The Impact of Yeast Encapsulation in Wort Fermentation and Beer Flavor Profile

Abstract

The food and beverage industry is constantly evolving, and consumers are increasingly searching for premium products that not only offer health benefits but a pleasant taste. A viable strategy to accomplish this is through the altering of sensory profiles through encapsulation of compounds with unique flavors. We used this approach here to examine how brewing in the presence of yeast cells encapsulated in alginate affected the sensory profile of beer wort. Initial tests were conducted for various combinations of sodium alginate and calcium chloride concentrations. Mechanical properties (i.e., breaking force and elasticity) and stability of the encapsulates were then considered to select the most reliable encapsulating formulation to conduct the corresponding alcoholic fermentations. Yeast cells were then encapsulated using 3% (w/v) alginate and 0.1 M calcium chloride as a reticulating agent. Fourteen-day fermentations with this encapsulating formulation involved a Pilsen malt-based wort and four S. cerevisiae strains, three commercially available and one locally isolated. The obtained beer was aged in an amber glass container for two weeks at 4 °C. The color, turbidity, taste, and flavor profile were measured and compared to similar commercially available products. Cell growth was monitored concurrently with fermentation, and the concentrations of ethanol, sugars, and organic acids in the samples were determined via high-performance liquid chromatography (HPLC). It was observed that encapsulation caused significant differences in the sensory profile between strains, as evidenced by marked changes in the astringency, geraniol, and capric acid aroma production. Three repeated batch experiments under the same conditions revealed that cell viability and mechanical properties decreased substantially, which might limit the reusability of encapsulates. In terms of ethanol production and substrate consumption, it was also observed that encapsulation improved the performance of the locally isolated strain.

Keywords: alcoholic fermentation; alginate encapsulation; beer brewing; flavor modification; sensory profile.

Figure 1

Experimental design for the calcium alginate–yeast encapsulate formulation.

Figure 2

Temperature profile for the mashing process. The enzymatic activation takes place sequentially in the following order: 1. phytase (10 min at 38 °C); 2. β–Glucanase (10 min at 45 °C); 3. protease (10 min at 55 °C); 4. β–amylase (45 min at 65 °C); 5. α–amylase (30 min at 68 °C); 6. remaining enzymes (30 min at 70 °C). Finally, enzymes are inactivated in a mashup stage (10 min at 75 °C).

Figure 3

Swelling percentage profiles of the encapsulates were obtained after 188 h in wort for 1.5% and 3% alginate contents and for all three concentrations of calcium chloride.

Figure 4

FT-IR spectra for yeast–calcium alginate encapsulates: (a) spectra for the initial encapsulates of all the formulations; (b) spectra for the after-fermentation capsules of all the strains.

Figure 5

Mechanical properties for initial capsules: (a) breaking force; (b) elasticity; (c) reduction of the breaking force of encapsulates used in repeated batches (* Significantly different sample when compared between them).

Figure 6

Thermograms for encapsulates: (a) TG curves for 1.5% alginate capsules; (b) TG curves for 3% alginate capsules; (c) DTG curves for 1.5% alginate capsules; (d) DTG curves for 3% alginate capsules.

Figure 7

Comparative thermograms for the encapsulates post–fermentation in repeated batches: (a) initial capsules IC–US–05; (b) encapsulates after one repeated batch (FC–1); (c) encapsulates after two repeated batches (FC–2); (d) encapsulates after three repeated batches (FC–3).

Figure 8

SEM images for 1.5% alginate encapsulates: (A) general view of C–1.a formulation; (B) encapsulate center of C–1.a formulation; (C) encapsulate edge of C–1.a formulation; (D) general view of C–1.b formulation; (E) encapsulate center of C–1.b formulation; (F) encapsulate edge of C–1.b formulation; (G) general view of C–1.c formulation; (H) encapsulate center of C–1.c formulation; (I) encapsulate edge of C–1.c formulation. Yeast cells are shown with yellow dotted circles.

Figure 9

SEM images for 3% alginate encapsules: (A) general view of C–2.a formulation; (B) encapsulate center of C–2.a formulation; (C) encapsulate edge of C–2.a formulation; (D) general view of C–2.b formulation; (E) encapsulate center of C–2.b formulation; (F) encapsulate edge of C–2.b formulation; (G) general view of C–2.c formulation; (H) encapsulate center of C–2.c formulation; (I) capsule edge of C–2.c formulation. Yellow dashed circles represent yeast cells.

Figure 10

SEM images for encapsulates post–fermentation in repeated batches: (A) surface view of FC–1 formulation; (B) encapsulate center of FC–1 formulation; (C) encapsulate edge of FC–1 formulation; (D) surface view of FC–2 formulation; (E) encapsulate center of FC–2 formulation; (F) encapsulate edge of FC–2 formulation; (G) surface view of FC–3 formulation; (H) encapsulate center of FC–3 formulation; (I) encapsulate edge of FC–3 formulation.

Figure 11

(a) Pore size for tested capsules (* Significantly different sample when compared between them); (b) porosity for tested capsules.

Figure 12

Confocal microscopy images for yeast viability 40× (Total cells: blue; live cells: red): (a) IC–US–05 encapsulates; (b) encapsulates after one repeated batch (FC–1); (c) encapsulates after two repeated batches (FC–2); (d) encapsulates after three repeated batches (FC–3).

Figure 13

Time evolution of yeast growth. (a) Log(OD₆₀₀/OD_600t=0) for all strains; (b) Log(CFU_t/CFU_t=0) for BE–134 and K–97 strains; (c) Log(CFU_t/CFU_t=0) for US–05 and CW–12 strains.

Figure 14

Turbidity results for the fermentations performed with encapsulated and free yeast and from various batches.

Figure 15

Comparative ethanol production profile and sugar consumption during fermentation with encapsulated and free yeast for (a) BE–134 strain, (b) K–97 strain, (c) CW–12 strain, (d) US–05 strain.

Figure 16

Comparative aromatic profiles of encapsulated and free yeast for the BE–134 and K–97 strains.

Figure 17

Comparative aromatic profiles of encapsulated and free yeast for the CW–12 and US–05 strains.

Figure 18

Comparative aromatic profiles of repeated batch fermentations with reused encapsulates.

Figure 19

Comparative electronic tongue results for encapsulated and free yeast: (a) BE–134 strain; (b) K–97 strain; (c) CW–12 strain; (d) US–05 strain.

Figure 20

Electronic tongue results for reused encapsulates after repeated batches.