Effect of relative humidity and chlorophenol content on the fungal conversion of chlorophenols to chloroanisoles in fibreboard cartons containing dried fruit

The effect of relative humidity and chlorophenol content on the fungal conversion of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol to the corresponding chloroanisoles in fibreboard cartons was studied under temperature and humidity conditions similar to those that could occur in shipping containers during the transportation of packaged dried fruit. The conversion was studied in cartons manufactured from virgin Kraft fibreboard (total chlorophenol content 66 μg kg^?1) and fibreboard prepared from recycled waste paper (total chlorophenol content 1375 μg kg^?1). Positive correlations were established between both storage humidity and fungal population with chloroanisole production in the fibreboard. The concentration of the chloroanisoles in the packaged fruit increased with increasing relative humidity. The roles of relative humidity and chlorophenol content in fibreboard are discussed with respect to the development of chloroanisole-induced mustiness in packaged dried fruit.     

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.     

环境湿度对明胶—普鲁兰多糖可食性膜性能的影响

明胶-普鲁兰多糖膜是一种可以快速溶解于热水的可食性包装材料,研究环境湿度对明胶-普鲁兰多糖膜机械性能、氧气透过率、水蒸气透过率、油脂透过率、颜色以及水溶性的影响,并比较环境湿度对明胶膜、明胶-普鲁兰多糖膜和普鲁兰多糖膜性能的影响。结果显示,较高的环境湿度(80%)会降低明胶-普鲁兰多糖膜的抗拉强度,提高其柔韧性,而对其阻氧性、阻油性和透明度没有显著的影响;明胶-普鲁兰多糖膜的各方面性能优于明胶膜和普鲁兰多糖膜。     

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%。     

Textural attributes of commercial biscuits. Effect of relative humidity on their quality

Two commercial biscuits of semi‐sweet type, ‘Marie’ and ‘Petit Beurre’ were used for investigating: (i) their texture variability as a function of the location and the side of puncturing and (ii) the influence of storage under different relative humidity on their texture, porosity and colour. Significant texture differences were found as a function of the location of puncturing (centre or periphery of biscuit area), as well as between the upper and the opposite side of a biscuit. At small relative humidity changes (11–32%) a distinct relationship between texture and moisture content was not noticed. In ‘Petit Beurre’ at a_w 0.32 a peak was observed in the puncture force values. In both biscuits porosity increased with their moisture content, accompanied by an area expansion. Significant differences in colour were mainly noticed between the upper and opposite side of the biscuits. Colour was less influenced by relative humidity changes.     

相对湿度对大豆调和油氧化酸败的影响

研究相对湿度(RH)对大豆调和油(BSO)氧化酸败的影响。采用自组装氧化装置,在温度50℃、大气氧分压21 kPa、初始顶空率50%和室内光照强度(840 lx)的条件下,通过磷酸氢二钾溶液分别控制RH为50%、60%、70%、80%和90%,氧化BSO试样,测定不同氧化时间(t)时BSO的过氧化值(POV)和酸价(AV),由POV-t和AV-t回归曲线分析RH对BSO氧化酸败的影响。结果表明:BSO氧化酸败符合零级反应动力学特征,POV与AV随RH的增大和t的延长而升高;反应速率常数(k)随RH增大而增大。RH越大,氧化酸败速率越快,二者遵循二项式关系k_(POV)=-1E-05 RH~2+0. 002 4 RH-0. 049 6和k_(AV)=2E-07 RH~2-2E-05 RH+0. 000 5。因此,在生产、贮存、运输和消费过程中,应尽量降低BSO的贮存环境湿度,以减缓BSO的氧化酸败速率。     

不同湿度条件对肉鸡浓缩料中霉菌污染的影响

研究了室温条件下不同湿度(RH)贮存饲料的霉菌污染情况,在湿度条件分别为65%RH、75%RH、85%RH,利用国标检测法进行霉菌总数、产毒菌种类及毒素含量分析。结果表明,在20℃、65%RH条件下,饲料存放到第17天前就应该采取防霉措施。在75%RH条件下,存放到第10天前就应该采取防霉措施。在85%RH条件下,在生产饲料的时候就应该采取防霉措施。     

Physical,chemical and oxidative changes in raw peanuts: Effect of relative humidity

Peanuts are susceptible to oxidative deterioration due to various factors during storage. This research studied the proximate composition (lipid, protein, total sugar, moisture and ash.), composition and content of amino acids and fatty acids, peroxide value (PV), carbonyl value (CV), malondialdehyde content (MDA), protein composition and structure changes in the peanuts stored for 320 days under different relative humidity (RH; 50%, 65% and 80%) conditions. Lipid oxidation was delayed at low RH (50% and 65%) storage conditions. At high RH (80%), the contents of unsaturated fatty acids, amino acids, protein and lipids decreased significantly during storage (P < 0.05), whereas the PV, CV and MDA contents increased significantly (P < 0.05). The CV values of YH-9326 and YH-22 increased by 14.46 and 17.48 times respectively. In addition, the protein structure changed throughout the whole storage period (P < 0.05). This research provides a theoretical reference for maintaining storage quality and extending shelf life.     

通风过程中进风相对湿度对仓储粮堆温度和水分的影响研究

温度和水分含量是两个重要的物理变量,在研究谷物储存时品质变化起到很大作用。通风用于冷却粮堆并保持温度恒定,以防止水分迁移。良好的通风条件对粮仓内存储安全有显著影响。目前,通风空气相对湿度对粮堆水分影响的研究相对较少。采用数值模拟和实验研究相结合的方式,探索和比较因不同进风相对湿度而引起的通风过程中仓储的小麦温度和水分变化规律。结果表明:进风相对湿度较低时冷却干燥效率更高,小麦粮堆降温更快速,并将昆虫和霉菌的活动保持在较低水平。     

Effect of relative humidity and temperature on absorption kinetics of two types of oxygen scavengers for packaged food

To investigate the effect of temperature and relative humidity (RH) on the absorption kinetics of self‐activated and moisture‐activated O₂ scavengers for packaged food, kinetic parameters of each O₂ scavenger were evaluated at 43%, 75% or 100% RH and at 10, 25 and 40 °C respectively. Absorption kinetics was well described by a first‐order reaction with an Arrhenius type behaviour. For moisture‐activated O₂ scavengers, a proper high RH was needed to ensure a high O₂ absorption capacity, as average O₂ absorption capacity was 3.82 mL at 43% RH and 43.40 mL at 75% RH. When the temperature increased, O₂ absorption rate constant ascended from 10 °C to 40 °C on an average of 0.153 and 0.306 h^?1 in moisture‐activated and self‐activated O₂ scavengers respectively. We could take the effect of temperature and RH into account when we chose different types of iron‐based O₂ scavengers for packaged food.     

Physicochemical and sensory evolutions of the lactic goat cheese Picodon in relation to temperature and relative humidity used throughout ripening

To produce a wide variety of cheeses, it is necessary to control the ripening process. To do that, artisanal goat cheeses were ripened to evaluate the effects of temperature (10 and 14°C) and relative humidity (RH; 88 and 98%) on (1) 16 physicochemical characteristics throughout ripening and (2) 19 sensory characteristics at the end of ripening (d 12). Whatever the ripening time, the physicochemical characteristics were strongly dependent on the daily productions, which affected the sensory perception of the cheeses. Both physicochemical and sensory characteristics were strongly reliant on RH, whereas only a few of the characteristics were influenced by temperature changes. On d 12, whatever the ripening temperature, an RH increase from 88% to 98% modified many cheese characteristics (core pH, lactate consumption, underrind thickening, dry matter content, and hardness). As a result of these physicochemical properties, changes in perception were observed: the cheeses ripened under 88% RH were dry and hard compared with those ripened under 98% RH. An RH of 98% led to an acceleration of the ripening process, inducing a slightly ammonia and milky flavor and a sticky and creamy texture in the mouth. However, cheeses ripened under 14°C and 98% RH were also indicative of overripened cheeses: a temperature of 14°C induced an acceleration of the ripening process due to physicochemical modifications compared with a temperature of 10°C. Nevertheless, when the cheeses on d 0 were still very humid and soft, those ripened under 98% RH collapsed and were overripened with a liquid underrind. This study provides a means for achieving a better and more rational control of the ripening process in artisanal lactic goat cheeses.     

Effect of relative humidity and light conditions on the oxidative stability of sunflower oil blends stabilised with synthetic and natural antioxidants

The effect of relative humidity (RH) and light conditions on the oxidative stability of sunflower oil (SO) stabilised with oleoresin rosemary + ascorbyl palmitate (SOR), sage + ascorbyl palmitate (SOS) and tertiary butyl hydroquinone (SOT) was investigated. The SO without additive (SOC) served as positive control. Oil samples were subjected to 3 RH (29%, 52% and 75%) and two light conditions (dark, D and fluorescent light (600 lx), L) at 60 °C for 7 days. The oxidative stability was monitored by peroxide value (PV), conjugated diene value (CDV), free fatty acids (FFAs) and Rancimat induction period (IP). A direct relationship was noted between RH and increase in PV, CDV and FFA levels irrespective of light conditions. The detrimental effect of light on the oxidative stability was prominently noted at higher RH (75%) which followed an order: SOC > SOT > SOR > SOS. The samples stored under lower RH (29% and 52%), and dark conditions were better stabilised than light‐exposed counterparts.     

Effects of increasing air temperature on physiological and productive responses of dairy cows at different relative humidity and air velocity levels

This study determined the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on the physiological and productive responses of dairy cows. Twenty Holstein dairy cows were housed inside climate-controlled respiration chambers, in which the climate was programmed to follow a daily pattern of lower night and higher day T with a 9°C difference, excluding effects from sun radiation. Within our 8-d data collection period, T was gradually increased from 7 to 21°C during the night (12 h) and 16 to 30°C during the day (12 h), with an incremental change of 2°C per day for both nighttime and daytime T. During each research period, RH and AV were kept constant at 1 of 5 treatment levels. A diurnal pattern for RH was created, with lower levels during the day and higher levels during the night: low (RH_l: 30–50%), medium (RH_m: 45–70%), and high (RH_h: 60–90%). The effects of AV were studied during the day at 3 levels: no fan (AV_l: 0.1 m/s), fan at medium speed (AV_m: 1.0 m/s), and fan at high speed (AV_h: 1.5 m/s). Effects of short and long exposure time to increasing T were evaluated by collecting data 2 times a day: in the morning [short: 1 h (or less) ? exposure time] and afternoon (long: 8 h ? exposure time). The animals had free access to feed and water and both were ad libitum. Respiration rate (RR), rectal temperature (RT), skin temperature (ST), dry matter intake, water intake, milk yield, and composition were measured. The inflection point temperatures (IPt) at which a certain variable started to change were determined for the different RH and AV levels and different exposure times. Results showed that IPt under long exposure time for RR (first indicator) varied between 18.9 and 25.5°C but was between 20.1 and 25.9°C for RT (a delayed indicator). The IPt for both RR and RT decreased with higher RH levels, whereas IPt increased with higher AV for RR but gave a minor change for RT. The ST was positively correlated with ambient T and ST was not affected by RH but significantly affected by AV. For RR, all IPt was lower under long exposure time than under short exposure time. The combination of higher RH levels and low AV level negatively affected dry matter intake. Water intake increased under all treatments except RH_l-AV_l. Treatment RH_h-AV_l negatively affected milk protein and fat yield, whereas treatments RH_m-AV_m and RH_m-AV_h reduced milk fat yield. We concluded that RH and AV significantly affected the responses of RR, RT, ST, and productive performance of high-producing Holstein cows. These responses already occurred at moderate ambient T of 19 to 26°C.     

激素对蝉拟青霉深层液体发酵生长代谢的调控作用

以生物量、腺苷产量、胞内多糖产量和虫草素产量为指标,考察不同添加量的细胞分裂素6- 苄氨基嘌呤(6-BA)和保幼激素Ⅲ对蝉拟青霉深层液体发酵的调控作用。各实验组在整个发酵过程中的生长代谢节奏与对照组有一定的差异性,两种激素均具有提高蝉拟青霉生物量的作用,其中6-BA 添加量为4mg/L 时比对照组提前12h 到达生物量最大值,并且其最大生物量较对照组最大生物量提高了28.96%。两种激素均可调节蝉拟青霉菌丝体中活性物质的代谢节奏,低剂量6-BA 可显著提高胞内多糖产量(P ＜ 0.05);而保幼激素Ⅲ中、高两剂量组则在培养36h以后表现出了明显抑制多糖合成的作用(P＜0.05)。虫草素和腺苷产量分析结果也表明激素可改变两种活性物质的代谢节奏。     

Short communication: Little change takes place in Camembert-type cheese water activities throughout ripening in terms of relative humidity and salt

Water activity (a_w) affects the growth and activity of ripening microorganisms. Moreover, it is generally accepted that a_w depends on relative humidity (RH) and salt content; these 3 variables were usually measured on a given day in a cheese without the microorganism layer and without accounting for a distinction between the rind, the underrind, and the core. However, a_w dynamics have never been thoroughly studied throughout cheese ripening. Experimental Camembert cheeses were ripened under controlled and aseptic conditions (temperature, gaseous atmosphere, and RH) for 14 d. In this study, only RH was varied. Samples were taken from the cheese (microorganism layer)–air interface, the rind, and the core. The a_w of the cheese–air interface did not change over ripening when RH varied between 91 and 92% or between 97 and 98%. However, on d 5, we observed a small but significant increase in a_w, which coincided with the beginning of growth of Penicillium camemberti mycelia. After d 3, no significant differences were found between the a_w of the cheese–air interface, the rind, and the core. From d 0 to 3, cheese rind a_w increased from 0.94 to 0.97, which was probably due to the diffusion of salt from the rind to the core: NaCl content in the rind decreased from 3.7 to 1.6% and NaCl content in the core increased from 0.0 to 1.6%. Nevertheless, a_w did not significantly vary in the core, raising questions about the real effect of salt on a_w.     

Effect of grape seed extract on physicochemical properties of ground, salted, chicken thigh meat during refrigerated storage at different relative humidity levels

ABSTRACT:  The effect of grape seed extract (GSE, 0.1%) ± NaCl (1%) in ground chicken thigh meat during refrigerated storage at 59%, 76%, 88%, and 99% relative humidity (RH) was examined. Compared to the untreated control, GSE (0.1%) delayed the reduction of water activity (a_w) that occurred during refrigerated storage at different relative humidity levels but had no effect on moisture content or pH compared to the untreated control. GSE inhibited the formation of a secondary marker of lipid oxidation (TBARS) compared to the untreated control and altered the effect of NaCl on TBARS formation. The formation of TBARS was affected by RH level across all treatment groups in the order of 99% > 88% > 76% > 59%. Further analysis revealed that this effect likely is due to the presence of NaCl, which suggests that RH storage does not affect the formation of TBARS except in salted patties, the effect of which is mitigated by the addition of GSE. NaCl, but not GSE, increased both sarcoplasmic and myofibrillar protein solubility after 12 d of refrigerated storage, suggesting increased protein denaturation. This study shows that GSE is an effective antioxidant in ground chicken thigh meat that does not affect moisture content or pH during storage, inhibits TBARS formation, helps to mitigate the prooxidative effects of NaCl, and may alter the effect of NaCl on protein solubility in salted chicken patties. Future work is needed to determine how the physicochemical interactions of GSE affect important cooked meat quality attributes.     

Effect of the relative humidity of drying air during the resting period on the composition and appearance of dry-cured ham surface

This study evaluates the effect of three different relative humidities (RH) during the resting period on the composition of the external part of Semimembranosus muscle (2 mm thick) and the appearance of the surface of the dry-cured ham after resting and ageing. Forty-eight hams stored after salting for 40 days at 4±1 °C and three different RH (52±3, 78±3 and 85±3%) were studied. Half of the hams in each treatment were sampled after the resting period and the rest were aged for 8 additional months at the same temperature and RH. Storage of hams at 52% RH during resting produced a white appearance in some parts of the rind and increased the surface covered with oil drip. Hams stored at 78% showed a similar composition to those stored at 52%, except for the higher moisture content and lower Na/moisture ratio at the end of the resting period, and potassium content (on dry matter, dm) at the end of the process. At the end of resting no white rind was observed, and at the end of the process the surface covered with oil drip was slightly lower than at 52%. Storage of hams at 85% RH increased the surface pH, Na2HPO4.12H2O crystallisation, Mg (dm), Mg/moisture, K (dm) and NPN/NT at the end of the resting period, and increased the pH and Mg (dm), Mg/moisture, Na/moisture, K/moisture, the ash (dm) and ash/moisture contents and decreased the a_w and the surface covered with oil drip at the end of the process.     

Use of ramping and equilibrium water vapor sorption methods to determine the critical relative humidity at which the glassy to rubbery transition occurs in polydextrose

Recent research has demonstrated that the critical relative humidity (RHc) values, obtained using automatic water vapor sorption instruments, can be used to detect the glassy to rubbery transition. However, reported time dependency of these RHc values suggests that additional research be carried out using equilibrium water vapor sorption methods. Thus, the objectives of this study were to: (1) determine the RHc for amorphous polydextrose at various temperatures using both instrumental (Dynamic Vapor Sorption [DVS] ramping and equilibrium) and saturated salt slurry methods, and (2) compare the RHc values obtained via sorption methods to the glass transition temperature (Tg) values obtained via differential scanning calorimetry (DSC). When plotted as a "glass curve" on a state diagram, the RHc values (plotted as a function of temperature) were found to be similar to the Tg values (plotted as a function of relative humidity). Of the 3 sorption methods employed, at 25 °C, the saturated salt slurry exhibited the lowest RHc value (34.3%), followed by the DVS equilibrium method (41.7%), and the DVS ramping method (49.9%). The RHc DVS equilibrium method was closest to the calculated DSC Tg onset RHc value (41.6% at 25 °C). These water sorption methods show promise as practical tools for predicting the quality and stability attributes of amorphous materials by being able to routinely determine the location of the glassy to rubbery transition. Future research applying these sorption methods to more complex amorphous food systems is suggested. Practical Application: Despite its extreme usefulness, the Tg, a key element of the Food Polymer Science approach, remains a challenging parameter to routinely measure in amorphous food materials. Recent research has demonstrated that the RHc values can be used to detect the glassy to rubbery transition. However, reported time dependency of these RHc values suggests that additional research be carried out using equilibrium water vapor sorption methods. Therefore, in this research 2 instrumental (DVS ramping and equilibrium) methods and the traditional saturated salt slurry method were used to obtain RHc values, comparing them to DSC obtained Tg values. The water sorption methods show promise as practical tools for predicting the quality and stability attributes of amorphous materials by being able to routinely determine the location of the glassy to rubbery transition. Future research applying these sorption methods to more complex amorphous food systems is suggested.     

Nucleation of amino acid‐rich crystals on the surface of dried scallop (Chlamys farreri) during storage: formation mechanism and influence of environmental relative humidity

Formation of crystals on the surface of dried scallop (Chlamys farreri) adductor muscle is often observed during storage. The composition of these white crystals was determined, and the effect of relative humidity (RH) during storage on their formation was also studied. The white crystals were determined as the crystal of free amino acids, mainly composed of taurine (Tau) and glycine (Gly). The main polymorphic form of glycine in the crystals was further confirmed as the γ‐form. Besides free amino acids, another major part of the crystal composition was ions, such as Na⁺, NH₄⁺, K⁺, PO₄^3? and Cl^?. The presence of various free amino acids and Na⁺ and K⁺ might contribute to the crystallisation of γ‐glycine. RH particularly at 65% and above significantly increased the amount of crystals. RH of 43% and below was recommended to prevent the formation of amino acid‐rich crystals on dried scallops during storage.