Respiration Rates Of Samples Research Articles

Effects of modified atmosphere packaging on the postharvest quality of mulberry leaf vegetable

Fresh mulberry leaf vegetable is nutritive and becoming popular. However, available preservation technologies are deficient. In present work, the effects of two kinds of modified atmosphere packaging on postharvest quality of fresh mulberry leaf vegetable stored at 4 °C were evaluated. The respiration rate of samples in the modified polyethylene packages (MP20) was 12.88–22.65% lower than that in normal polyethylene packaging (CK). The content of total soluble solids, soluble protein, and total polyphenol in MP20 was less changed than that in CK, and the vitamin C retention was higher as well. Moreover, the lignin content in MP20 was lower than that in CK during storage (19.79% vs 13.38% at day 8), and that was significantly positively related to the polyphenol oxidase and peroxidase activities inhibition. Taken together, a packaging with moderate gas permeability (MP20) is suitable for nutrition maintenance and lignification inhibition of fresh mulberry leaf vegetable during cold storage.

Effect of chitosan–lemon essential oil coatings on storage-keeping quality of strawberry

Film-forming dispersions (FFD) were prepared with 1% high molecular weight chitosan and 3% lemon essential oil and were submitted to two different homogenization treatments. The particle size and viscosity of the FFD were evaluated and stand-alone coatings were characterized in terms of water vapour permeability (WVP) and antimicrobial activity. The FFD were applied to cold-stored strawberries, cv. Camarosa, and the physicochemical properties, fungal decay and respiration rate of strawberries were determined throughout cold storage at 5°C. The use of microfluidization to prepare chitosan-based FFD led to a significant reduction in the particle size and apparent viscosity of the dispersions, with no significant effect on the decrease in the WVP of the stand-alone coatings. Chitosan coatings did not show a significant effect in terms of the acidity, pH and soluble solid content of strawberries throughout storage. In contrast, coatings slowed down the respiration rate of samples when lemon essential oil was added to the FFD. Adding lemon essential oil enhanced the chitosan antifungal activity both in in vitro tests and during cold storage in strawberries inoculated with a spore suspension of Botrytis cinerea.

Exchange of reduced volatile sulfur compounds between leaf litter and the atmosphere

Leaf litter collected from the uppermost litter horizon and the fermentation horizon from a 60-yr-old beech forest was investigated for its exchange of volatile reduced sulfur compounds with the atmosphere. A close linear correlation between the water content and the microbiological respiration was found. This biological activity was closely related to the exchange of dimethyl sulfide (DMS) and carbonyl sulfide (COS). We found a DMS emission exponentially correlated with the respiration rates of samples from both horizons. In contrast, COS was deposited to the leaf litter samples, and the uptake was not found to correlate linearly or exponentially with either the water content or the respiration rates. Deposition of COS was high when respiration was low. At higher respiration rates, as observed with increasing high water content, no COS uptake was detected. Under these conditions, we assume high levels of CO 2, inferred from the high respiration rates observed, to cause a competitive inhibition of carbonic anhydrase, the well-known key enzyme for the consumption of COS. Though the enclosure technique results in gas exchange rates which provide an upper limit to the actual rates that might occur in situ within a forest, the measured exchange rates indicate that the contribution of the leaf litter to the atmospheric burden is not significant in the case of DMS but might be of relevance as a sink for COS.

Development and Demonstration Of a Thermogradient Respirometer

A reliable method for monitoring the composting process evolution and assessing compost stability is a key factor for successful composting. Respirometric methods are commonly used, but they usually measure the activity at one specific temperature. In this study the objective was to determine simultaneously the respiration activity, in terms of oxygen uptake rate, at a number of different temperatures. The “thermogradient respirometer” developed consists of a solid aluminum cylinder (1.5 m long, 155 mm diameter), in which a controlled and stable temperature gradient was achieved by attaching an electrically heated plate to one end and a cooling system to the other.The respiration rate of samples obtained from a 0.6 m3 pilot scale bioreactor, where olive mill wastewater was cocomposted with extracted olive press-cake, was determined at eight different temperatures, from 20 to 66°C. The thermogradient respirometer revealed more information about the history and the origin of the samples than respirometry at...

Ecological studies on the timberline of Mt. Fuji

An ecological study of dry matter production was made in a dwarf forest dominated byAlnus maximowiczii at the timberline of Mt. Fuji. Annual gross production was estimated by two methods, namely the summation method using stem analysis and total photosynthesis calculated from leaf area and photosynthetic rate per leaf area. Seasonal changes in relative light intensity and in leaf area were measured in a quadrat. Photosynthesis and respiration rates of samples were measured in temperature-regulated assimilation chambers. The phytomass was 2,989 g d.w.m−2, and those of stems and branches, leaves, and roots were 1,672 g, 293 g, and 1,024 g respectively. The growing period of this plant was about four months and this plant expanded leaves quickly. The maximum gross photosynthetic rate was 21 mg CO2dm−2 h−1 on September 1. Annual net production estimated by examining the annual rings was 922 g d.w.m−2 year−1 and annual respiration was 735 g. Annual gross production estimated from photosynthetic rates was 1,747 g d.w.m−2 year−1. The sum of annual net production by stem analysis and respiration agree closely with gross production estimated from photosynthetic rate. Gross production of this dwarf forest is comparable to the beech forest of the upper cool temperate zone owing to the high photosynthetic rate ofAlnus maximowiczii.