Polyanna Silveira Hornung

Factors affecting mushroom Pleurotus spp.

Pleurotus genus is one of most extensively studied white-rot fungi due to its exceptional ligninolytic properties. It is an edible mushroom and it also has several biological effects, as it contains important bioactive molecules. In basidiomycete fungi, lignocellulolytic enzymes are affected by many typical fermentation factors, such as medium composition, ratio of carbon to nitrogen, pH, temperature, air composition, etc. The survival and multiplication of mushrooms is related to a number of factors, which may act separately or have interactive effects among them. Out that understanding challenges in handling Pleurotus species mushroom requires a fundamental understanding of their physical, chemical, biological and enzymatic properties. This review presents a practical checklist of available intrinsic and extrinsic factors, providing useful synthetic information that may help different users. An in-depth understanding of the technical features is needed for an appropriate and efficient production of Pleurotus spp.

Brazilian Dioscoreaceas starches

Abstract Determination of the characteristics of native starches is crucial in order to select their best application in various industrial fields. Thus, two different types of non-traditional native starches from the Dioscoreaceas species (Dioscorea sp. and Dioscorea piperifolia Humb. var. Wild) were studied regarding their thermal, structural and rheological properties. The results were contrasted with traditional commercial starch sources (potato, cassava and corn). From the thermogravimetric results (TG/DTG), D. piperifolia starch obtained the highest thermal stability of the samples, except for potato starch. Furthermore, using differential scanning calorimetry and viscoamylograph profiles (RVA), it was found that the Dioscoreaceas starches presented a higher onset (To) temperature and susceptibility to retrogradation. They also showed lower values in relation to relative crystallinity, which was calculated from their X-ray patterns and tendency to white (L*) colour. The shapes of the Discoreaceas starch granules were determined using electron microscopy; it was found that as the potato starch the Dioscoreaceas starches showed a wide range of particle size.

Natural bioactive starch film from Amazon turmeric (Curcuma longa L.)

It is evermore imperative to develop green processes and products due to the environmental and health problems facing modern society. Thus, the aims of this study were as follows: to use HPLC–MS to identify and quantify the phenolic compounds in Amazon Curcuma longa L. starch; to develop a bioactive starch film and to characterise its phenolic compounds (HPLC–MS) and antioxidant capacity (DPPH, ABTS and ORAC), as well its thickness and granular structure (SEM), mechanical (tensile strength and elongation at break) and colour (CIE-lab scale: L*, a*, b*) properties. HPLC–MS revealed eight major phenolic compounds in the C. longa starch and six in its film. The starch and the film from C. longa had high levels of antioxidant capacity, 65–92% (as measured by DPPH and ABTS). Furthermore, C. longa exhibited a smooth structural surface and strong resistance to tensile force, as well as maintaining its elasticity as measured by mechanical assays (tensile strength and elongation at break). Based on the obtained results a novel biodegradable starch film was obtained applying a single matrix, the Amazon Curcuma longa L. starch.

Brazilian Amazon white yam (Dioscorea sp.) starch

The functional properties of starch granules define its application in food and non-food industries. Thus, in this study we investigated thermal, rheological, structural and colour properties of the native and modified starch of the Amazon Dioscorea sp. (white yam) tuber. The Dioscorea sp. native starch was modified by applying single, simultaneous and combined modification agents (sodium hypochlorite, ultraviolet (UV) radiation and microwave irradiation). The thermogravimetric curves showed three main mass losses and increased thermal stability for the triple (NaClO + UV + microwaves) modified sample. The UV-irradiated samples required less energy (enthalpy) to gelatinize as registered by the differential scanning calorimetry. Performing modification using microwaves resulted in starches of highly viscous pastes as recorded by the rapid visco analyser. All the starch gel samples presented thixotropic behaviour, in which pseudoplastic characteristics were adequately described by Ostwald–de Waele and Herschel–Bulkley models. Rheological evaluation also revealed that one-step modified starches could produce stronger gels than the native one. Lower degree of relative crystallinity and a wide range of granule sizes were demonstrated by X-ray diffraction patterns and scanning electron microscopy. The colour measurement revealed the brightening and browning action of NaClO and microwaves, respectively.

A chemometric approach for moisture control in stingless bee honey using near infrared spectroscopy

Honey is a product that is often adulterated by the addition of water. Stingless bee honey naturally has a higher moisture content than that produced by the traditional Apis mellifera. In most countries, there is a lack of quality standards and methods to characterise and assure the authenticity of stingless bee honey, which demands for the development of fast methods to assess its main properties, avoiding potential fraud. Thus, this work aimed to develop a non-destructive moisture determination method for stingless bee honey based on diffuse reflectance near infrared spectroscopy combined with chemometrics. Thirty-two honey samples from four stingless bee species (Melipona quadrifasciata, Melipona marginata, Melipona bicolor and Scaptotrigona bipuncata) were used to develop calibration models using partial least squares regression analyses. Results revealed intense absorption bands in C–H, O–H and C–O vibrations in the spectra of stingless bee honey. The calibration model was used to predict the moisture content in honey from an external group. The prediction of the honey’s moisture showed good correlation (r2 = 0.93) with the refraction index method and an average error of 2.14%. The statistics variables for the calibration (R2 = 0.947, SEP = 1.005 and RPD = 4.3) revealed that this model can be used to predict the moisture from stingless bee honey and that near infrared spectroscopy is a reliable tool to be applied in quality control with rapid, simple and accurate results.

Induced effects by oxidation with potassium permanganate on the thermal, morphological, colorimetric and pasting properties of corn starch.

Introduction. Native starches are the most consumed polysaccharides in human diet. They are used in several industries as food, textile, pharmaceutic, etc. However due to some limitations starches should be modified chemically. Materials and methods. Corn starch modified with standard solutions of potassium permanganate (KMnO4) was analysed by simultaneous thermogravimetry-differential thermal analysis, differential scanning calorimetry, rapid viscoamylographic analysis, field emission gun-scanning electron microscopy/energy dispersive spectroscopy, X-ray powder diffraction and colorimetric analysis. Results and discussion. Corn starch was oxidised with KMnO4 at different concentrations (0.01; 0.02 and 0.05 mol L-1) at pH = 6.0 for 1 hour. (0.01; 0.02 and 0.05 mol L-1), pH = 6.0 for 1 hour. After filtered, washed and dried at 40 oC by 24 hours, the properties of the samples were investigated. Thermogravimetric curves showed an endothermic peak attributed to evaporation of water and two exothermic peaks, which refer to the decomposition and oxidation of organic matter until the formation of ash. A period of stability was observed, which decrease after modification. The gelatinisation of oxidised starch occurred at higher peak temperatures and also required higher gelatinisation enthalpy. The viscosity of the samples was significantly reduced and the relative crystallinity increased in proportion to the oxidant concentration used. Manganese and potassium content increased with the modification. There were no morphological changes after oxidation; however a darkening of the samples was identified due to the presence of potassium and manganese observed by energy dispersive spectroscopy (EDS). Conclusions. The obtained fluid paste with low retrogradation tendency suggests the application of oxidised starch in the paper industry.