Título da Tese: “Extração, caracterização e aplicação das proteínas do trub: um subproduto oriundo da cervejaria”.

Orientadora: Profa. Dra. Paula Toshimi Matumoto Pintro

Data da Defesa: 21/02/2022



INTRODUCTION. The search for alternative sources of nutrients has been driven by increase in world demand for food, resulting from an estimated population increase of up to 50% in 2050. Increase in demand compromises food sustainability, as resources for food production are limited. Alternative for obtaining nutrients is agricultural and agroindustrial by-products recycling. Among them, spent brewery grain, residual yeast and hot trub are generated from beer production, which increased by about 40% from 1998 to 2020. Hot trub is a precipitate formed during wort boiling, its composition is rich in nutrients, such as proteins and carbohydrates, and can be reused as an alternative source
of these compounds for food. During trub formation, proteins can adsorb bitter
compounds (from hops), imparting a bitter taste to by-product, which has limited its use in large quantities. Technologies development is necessary to reduce these limiting bitter compounds content for trub use as ingredient for foods nutritional enrichment and to enable compounds of interest extraction, such as proteins and phenolic compounds, enabling using trub new ways.
AIMS. This work had general objective of developing and optimizing processes to
increase possibilities of trub using. As specific objectives, to determine optimal
conditions for extracting proteins from trub to produce a protein isolate of vegetable origin; and to determine optimal conditions for extracting bitter compounds from trub, using it for nutritional enrichment of pasta, a product that has been used as vehicle for adding new food ingredients.
MATERIAL AND METHODS. Different variables were studied to determine optimal
conditions for extracting proteins and bitter compounds from trub in water. For protein isolate production, independent variables studied at different levels were pH (11, 12 and 13), concentration (2.5, 5.0 and 7.5 g/L) and extraction time (30, 60 and 90 min). For bitter compounds extraction, variables were pH (7, 10 and 13), extraction steps (1, 2 and 3) and extraction time (20, 40 and 60 min). Optimal extraction conditions were determined using response surface methodology of Box-Behnken and desirability function. Protein isolate was obtained after precipitation of extracted proteins and centrifugation steps, and precipitate was lyophilized to carry out solubility, phenolic compounds and antioxidant activity analyses. The reduced bitterness trub obtained under optimal extraction conditions was lyophilized and evaluated for technological properties,
phenolic compounds, antioxidant activity, proximate composition, color, and protein conformation and differences in relation to trub before processes were also evaluated. Reduced bitterness trub was used in pasta nutritional enrichment in place of wheat flour at 5, 7.5 and 10%. Proximate composition, color, quality properties, texture and scanning electron microscopy were evaluated in pasta with and without addition (control) of reduced bitterness trub.
RESULTS AND DISCUSSION. Optimal conditions for trub proteins extraction were
pH 12.31, 5.37 g/L concentration and 51.78 min extraction time at 80 °C, obtaining more than 80% extraction efficiency. Protein isolate obtained showed 94.56% of water-soluble proteins in a wide pH range (6-12), and phenolic compounds content and antioxidant activity indicate its use in functional foods as protein antioxidants. Optimal conditions for bitter compounds extracting from trub were pH 10 and two extraction steps of 40 min at 90°C. The extraction process used reduced phenolic compounds content, which are associated with trub bitterness, with a consequent reduction in the antioxidant activity.
Protein conformation was also altered, which may be related to solubility reduced of reduced bitterness trub in relation to trub. After bitter compounds extraction process, trub protein content was concentrated to 45.72% and fiber content to 9.27%, becoming a potential ingredient for nutritional enrichment. Use of reduced-bitter trub in pasta resulted in a protein enrichment of up to 33.51% in relation to control, also increasing fiber content and reducing total carbohydrate content. Scanning electron microscopy images showed that starch was more incorporated into control pasta protein matrix when compared to enriched pasta matrix, which is related to increase in cooking time and greater water absorption of pasta with trub addition, but did not influence pasta mass loss. Regarding texture, the trub addition increased cohesiveness, elasticity and reduced its adhesiveness and hardness.
CONCLUSIONS. Optimal regions for extraction processes of proteins and bitter
compounds from trub were successfully obtained using response surface methodology. Protein isolate of plant origin produced in optimal conditions determined showed solubility in water in a wide pH range (6-12), antioxidant capacity and bioactive compounds. Reduced bitterness trub produced under optimal extraction conditions presented high process yield and had its nutritional content concentrated, providing pasta enriched preparation with proteins and fibers and reduced total carbohydrate content. Pasta with reduced bitterness trub addition presented a soft and cohesive texture, greater water absorption without altering the cooking loss. Trub, after different processes, can be used to nutritionally enrich foods and as a protein ingredient of plant origin, adding value
to by-product and increasing opportunities for its application in food.
Key words: By-products, protein isolate, bitter compounds, Box-Behnken design,
process optimization, vegetable protein.


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