Alexandra Manzoli

This work aimed to develop cantilever nanobiosensor functionalized with tyrosinase enzyme to detect 17β-estradiol and estrone hormones. In this system, the tyrosinase enzyme was covalently immobilized by self-assembled monolayer onto the cantilever sensor surface. It was possible to verify that the high hormone concentration investigated resulted in high voltage response. The nanobiosensor presented a distinction between the concentrations evaluated and was verified sensitivities of 0.497 and 0.101 V/μg, limit of detection of 0.1 and 0.4 ng/L for the hormones 17β-estradiol and estrone, respectively. The device showed good reversibility and during 30 days of storage maintained about 99% of the original signal. The cantilever nanobiosensor applied in different water samples (ultrapure, river, tap, and mineral) showed good performance, so could be readily extended toward the on-site monitoring of the other trace small molecular pollutants in environmental water matrices.

The objective of this work is to characterize two types of bovine collagen (fibre and powder), evaluating its application in mixed hamburger formulations, as well as the quality characteristics of the products. The collagen fibre had a fibrillar structure, molecular mass 100 kDa and greater gel strength (146 315 Pa) and protein content (97.81 %) than the powdered collagen, which had molecular mass from 50 to 100 kDa, greater hydroxyproline content, and a morphological structure with spherical microparticles more amorphous than the collagen fibre. In this study we found that the addition of 1.5 % powdered collagen and 2.5 % flocculated soybean flour and/or 0.75 % powdered collagen and 3.5 % flocculated soybean flour did not deteriorate the technological properties or the sensory attributes of hamburgers. The use of collagen is a promising alternative, since it has functional properties, improves the texture characteristics of a product, and is of low cost.

This paper presents a gas sensor array designed to be an electronic nose system characterized for the detection of different aromas (grape, apple, and strawberry). The gas sensors were prepared on printed graphite interdigitated electrodes (PGIEs with a tracing paper substrate) or gold interdigitated electrodes (IDEs with a glass substrate). The polyaniline (Pani) sensitive layers, obtained by interfacial and in situ synthesis, were deposited using layer-by-layer (LbL) and direct in situ adsorption polymerization. Experimental results showed that the substrate significantly affected the sensor responses, where sensors fabricated on PGIEs presented the highest sensitivity. On the other hand, the IDE sensors showed the best limit of detection (LOD), and short response times and recovery times for different aromas. The atomic force microscopy technique showed a typical morphology for all Pani films, where films deposited using the LbL technique presented the highest roughness. The sensor array was efficient in aroma discrimination, so it demonstrates excellent potential for food analysis in industrial applications.

The aim of this study is to elaborate and evaluate structural characteristics of soybean gelato by varying the content of soybean protein concentrate (2.95 to 17.05%) and vegetable fat (7.95 to 22.05%) using experimental design. The replacement of milk by hydrosoluble extract and soybean protein concentrate presented itself as an alternative to gelato production with unique characteristics, especially in terms of protein, solubility, viscosity, melting point, overrun and acceptability. The addition of up to 5% (m/V) protein concentrate, 14% (by volume) soybean hydrosoluble extract, and 15% (by mass) vegetable fat to gelato formulations resulted in better structural characteristics, with viscosity ranging from 0.45-0.70 Pa∙s at 10 °C, a non-Newtonian behaviour and protein stability (total protein content 8.44% and solubility 41%). Soybean gelato structural analysis using X-ray diffraction revealed 15° and 35° diffraction angles at 2Θ, characterizing the crystalline part of the product. The thermal analyses showed four bands of mass loss in the temperature range of 40-600 °C, characterizing loss of moisture, decomposition of the soy protein and the fat/emulsifier of the formulations. Thus, the soybean gelato is an innovative product, lactose and milk protein-free with outstanding characteristics for the general public, mainly, for the populations with intolerance to such components.

LbL films of AgCl–PANI nanocomposites synthesized by the one-step chemical route were shown to be a potential material for sensing application in which PANI de-doping at high pH is to be avoided.