Stabilising effect of α-lactalbumin on concentrated infant milk formula emulsions heat treated pre- or post-homogenisation

Although mothers’ milk is the ideal food for babies, infant formula has become an alternative when breastfeeding is not possible or inadequate for babies. To design a proper formula for babies, it is essential to understand the digestibility of macronutrients and their bio-accessibility in the infant gastrointestinal tract. Because in vivo gastrointestinal studies on human infants are restricted by ethical constraint, cost issues, and intensive resource, in vitro models could be a better replacement. In vitro models offer advantages with low cost, easy sampling accessibility and no ethical issues. This thesis aims to assess the digestibility of each ingredient proteins, lipids, and carbohydrates in infant formulation then compare with mothers’ milk. A static bench-top in vitro model for infant digestion was set up with infant gastric pH (4.0-4.5) and the activity of simulated digestive enzymes suitable for human infants with 60 minutes of gastric phase and 120 minutes of intestinal phase.Popular protein sources of caseins, whey, and soy proteins were employed in infant formulations. The in vitro digestion of these proteins in infant formulations was studied in the presence of enzyme proteases only (without lipolytic enzymes). Obtained results showed around 20% of caseins and no components of whey were hydrolysed after 60 minutes in the simulated stomach. In the simulated intestinal phase, 8% of α–lactalbumin was hydrolysed while caseins and β–lactoglobulin were completely digested immediately and 30 minutes respectively after addition of intestinal digestive proteases. Overall, soy proteins indicated lower level of hydrolysis than dairy proteins during in vitro infant digestion as observed by SDS-PAGE. The soy protein fractions glycinin and β-conglycinin were partially hydrolysed during the gastrointestinal phase. The observed pH drop confirms that caseins are easily digested in the intestinal phase compared to whey and soy protein. Gastric digestion resulted in a decrease of the particle size of protein aggregates, but no fat coalescence was observed during both gastric and intestinal digestion in the given conditions.The in vitro digestion of hydrolysed and non-hydrolysed dairy (casein and whey proteins) was studied under conditions without lipolytic enzymes. Results show hydrolysed proteins were completely digested in the small intestine while non-hydrolysed proteins (caseins, α-lactalbumin, β-lactoglobulin, conglycinin, glycinin) were only partially digested in the simulated gastrointestinal tract. Although observed pH-drop for non-hydrolysed protein formulations was lower, significantly higher levels of ninhydrin-reactive amino nitrogen in hydrolysed proteins suggested higher digestibility of hydrolysed proteins than their non-hydrolysed counterparts. Only formulations containing caseins showed a decrease in particle size of protein aggregates during gastric digestion. No fat globule coalescence was observed during both gastric and intestinal digestions in the given conditions.Lipid digestion of infant formula emulsions based on both hydrolysed and non-hydrolysed proteins (dairy and soy) with vegetable oils was studied under an in vitro gastrointestinal environment (with and without proteases). The size and distribution of oil droplets, released free fatty acids, and micro-structure of the digesta were monitored over the digestion period. Oil droplet coalescence was observed during gastric phase but not in the intestinal phase for most of formulations in both the matrices. Higher rate of lipolysis in infant formula emulsion stabilized by hydrolysed proteins was noted. The obtained results suggested that digestive proteases had a limited impact on lipolysis of these particular infant formula systems.The in vitro digestion of carbohydrate in infant formulations and control formulations (solution of carbohydrate without proteins and vegetable oils) suggests infant formulations with precooked starch or locust bean gum have a higher viscosity than other formulation without thickening agents. No carbohydrate was digested in stomach phase. Precooked starch is well digested in the simulated intestine, but locust bean gum in infant formula resisted in vitro digestion. Higher amount of released glucose were observed in the digesta of the formulations with lactose than in the formulations with glucose syrup.The in vitro digestion of mothers’ milk and infant formulation based on bovine proteins and vegetable oils in the presence of all the digestive enzymes showed caseins digested quicker than whey proteins in the gastrointestinal tract. Lipolysis of mothers’ milk releases free fatty acids with medium carbon chain from C10 to C14, which are very little in infant formulation. However, similar amount of total free fatty acids was obtained from the digestion of the fat in mothers’ milk and in the infant formulation. Lactose in mothers’ milk or in infant milk formulae behaved the same in the in vitro infant digestion as the same type of lactose was used which is in water soluble state without any effect of pH, thus is easily accessible to enzyme.

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

Pre-spray-drying processing may affect stability after reconstitution of emulsion-based powders, such as infant formulas. This study aimed to evaluate the effects of pasteurization temperature and total solids (TS) of the feed on the stability of the emulsions obtained from the reconstituted powders. Four infant formula powders (50%-75 °C, 50%-100 °C, 60%-75 °C, and 60%-100 °C) were produced at pilot scale, from emulsions with 50 or 60% TS pasteurized at 75 or 100 °C for 18 s. Both the emulsion feeds and the emulsions from the reconstituted powders (12.5% TS) were analyzed. The results showed that feeds with 60% TS were flocculated, as indicated by the large particle size and viscosity and the pseudoplastic behavior. Light microscopy revealed that, during spray drying, the flocs were disrupted in 60%-100 °C, while the 60%-75 °C emulsion remained flocculated, reducing its stability post-reconstitution. Although all four emulsions were mainly stabilized by caseins, the presence of β-lactoglobulin was also detected at the oil–water interface, in native state in the formulas preheated at 75 °C and aggregated in the formulas preheated at 100 °C. In conclusion, both the degree of whey protein denaturation (resulting from pasteurization) and the TS of the concentrates during infant formula production affected the emulsion stability of the reconstituted powders.

The demand for high-quality plant protein products is increasing and the aim of this work was to evaluate the impact of increasing the total solids content on the formation and stability of lentil protein stabilised oil-in-water emulsions. A series of emulsions were formulated using different proportions of total solids: 23, 26, 29, 32, and 35% (w/v). The emulsions were formulated using three ingredients—lentil protein, sunflower oil, and maltodextrin—which made up 15.85, 27.43, and 56.72% (w/w) of the total solids, respectively. The changes in apparent viscosity, particle size distribution, and colour during thermal processing were evaluated, with the physical stability investigated using an analytical centrifuge. The apparent viscosity of the solutions increased with total solids content (25.6 to 130 mPa.s−1), as did redness colour intensity (a* value increased from 5.82 ± 0.12 to 7.70 ± 0.09). Thermal processing resulted in greater destabilisation for higher total solids samples, as evidenced by greater changes in particle size, along with decreased redness colour. These results bring a better understanding of high total solids plant protein emulsions and factors affecting their stability, which could be used for the development of cost-effective and sustainable processing solutions in the production of plant protein young child formulae.

Current knowledge in the stabilization/destabilization of infant formula emulsions during processing as affected by formulations

Influence of emulsifier type on the spray-drying properties of model infant formula emulsions

Infant milk formulae processing: Effect of wet-mix total solids and heat treatment temperature on rheological, emulsifying and nutritional properties

Quantitation of the major whey proteins in human milk, and development of a technique to isolate minor whey proteins

Effect of water activity on the functional, colloidal, physical, and microstructural properties of infant formula powder

Increasing the heat stability of whey protein-rich emulsions by combining the functional role of WPM and caseins

Effect of added calcium chloride on the physicochemical and rheological properties of aqueous mixtures of sodium caseinate/sodium alginate and respective oil-in-water emulsions

Chapter 12 - Whey Proteins in Infant Formula

Coagulation of model infant formulae: Impact on their in vitro dynamic gastric digestion

Plant proteins partially replacing dairy proteins greatly influence infant formula functionalities

All Formulas Are Not the Same - Variation in Protein and Carbohydrate Ingredients in Infant Formula Are Associated with Infant Growth Outcomes (P11-102-19)