Risk for Mould Growth on Hemp-Lime at Different Relative Humidity

Microbial growth often thrives in humid conditions, at high relative humidity. Moulds are complex organisms; many types of mould are able to survive strong variations in humidity and temperature, such as those on building façades. For some building materials a critical relative humidity is determined, which functions as a theoretical threshold; at this (or lower) relative humidity microbial growth will likely not occur. Hemp-lime is a building material that consists of hemp shiv (the woody core parts of the hemp stem) and building lime. It is a material that can be used for walls, and even though it has been used for more than 20 years, thusfar little is known about its critical moisture levels for microbial growth. The aim of this research was therefore to determine at what relative humidity microbial growth occurs on carbonated hemp-lime material, and to study if there is a protective influence of a carbonated lime binder on the hemp shiv. The objective was to study microbial growth on hemp shiv, hemp-lime and on hemp with a thin layer of lime at three relative humidity (75 %, 85 % and 95 %) and at two different temperatures (15°C and 23°C); conditions that could occur naturally in a hemp-lime façade exposed to high rain loads in a northern European climate. Hemp shiv seems to have a relatively low resistance to microbial growth, similar to that of wood. However, because the hemp is protected by lime it can withstand much higher relative humidity without microbial growth occurring on the material. The critical moisture level for hemp-lime seemed to occur between 75 and 85 % RH, while the material was completely without microbial growth at 75 % RH. The lime had a protective effect on the hemp and acted as a mould inhibitor, both over time and with varying temperature and humidity.

Assessment of moisture and mould of hempcrete and straw panels

At present buildings contribute a third of total greenhouse gas emissions. There is a need for sustainable solutions and natural materials, which offer low-embodied energy and their low impact has a promising potential as construction alternatives. Hempcrete is a lightweight insulation material, which provides natural, airtight, and vapor-permeable insulation. Straw panels are also natural construction materials and they consist of extruded wheat straw and are surrounded with recycled paper on all sides. There are some risks, which can be associated with the use of such materials - infestation, biological degradation, presence of moisture, and structural degradation. The aim of the study is to determine the critical moisture level and mould resistance of hempcrete and straw panels. The results of this study are valuable to both scientists and structural engineers.

The Drying Rate of Chlorella pyrenoidosa Using an Oven in Bioethanol Production

The production of bioethanol from microalgae goes through several stages, including cultivation, harvesting, drying, storage, and conversion to bioethanol. Nearly 40% of the total energy consumed in the bioethanol production from microalgae is from drying. This research aims to study the drying rate model of Chlorella pyrenoidosa using an oven. The drying is carried out at the temperatures of 50, 60, and 70 oC. The initial moisture content of Chlorella pyrenoidosa was 317.798% dry weight. The results showed that at the temperatures of 50, 60, and 70 oC, the critical moisture content was 9.108, 7.583, and 6.93% dry weight, while the equilibrium moisture content was 3.172, 3.158, and 3.109% dry weight. The most optimal drying is at 70 oC and the drying rate gets faster as the temperature does too. The Page model is better at describing the drying rate of Chlorella pyrenoidosa using an oven than the Newton model. The drying speed constants (k) were 0.00056, 0.00061, and 0.00208, at 50, 60, and 70 oC, respectively.

Understanding wet tear strength at varying moisture content in handsheets

A laboratory study was conducted looking at the effects of moisture content on wet tear strength in handsheets. Three different wetting techniques were used to generate the wet tear (Elmendorf-type) data at varying moisture levels, from TAPPI standard conditions (dry) to over 60% moisture content (saturated). Unbleached hard-wood and softwood fiber from full-scale kraft pulp production were used. The softwood fiber was refined using a Valley beater to reduce freeness. Handsheets were made with a blend of hardwood and softwood and with refined softwood, without the addition of wet-end chemistry. The resulting grams-force tear data obtained from the test was indexed with basis weight and plotted versus both moisture content and dryness. As moisture content levels in the handsheets increased, the wet tear strength also increased, reaching a critical maximum point. This marked a transition point on the graph where, beyond a critical moisture content level, the tear strength began to decline linearly as moisture increased. This pattern was repeated in handsheets made from a blend of hardwood and softwood and from 100% refined softwood.

PENDUGAAN UMUR SIMPAN MAKANAN TRADISIONAL BERBAHAN DASAR BERAS DENGAN METODE ACCELERATED SHELF-LIFE TESTING (ASLT) MELALUI PENDEKATAN ARRHENIUS DAN KADAR AIR KRITIS

The expired date is important information that consumers should know. However, many traditional foods have not written an expiration due date. The purpose of this study was to estimate the shelf life of two (2) types of traditional rice-based foods intip and kembang goyang. Estimation of shelf life was carried out using the Accelerated Shelf-life Testing (ASLT) method using the Arrhenius approach and the critical moisture content approach. The calculation of shelf life in the Arrhenius approach to kembang goyang has been obtained respectively 0.45 months, 0.50 months, and 0.47 months at respective temperatures (25oC, 35oC and 45oC). The results of shelf life kembang goyang through the water content approach obtained 0.43 months at 75% RH. The results of the arrhenius approach to intip showed that shelf life of 0.37 months, 0.45 months, and 0.53 months at each temperature (25oC, 35oC, and 45oC). The critical water content approach for intip has obtained a shelf life of 0.58 months (RH 75%). Intip has a slightly larger shelf life when analyzed using the critical moisture content method. Keywords: ASLT, intip, kembang goyang, shelf life

Isotermas de adsorção de umidade e cinética de secagem de sementes de trevo persa (Trifolium resupinatum L.) e trevo vesiculoso (Trifolium vesiculosum) ¬¬¬¬

The aim of this work was to obtain adsorption isotherms and to study the drying kinetics of persian clover (Trifolium resupinatum L.) and arrowleaf clover (Trifolium vesiculosum) seeds, in addition, fitting the experimental data by the predicted models of the literature. The equilibrium moisture content and the moisture adsorption behavior were found by isotherms curves at 40, 45 and 50 ºC, and the Peleg model was the most suitable. The drying kinetics was determined by thin layer assays in an air parallel flow dryer at all three temperatures. In addition, it was demonstrated the predominance of the falling drying rate period for the two species of seeds, and the critical moisture content values were approximately of 0.20 and 0.25 gwater gdry matter-1 for persian clover and arrowleaf clover seeds, respectively. The effective diffusivity values were estimated in ranges of values of 3.61×10-11 – 6.81×10-11 m² s-1 for persian clover and 6.76×10-11 – 1.15×10-10 m²s-1 for arrowleaf clover seeds and the temperature effect was expressed by an Arrhenius relation. Thus, drying kinetics confirmed the greater difficulty in moisture removal from the arrowleaf clover seeds, compared to the persian clover seeds drying, in agreement with the results obtained through adsorption isotherms.