Initial Respiration Rate Research Articles

Hydrogen Peroxide Can Enhance the Synthesis of Bioactive Compounds in Harvested Broccoli Florets

Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) which participates in the signal transduction responses of plants toward biotic and abiotic stresses. Therefore, the objective of this study was to link the exposure of low doses of H2O2 to the improvement of the phytochemical composition of broccoli florets, in particular the content of glucosinolates (GLS), and hydroxy-cinnamates (HCA) without affecting the quality parameters of the vegetable. A dose of 1.25 mM H2O2 applied for 180 min was effective (hormetic) in maintaining the color of broccoli florets, which was also compared with a higher dose of 5.0 mM H2O2 applied for 180 min. The intensity of the treatments was related to respiration rate, which was monitored for 21 d at 4◦C along to weight loss. The initial respiration rate of florets exposed to both doses of H2O2 was significantly (p < 0.0001) higher relative to controls and resulted in weight loss in florets treated with the hormetic dose. The antioxidant capacity of florets, measured indirectly as Oxygen Radical Absorbance Capacity (ORAC) and ascorbic acid (AA), decreased in florets exposed to both doses. The concentration of glucobrassicins, aliphatic GLS, and HCA was consistently higher in florets treated with the two doses, compared to non-exposed florets. The enhancement of these compounds was accompanied by the over expression, immediately (6 h) after treatments, of tryptophan N-hydroxylase 2 (CYP79B3), dihomomethionine N-hydroxylase (CYP79F1), and phenylalanine ammonia-lyase (PAL) genes. Overall, the tested doses of H2O2 positively influenced the augmentation of indole-type and aliphatic GLS, as well as HCA in broccoli florets.

UV-B radiation hormesis in broccoli florets: Glucosinolates and hydroxy-cinnamates are enhanced by UV-B in florets during storage

Abstract Abiotic stresses are oxidative in nature and cause generation of reactive oxygen species (ROS) in plant bodies. Severe stresses can be harmful to the plant tissue, whereas sub-acute or lower doses of stresses could enhance or induce protective mechanisms, a biological phenomenon known as hormesis. The objective of this work was to examine the effect of hormetic as well as high doses of UV-B on the quality along with glucosinolate and hydroxy-cinnamate contents in broccoli florets during storage. An UV-B dose of 1.5 kJ m-2 was found to be hormetic from the color retention response. Color development, weight loss and respiration rate were monitored during 21 d of storage at 4 °C. The gene expression of dihomomethionine N-hydroxylase (CYP79F1), tryptophan N-hydroxylase 2 (CYP79B3), phenylalanine N-hydroxylase (CYP79A2), phenylalanine ammonia-lyase (PAL), chalcone synthase (CH) and flavanone 3-hydroxylase (F3H1) in the treated broccoli was also evaluated. The antioxidant capacity and the profiles of glucosinolates and hydroxy-cinnamates were determined for up to 14 d in broccoli florets stored at 4 °C by LC–MS. The hormetic dose of UV-B was effective in delaying the yellowing of broccoli florets. The initial respiration rate of the florets treated with the hormetic and a high dose (7.2 kJ m-2) was significantly high. The antioxidant capacity of florets was higher in UV-B treated florets relative to the control. The titers of indole-type glucosinolates and hydroxycinnamates in broccoli were significantly (p

Impact of Heating and Rewetting on Soil Respiration and Nutrient Availability Is Enhanced by Prior Growth of Plants

The effects of heating and rewetting on nutrient availability and microbial activity have been studied extensively. But little is known about the effect of prior presence of plants on the impact of heating on microbial activity and nutrient availability. Soil was planted with wheat or left unplanted. After 4 weeks, roots were removed from the planted soil, washed and then added to half of the previously planted and unplanted soil at 1 g dw kg−1. Half of the replicates from each treatment were heated and then maintained at 60 °C for 30 min followed by rapid rewetting, while others remained unheated. Soil respiration was measured continuously for 14 days. Soils were sampled 2, 7 and 14 days after rewetting for available N and P pools. Heating and rewetting induced a flush of respiration and increased available N and P. The heating-induced increase in initial respiration rate, cumulative respiration and available N and P was greater in previously planted soil than unplanted soil. Heating increased available N and P three- to fivefold in planted soil, but only twofold in unplanted soil. Plant-induced changes in nutrient availability increase the impact of heating on soil respiration and nutrient availability.

Improved accuracy of optode‐based oxygen consumption measurements by removal of system drift and nonlinear derivation

AbstractThis method evaluation aimed to improve the accuracy and precision of the previously published method to measure oxygen consumption using optodes with integrated temperature and salinity correction in dark incubations. Significant short‐term system drift currently requires a correction to remove the drift, thus reducing the precision of the oxygen consumption rates. Frequent nonlinear declines in oxygen concentration with time also call for improved data analysis and identification of its origin. Optodes in titanium casings (Aanderaa™ model 4330) with low oxygen binding properties showed no significant system drift in autoclaved seawater. Nonlinear oxygen dynamics fitting a quadratic polynomial occurred in 28% of 230 field samples, independent of season and water depth. Polynomial curve fit resulted in 64% higher respiration rates when derived within 1 h of the quality assured incubation, than obtained when using linear fit. Carbon substrate limitation explained the nonlinearity of oxygen decline during dark incubations. Pretreatment of the optode attached to stoppers with 0.3 mol dm−3 hydrochloric acid resulted in the most stable performance of the sensor and simultaneously provided proper cleaning of the equipment. A conservative detection limit of 0.97 μmol O2 dm−3 d−1 was calculated for the titanium optodes, matching other methods for oxygen consumption reported in the literature. Thus, we recommend the use of model 4330 optode pretreated with HCl and the derivation of initial respiration rates by a quadratic polynomial function for best accuracy and precision of oxygen consumption in oxygenated surface waters.

Влияние свободных жирных кислот на поглощение кислорода изолированными кардиомиоцитами крыс при ишемическом или диабетическом поражении сердца

Цель исследования - оценка влияния свободных полиненасыщенных и насыщенных жирных кислот (ЖК) на поглощение кислорода изолированными кардиомиоцитами интактных крыс и крыс с ишемическим или диабетическим поражением сердца. Методика. Опыты проведены на крысах-самцах Вистар (250-300 г). Инфаркт миокарда вызывали перевязкой левой коронарной артерии, сахарный диабет (СД) - однократной инъекцией стрептозотоцина в дозе 60 мг/кг, внутрибрюшинно. Изолированные кардиомиоциты получали ферментативным способом. Потребление кислорода оценивали полярографически при разной насыщенности инкубационной среды кислородом ([O] <8 мг/л и ([O] >16 мг/л). В качестве жирных кислот, добавляемых в инкубационную среду, использовали арахидоновую и пальмитиновую кислоты (20 мкМ/л). Результаты. Установлено, что в среде инкубации с высоким содержанием кислорода скорость его потребления изолированными кардиомиоцитами, из сердец крыс с ишемическим или диабетическим поражением сердца, в 2-2,5 раза превышает таковую в кардиомиоцитах из сердца интактных крыс. Введение в среду инкубации 20 мкМ арахидоновой или пальмитиновой ЖК статистически значимо увеличивало потребление кислорода кардиомиоцитами интактных крыс. При моделируемых патологиях был получен прямо противоположный результат. В среде инкубации с низким содержанием кислорода была зафиксирована более низкая исходная скорость дыхания кардиомиоцитов, независимо от того, из сердец крыс какой группы они были выделены. Присутствие жирных кислот приводило к еще большему снижению скорости потребления кислорода кардиомиоцитами интактных крыс. В кардиомиоцитах из сердец с ишемическим поражением жирные кислоты снижали скорость потребления кислорода практически до значений, полученных для кардиомиоцитов интактных крыс. Напротив, жирные кислоты не оказывали заметного влияния на дыхание кардиомиоцитов из сердца крыс с диабетическим поражением. Заключение. Полученные результаты свидетельствуют, что и насыщенные, и ненасыщенные свободные ЖК, на клеточном уровне, способны поддерживать баланс между поступлением и расходом кислорода. Действие ЖК определяется функциональным состоянием кардиомиоцитов и содержанием кислорода во внеклеточном пространстве. Это обстоятельство, вероятно, влияет на состояние энергетического метаболизма кардиомиоцитов и при реальном ишемическом или диабетическом поражении сердца пациентов.Aim. To evaluate the effect of free polyunsaturated and saturated fatty acids on oxygen uptake by isolated cardiomyocytes in intact rats and animals with ischemic or diabetic heart disease. Methods. This was a non-randomized, controlled study on three groups of male Wistar rats each containing 10 rats weighing 250-300 g. Myocardial infarction («heart attack») was produced by ligation of the left coronary artery; diabetes mellitus («diabetes») - by a single injection of streptozotocin 60 mg/kg, i.p. The control group consisted of intact animals. Cardomyocytes were isolated by an enzymatic method. Oxygen consumption was assessed polarographically at different saturation of the incubation medium with oxygen ([O] <8 mg/l and ([O] >16 mg/l). Arachidonic and palmitic acid were used as fatty acids to be added to the incubation medium. Results. In the high-oxygen incubation medium, the rate of O consumption by isolated cardiomyocytes from hearts of rats with ischemic or diabetic heart lesions was 2-2.5 times higher than in cardiomyocytes from heart of intact rats. Supplementing the incubation medium with 20 mkM arachidonic or palmitic acid statistically significantly increased oxygen consumption by cardiomyocytes of intact rats. An opposite result was obtained in models of diseases. In the low-oxygen incubation medium, the baseline rate of cardiomyocyte respiration was lower, no matter from which group of rats they had been isolated. The presence of fatty acids led to an even greater decrease in the rate of oxygen consumption by cardiomyocytes of intact rats. In cardiomyocytes from hearts with ischemic injury, fatty acids reduced the rate of oxygen consumption practically to the values observed for cardiomyocytes of intact rats. In contrast, fatty acids did not exert a noticeable effect on respiration of cardiomyocytes from the heart rats with diabetic lesions. Conclusion. The results suggested that saturated and unsaturated free fatty acids are able to maintain a balance between O supply and utilization. The effect of fatty acids is determined by functional state of cardiomyocytes and oxygen content in the extracellular space. This fact apparently influences cardiomyocyte energy metabolism in patients with ischemic or diabetic heart disease.

ВПЛИВ ГІПЕРВЕНТИЛЯЦІЇ НА ДИНАМІКУ РІВНЯ КАРБОН (IV) ОКСИДУ В АЛЬВЕОЛЯРНОМУ ПОВІТРІ

Introduction . Hyperventilation occurs under the influence of environmental factors, neuro-psychic stress, in sports activities, with the introduction of pharmacological substances, accompanies a number of diseases. However, there are insufficient studies of the individual peculiarities of СО 2 change dynamics in the alveolar air at hyperventilation test and after it. Purpose . To analyze the dynamics of changes in the level of carbon (IV) oxide in the alveolar air while testing the regulated respiration with a frequency of 30 cycles per minute in healthy young men. Methods . Measurements were performed on 81 healthy young men aged 18-22. The level of СО 2 in the exhaled air was determined in the lateral flow by the infrared spectrometry method on the capnograph Datex Normocap (Finland). The stress of СО 2 in the alveolar air was estimated according to its level at the end of the exhalation (PetCO 2 ). Results . At the respiration with a frequency of 30 cycles per minute 1 for 10 minutes, the level of PetCO 2 decreases from 40.12 ± 0.361 mm Hg to 18.59 ± 0.542 mm Hg. In the 40-minute recovery period after the test, the return of PetCO 2 to the initial level does not occur. There are significant individual peculiarities of PetCO 2 reactivity to hyperventilation and recovery after it. Originality . It has been shown that the stress reactivity of carbon (IV) oxide in the alveolar air to a sample with respiration of 30 cycles per minute and after recovery after it depends on its initial level – the lower the level of Pet CO 2 , the lower the reactivity and the faster recovery. The stress reactivity of carbon (IV) oxide in the alveolar air to testing respiration of 30 cycles per minute and to the recovery during the first 5-10 minutes after it depends on the initial respiration rate. Conclusion . When evaluating a hyperventilation test, the initial level of СО 2 in the alveolar air and respiratory rate should be taken into account.

Zoledronic acid and bone cellular respiration

Phosphorescence O2 analyzer was used to measure calvarial bone cellular respiration (cellular mitochondrial O2 consumption) in Taylor Outbred mice in the presence and absence of zoledronic acid. This potent bisphosphonate inhibits osteoclast-mediated calcium resorption, and its effects on bone respiration have not been previously investigated. The change of O2 concentration with time was measured in closed vials containing phosphate-buffered saline (PBS), 5mM glucose and 5-25mg calvarial bone fragments, and it was complex for t=0-30h. Cyanide (specific inhibitor of cytochrome oxidase) halted O2 consumption, confirming the oxidation occurred in the respiratory chain. Initial rate of respiration was estimated from the zero-order plots d[O2]/dt for t=0-4h. For untreated specimens, the rate (mean±SD) was 2.0±1.2µM O2h-1mg-1 (n=6). This value was 7-10 times lower than that of other murine organs, but similar to that reported for rat and Guinea pig calvaria (averaging, 2.7nmolO2h-1mg-1). The corresponding rate in the presence of 10-100µM zoledronic acid was 2.7±0.7µM O2h-1mg-1 (n=11), p=0.216. The first-order plots ln ([O2] t ÷[O2] t=0) versus time for t=0-30h were also used to compare treated and untreated specimens. The rate (h-1mg-1103) for specimens incubated in PBS without glucose was 1.3±0.6 (n=3, p=0.007), in PBS+glucose it was 10.7±6.9 (n=10), in PBS+glucose+10µM zoledronic acid it was 12.1±6.7 (n=10, p=0.579), in PBS+glucose+20µM zoledronic acid it was 12.9±3.3 (n=9, p=0.356), and in PBS+glucose+100µM zoledronic acid it was 13.7±7.7 (n=9, p=0.447). Thus, exposure to high-doses of zoledronic acid over several hours imposed a statistically insignificant increase in calvarial bone cellular respiration.

Potential use of microwave treatment on fresh-cut carrots: physical, chemical and microbiological aspects.

The effect of microwave treatments (900 and 750 W for 45 and 60 s) on the microbial, physicochemical and sensory properties of fresh-cut carrot slices and the contents of several bioactive compounds was studied. Carrot samples were stored for 7 days at 5 °C. The microwaving of fresh-cut carrots reduced the initial respiration rate (8.6 CO2 mL kg(-1) h(-1)) by 55-74% compared with untreated samples, although the rates then increased during storage. The initial pH (6.7), titratable acidity (0.036%), soluble solid content (8.2 °Brix) and shelf-life of the samples did not differ greatly from those of the untreated samples. Microwaving prevented the incipient whitening and surface dryness during storage. In general, no significant changes in phenylalanine ammonia lyase activity (5.5 µmol t-cinnamic acid kg(-1) h(-1)), total phenolics (TP, 81.3 mg chlorogenic acid equivalent kg(-1) fresh weight (FW)) or total antioxidant capacity (TAC, 74.2 µmol Trolox equivalent kg(-1) FW) were observed on the processing day or over storage. However, the mildest treatment (750 W for 45 s) caused TP and TAC enhancements of 118 and 394% respectively after 7 days of shelf-life. Microwave treatments reduced the initial microbial loads of the samples by up to 1.8 log units, although their microbial growth was greater than that of the untreated samples throughout storage. Mild microwave treatments such as 750 W/45 s and 750 W/60 s are a good sustainable alternative to the use of NaOCl; however, combining them with other sanitizing techniques is needed to control microbial growth throughout the shelf-life of fresh-cut carrot slices.

The Effects of Tocopherol Nanocapsules/Xanthan Gum Coatings on the Preservation of Fresh-Cut Apples: Evaluation of Phenol Metabolism

The aim of this study was to evaluate the effect of different xanthan gum coatings with nanoparticles (nanocapsules and nanospheres) on the production and oxidation of phenolic compounds generated by enzymatic activity (phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO)) on fresh-cut Red Delicious apples stored for 21 days at 4 °C. The nanoparticles were prepared using the emulsification-diffusion method. The film systems formed had particle sizes (Ps) of 190 to 260 nm, the polydispersity index (Pdi) was |35| mV parameters that suggest good physical stability. While all the nanoparticulate coatings proved to be effective, the best coating was the nanocapsules/xanthan gum combination because it decreased the initial respiration rate by 63 % compared to controls. The effect on PPO and PAL activity was associated with the protection of phenolic compounds, whose concentrations remained unchanged. Also, lower variations in total color differences were found.

Modelling the influence of time and temperature on the respiration rate of fresh oyster mushrooms.

The respiration rate of mushrooms is an important indicator of postharvest senescence. Storage temperature plays a major role in their rate of respiration and, therefore, in their postharvest life. In this context, reliable predictions of respiration rates are critical for the development of modified atmosphere packaging that ultimately will maximise the quality of the product to be presented to consumers. This work was undertaken to study the influence of storage time and temperature on the respiration rate of oyster mushrooms. For that purpose, oyster mushrooms were stored at constant temperatures of 2, 6, 10, 14 and 18 ℃ under ambient atmosphere. Respiration rate data were measured with 8-h intervals up to 240 h. A decrease of respiration rate was found after cutting of the carpophores. Therefore, time effect on respiration rate was modelled using a first-order decay model. The results also show the positive influence of temperature on mushroom respiration rate. The model explaining the effect of time on oyster mushroom's respiration rate included the temperature dependence according to the Arrhenius equation, and the inclusion of a parameter describing the decrease of the respiration rate, from the initial time until equilibrium. These yielded an overall model that fitted well to the experimental data. Moreover, results show that the overall model is useful to predict respiration rate of oyster mushrooms at different temperatures and times, using the initial respiration rate of mushrooms. Furthermore, predictive modelling can be relevant for the choice of an appropriate packaging system for fresh oyster mushrooms.

Use of Alternative Sanitizers on Minimally Processed Watercress Harvested in Two Different Seasons

There is an increasing concern about the formation of halogenated compounds when sodium hypochlorite (SH) is used as food sanitizer. This research evaluated the quality of watercress harvested in two seasons treated with alternative sanitizers combined with modified atmosphere packaging. Chlorine dioxide (5–10 mg/L), acidified sodium chlorite (250–500 mg/L), peroxyacetic acid (50–90 mg/L) and SH (100 mg/L) were used. Initial respiration rate decreased from 80–135 to 40–72 mg CO2 kg/h in spring- and summer-harvested watercress. Chlorine dioxide and SH caused a reduction in aerobic mesophilic bacteria of 1.8 and 1.3 log colony-forming unit (cfu/g), respectively. Enterobacteriaceae reductions of 1.1 log cfu/g were achieved using SH and peroxyacetic acid in spring and 1.4 log cfu/g by applying acidified sodium chlorite in summer. None of the sanitizers could handle high initial microbial loads for more than 8 days, showing that a raw material with low initial microbial count is required to guarantee the product safety. Practical Applications Nowadays, the food market is challenging an increasing demand for safer products that must be elaborated under strict food and environmental standards. In this sense, the application of nontraditional sanitizers could be an alternative to sodium hypochlorite that is being questioned due to the potential formation of halogenated compounds during sanitation. The use of alternative sanitizers in high doses represents a feasible choice for minimally processed vegetables because this technology does not leave toxic residues in foods and neither requires additional investment on industrial facilities, preserves the sensory attributes of vegetables and helps to improve the microbiological quality of ready-to-eat products.

Measuring basal soil respiration across Europe: Do incubation temperature and incubation period matter?

The European Commission recognises the essential role of soil biology in soil functioning and delivery of ecosystem services, but information is currently lacking evaluate of how these vary across soil and land-use types at a European scale. This study evaluated the measurement of the initial rate of soil basal respiration (BR) as a potential biological indicator of ecosystem service provision. The purpose of this study was to test ISO 16072:2002 (Soil Quality: Laboratory methods for the determining of microbial soil respiration). In the literature a range of pre-incubation temperatures (pre-inc) and experimental incubation temperatures (exp-inc) have been applied when using the ISO method for the establishment of basal respiration. This study evaluated whether the range of temperatures applied during pre- and exp- incubation had a significant effect on the rate of respiration determined when following the protocol established in ISO 16072:2002. The evaluation was carried out on a pedo-climatic gradient spanning ten countries across Europe and covering four biogeographical regions. Three sites were sampled in each country providing a range of soil and land-use parameters. Our results suggest that experimental incubation temperatures of 20°C or above should be used in the application of the methodology ISO 16072:2002 (incubation at 15°C resulted in erratic variation between replicates). However, pre-incubation temperature did not affect the soil basal respiration rate, when following the standard recommendations. The time interval with the best prediction of the initial rate of basal respiration was 6h.

Method for Determining the Respiration Rate of Horticultural Produce Under Hyperbaric Treatment

A method was developed to determine the metabolic respiration rate (RRm) of fresh produce during the transient period at the beginning of a hyperbaric treatment. This method allowed for the correction in the apparent respiration rate (RRap) by considering the dilution effect of flushing the system and the error associated with gas solubilisation as the gas partial pressure varied. The dilution process was simulated by using the general equation for exhaust ventilation, thus allowing for the elimination of the dilution effect during the calculation of the net respiration rate (RRN). The error associated with the CO2 solubilisation in the flesh of the produce was solved by measuring the CO2 solubility in the tissues of tomato at various CO2 partial pressures and using this value to generate a mass balance of CO2 within the system. The RRm was estimated by incorporating the initial respiration rate (RRi) of untreated fruits with the respiration rate at equilibrium (RRe). The kinetic of the RRm was proposed to follow a negative exponential equation. The constant value (k) of the RRm model was found to decrease exponentially with the partial pressure of CO2 at equilibrium which affected the amount of gas solubilised and the time to reach equilibrium. The developed method should be validated for the RRm of other produce during the transient period at the beginning of a hyperbaric treatment.

Modelling respiration in fresh-cut pineapple and prediction of gas permeability needs for optimal modified atmosphere packaging

This study investigated the effects of intrinsic factors (origin, physiological age and seasonality) and extrinsic factors (cut-size, blade-sharpness and dipping treatments) on respiration rate (RCO2) of fresh-cut pineapple chunks. A mathematical model for respiration rate based on exponential decay was developed that showed a gradual decrease in rate with time. The model parameters (Ri and Req, initial respiration rate and equilibrium respiration rate, respectively) were found useful to compare respiration rates for the factors studied. The average values were 8.52±4.68 and 2.64±0.68ml/kgh for Ri and Req, respectively. Ri was affected to a greater extent by physiological age and origin than by season. Cut size had a considerable effect on Ri and Req, with larger cut pieces having the lowest Ri and Req of 5.9 and 2.7ml/kgh, respectively. In contrast, smallest cut pieces had highest Ri (7ml/kgh) and Req (3.2ml/kgh). Cutting the fruit with a razor sharp blade versus a blunt blade decreased the Ri, while only caused a slight reduction in Req. The target O2 and CO2 transmission rate required for optimal modified atmosphere packaging were 7300–12,500 and 13,900–23,500ml/m2dayatm covering variability in respiration rate due to intrinsic and extrinsic factors studied.

Effect of Tapioca Starch/Decolorized Hsian-tsao Leaf Gum-Based Active Coatings on the Qualities of Fresh-Cut Apples

The effect of tapioca starch/decolorized hsian-tsao leaf gum (dHG)-based edible coatings with various food additives (including ascorbic acid, calcium chloride, and cinnamon oil) on the qualities and shelf life of fresh-cut “Fuji” apple pieces was investigated during the refrigerated storage. The initial respiration rate, headspace gas composition, color, texture, microbial quality, peroxidase activity, and sensory qualities were analyzed. The results were also compared to those for samples submerged in distilled water and the samples treated with 120-ppm chlorine solution widely used in the industry. It was found that ascorbic acid and cinnamon oil delayed the browning of fresh-cut apples effectively when being applied in the starch/dHG-based edible coating solutions. In combination with calcium chloride, starch/dHG coated fresh-cut apples retained satisfactory firmness. Incorporation of cinnamon oil in starch/dHG coatings significantly reduced the growth of microorganisms, respiration rate, CO2, and ethylene production of fresh-cut apples, but these apple pieces received lower scores in overall preference during sensory evaluation. Among the starch/dHG-based active coatings studied, starch/dHG coatings with ascorbic acid and calcium chloride are suggested for fresh-cut apples, as they could enhance qualities in terms of color and firmness, and prolong the shelf life up to 5–7 days by providing reasonable microbial quality.

Effect of Long-Term Zinc Pollution on Soil Microbial Community Resistance to Repeated Contamination

The aim of the study was to compare the effects of stress (contamination trials) on the microorganisms in zinc-polluted soil (5,018 mg Zn kg−1 soil dry weight) and unpolluted soil (141 mg Zn kg−1 soil dw), measured as soil respiration rate. In the laboratory, soils were subjected to copper contamination (0, 500, 1,500 and 4,500 mg kg−1 soil dw), and then a bactericide (oxytetracycline) combined with a fungicide (captan) along with glucose (10 mg g−1 soil dw each) were added. There was a highly significant effect of soil type, copper treatment and oxytetracycline/captan treatment. The initial respiration rate of chronically zinc-polluted soil was higher than that of unpolluted soil, but in the copper treatment it showed a greater decline. Microorganisms in copper-treated soil were more susceptible to oxytetracycline/captan contamination. After the successive soil contamination trials the decline of soil respiration was greater in zinc-polluted soil than in unpolluted soil.

Effects of Tapioca Starch/Decolorized Hsian-Tsao Leaf Gum-Based Active Coatings on the Quality of Minimally Processed Carrots

Edible coatings made from tapioca starch/decolorized hsian-tsao leaf gum (dHG) containing cinnamon essential oil or grape seed extract (GSE) were developed and applied to minimally processed carrots. Coatings based on 0.3% dHG and 1.7% tapioca starch were prepared and incorporated with 0.1–0.3% cinnamon oil or 0.3–0.6% GSE as antimicrobial agents. Fresh-cut carrots were immersed into coating solutions, placed in expanded polystyrene trays, and sealed in polypropylene bag. Changes in the initial respiration rate, the headspace atmosphere, color, microbial growth, and sensory evaluation were then measured. During refrigeration, the initial respiration rates for carrots with various coating treatments slightly increased as compared to the control group carrots, and the coatings with cinnamon oil showed the highest rates. Headspace analysis revealed that coated samples also had higher CO2 and lower O2 concentrations, which were consistent with the initial respiration rate results. Though samples coated with the antimicrobial solutions (cinnamon oil or GSE) did not show advantages in reducing microbial growth as compared to the control group carrots, they presented better acceptance during the sensory evaluations. The use of edible coatings successfully maintained the surface appearance and retarded the formation of “white blush” on the surface of carrots during refrigeration. While the visual appearance quality of minimally processed carrots was significantly improved by the coating treatments, the microbial growth was the same or even worse in some cases. Based on the pronounced improvements of the carrots’ appearance and the comparable microbial control, the plain starch/dHG coating without cinnamon oil or GSE was recommended for extending the shelf life of minimally processed carrots.

Extending shelf-life of Fresh-cut ‘Fuji’ apples with chitosan-coatings

Abstract The effect of coatings in combination with anti-browning agents (1%chitosan; 2%ascorbic acid + 0.5%CaCl2 and 2% ascorbic acid + 0.5%CaCl2 + 1% chitosan) on minimally processed apple slices was studied during storage. Chitosan-coating treatments effectively retarded enzymatic browning on minimally processed apples during storage and they effectively retarded or avoided tissue softening, apple slices underwent a little loss of firmness. Chitosan-coating did not perform very well as water vapor barriers in apple slices. To control initial respiration rate of apple slices, edible coatings were applied to cut apples as semi-permeable barriers against air. Initial respiration rate showed a decrease in 2% ascorbic acid + 0.5%CaCl2 + 1% chitosan apple slices at 5 °C. Industrial relevance Recently, there has been an increasing market demand for minimally processed fruits and vegetables due to their fresh-like character, convenience, and human heath benefits. Minimal processing includes grading, washing, sorting, peeling, slicing, chopping, and then packaging. Since minimal processing results in quality deterioration associated with water loss, softening, microbial contamination, increased respiration and ethylene, and cut-surface browning, minimally processed products become more perishable. Edible coating was used for cut apples to reduced respiration and control physiological changes. The color of products, such as apple slices, is an important quality index. Brown apple slices are aesthetically unattractive. Chitosan has been reported to maintain the quality of fruit and vegetables (EI Ghaouth et al.,1991). The objective of this study was to develop procedures for the use of edible coatings in combination with anti-browning agent and to extend the shelf-life of minimally processed apple slices.

Tomato pollen respiration in relation to in vitro germination and pollen tube growth under favourable and stress-inducing temperatures

Tomato pollen germination, pollen tube growth and respiratory activity were recorded during incubation in a liquid medium for 7 h over a temperature range of 15-35 degrees C. Although the initial rate of respiration was highest at 30 degrees C, both at 30 degrees C and 35 degrees C respiration decreased after the first hour of incubation due to high temperature impairment of germination and pollen tube growth. The total per cent germination of pollen over the 7-h period was maximal at 15 degrees C whereas pollen tube length was maximal at 25 degrees C. Although the production of CO(2) measured at hourly intervals throughout the incubation period did not correlate to a statistically significant level with either the per cent pollen germination or the length of the pollen tubes alone, nevertheless from 2 h after the start of incubation, it closely correlated with the values for germination x pollen tube length, indicating that the respiratory activity of tomato pollen at a given time is a function of both the per cent germination and the pollen tube growth. We suggest therefore that the rate of respiration might be preferable to a simple germination test for the assessment of pollen germination ability since it expresses not only the pollen germination potential but also the growth vigour of the pollen tubes. In addition, where in vitro tests are designed to assess pollen germination-temperature interactions, they should employ a long incubation period (e.g. 7 h) to permit differences in sensitivity to temperature to be observed.

EVALUATING PERFORMANCE AND STABILITY OF POLYETHYLENE TEREPHTHALATE (PET) AND CELLULOSE POLYMER AS SOILLESS MIX COMPONENTS

In the U.S., concerns over the long-term sustainability of peat, perlite, and other media components have led to searches for alternative materials. FiberFill, a synthetic fiber made of recyclable polyethylene terephthalate, and Tencel, a cellulose fiber, are new materials with potential as substrate components. FiberFill blocks have already been used for hydroponic vegetable production, but its suitability as well as the suitability of Tencel has not yet been tested as soilless mix components. The growth of several floriculture crops was tested using substrates containing different proportions of the two polymers. Furthermore, the long-term stability of the materials was tested by measuring respiration rates of the different components by themselves or as blends with peat. A peat- or coir-based mix was amended with the polymers up to 100% of the final volume and fertigated with water-soluble fertilizer as needed. Visual observations of plants, dry weight (DW), leaf area (LA), and consumer preference were measured. Plants grown in 100% FiberFill or Tencel were shorter and had smaller DW and LA than plants grown in partially-amended substrates with the exception of begonia, which were largest in 100% and 75% FiberFill. Substrates containing 50% FiberFill produced plants that were equal to or larger than substrates containing less polymer. Plants grown in Tencel-containing mixes were consistently smaller than plants grown in substrates containing an equal amount of FiberFill. Initial respiration rates of Tencel were lower than those of peat or peat:perlite blends, but after only ten days, respiration rates of Tencel increased after saprophytic organisms colonized the material. These results indicate that FiberFill has potential as soilless mix component, but the high respiration rates suggest Tencel would not be suitable for long-term (>6 months) production. However, the movement of the U.S. floriculture industry towards sustainability likely favors the adaptation of the cellulose-based component, Tencel.