Recent advances in ß-galactosidase and fructosyltransferase immobilization technology.

The highly demanding conditions of industrial processes may lower the stability and affect the activity of enzymes used as biocatalysts. Enzyme immobilization emerged as an approach to promote stabilization and easy removal of enzymes for their reusability. The aim of this review is to go through the principal immobilization strategies addressed to achieve optimal industrial processes with special care on those reported for two types of enzymes: ß-galactosidases and fructosyltransferases. The main methods used to immobilize these two enzymes are adsorption, entrapment, covalent coupling and cross-linking or aggregation (no support is used), all of them having pros and cons. Regarding the support, it should be cost-effective, assure the reusability and an easy recovery of the enzyme, increasing its stability and durability. The discussion provided showed that the type of enzyme, its origin, its purity, together with the type of immobilization method and the support will affect the performance during the enzymatic synthesis. Enzymes' immobilization involves interdisciplinary knowledge including enzymology, nanotechnology, molecular dynamics, cellular physiology and process design. The increasing availability of facilities has opened a variety of possibilities to define strategies to optimize the activity and re-usability of ß-galactosidases and fructosyltransferases, but there is still great place for innovative developments.

Nutritional and technological properties of a quinoa (Chenopodium quinoa Willd.) spray-dried powdered extract.

The relevance of an appropriate nutrition requires innovation in the design of food ingredients. The goal of this work was to obtain a powdered extract of quinoa by using spray-drying. To this aim, quinoa flour was suspended in water to obtain a soluble fraction mainly composed of proteins, starch, fiber, lipids, antioxidants and minerals. The spray-drying conditions of this quinoa soluble fraction were set-up in terms of inlet temperatures (150, 160, 170 and 180 °C) and feed flow (4.5, 7.5, 10.5 mL/min). The obtained powders were characterized by determining the proximate composition, antioxidant activity, microstructure, fatty acids' profile, and starch and proteins' structures. A correlation among the drying parameters and the chemical and functional attributes of the powders was addressed using principal component analysis. From a technological viewpoint the use of moderate feed flows (7.5 mL/min) and high inlet temperatures (180 °C) was the best combination to obtain high powder yields (85% d.b.), low aw (0.047 ± 0.005) and high solids content (0.956 ± 0.005). The drying temperature positively affected the structure of starch, improving swelling and favoring moderate agglomeration which increases the encapsulation properties of quinoa. These results support the use of spray-drying as a suitable method to obtain powdered extracts of quinoa without affecting the nutritional value, thus supporting their use as functional ingredients in the formulation of ready-to-eat foods.

Synthesis of fructo-oligosaccharides using grape must and sucrose as raw materials.

Grape must market has been rising and there is an increasing interest to use it as a "natural" replacement for traditional sugars. Food or beverages with prebiotic compounds, including fructo-oligosaccharides (FOS), emerge as an alternative for the new health style trend. The aim of this work was to investigate whether the combination of grape must with sucrose was a suitable raw material for the synthesis of FOS. This way, a prebiotic syrup containing fructose and FOS, potentially useful for the formulation of foods and beverages, could be obtained. The main process consisted of three stages, namely conditioning of grape must (oxidation of the initial glucose concentration, stage 1), synthesis of FOS [incorporation of 20, 30 and 55% (w/w) sucrose, and 3.5% v/v Viscozyme L - 4.2 U/mg-, stage 2], and conditioning of the final product (oxidation of the glucose generated during the synthesis, stage 3). At stage 1, glucose concentration decreased from 222.8 mg/mL to 47.2 mg/mL, representing a decay of about 80% regarding the initial concentration of glucose. At stage 2, incorporating 20% (w/w) sucrose was not enough to impulse FOS synthesis. In turn, although 30 and 55% (w/w) sucrose produced very similar concentrations of total FOS (DP3 + DP4), 55% (w/w) sucrose led to higher glucose generation and less DP4 formation. Hence, 30% (w/w) sucrose was the condition selected for the synthesis and further conditioning of the obtained product (stage 3). In these conditions, the final product consisted of more than 30% of short chain FOS (19% and 13% of DP3 and DP4, respectively), 55% fructose and less than 11% of glucose and sucrose. Considering that fructose has approximately double sweetening power than glucose, the obtained syrup has a bigger sweetening power in comparison with the original grape must, also providing the prebiotic benefits of FOS.

Technological Aspects of the Production of Fructo and Galacto-Oligosaccharides. Enzymatic Synthesis and Hydrolysis.

Fructo- and galacto-oligosaccharides (FOS and GOS) are non-digestible oligosaccharides with prebiotic properties that can be incorporated into a wide number of products. This review details the general outlines for the production of FOS and GOS, both by enzymatic synthesis using disaccharides or other substrates, and by hydrolysis of polysaccharides. Special emphasis is laid on technological aspects, raw materials, properties, and applications.