Intermediate Moisture Content Research Articles

A review of food safety in low-moisture foods with current and potential dry-cleaning methods.

Food is one of the basic needs of human life. With the increasing population, the production and supply of safe and quality foods are critical. Foods can be classified into different categories including low moisture, intermediate moisture, and high moisture content. Historically, low-moisture foods have been considered safe for human consumption due to the limited amount of moisture for microbial activity. Recalls of these foods due to pathogens such as Salmonella and undeclared allergens have brought attention to the need for improved cleaning and sanitization in dry food manufacturing facilities. In the food industry, cleaning and sanitation activities are the most efficient methods to prevent microbial contamination; however, water is most often required to deliver cleaning and sanitation agents. A well-written and properly implemented sanitation standard operating procedure can take care of microbial and allergen cross-contamination. Nevertheless, there are unique challenges to cleaning and sanitation processes for low-moisture food manufacturing facilities. The introduction of moisture into a low-moisture food environment increases the likelihood of cross-contamination by microbial pathogens. Hence, the use of water during cleaning and sanitation of dry food manufacturing facilities should be limited. However, much less research has been done on these dry methods compared to wet sanitation methods. This review discusses recent foodborne outbreaks and recalls associated with low-moisture foods the accepted methods for cleaning and sanitation in dry food manufacturing facilities and the limitations of these methods. The potential for air impingement as a dry-cleaning method is also detailed.

Economic viability and market potential of combined intermediate moisture dairy products production in Kazakhstan

In recent years, the Republic of Kazakhstan has prioritized the enhancement of its domestic food production industry as a strategic economic initiative. This is driven by the dual goals of improving public health outcomes and stimulating economic growth. Dairy products, a staple in the Kazakh diet, have been identified as a key sector for development. However, the domestic dairy industry faces significant economic challenges. Firstly, the industry is in its nascent stages of recovery following a prolonged period of economic stagnation. Secondly, high-quality domestic dairy products are facing stiff market competition from inexpensive foreign imports, which often do not meet the necessary quality and nutritional standards. This has implications for both public health and the economic viability of domestic dairy producers. Thirdly, the country is at the initial stages of exploring combined technologies to produce dairy products enriched with herbal supplements, known as combined dairy products. This emerging sector represents a potential avenue for economic diversification and value addition within the dairy industry. The objective of the study outlined in the provided paper is multifaceted, encompassing economic, technological, and public health dimensions within the context of Kazakhstan’s domestic dairy industry. Specifically, the study aims to explore the economic potential and viability of producing combined cheeses with intermediate moisture content. To achieve this objective, we propose to examine the organoleptic and physico-chemical characteristics of such dairy products. By investigating these attributes, the study seeks to shed light on the implications of producing these combined cheeses for production costs, marketability, and potential profitability. This endeavor is situated within the broader strategic goal of enhancing Kazakhstan’s domestic food production industry, particularly focusing on dairy products, which are a staple in the Kazakh diet. The research is driven by dual imperatives: improving public health outcomes and stimulating economic growth. To gain empirical data and real market needs understanding, the authors conducted a poll of the residents of three major cities of Kazakhstan: the capital Astana, Almaty and Shymkent. The poll involved 1,000 residents of each of the named cities, which is approximately 0.5-1% of the population of such cities as of 2020. The poll was conducted over a one-month period among supermarket customers of different ages who choose dairy products – soft cheeses. Respondents were asked three questions, namely: In your opinion, is there a need in the Republic of Kazakhstan to produce a new dairy product, in particular soft cheese, with high vitamin content and low-fat content, based on organic fermented vegetables? What price would you be willing to pay for such a product? Should the new product be produced by national producers? The findings show that almost every resident of large cities of the Republic of Kazakhstan who buys soft cheese wants to see on the supermarket shelves more high-quality and useful national cheeses. The above study of consumer opinion on the need for high-quality soft cheese with vegetable additives suggests that in terms of production of new soft cheeses market can be called promising. The results of economic analysis example presented in our paper also support this conclusion.

Трегалоза и изомальтулоза в технологии сладких молочных консервов

Sucrose is an important component in many foods. However, it can be dangerous for consumers’ health, if overconsumed. For instance, it may cause tooth decay. As a rule, sucrose provides sweetness and a certain dry matter content. Alternative sweeteners and bulking agents can also perform these two functions. Unfortunately, they almost always fail to serve as an osmotically active agent in canned products. The research objective was to study the properties of trehalose and isomaltulose as sugar substitutes in sweetened condensed milk.
 The study covered fifteen years of domestic and foreign research reported in the open databases of the Russian Scientific Citation Index, Scopus, and Web of Science. The list of search descriptors included twelve words and word combinations, e.g., sweetened condensed milk, water activity, sucrose, trehalose, isomaltulose, etc.
 The review focused primarily on the important properties of sucrose in the sweetened condensed milk and the physico-chemical features of the milk system. The analysis provided a system of criteria to evaluate the optimality of alternative substances for sweet concentrated milk production. These criteria were applied to trehalose and isomaltulose.
 The article introduces a list of criteria that can be used to evaluate sweeteners and sugar substitutes as regulators of certain technological properties in the production of sweetened concentrated milk products with intermediate moisture content. According to these criteria, trehalose and isomaltulose can serve as alternative sweeteners in condensed milk. However, the review revealed some gaps in experimental data on a number of properties of considered carbohydrates in sweetened concentrated milk products, which imposes further research.

Effect of Moisture and Feedstock Variability on the Rheological Behavior of Corn Stover Particles

Continuous feeding, processing, and handling of biomass powders is pivotal to the economic viability of integrated biorefineries. However, current challenges associated with the operational reliability of bulk solids handling and transport greatly impact the process economics and ultimately the widespread commercialization of integrated biorefineries. In this work, we examine the effect of moisture and feedstock variability on the flow behavior of corn stover biomass particles. The total flow energy, compressibility, shear properties, and wall friction angles were measured for corn stover samples A and B containing 0%, 15%, 25%, 50%, and 75% (mass fraction) moisture contents using a FT4 powder rheometer. In general, the flowability of both A and B was reduced when moisture was present as indicated by the stability and variable flow rate, compressibility, and shear tests. The 15% moisture sample had the highest flow energy, revealing the interplay between the increased surface tension and looser packing both of which were caused by liquid bridging. The 75% moisture sample had the highest compressibility and the lowest flowability factor (ffc). The trend in wall friction angle was found to be dependent upon the surface hydrophobicity of the wall material. The wall friction angle on the hydrophilic, stainless-steel surface increased with moisture and therefore poses additional handling challenges. On the other hand, the wall friction angle on the hydrophobic polymer surfaces were the lowest for samples with intermediate moisture contents. Sample B had greater bulk density, smaller compressibility, and greater flowability than the sample A, as suggested by the compressibility and shear tests. The wall friction angle of sample B was higher than or equal to that of sample A depending on both the type and the surface roughness of the wall material.

Forecasting the safety of confectionery products by microbiological indicators

The moisture content in confectionery products influences the processes of microbiological changes. A high mass fraction of moisture (more than 20%) in cakes predetermines the presence of a favorable environment for the development of all types of microorganisms. Studies of potential sources of microbiological contamination of products and identification of the microorganism type make it possible to identify the source of its origin. So, in the test sample of the cake, the presence of a yeast strain of the Cystobasidium slooffiae species was detected, which indicates violations of sanitary and hygienic production. The issues of increasing the shelf life are especially relevant for confectionery products with intermediate moisture content (from 10 to 20%). The use of modified E1442 starch in the filling made it possible to reduce the content of yeast and mold during storage of gingerbread by 2–3 times compared to E1422 starch. For low moisture confectionery, when using lauric-type cocoa butter substitutes, there is a risk of a soapy taste due to the formation of free lauric acid under the action of lipolytic enzymes.

Effects of catalytic infrared drying in combination with hot air drying and freeze drying on the drying characteristics and product quality of chives

The effects of hot air drying (HAD), freeze drying (FD), and catalytic infrared drying in combination with hot air drying (CIRD-HAD) and freeze drying (CIRD-FD) on the drying characteristics and product quality of chives were studied. The intermediate moisture contents for CIRD-HAD and CIRD-FD were 70%, 75%, 80% and 85%. The relationships among moisture content, drying rate, colour, structure, odour and nutrient retention were analysed. The results showed that, on the premise of the moisture content of the final product being lower than 8%, compared with HAD, CIRD-HAD significantly shortened the drying time by 23–77.5 min for the various intermediate moisture contents, and better preserved the nutrients (chlorophyll, allicin, vitamin c and volatile components) in the dried products; compared with FD, CIRD-FD significantly shortened the drying time by 1.1–3.8 h for the various intermediate moisture contents while the qualities were comparable. Overall, catalytic infrared combined drying is a promising method for obtaining high-quality dried chives. Among various drying conditions, intermediate moisture contents of 75%–80% for CIRD-HAD and 80%–85% for CIRD-FD are recommended as the most suitable for chives in terms of drying time and quality of the final product.

Physical and morphological characteristics of edible coatings based on pectin and guava by-products applied to guava pieces

ABSTRACT: Edible coatings based on polysaccharides have been applied on pieces of fruits and vegetables before drying because of their potential to improve physical and nutritional characteristics of dehydrated plant foods. In the present study, physical and thermal properties of pectin-based films, with and without the incorporation of by-products obtained from the processing of red guava, were determined. These properties allow one to predict the likely behaviour of these films when used as edible coatings on guava pieces, during and after their dehydration. Thus the structural and morphological characteristics and the physical, thermal and sorption properties of the films and of the fruit pulp were determined, using scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and the static gravimetric method to determine the water-sorption curves. The addition of by-products provided crystallinity to the pectin film, attributed to their cellulose content, and hardly altered the water retention capacity of the pectin films. However, the pectin contributed to presenting a slightly higher sorption moisture at equilibrium, as compared to the guava pulp. The glass transition temperatures reported at extremely low moisture contents, both in the pulp and in the films with added by-products, indicated that at intermediate moisture contents, the fruit/film ensemble was in the rubbery state at room temperatures, providing softness to the dehydrated product. The images showed good integration of the edible films with the surface of the guava pieces.

Ultrasonic induced effect on mass transfer characteristics during osmotic dehydration of aonla (Phyllanthus emblica L.) slices: A mathematical modeling approach

AbstractThe present work aimed to investigate the effect of ultrasound pretreatment on osmotic dehydration of aonla slices. The aonla slices were subjected to an ultrasonic treatment with a frequency of 40 kHz for 10 min and then subjected to osmotic dehydration in 60°Bx sucrose solution for 300 min. Empirical models such as Azuara, Peleg, Weibull, Page, and Crank model were utilized to predict the kinetics of water loss and solid gain. Artificial Neural Network technique was also used to predict the parameters with immersion time and temperature as input. All models were found to have a good fit. From the analysis, the ultrasound pretreated samples were found to have enhanced rate of mass transfer compared to control samples especially at the early stages of the process. From Azuara Model, the equilibrium water loss and solid gain were ranged between 49.95–53.65 g/100 g and 11.10–22.01 g/100 g. From Crank model, the effective moisture diffusivities in osmotic dehydration were observed to be varied between 9.28 × 10−10–12.47 × 10−10 m2/s and 10.06 × 10−10–19.17 × 10−10 m2/s for atmospheric and ultrasonic conditions. While for solid gain, the values were ranged between 2.36–2.67 × 10−10 m2/s (untreated) and 2.49–2.73 × 10−10 m2/s (treated). The Vitamin C content and color of sample were found to be affected by ultrasound pretreatment (p <.05) and temperature (p <.05). The effective diffusivities attributed to have a significant Arrhenius relationship (R2 ≥.92, p ≤.05). The enhanced moisture loss and solid gain in the product can be explained by the microscopic channels and cell disruption caused by ultrasonic waves.Practical ApplicationThe aonla fruit, native to South Asia, is a very important commodity because of its health and nutritional benefits. Despite its advantages, it is less popular as table fruit because of its low shelf life and astringency. Osmotic dehydration can be used to preserve the fruit, and it causes the partial removal of water from the fruit and improves its taste. Osmotic dehydration being a slow process, can be enhanced by the ultrasound application. The data and findings can be applied to produce stable intermediate moisture content food that can be used as dried fruit or additive with other food products. This study investigates the modeling of ultrasound‐induced osmotic dehydration in order to design the process with low energy and cost.

Inactivation of Zygosaccharomyces rouxii in organic intermediate moisture apricot and fig by microwave pasteurization

Zygosaccharomyces rouxii is an osmotolerant yeast that is responsible for the spoilage of high sugar content foods. Microwave heating technology is used as an alternative to conventional pasteurization. Main purpose of this research was to determine the thermal resistance of Z. rouxii in organic intermediate moisture content (IMC) fruits (apricot and fig) during the microwave pasteurization process and comparing the D, z and F values with the conventional method. F85 values were calculated both theoretically and experimentally. Additionally, the effects of the pasteurization methods on the quality properties (total soluble solid, pH, acidity, water activity, moisture content, rehydration capacity, weight loss, hydroxymethylfurfural (HMF) and color) of the samples were investigated. The results show that come up time (CUT) and D values were significantly reduced by microwave treatment. The yeast reached a five log10 reduction by the microwave heating method with the F8533.8 value of 3.6 min for apricot and F8532.15 value of 3.35 min for fig. Total soluble solids, weight loss, and color values were preserved better in microwave pasteurization than the conventional method in both samples. Hydroxymethylfurfural content of the microwave pasteurized samples was 23.5% and 32% less than the samples pasteurized conventionally for apricot and fig samples, respectively.

Регулирование качественных показателей молозива и белковых композиций заменителей молока

Introduction. Improving technologies and providing young farm animals with high-quality feed are the primary tasks for successful reproduction and maintenance of dairy cattle. The research objective was to assess the quality characteristics of colostrum and milk replacers, as well as their technological prospects.
 Study objects and methods. The research featured colostrum, calf milk replacers (CMR), processing methods, and quality characteristics. The paper introduces an analysis of various sustainable processes of obtaining new CMRs.
 Results and discussion. The article describes colostrum: recommended intake for young calves, qualitative characteristics, and control methods. It focuses mostly on the microbiological characteristics of colostrum, as well as on its role in developing the immune system of calves and the prospects of enzymatic regulation of its functional properties. Enzymatic regulation is based on deep proteins hydrolysates and a highly active serine protease (alcalase). The authors studied variants of using various enzyme preparations and bacterial starter cultures for obtaining hydrolyzed and fermented colostrum, analyzed the main process indicators of milk replacers with intermediate moisture content, and tested various methods for assessing the fatty acid and protein composition of concentrated milk replacers. Production methods proved to have a significant impact on the indicators in question.
 Conclusion. Reproduction of the dairy herd genetic potential depends on the diet of the young farm animals, and so does the economy of agricultural production. Enzymatic processing of raw materials proved to be the most promising approach for obtaining products with improved functional properties. Deep colostrum hydrolysates can also be an important part of functional foods for children, athletes, in dietary foods, etc.

Methods of producing parboiled rice by hot air and combined microwave-hot air fluidized bed drying

Conventional parboiled rice requires many components such as boiler, steam pipe and auxiliary devices. To reduce the complexity of the process, in this work, the new method of producing parboiled rice by hot air fluidized bed (HAFB) and microwave-hot air fluidized bed (MWHAFB) was proposed and investigated. In the experiment, the soaked paddy with an initial moisture content of 47 ± 1% d.b. and initial grain temperatures of 32–65 °C were dried at the drying air temperatures of 110–170 °C with microwave powers of 0.8–4.0 W/gwet paddy (1.6–4.0 kW). The superficial air velocity at 4.6 m/s and bed depths of 5 cm (1 kgwet paddy) and 10 cm (2 kgwet paddy) were used. The experimental results showed that the drying time to reach an intermediate moisture content of 20 ± 2% d.b. was shorter with smaller bed depth, higher drying air temperature and higher microwave power. The MWHAFB and HAFB dryings could produce parboiled rice with a complete degree of starch gelatinization as the operating condition was suitable. The head rice quality of parboiled rice produced by MWHAFB and HAFB was not different. The parboiled rice had yellowish white for drying with excluding the tempering and had yellowish brown with including tempering as indicated by whiteness index (WI) with a value of 51–52. The consumption of energy was significantly lower in HAFB than that in the conventional process whilst the energy consumption between MWHAFB and conventional one was relatively comparable.

The physical properties of dried-growol produced with different cassava varieties and fermentation time

Growol is a staple food made from cassava and obtained through fermentation process. It is usually produced under 2-3 days fermentation and has been observed to have an intermediate moisture content, so it needs to be dried preserved. The purposed of this study was to evaluate the chemical characteristics of fermented cassava as well as the physical attributes of dried-growol produced using different cassava varieties and fermentation time. This study used local cassava varieties: Martapura, Meni, Ketan, and Lanting; while the fermentation durations were 2 and 4 days. Each variety of fermented cassava was analyzed for moisture content, starch, and amylose and then was steamed for 15 minutes. The fresh growols were dried at 50°C until the moisture content was approximately 10% and then the dried-growols were determined their texture and color. The results showed that cassava variety and fermentation time affected the chemical properties of the fermented cassava as well as the physical attributes of dried-growol. Moreover, the starch content of fermented cassava was found to be between 18.25-34.03% with the highest indicated in Martapura; while amylose content was between 7.50-18.30%. Martapura was observed to have a bright color and a little hard texture.

The Arctic Ocean Observation Operator for 6.9 GHz (ARC3O) – Part 1: How to obtain sea ice brightness temperatures at 6.9 GHz from climate model output

Abstract. We explore the feasibility of an observation operator producing passive microwave brightness temperatures for sea ice at a frequency of 6.9 GHz. We investigate the influence of simplifying assumptions for the representation of sea ice vertical properties on the simulation of microwave brightness temperatures. We do so in a one-dimensional setup, using a complex 1D thermodynamic sea ice model and a 1D microwave emission model. We find that realistic brightness temperatures can be simulated in cold conditions from a simplified linear temperature profile and a simplified salinity profile as a function of depth in the ice. These realistic brightness temperatures can be obtained based on profiles interpolated to as few as five layers. Most of the uncertainty resulting from the simplifications is introduced by the simplification of the salinity profiles. In warm conditions, the simplified salinity profiles lead to brine volume fractions that are too high in the subsurface layer. To overcome this limitation, we suggest using a constant brightness temperature for the ice during warm conditions and treating melt ponds as water surfaces. Finally, in our setup, we cannot assess the effect of wet snow properties. As periods of snow with intermediate moisture content, typically occurring in spring and fall, locally last for less than a month, our approach allows one to estimate realistic brightness temperatures at 6.9 GHz from climate model output for most of the year.

Combined single-stage tempering and microwave vacuum drying of the edible mushroom Agrocybe chaxingu: Effects on drying characteristics and physical-chemical qualities

To reduce the moisture content gradient during drying, a single-stage tempering treatment based on parameters including intermediate moisture content (M), tempering temperature, tempering time and relative humidity was used to assist microwave vacuum drying (MVD) of the edible mushroom Agrocybe chaxingu. The influences of these parameters on product quality were analyzed by response surface methodology. The tempering treatments led to the increased effective moisture diffusivity and shortened effective drying time when compared with continuous MVD. Analysis of variance results showed M has the most significant impact on the quality parameters of A. chaxingu including the rehydration ratio, polysaccharide content, free amino acid content (FAA), and color, while the other three parameters only had a small but significant effect on some of those characteristics. Compared to continuous MVD, the total FAA content of tempering treatments enhanced by 10.81%–32.08%, especially aspartic, glutamic acid, isoleucine, leucine and valine. Overall, tempering-assisted MVD was found to be a potential drying of A. chaxingu, as it offers a more efficient drying process with better quality.

Antioxidant and antimicrobial properties of organic fruits subjected to PEF-assisted osmotic dehydration

The effect of PEF pre-treatment prior to osmotic dehydration on mass transfer parameters, colour, antioxidant and antimicrobial properties in organic strawberries and kiwifruits was evaluated. An increase of water loss in both fruits upon the application of combined processes was noticed (up to 21.6%), while a decrease of solid gain was observed only in kiwifruit samples dehydrated in sucrose (about 45%). In general, the combined treatments were beneficial for colour maintenance in both fruit tissues. The antioxidant capacity (DPPH) and activity (ORAC) increased after PEF treatment, however, all the combined treatments reduced significantly these values (of about 20 and 28% for strawberry and of about 56 and 35% for kiwifruit, respectively for DPPH and ORAC methods). In general, PEF treatment alone was also effective with regard to an increase in the antimicrobial activity of the samples against the tested microorganisms (B. subtilis, E.coli, S. cerevisiae). Industrial relevancePEF pre-treatment coupled with osmotic dehydration could be applied at industrial level to obtain semi-dried fruit products. Moreover, both processes could be used as pre-treatments for drying process, in order to develop healthy and microbiologically stable fruit snacks. In fact, in the present work we observed that PEF pre-treatment alone promoted higher antioxidant and antimicrobial activity. The combined process decreased both parameters, suggesting that an accurate study is necessary to evaluate the benefits of these processes in terms of bioactive compounds retention and time and energy consumption in further drying process. The results of the present study could be used as a starting point for the industries to design novel products with intermediate moisture content intended for further processing.

Machine Learning Driven Approach Towards the Quality Assessment of Fresh Fruits Using Non-Invasive Sensing

In agriculture science, accurate information of moisture content (MC) in fruits and vegetables in an automated fashion can be vital for astute quality and grading evaluation. This demands for a viable, feasible and cost-effective technique for the defect recognition using timely detection of MC in fruits and vegetables to maintain a healthy sensory characteristic of fruits. Here we propose a non-invasive machine learning (ML) driven technique to monitor variations of MC in fruits using the terahertz (THz) waves with Swissto12 material characterization kit (MCK) in the frequency range of 0.75 THz to 1.1 THz. In this regard, multi-domain features are extracted from time-, frequency-, and time-frequency domains, and applied three ML algorithms such as support vector machine (SVM), k-nearest neighbour (KNN) and Decision Tree (D-Tree) for the precise assessment of MC in both apple and mango slices. The results illustrated that the performance of SVM exceeded other classifiers results using 10-fold validation and leave-one-observation-out-cross-validation techniques. Moreover, all three classifiers exhibited 100% accuracy for day 1 and 4 with 80% MC value (freshness) and 2% MC value (staleness) of both fruits’ slices, respectively. Similarly, for day 2 and 3, an accuracy of 95% was achieved with intermediate MC values in both fruits’ slices. This study will pave a new direction for the real-time quality evaluation of fruits in a non-invasive manner by incorporating ML with THz sensing at a cellular level. It also has a strong potential to optimize economic benefits by the timely detection of fruits quality in an automated fashion.

Investigation of hot-air assisted radio frequency (HARF) dielectric heating for improving drying efficiency and ensuring quality of dried hazelnuts (Corylus avellana L.)

Hot-air assisted radio frequency (HARF) dielectric heating was utilized to dry inshell hazelnuts (Barcelona and Jefferson) in order to achieve rapid, uniform drying and better nut quality. The process parameters studied were electrode gap (EG) (14, 15 and 16 cm) and sample thickness (ST) (3, 5 and 7 cm) for HARF drying, 2-step hot-air (HA)-HARF drying at different intermediate moisture contents (MC) (16, 14 and 12%, wet basis), and two HARF modes (continuous and intermittent). The optimal intermittent HARF operations were identified as 15 cm EG and 5 cm or 7 cm ST, resulting in drying time of 100.5 min and 180.9 min for Barcelona and Jefferson, respectively, vs. 22 h using HA drying. The 2-step HA-HARF drying at 12% intermediate MC reduced shell cracking ratio <15%, provided fast drying rate and improved heating uniformity, whereas a longer HA pre-drying time resulted in undesirable high lipid oxidation of dried kernels. The HARF and 2-step HA-HARF in the continuous mode increased drying rate and better retention of bioactive compounds in comparison with the intermittent mode. This study generated important information of HARF technology for drying hazelnuts with improved drying performance and nut quality compared with conventional HA drying.

A Spherical Steady-State Method to Measure Soil Thermal Conductivity

The reliable prediction of coupled heat and moisture transfer in three-phase soils involves authentic estimation of soil thermal conductivity. In the current work, a steady-state method was developed to measure soil thermal conductivity. Soil samples for two soils were packed in a plastic of 6.6 cm inner diameter and 3 mm thickness. A 130 Ohm resistor as a heat generator being connected to 5 V electricity source was located in the center of the ball. Three thermocouples were installed at the distances of 0.5, 1.5, and 2.5 cm from the center, respectively. After unpacking the ball, thermal conductivity was measured using the single probe method. The thermal conductivity values measured by both methods were almost the same in air dry soils; overall, the observed differences between the two methods were less than 3%. However, in the intermediate moisture content ranges, the values measured by the steady-state method were slightly lower than those obtained by the single probe method. Considering the effect of convective vapor flux due to thermal expansion of soil air in the single probe method, values measured with the new steady-state method may be more reliable.

Moisture and temperature induced swelling/shrinkage of softwood and hardwood glulam and LVL: An experimental study

Abstract To investigate the hygroscopic behaviour of engineered timber, glued-laminated (glulam) timber made of Pacific Teak (Tectona grandis), Tasmanian Oak (Eucalyptus regnans/obliqua/delegatensis), Blackbutt (Eucalyptus pilularis), Radiata Pine (Pinus radiata) and Slash Pine (Pinus elliottii) and laminated veneer lumber (LVL) made of Radiata Pine were exposed to sorption and desorption cycles at two temperatures (i.e. 15 and 50 °C) and the shrinkage and swelling of samples were measured in three orthogonal directions. The samples were conditioned in different relative humidity to produce eight intermediate moisture contents (reading points) between the oven-dried and saturated states. A bilinear model was fitted to the swelling/shrinkage strain-moisture content data to accurately determine the Coefficient of Moisture Expansion (CME) and Moisture Contraction (CMC), and Coefficient of Thermal Expansion (CTE), as well as the Fibre Saturation Point (FSP) for each group of specimens. The experimental results demonstrated a significant difference in swelling/shrinkage behaviour of large glulam and LVL samples compared to small clear wood samples as well as a significant effect of temperature on moisture-induced swelling/shrinkage of glulam and LVL beams in the transverse direction. The CME and/or CMC in the transverse direction were found to decrease with increasing temperature, while swelling/shrinkage coefficients in the longitudinal direction exhibited an opposite pattern. The results of this study can potentially improve the accuracy of the hygro-thermo-mechanical and long-term analysis of glulam and LVL members.

Change of mechanical properties related to starch gelatinization and moisture content of rice kernel during fluidized bed drying

Rice fissuring during the drying process is a major problem affecting rice quality. To alleviate this critical issue, it is necessary to understand the change of mechanical properties and the drying kinetics of paddy during drying. The objective of this work is therefore to study the drying characteristics and changes of mechanical properties, i.e., breaking force (F), ultimate tensile strength (UTS), and apparent modulus of elasticity (AMOE) during fluidized bed drying. Suphanburi 1 paddy variety with three initial moisture contents (Mi) of 29.5, 30.2, and 42.8% dry basis was used as the raw material, which was dried at drying air temperatures (Ta) of 110, 130, and 150 °C. A three-point bending method was used for testing the mechanical properties with a texture analyzer. The experimental results showed that the breaking force and the ultimate tensile strength of paddy during drying were more strengthened with higher drying temperatures and higher initial moisture content while its apparent modulus of elasticity was changed only with the moisture content. However, both operating parameters positively affected the apparent modulus of elasticity when evaluated at a 16% dry basis. The maximum changes in F, UTS, and AMOE concerning the initial moisture content were 25.1, 25.2, and 19.5%, respectively. Besides, the maximum changes in F, UTS, and AMOE concerning drying temperatures during drying were 14.2, 14.3, and 13.5%, respectively. The improvement of the mechanical properties could be attributed to the starch gelatinization of which the degree was higher in cases of higher initial moisture content and higher drying temperatures. The empirical models of ultimate tensile strength and apparent modulus of elasticity were developed and related to intermediate moisture content and the degree of starch gelatinization.