Gerson Lopes Teixeira

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 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.