Equilibrium Relative Humidity Research Articles

Drying banana seeds for ex situ conservation.

The ability of seeds to withstand drying is fundamental to ex situ seed conservation but drying responses are not well known for most wild species including crop wild relatives. We look at drying responses of seeds of Musa acuminata and Musa balbisiana, the two primary wild relatives of bananas and plantains, using the following four experimental approaches: (i) We equilibrated seeds to a range of relative humidity (RH) levels using non-saturated lithium chloride solutions and subsequently measured moisture content (MC) and viability. At each humidity level we tested viability using embryo rescue (ER), tetrazolium chloride staining and germination in an incubator. We found that seed viability was not reduced when seeds were dried to 4% equilibrium relative humidity (eRH; equating to 2.5% MC). (ii) We assessed viability of mature and less mature seeds using ER and germination in the soil and tested responses to drying. Findings showed that seeds must be fully mature to germinate and immature seeds had negligible viability. (iii) We dried seeds extracted from ripe/unripe fruit to 35-40% eRH at different rates and tested viability with germination tests in the soil. Seeds from unripe fruit lost viability when dried and especially when dried faster; seeds from ripe fruit only lost viability when fast dried. (iv) Finally, we dried and re-imbibed mature and less mature seeds and measured embryo shrinkage and volume change using X-ray computer tomography. Embryos of less mature seeds shrank significantly when dried to 15% eRH from 0.468 to 0.262mm3, but embryos of mature seeds did not. Based on our results, mature seeds from ripe fruit are desiccation tolerant to moisture levels required for seed genebanking but embryos from immature seeds are mechanistically less able to withstand desiccation, especially when water potential gradients are high.

Modeling Heat and Mass Transfer of Long-Grain Hybrid Rice in a Chilled Environment

HighlightsThis study determined adsorption and desorption isotherms of long-grain hybrid rough rice in chilled environments.Parameters of the sorption models were evaluated by fitting experimental data in a thin layer drying equation.The moisture diffusivity and activation energy values of rough rice subjected to chilled environments were determined.The finite element method was used to simulate the heat and mass transfer of long-grain hybrid rice at low temperatures. Abstract. While chilling aeration technology for grains has found use in other countries, application in the U.S. for rice has not yet been widely adapted by the industry. The aim of this study was to determine the moisture sorption behavior of rough rice in chilled environments. Such data is vital for automated grain conditioning monitoring and control of aeration systems at cool ambient conditions. Adsorption and desorption isotherms of hybrid long-grain rough rice (XL745) subjected to temperature environments which are typical in U.S. storage conditions (5°C to 15°C) were measured. A dynamic vapor sorption analyzer, the IGAsorp, which consists of an ultrasensitive microbalance within a controlled environment was used to accurately measure water sorption in rice. Changes in sample weight were continuously monitored across a range of equilibrium relative humidity (10% to 70%) until a steady-state mass was attained. Nonlinear regression analysis was used to estimate empirical constants of five models used for describing grain sorption isotherms. The appropriateness of each model in describing the equilibrium data was evaluated to minimize the root mean square error (RMSE). The modified Chung-Pfost equation best described the experimental data with RMSEs of 0.557 and 0.912 for adsorption and desorption data, respectively. The equilibrium moisture content (EMC) of rice measured at 5°C with 10% relative humidity (RH) was 12.5% (dry basis), which was higher than the EMC value predicted from other studies by extrapolation at 30°C (9.1% d.b.). All five prediction models (modified Chung-Pfost, modified Henderson, modified Oswin, modified Halsey, and GAB) were in good agreement for experimental data at moderate temperature conditions (e.g., at 30°C). The results indicated that it is more accurate to use newly developed constants for EMC models of rice in chilled environments. A three-dimensional ellipsoid shape was used to describe rough rice geometry. Mathematical models were developed to predict the moisture and temperature distribution during the drying processes at 5°C and 15°C. Models were solved by the finite element method using Comsol Multiphysics® simulation program. Increasing the drying temperature from 5°C to 15°C increased the effective moisture diffusivity from 9.0×10-13 to 1.1×10-12 m2/s. The drying activation energy value was 25.1 kJ/mol in the chilled environments investigated. Keywords: Activation energy, Chilled environment, Equilibrium moisture content, Mathematical modeling, Moisture diffusivity, Rough rice.

Sorption equilibrium moisture and isosteric heat of Chinese wheat bran products added to rice to increase its dietary fibre content

More and more people concern about supplementing dietary food with wheat bran to increase fibre content, but there has been little study of the sorption isotherms and isosteric heats of wheat bran fibre products, which are important to the quality and storage durability of such commodities. This study collected equilibrium moisture content (EMC) and equilibrium relative humidity (ERH) data on six Chinese wheat bran products via the static gravimetric method and analysed their sorption isosteric heats. Results showed that all six wheat bran products had sigmoidal isotherms. The data were best fitted by polynomial, modified GAB, modified Oswin, and modified Halsey models. The relative safe moisture contents of the six wheat bran products were 12.20%–13.86% wet basis (w.b.). The heat of vaporization of wheat bran products approached the latent heat of pure water at around a moisture content (MC) of 22.5% and approximately 2450 kJ/kg. A process of extrusion and ultrafine grinding reduced the solid surface area and sorption isosteric heats of the monolayer, multilayer and condensed water regions in the wheat bran products. In the temperature range of 10–37 °C, the EMC of sorption in monolayer, multilayer and condensed water regions decreased with increasing temperature. The milled rice to which 1%–3% 200-mesh wheat bran product was added maintained its texture when made into cooked rice and its thermomechanical properties when made into rice dough. After processing by extrusion and ultrafine grinding, wheat bran products have a lower solid surface area and lower monolayer water content ( M m ) and sorption isosteric heat values. Some 3% 200-mesh wheat bran product can be added to cooked rice for increasing its fibre content and making it more nutritious.

Polymorphic transitions of V-type amylose upon hydration and dehydration

In the current study, V6, V7 and V8 amyloses were prepared, their crystalline polymorphic transitions upon hydration at different moisture conditions examined by wide-angle X-ray diffraction (XRD), and the relative degrees of crystallinity calculated. Upon the formation of V7 or V8 crystals, the XRD peaks shifted to lower Bragg angles as compared to V6h due to the expansion of the amylose helices. Conditioning at 75% equilibrium relative humidity (ERH) transformed V6a and V7 amyloses to the V6h pattern. Long-term vapor hydration at 100% ERH or total hydration by immersion in water transformed all V-type XRD patterns to the B-type with decreased degrees of crystallinity. Upon dehydration by ethanol wash, the relative crystallinities of all V-type amyloses were increased, while the crystalline patterns remained mostly unchanged. Such explicit study of polymorphic transitions revealed by XRD can help establish optimal conditions for the encapsulation of bioactive compounds with V-type amyloses and provide insights for novel food product developments.

Microbial growth and volatile organic compound (VOC) emissions from carpet and drywall under elevated relative humidity conditions

BackgroundMicrobes can grow in indoor environments if moisture is available, and we need an improved understanding of how this growth contributes to emissions of microbial volatile organic compounds (mVOCs). The goal of this study was to measure how moisture levels, building material type, collection site, and microbial species composition impact microbial growth and emissions of mVOCs. We subjected two common building materials, drywall, and carpet, to treatments with varying moisture availability and measured microbial communities and mVOC emissions.ResultsFungal growth occurred in samples at >75% equilibrium relative humidity (ERH) for carpet with dust and >85% ERH for inoculated painted drywall. In addition to incubated relative humidity level, dust sample collection site (adonis p=0.001) and material type (drywall, carpet, adonis p=0.001) drove fungal and bacterial species composition. Increased relative humidity was associated with decreased microbial species diversity in samples of carpet with dust (adonis p= 0.005). Abundant volatile organic compounds (VOCs) that accounted for >1% emissions were likely released from building materials and the dust itself. However, certain mVOCs were associated with microbial growth from carpet with dust such as C10H16H+ (monoterpenes) and C2H6SH+ (dimethyl sulfide and ethanethiol). CO2 production from samples of carpet with dust at 95% ERH averaged 5.92 mg hr-1 kg-1, while the average for carpet without dust at 95% ERH was 2.55 mg hr-1 kg-1.ConclusionMicrobial growth and mVOC emissions occur at lower relative humidity in carpet and floor dust compared to drywall, which has important implications for human exposure. Even under elevated relative humidity conditions, the VOC emissions profile is dominated by non-microbial VOCs, although potential mVOCs may dominate odor production.5qHJBwjppp9jyb9CEJTu9oVideo

Structural characterisation and sorption capability of whey protein aerogels obtained by freeze-drying or supercritical drying

Whey protein isolate (WPI) hydrogels were converted into aerogels by freeze-drying (FD) or supercritical drying (SCD). SCD resulted in denser aerogels, with a network of closely-associated WPI microgel aggregates, and pore size <1 μm in diameter. In the FD aerogels, individual aggregates were fused and formed a self-supporting protein matrix with larger pores (2–5 μm in diameter). Both aerogels showed a glass transition at 161 ± 4 °C and maintained their original porosity at room temperature at an equilibrium relative humidity <80%. The kinetics of both water and oil uptake were slower in the SCD aerogel than in the FD aerogel. While water absorption caused aerogel swelling and destructuring, the oil-loaded aerogels retained their integrity and adsorbed up to 75% (w/w) oil. The oil-loaded aerogels showed differences in firmness and oil holding capacity (OHC) depending on the drying procedure applied: SCD samples presented a higher firmness (~30 N) and OHC (~96%) than the FD samples (~19 N, OHC ~ 45%). This study demonstrates that the drying technique selected can substantially alter the functional attributes of whey protein aerogels.

Direct Measurements of the Deliquescence Relative Humidity in Salt Mixtures Including the Contribution from Metastable Phases.

Accelerated salt-induced deterioration occurs by frequent changes across the equilibrium relative humidity (RHeq). Therefore, knowledge of the actual RHeq of a salt mixture has a major impact on preventive conservation to ensure that the relative humidity (RH) does not cause a salt-phase transition. In addition, knowledge of the RHeq is essential in relation to in situ desalination as the dissolution of salt is an essential criterion to enable transport of salt (ions) in materials. For decades, it has been possible to determine the RHeq in salt mixtures with thermodynamic-based ECOS-Runsalt software. However, the ECOS-Runsalt model is challenged by the influence of kinetics along with some limitations in regard to possible ion types and combinations. A dynamic vapor sorption (DVS) instrument is used for the direct measurement of RHeq and to deduce knowledge on the physicochemical nonequilibrium process related to the phase changes in salt mixtures. The experimentally measured RHeq values in this study of NaCl–Na2SO4–NaNO3, NaNO3–Na2SO4, NaCl–NaNO3, NaCl–Na2SO4, and (NH4)2SO4–Na2SO4 are in agreement with values from the literature. A comparison with thermodynamically calculated results makes it probable that the phase transition for some salts is significantly influenced by nonequilibrium conditions. The present work bridges some of the existing gaps in regard to improving the accuracy of ECOS-Runsalt, including the effects of kinetics and the possible ions and combinations that may be found in situ. The proposed method makes it possible to determine a more representative RHeq in relation to real conditions for the improved treatment of salt-infected constructs.

Water from Air: Desiccant System Design and Simulation

Air water generators that harvest water from air humidity have the potential to counter the ever-rising problem of drinking water scarcity. There are many different types of air water generation systems that work on various different principles. Desiccant based air water generation systems work on the principle of moisture absorption, consisting of a packed bed dehumidifier that absorbs the moisture from air. This reduces the energy requirement of the system. To discuss the efficiency of the system, it is crucial to understand the working of the packed bed column. In this paper, a mathematical model has been developed for a packed bed dehumidification system using aqueous CaCl2 as the liquid desiccant. This model has been developed using water saturation pressure and equilibrium relative humidity models. The packed bed model has been used to study the effect of various input parameters like air and desiccant flow rate, packing material, relative humidity and desiccant concentration, on the capacity of the desiccant to absorb water from air. The results so obtained can be used to predict the water that can be absorbed by the desiccant in the packed bed column for given inlet conditions.

THERMODYNAMIC PROPERTIES OF WHITE BEAN GRAINS FOR DIFFERENT EQUILIBRIUM WATER CONTENTS

In drying processes and in the storage of agricultural products, the study of thermodynamic properties is indispensable in the search for solutions to issues of stability and optimization of the conditions of agro-industrial processes. The aim of this work was to determine hygroscopic equilibrium isotherms and study the thermodynamic properties of white bean grains submitted to different equilibrium temperatures and relative humidity levels. Phaseolus vulgaris L. grains were used, with an initial water content of 0.142 (dry basis), temperature variations ranging between 18 and 50 °C, and relative humidity between 19% and 78%. Fifteen mathematical models were tested to determine the hygroscopic equilibrium isotherms, and the Sigma model was the one that best suited the experimental data. The thermodynamic properties of the beans were determined from Sigma-Copace model. The integral isosteric heat of desorption and the differential entropy increased with the reduction of the water content, and the phenomenon of water desorption of white bean grains was a non-spontaneous process controlled by enthalpy.

Effects of Post-Harvest Conditions on Sorption Isotherms of Soybeans

Abstract. This study focuses on the modeling of sorption characteristics of three varieties of soybeans (Akras R2, Lono R2, and Podaga R2). Three pretreatments related to post-harvest conditions were tested on the soybean varieties: (1) freshly harvested soybeans, (2) soybeans subjected to three drying and wetting cycles, and (3) soybeans subjected to three freezing and thawing cycles. The adsorption and desorption experiments were conducted at 5°C, 10°C, 15°C, 20°C, 25°C, and 30°C using a dynamic equilibrium relative humidity (ERH) apparatus. Equilibrium moisture content (EMC) and the corresponding ERH were measured. The parameters calculated for the modified Halsey equation are applicable for storage temperatures above 10°C in the relative humidity (RH) ranges of 10% to 80% for desorption and 30% to 80% for adsorption. No significant differences were found in sorption isotherms among the soybean varieties. However, the soybean varieties responded differently to the different pretreatments (i.e., drying/wetting and freezing/thawing cycles). The adsorption isotherms of Akras and Lono soybeans showed significant differences at 10°C to 30°C when subjected to drying and wetting cycles, while Akras and Podaga soybeans showed significant differences in the same temperature range when subjected to freezing and thawing cycles. The effect of drying and wetting cycles on the desorption isotherms was found only for Akras soybeans at 10°C and 15°C below 63% and 71% RH, respectively, and for Lono soybeans at 25°C and 30°C above 69% RH for both temperatures. In general, the effect of both pretreatments on the sorption isotherms of soybeans was a reduction in EMC of up to 20%, when compared to fresh samples at selected storage temperatures. The findings of this study serve as a primary tool for developing a lookup table for safe storage guidelines for soybeans. Keywords: Equilibrium moisture content, Equilibrium relative humidity, Halsey equation, Oswin equation, Soybeans.

Moisture adsorption isotherms of dried Ficus deltoidea herbal leaves

Ficus deltoidea is a popular traditional medicine that widely used to treat various kind of diseases because of its high number of phenolic contents. In order to meet the demand of the high usage in the market, it is very important to study the behaviour of the dried herbal leaves to prolong the shelf life during storage. Hence, the study of moisture adsorption isotherm is one of the crucial parameters to minimize the deterioration of the quality. The moisture adsorption data of dried Ficus deltoidea leaves were monitored using gravimetric static method. Six different saturated salts such as potassium chloride, sodium chloride, sodium nitrate, magnesium nitrate, magnesium chloride and potassium acetate were utilized in this experiment. The equilibrium relative humidity range was setup between 23 to 86 %. Three different temperatures of 8, 30, 40 °C were used as a treatment of experiment. From the final results, it is clearly claimed that the moisture adsorption isotherm data exhibited J shaped and type III of Brunauer, Emmet and Teller (BET) classification. In addition, the results of experimental data as shown that the best mathematical model fitted to Peleg model compared to GAB and Oswin models.

Effect of Drying Systems on the Parameters and Quality of Dried Basil

The main aim of this study is to investigate the possibility of drying the basil plants under different conditions. Fresh basil was dried using different systems: sun-drying, shadow-drying, room-drying, solar-drying and oven-drying systems. Weight losses, moisture content and oil content were recorded. Drying parameters were studied to determine the equilibrium moisture contents (EMC) using different models. The obtained results indicated that the accumulated weight loss of basil plants increased from 3.57 to 83.76, 2.12 to 70.48, 0.72 to 82.07, 0.44 to 84.34 and 1.29 to 84.90 %, for sun-drying system, shadow-drying system, room-drying system, solar-drying system and oven-drying system, respectively. The moisture content of basil plants decreased from 515.95 to 6.91, 490.18 to 6.59, 479.97 to 4.66, 538.02 to 0.93 and 565.40 to 5.40 % d.b. for sun-drying system, shadow-drying system, room-drying system, solar-drying system and oven-drying system, respectively. The highest value of equilibrium moisture contents were 13.25 and 35.16 % at 10 and 90 % equilibrium relative humidity was found from Modified Chung-Pfost equation under room system. The lowest value of equilibrium moisture contents were 0.91 and 16.58 % at 10 and 90 % equilibrium relative humidity was found for modified Oswin equation for oven system. The basil oil content values were 2.3, 2.5, 2.9, 2.7 and 2.0 % for the sun-drying, shadow-drying, room-drying, solar-drying and oven-drying, respectively.

Understanding water activity change in oil with temperature

Our recent studies and several publications suggest that the low water activity (aw) of oil in thermal processing might be a major contributing factor towards the increased thermal resistance of bacteria in oils. In this study, we developed a reliable method to measure the water activity of oil by measuring the equilibrium relative humidity in a small headspace. Using this method, water activity of peanut oil was found to decrease exponentially with increasing temperature. A model derived from excess Gibbs free energy was fitted to the observations with an R2 = 99.6% and RMSE = 0.01 (aw). Our results suggest that the sharply reduced water activity of oil resulting from a rise in temperature could cause desiccation of bacteria. This is a possible explanation for the protective effect of oil in thermal processing.

Morphology and quantification of fungal growth in residential dust and carpets

Mold growth indoors is associated with negative human health effects, and this growth is limited by moisture availability. Dust deposited in carpet is an important source of human exposure due to potential elevated resuspension compared to hard floors. However, we need an improved understanding of fungal growth in dust and carpet to better estimate human exposure. The goal of this study was to compare fungal growth quantity and morphology in residential carpet under different environmental conditions, including equilibrium relative humidity (ERH) (50%, 85%, 90%, 95%, 100%), carpet fiber material (nylon, olefin, wool) and presence/absence of dust. We analyzed incubated carpet and dust samples from three Ohio homes for total fungal DNA, fungal allergen Alt a 1, and fungal morphology. Dust presence and elevated ERH (≥85%) were the most important variables that increased fungal growth. Elevated ERH increased mean fungal DNA concentration (P < 0.0001), for instance by approximately 1000 times at 100% compared to 50% ERH after two weeks. Microscopy also revealed more fungal growth at higher ERH. Fungal concentrations were up to 100 times higher in samples containing house dust compared to no dust. For fiber type, olefin had the least total fungal growth, and nylon had the most total fungi and A. alternata growth in unaltered dust. Increased ERH conditions were associated with increased Alt a 1 allergen concentration. The results of this study demonstrate that ERH, presence/absence of house dust, and carpet fiber type influence fungal growth and allergen production in residential carpet, which has implications for human exposure.

Moisture migration analysis of Chinese naked oat during different storage conditions by sorption isotherm model and low‐field NMR

Moisture migration is considered to be one of the most important influencer on crop quality during storage, which is easily affected by storage conditions, such as ambient humidity and temperature. The aim of this work was to determine the effect of storage condition on moisture content of Chinese naked oat by simulating 9 equilibrium relative humidity (ERH) and 5 temperatures. The equilibrium moisture content (EMC) of dry sample was achieved by adsorption, while EMC of wet one was achieved by desorption. EMC of oat increased with the increase in ERH and decreased when temperature increased. The sorption isotherm was a typical “S” shape and fitted using current EMC/ERH models. Modified Chung–Pfost (MCPE) model was the most suitable for describing the dynamic sorption process of Chinese naked oat during storage with a ERH range from 10% to 90%. There was an obvious hysteresis between adsorption and desorption isotherms, whose range decreased with the increase of temperature. High temperature accelerated moisture migration by increasing the hydrophilicity of oat surface. Moreover, dynamic moisture migration was imaged by low‐field nuclear magnetic resonance (NMR), showing that moisture migrated between ambient environment and oat mainly through endosperm where most moisture accumulated. During sorption, free water migrated firstly, followed by bound water and the change in content of bound water was more stable than that of free water. The results of this study can provide a useful information for future work on quality control of oat during storage.

Conservation seed physiology of the ciénega endemic, Eryngium sparganophyllum (Apiaceae).

Knowledge of seed dormancy and optimal propagation techniques is crucial for successful ex situ restoration and reintroduction projects, and determining the seed storage behaviour of a species is critical for the long-term conservation of seeds, further supporting future ex situ efforts. Eryngium sparganophyllum (Apiaceae) is a globally critically endangered plant species endemic to ciénega wetlands of southwest North America. To support in situ and ex situ conservation efforts of E. sparganophyllum, we asked (i) how does the embryo: seed (E:S) ratio change over time once imbibed, (ii) how does germination respond with varying periods of exposure to cold (5°C) and warm (25°C) stratification, and concentrations of gibberellic acid (GA3). By answering these questions, (iii) can dormancy class be inferred, and (iv) what storage behaviour category is exhibited? To answer these questions, we collected seeds in Southern Arizona from one of the few remaining wild populations. We measured embryo growth and tested the effects of cold (0–18 weeks) and warm (0 and 4 weeks) stratification, and 0–1000 ppm gibberellic acid on germination. We also tested the effects of cold (−80°C) dry (~20% equilibrium relative humidity) storage on germination. We found that (i) embryos grow inside seeds prior to germination; (ii) compared to control, cold stratification for at least 6 weeks increased germination and warm stratification had no effect; (iii) 1000-ppm GA3 had the highest germination success; (iv) therefore this species exhibits morphophysiological dormancy; and (v) seeds are orthodox and can therefore be conserved using conventional storage methods. This information will aid managers in the propagation of E. sparganophyllum that is crucial for in situ reintroduction and restoration projects, and seed banking represents a critical ex situ conservation strategy for the preservation of this species.

Determination of Moisture Sorption Isotherms of Rice and Husk Flour Composites

HighlightsMoisture sorption isotherms of rice and husk flour composites were determined.Adsorption isotherms were best modeled by the Chung-Pfost and Oswin equations.Desorption isotherms were best modeled by the Polynomial and Chung-Pfost equations.The Modified Oswin model was the best for both adsorption and desorption.Abstract. Empirical models describing isotherms specifically for adsorption and desorption have not been described for rough rice and husk flour composites. Such models are vital for process control and monitoring operations which use rice husk and rice flours or their mixtures for food or material processing. The current study was undertaken to determine the moisture sorption isotherms of rice husk flour, rough rice flour and their mixtures subjected to different temperature levels. Effects of rice husk flour to rough rice flour ratio of 0:1 (0.0%), 1:49 (2.0%), 1:16 (5.9%), and 1:0 g/g (100.0%) on rough rice moisture isotherms at temperature levels of 20°C, 40°C, and 60°C were investigated. The dynamic dewpoint isotherm technique (DDI) was used to generate accurate isotherms. Several empirical models were tested to fit the experimental EMC data. All the isotherms showed typical sigmoidal type 2 shapes. The equilibrium moisture content (EMC) over equilibrium relative humidity (water activity) ranging from 10% to 95% showed temperature dependence. Hysteresis was evident for all samples, with a decreasing level at a higher temperature. Rice husk flour to rough rice flour ratio, as a factor, showed a significant effect on the EMC of rough rice. The EMC decreased with an increase in rice husk flour levels. Chung-Pfost and Oswin were the two best models for describing adsorption isotherm, and Polynomial and Chung-Pfost were the best models for fitting the desorption isotherm. Modified Oswin model was the best model amongst the two-variable models for describing both adsorption and desorption isotherms. Keywords: Empirical models, Equilibrium moisture content, Rice husk flour, Rough rice flour, Sorption isotherms.

К вопросу оценки факторов сохранности пряников с фруктовой начинкой

The ratio of ‘bound’ and ‘free’ water plays an important role in the studies of staling of various baked confectionery products. Gingerbread with fruit filling is a traditional flour confectionery product with intermediate moisture, which causes transfer processes during storage. Temperature, relative humidity, light exposure, mechanical stress, and pressure affect the staling speed of such confectionery products. The shelf life of raw gingerbread was increased from 10–20 days to more than two months, which caused microbiological deterioration during storage. Moisture transfer between the filling and the crumb increases water activity&#x0D; and ruins the capillary structure of gingerbread during storage, thus significantly increasing the risk of microbiological damage. The present research featured the changes in the mass fraction of moisture and water activity of individual parts of raw gingerbread with fruit filling during storage at different temperatures and relative air humidity. The samples were packed in a 40-micron polypropylene film. During storage, the mass fraction of moisture and water activity may change in various parts of the product, which can lead to their molding. In this case, starch degradation processes led to the destruction of the structure and a decrease in the content of mechanically-bound moisture, as well as to the release of ‘free’ water and an increase in water activity. As a result, the risk of molding increased significantly. The water activity increased from 0.71 to 0.79 on the sample surface after six weeks of storage at 30°C and a 40% of equilibrium relative humidity. A set of experiments in microbiological indicators revealed no signs of molding in the freshly prepared samples. After one month of storage, the amount of mold reached 10 CFU/g. The quantity of mesophilic aerobic and facultative anaerobic microorganisms in different parts of the crumb increased from 3×10 to 9×102 CFU/g and in the filling – from 1×10 to 2.3×103 CFU/g. After two months of storage, the amount of mold reached more than 103 COE/g, which greatly exceeds safety norms. As the relative air humidity increased from 30% to 40%, the moisture transfer rate between the products and the environment was reduced by half. As a result, the shelf life decreased by 1–2 weeks. The research also studied the patterns of moisture transfer processes in summer and winter conditions. The research results contribute to the development of technology and shelf life forecasting for complex flour confectionery products with intermediate moisture.

Dormancy and endosperm presence influence the ex situ conservation potential in central European calcareous grassland plants.

The preservation of plant species under ex situ conditions in seed banks strongly depends on seed longevity. However, detailed knowledge on this seed ecological aspect is limited and comparative studies from central European habitats are scarce. Therefore, we investigated the seed longevity of 39 calcareous grassland species in order to assess the prospects of ex situ storage of seeds originating from a single, strongly threatened habitat. Seed longevity (p50) was determined by artificially ageing the seeds under rapid ageing conditions (45 °C and 60 % eRH (equilibrium relative humidity)), testing for germination and calculating survival curves. We consulted seed and germination traits that are expected to be related to seed longevity. P50 values strongly varied within calcareous grassland species. The p50 values ranged between 3.4 and 282.2 days. We discovered significantly positive effects of physical dormancy and endosperm absence on p50. Physiological dormancy was associated to comparatively short longevity. These relationships remained significant when accounting for phylogenetic effects. Seed mass, seed shape, and seed coat thickness were not associated with longevity. We therefore recommend more frequent viability assessments of stored endospermic, non-physically and physiologically dormant seeds.

Effect of selected pretreatments prior to drying on physical quality attributes of dried mango chips.

This study investigated the effect of pretreatments namely citric acid, lemon juice and blanching on the physical attributes of dried chips from two popular commercial mango varieties grown in Kenya viz 'Apple' and 'Ngowe'. The pretreated mango chips were either subjected to a convective dryer or solar drying. Moisture content, extent of dryness, rehydration characteristics, water activity and color retention were determined to establish the effect of the pretreatments before drying on physical quality attributes of dried mango chips. Moisture content, water activity and color were determined using standard procedures. Equilibrium relative humidity was estimated using Drycard™. Results obtained indicated that optimal drying was achieved with dryer temperatures of 50°C and 65°C for 10 and 7h respectively that reduced moisture content to ~ 11% and water activity to below 0.65 (sufficient for inhibited spoilage). The best color parameters and rehydration characteristics were observed with 1% citric acid and 0.5v/v lemon acid pretreated samples. Blanched as well as control (untreated) samples showed relatively poor color retention in relation to flesh mango chips and had the least rehydration ratio (1.65 ± 0.01) and coefficient of rehydration (0.33 ± 0.1). As pretreatments before drying affect physical parameters of dried mango chips, the best choice of pretreatments should be made to produce high quality end products. Citric acid and lemon juice pretreatments before drying at 50°C and 65°C had the optimal outcome and produced the best physical quality parameters.