Effect of temperature and relative humidity on yellowing rate of paddy

The effects of temperature and relative humidity (or water activity) in storage chambers on yellowing rate of paddy were investigated and then an empirical equation for predicting the yellowing rate was developed. Paddy was conditioned using saturated salt solutions at relative humidities ranging from 0.80 to 0.95 and temperatures of 35, 45, 55, 60 and 65°C. The yellowing rate was found to follow the zero order kinetics. The yellowing constant value (k) increased exponentially with temperature and increased linearly with water activity. The magnitude of apparent activation energy varied from 130–145 kJ/mol. A predictive equation for determining yellowing rate was ln k=−δa_w−/T+(γa_w)/T where a_w was water activity (valid from 0.80 to 0.95), T was absolute temperature (valid from 308 to 338 K) and , δ, and γ were constants. The results of variance analysis showed that temperature, water activity and their interaction significantly influenced the yellowing rate of paddy.     

Modeling of the effect of relative humidity and temperature on proving rate of rice-flour-based dough

Proving is one of the key processes in bread making, where dough normally rests and grows under an environment of constant temperature and humidity. To better understand the effect of relative humidity (RH) and temperature on the kinetics of dough expansion during proving and be able to optimize the growth rate, rice-flour-based dough of same formulation was proved under various process conditions. Both RH and temperature showed significant effect on the dough expansion rate during proving. To describe the dough expansion, a first-order, non-Arrhenius kinetic model was developed. The influence of RH and temperature on the kinetic rate was described by an empirical model. Through verification, the model performance was proved to be reasonably good. The model was subsequently used to optimize the proving condition to maximize the kinetic rate constant therefore minimizing the proving time. The fastest proving condition for the rice-flour-based dough in this research was at 90% RH and 46.3 °C. According to the model, the kinetic rate constant under the optimal condition was estimated to be at 0.217 min⁻¹. From an initial height of 5 mm, the dough height could be increased to 11 mm within 6.4 min.     

温度和湿度对龙井绿茶和工夫红茶贮藏品质的影响

为探究环境湿度和温度对茶叶贮藏品质的影响,以龙井绿茶和工夫红茶为研究对象,通过将其贮藏于室温及4℃的高湿区(RH 65%)、中湿区(RH 45%)、干区(RH 25%)共6种贮藏环境中3个月后,分析茶叶的品质变化规律。结果表明,整体上环境湿度越低,茶叶生化成分含量及干茶色泽品质就会越高,其中中湿区部分生化成分含量已显著高于高湿区(P<0.05),且与干区无显著差异(P>0.05);相同湿度环境下,对于龙井绿茶,4℃更有利于其生化成分含量和干茶色泽品质的保持,对于工夫红茶,则4℃和室温均可;龙井绿茶和工夫红茶的感官品质分别在4℃和室温的中湿区最优。综上,4℃中湿区和室温中湿区可分别作为绿茶和红茶短期贮藏环境。同时逐步回归结果表明氨基酸、V_C、a值及茶黄素可分别作为表征其短期贮藏品质的主要指标。该研究为茶叶贮藏保鲜提供了理论参考。     

Colonization of tomatoes by Salmonella montevideo is affected by relative humidity and storage temperature

The influences of the relative humidity (RH) and storage temperature on the colonization of tomato surfaces by Salmonella Montevideo were studied. Red, ripe tomatoes (Lycopersicon esculentum) were spot inoculated in three separate trials with 100 pl (approximately 10(6) CFU) of Salmonella Montevideo and stored for 90 min at 22 degrees C under 97% RH to facilitate attachment of cells to the blossom end of tomato surfaces. Following this attachment step, tomatoes were washed to remove loosely adhered cells and then stored at 22 or 30 degrees C for up to 10 days under RH of 60, 75, 85, or 97%. At 0, 0.4, 1, 4, 7, and 10 days of storage, three tomatoes were individually hand massaged in 50 ml of 0.1% peptone water and the washes were separately analyzed to enumerate populations of Salmonella Montevideo. The number of Salmonella Montevideo cells attached after 90 min at 22 degrees C was 3.8 log CFU per tomato; this level was determined to be the initial colonizing population. After 10 days of storage at 30 degrees C, the Salmonella Montevideo population increased to 0.7, 1.0, 1.2, and 2.2 log CFU per tomato at 60, 75, 85, and 97% RH, respectively. A similar trend was observed at 22 degrees C, although populations were lower than at 30 degrees C. Scanning electron micrographs of tomato cuticles after storage revealed a well-defined biofilm containing bacteria. These findings reinforce the importance of maintaining stored tomatoes at temperatures that do not support growth of pathogenic bacteria and demonstrate the growth-promoting effects of high humidity.     

不同储藏温湿度对玉米中蛋白质的影响

以\     

蓝莓贮藏适宜温湿度条件研究

以蓝莓为试材,研究其贮藏适宜温湿度条件,分析蓝莓冰点与可溶性固形物含量的相关性,并探讨适宜温湿度条件下的耐贮性。研究发现,公爵、蓝丰、布里吉塔、埃利奥特、杰兔五个品种的果实冰点范围无显著差异,即-4.2^-0.4℃,而相对湿度由85%⁹5%每下降10%,日失重率增加0.2%⁰.5%,得出贮藏适宜温湿度为0⁰.5℃、85%⁹5%;不同品种冰点与可溶性固形物含量呈极显著（p<0.01）负相关,Pearson系数为0.552。蓝莓贮藏于0⁰.5℃、85%⁹5%条件下冷藏期可达30⁴0 d,贮藏后于10℃暂存7 d和25℃货架2 d好果率均控制在90%。      

Paddy rice stored under hermetic conditions: The effect of relative humidity,temperature and storage time in suppressing Sitophilus zeamais and impact on rice quality

The aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality.Hermetic bags, GrainPro^® SuperGrainbag^® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 °C, 17 °C and 24 °C, both monitored by Hobo^® Data loggers, with the probe placed inside the bags. CheckpointII Portable O₂ and CO₂ Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (a_w). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer.The results showed that the response of the stored-product insects changes with environmental conditions, O₂ and CO₂ contents. Other parameters were considered; a_w increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O₂ and high CO₂ contents, at different average temperatures, 14 °C and 17 °C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 °C, S. zeamais attained 100% mortality before producing progeny.The increase on respiration rate, registered by CO₂ increase and O₂ decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice.The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes.     

温度与湿度对沙糖桔储藏品质的影响

研究了温度和湿度对沙糖桔贮藏过程中的失重率、可溶性固形物含量、维生素C含量、可滴定酸含量、呼吸速率和感官品质的影响。实验得出在温度7℃和10℃,湿度85%和90%的贮藏条件下,沙糖桔的失重率、可溶性固形物含量、维生素C含量和可滴定酸含量的变化速度较缓慢,储藏10d后,呼吸速率显著下降并维持在较低水平,实验结束时,沙糖桔的外观、色泽和风味仍然接近新鲜状态。     

Effects of temperature,solid content and pH on the stability of black carrot anthocyanins

Anthocyanin stability of black carrots was studied at various solid contents (11, 30, 45 and 64° Brix) and pHs (4.3 and 6.0) during both heating, at 70–90 °C, and storage at 4–37 °C. Monomeric anthocyanin degradation fitted a first-order reaction model. Degradation of monomeric anthocyanins increased with increasing solid content during heating, while it decreased during storage. For example, at pH 4.3, half-life periods for anthocyanins at 30, 45 and 64° Brix were, respectively, 8.4, 6.9 and 5.2 h during heating at 80 °C and 18.7, 30.8 and 35.9 weeks during storage at 20 °C. At 30–64° Brix, increasing pH from 4.3 to 6.0 enhanced the degradation of anthocyanins during heating. The effect of pH on thermal stability of anthocyanins was also studied at six different pHs (2.5–7.0) in citrate-phosphate buffer solutions and significant decrease in anthocyanin stability was observed at pHs above 5.0. Higher activation energies (E_a) were obtained during heating than during storage with increasing solid contents. At 30–64° Brix, E_a values ranged from 68.8 to 95.1 kJ mol⁻¹ during heating and from 62.1 to 86.2 kJ mol⁻¹ during storage. Q₁₀ values at 20–37 °C were as high as 3.1 at 45° Brix and 3.6 at 64° Brix.     

Modelling the effect of different sterilisation treatments on antioxidant activity and colour of carrot slices during storage

The effect of F₀ treatment time (min) and storage on the antioxidant activity and Hunter colour parameters (L*, a*, b*) of carrot slices was investigated. Carrot slices were sterilised for 0 (control), 3, 15 and 50 min and subsequently stored for 0, 3 and 6 months. Significant differences were observed in colour values of carrot slices with no significant difference beyond F₀ treatment of 3 min. Regression modelling was used to investigate the main effects of treatment time and storage. Treatment time and storage period was found to be significant. Predicted models were found to be significant (p < 0.05) with low standard error and high coefficients of determination (R²). This study proposes the predicted models for quality parameters of sterilised carrot slices.     

醒发温湿度对馒头感官评定影响

选择对馒头醒发起关键作用两个关健因素:温度和相对湿度,以感官评分作为指标,找出较佳醒发温度和醒发相对湿度;结果表明,馒头醒发时最佳条件为:醒发温度40℃,醒发相对湿度85%。     

Some influences of storage fungi, temperatures and relative humidity on the germinability of grass seeds

Seeds of Poa pratensis, Festuca rubra, F. arundinacea, and Lolium multiflorum were stored at 10, 20, 30, or 35°C, and at 35, 55, 75, or 95 per cent r.h. for up to 12 months. Samples stored at 30°C and 95 per cent r.h. and 35°C and 75 or 95 per cent r.h. decreased in germinability after 2 months of storage. At 20°C and either 75 or 95 per cent r.h., seeds decreased more slowly in germinative ability than at the higher temperatures but this decrease was appreciable. Seeds stored at 10°C and at 35, 55, 75, or 95 per cent r.h. germinated well after 12 months.

Equilibrium moisture content of the seeds after storage at 35 to 75 per cent r.h. for 2, 4, and 8 months varied little among the four species at each relative humidity level and was not affected by temperature in the range of 10–35°C.

Fungi of the Aspergillus glaucus group could not always be isolated from large numbers of seeds in lots that had declined in germinability. Seeds of all four grasses apparently carried superficially-borne species of the A. glaucus group (primarily A. amstelodami) in a ‘dormant’ state at harvest. Members of this group were isolated from substantial numbers of seeds that had been stored for 3 months at 30°C and 75 per cent r.h. These fungi were not isolated from seeds stored for the same length of time at 30°C and 35 per cent r.h.; however, field fungi grew from many of these seeds.     

Effect of inoculum size, relative humidity, storage temperature, and ripening stage on the attachment of Salmonella Montevideo to tomatoes and tomatillos

The influence of inoculum populations and environmental factors on attachment of Salmonella Montevideo to the surface of tomatoes and tomatillos was evaluated. To study the effect of inoculum size, red, ripe tomatoes were spot-inoculated with bacterial suspensions (10(5) and 10(8) CFU/fruit) and stored at 22 degrees C under 100% relative humidity. The effects of temperature (12, 22, and 30 degrees C) and relative humidity (75, 85, and 97%) on attachment of the pathogen (10(7) CFU/fruit) to tomatoes (red and green) and ripe tomatillos were also evaluated. Inoculated fruits were stored for 90 min at all combinations of temperature and relative humidity, and after rinsing with water, the number of cells attached to the surface was determined. Salmonella Montevideo attached to the surface of tomatoes within 90 min. A direct correlation between the number of attached cells and the population in the inoculum was observed. The percentage of cells that attached immediately after inoculation was approximately 0.3% for the three test products. After storage for 90 min at various temperature and relative humidity conditions, the number of adhering cells ranged from 4.0 to 5.4 log CFU/fruit (1.2% of inoculum). Both the type of product and the temperature/relative humidity combination had a significant (P < 0.05) effect on attachment of Salmonella Montevideo to the surfaces of tomatoes and tomatillos. Scanning electron micrographs of the cuticles of inoculated washed tomatoes and tomatillos revealed typical skin cell patterns, and only a few randomly dispersed Salmonella Montevideo were observed. Deposition of Salmonella Montevideo on the surface of tomatoes and tomatillos could result in attachment and subsequent colonization under suitable conditions.     

Effect of relative humidity and storage time on the bioactive compounds and functional properties of grapefruit powder

The modified state diagram of freeze-dried grapefruit powder was obtained in order to determine the critical water content and critical water activity that cause the glass transition of the amorphous matrix at storage temperature. At 20 °C these values were in the ranges of 0.031–0.057 g water/g product and 0.089–0.210, respectively. Below those critical values, the glassy state of the amorphous matrix is guaranteed, thus avoiding an increase in the rate of the deteriorative reactions related to the loss of the bioactive compounds in the fruit (organic acids, vitamin C, main flavonoids, and total phenols) which contribute to the antioxidant capacity (AAO) of grapefruit. In the rubbery state, a certain time is needed for these degradative reactions to start. This time depends on the water content of the sample, the greater the water content the lower the time needed. In this study, the powder was stable for a relatively long storage time (3 months) regardless the relative humidity, due to the limited mobility of the molecular system. Between 3 and 6 months had to pass before a significant loss of bioactive compounds was observed; the higher the relative humidity, the greater the loss.     

The influence of air temperature and relative humidity on milling performance and flour properties

Three wheats, one Canadian and two from the UK, were used to investigate the effect of ambient temperature and relative humidity (r.h.) on milling performance and flour properties. When the temperature was varied from 25 to 15°C, a decrease in ambient temperature was accompanied by an increase in extraction rate but no change in flour moisture content. When the r.h. was varied from 70 to 50%, a decrease in r.h. was accompanied by an increase in extraction rate and a decrease in flour moisture content. Changes in r.h. had a greater influence on milling performance and flour properties than did changes in ambient temperature.