Spent brewer's yeast proteins and cell debris as innovative emulsifiers and carrier materials for edible oil microencapsulation.

Spent brewer's yeast is a by-product rich in proteins, polysaccharides, and fibres. In addition to being nutritive, this material is available in large amounts and can be considered a cheap and sustainable alternative as a carrier material for microencapsulation. The objective of this work was to use the protein hydrolysate of spent brewer's yeast as an emulsifying agent and carrier material for the microencapsulation of sunflower oil by spray drying. A Central Composite Rotational Design (CCRD) was used to determine emulsion's optimal conditions: protein concentration (1.5-6.0%), oil concentration (10-25%) and pH (5.5-7.5) regarding Turbiscan Stability Index (TSI), droplet size and zeta-potential. The validated optimised emulsion containing 4.4% protein and 17.5% oil was produced at a pH value of 6.5. This formulation had a mean droplet diameter of 6.6 ± 0.3 µm, a ζ- potential of -29.0 ± 1.7 mV and a TSI (24 h) of 0.9 ± 0.2%. This emulsion was spray-dried with and without maltodextrin (M20) at 150 and 180 °C. The highest encapsulation efficiency was 55%, achieved at 180 °C with M20, 87% higher than dry powder at the same temperature, but without M20. The water activity of powders without M20 were 58% and 14% lower (0.20 and 0.17) than powders with M20 dried at 150 and 180 °C, (0.13 and 0.15) respectively. The mean particle size was close to 50 µm. The powder without M20, dried at 150 °C, showed the highest stability against oxidation (45 °C for 4 weeks), with a peroxide index of 311 meq of peroxide per kg of oil. Powder properties were evaluated by SEM and FT-IR. Kinetically stable emulsions and particles were produced from spent brewer's yeast ingredients, which were able to act as both carrier materials and emulsifiers, providing a more noble use for an important brewing residue.

Maillard conjugates from spent brewer's yeast by-product as an innovative encapsulating material.

Yeast-based by-products are greatly available, have a rich nutritional composition and functional properties. The spent brewer's yeast (SBY) cells after enzymatic hydrolysis may be a sustainable and low-cost alternative as carrier material for encapsulation processes by spray drying. Our work had as main purpose to characterise the hydrolysed SBY cell debris after the Maillard reaction and to study their potential as a microencapsulation wall material. SBY-based Maillard reaction products (MRPs) were used to encapsulate ascorbic acid (AA) by spray drying. The Maillard Reaction was able to improve the solubility of solids and proteins by 15% and promoted brown color development (230% higher Browning Index). SBY-based MRPs resulted in particles of a high encapsulation yield of AA (101.90 ± 5.5%), a moisture content of about 3.4%, water activity of 0.15, hygroscopicity values ranging from 13.8 to 19.3 gH2O/100 g and a glass transition temperature around 71 °C. The shape and microstructure of the produced particles were confirmed by scanning electron microscopy (MEV), indicating very similar structure for control and AA encapsulated particles. Fourier Transform Infrared Spectroscopy (FT-IR) results confirmed the presence of yeast cell debris in the surface of particles. Ascorbic acid was successfully encapsulated in Maillard conjugates of hydrolyzsd yeast cell debris of Saccharomyces pastorianus and maltodextrin as confirmed by optical microscopy, differential scanning calorimetry, MEV and FT-IR.