalcic Aggregation of Milk Fat Globule Membrane Fragments from Acid Buttermilk Cheese Whey

Fragments originating from the milk fat globule membrane (MFGM), which is rich in polar lipids and membrane-specific proteins, are gaining interest for their functional and nutritional properties. Acid buttermilk cheese whey was used as a source for MFGM purification, because its MFGM content is more than 5 times higher than that of standard rennet whey. Because polar lipids are the main constituent of the MFGM and only occur in membranous structures, the polar lipid content was taken as a parameter for the total MFGM fragment content. The process of thermocalcic aggregation was evaluated on its recovery of MFGM fragments in the pellet. This method, originally intended for whey clarification and defatting, is a combination of calcium addition, a pH increase, and a thermal treatment. The influence of pH (6.5 to 8), temperature (40 to 70 degrees C), and calcium concentration (0.1 to 0.24 g/100 g) on the pellet mass and dry matter (DM) content and on recovery of protein and polar lipids (and thus indirectly on MFGM fragments) was investigated by means of a response surface Box-Behnken orthogonal design. Reduced quadratic models were fit to the experimental data and were found to be highly significant. No outliers were observed. The recovery of MFGM fragments was found to be highly dependent on the pH, and less dependent on temperature and calcium addition. Next to MFGM proteins, whey proteins were also found to be involved in the formation of aggregates. Optimal conditions were found at 55 degrees C, pH 7.7, and 0.205 g of calcium/L of whey. Under these conditions, 91.0% of the whey polar lipids were recovered in a firm and compact pellet of only 7.86% of the original whey mass, with a polar lipid concentration of 8.34% on pellet DM. Washing with water and centrifugation of the pellet was successful because after one washing step, virtually all sugars were removed, whereas 75.9% of the whey polar lipids could still be recovered. As such, the polar lipid content of the washed pellet increased to 10.70% on a DM basis. However, a second washing step resulted in serious losses of MFGM material.

Filtration of Milk Fat Globule Membrane Fragments from Acid Buttermilk Cheese Whey

The proteins and polar lipids present in milk fat globule membrane (MFGM) fragments are gaining attention for their technological and nutritional properties. These MFGM fragments are preferentially enriched in side streams of the dairy industry, like butter serum, buttermilk, and whey. The objective of this study was to recover MFGM fragments from whey by tangential filtration techniques. Acid buttermilk cheese whey was chosen as a source for purification by tangential membrane filtration because it is relatively rich in MFGM-fragments and because casein micelles are absent. Polyethersulfone and cellulose acetate membranes of different pore sizes were evaluated on polar lipid and MFGM-protein retention upon filtration at 40 degrees C. All fractions were analyzed for dry matter, ash, lipids, proteins, reducing sugars, polar lipid content by HPLC, and for the presence of MFGM proteins by sodium dodecyl sulfate-PAGE. A fouling coefficient was calculated. It was found that a thermocalcic aggregation whey pretreatment was very effective in the clarification of the whey, but resulted in low permeate fluxes and high retention of ash and whey proteins. By means of an experimental design, the influence of pH and temperature on the fouling and the retention of polar lipids (and thus MFGM fragments), proteins, and total lipids upon microfiltration with 0.15 microM cellulose acetate membrane was investigated. All models were highly significant, and no outliers were observed. By increasing the pH from 4.6 to 7.5, polar lipid retention at 50 degrees C increased from 64 to 98%, whereas fouling of the filtration membrane was minimized. A 3-step diafiltration of acid whey under these conditions resulted in a polar lipid concentration of 6.79 g/100 g of dry matter. As such, this study shows that tangential filtration techniques are suited for the purification of MFGM fragments.

Microfiltration of Butter Serum Upon Casein Micelle Destabilization

The gross composition of butter serum, the aqueous phase of butter, is comparable to that of buttermilk, except that it has a higher content of material derived from the milk fat globule membrane (MFGM). As such, butter serum is a good source for further purification of MFGM material. The purified fraction could be of interest for its emulsifying and nutritional properties. The effect of sodium citrate and ethanol on the dissociation of butter serum casein micelles, and their effect on casein retention upon tangential microfiltration were investigated. Optimal conditions of casein micelle dissociation were assessed by using an experimental design (response surface full central composite orthogonal design) with temperature and ethanol or sodium citrate concentration as design variables and the Hunter L* value as response variable. For both dissociating agents, a highly significant reduced quadratic model was fit to the data. Microfiltration tests were performed on pure butter serum, and on butter serum in the presence of sodium citrate, under optimal dissociation conditions (50 degrees C, 80 mM). A cellulose acetate membrane with a pore size of 0.15 microm was used. From the filtration curves and fouling coefficients it was clear that the addition of sodium citrate improved the permeation flux, and minimized fouling. All fractions were analyzed for dry matter, protein, lactose, lipid, and polar lipid contents. The protein fraction was further characterized by sodium dodecyl sulfate-PAGE. It was shown that sodium citrate greatly enhanced casein transmission through the membrane, but at the expense of substantial losses of polar lipids.

Analysis of Phospho- and Sphingolipids in Dairy Products by a New HPLC Method

Dairy phospho- and sphingolipids are gaining interest due to their nutritional and technological properties. A new HPLC method, using an evaporative laser light-scattering detector, was developed, which enabled excellent separation of glucosylceramide, lactosylceramide, phosphatidic acid, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, sphingomyelin, and lysophosphatidylcholine in less than 21 min, including the regeneration of the column. No loss of column performance was observed after 1500 runs because an acid buffer was used. The output signal of the evaporative laser light scattering detector was highly dependent of the flow of the carrier gas and the temperature of the nebulizer, and was maximized by means of a response surface experimental design. Finally, raw milk, cream, butter, buttermilk, Cheddar whey, quarg, and Cheddar cheese were analyzed for their polar lipid content. The absolute values varied substantially (0.018 to 0.181 g/100 g of product). Significant differences were found in the relative content of each polar lipid class among the analyzed products.

Exudate gums: occurrence, production, and applications

This paper presents a review of the industrially most relevant exudate gums: gum arabic, gum karya, and gum tragacanth. Exudate gums are obtained as the natural exudates of different tree species and exhibit unique properties in a wide variety of applications. This review covers the chemical structure, occurrence and production of the different gums. It also deals with the size and relative importance of the various players on the world market. Furthermore, it gives an overview of the main application fields of the different gums, both food and non-food.

CFD approach for modelling microbial inactivation during thermal processing of intact eggs

Combined conductive and convective heat transfer during thermal pasteurisation of intact eggs was studied using a commercial Computational Fluid Dynamics (CFD) package. A kinetic inactivation model for Salmonella enteritidis was combined with the CFD model, enabling evaluation and assessment of egg pasteurisation processes. Simulated temperature profiles were found to be in good agreement with experimentally observed data. The obtained results offer a useful tool for assessment and optimisation of egg pasteurisation processes.