Sealed Plastic Containers Research Articles

Environmental allergen avoidance: An overview

Environmental allergen avoidance: An overview

Dielectric properties of cottage cheese and surface treatment using microwaves

This research determines the dielectric properties of cottage cheese and explores the application of microwave treatment to reduce surface spoilage microorganisms, extending the shelf-life of cottage cheese in sealed plastic containers. Dielectric properties of cottage cheese of 0, 2 and 4% fat content were measured at temperatures between 5 and 65 °C. The penetration depths of microwaves of 2450 and 915 MHz were estimated to be between 1.2 and 3.2 cm. Microwaves were then used to treat the surface of the cheese in containers shielded on the sides and the bottom. Temperature distribution followed an exponential decay along the depth, as described by a model derived from Lambert's law. Microbiological, sensory and pH analyses of samples after treatment and 1–4 weeks after storage at 3 °C showed that microwave surface treatment could contribute to extending the shelf-life of cottage cheese, but further studies are necessary to identify optimum conditions that would maintain appearance and texture.

Effect of Extended Storage Time on the Toxicity of Sediment-Associated Cadmium on Midge Larvae (Chironomus tentans)

The effect of the duration of spiked sediment storage on cadmium toxicity was studied. Sediment samples were spiked with cadmium to obtain concentrations of 0.6,16.0, 29.0 and 53.0 μg Cd per g sediment (dry weight). The spiked sediment was then stored in sealed plastic containers at 4°C in the dark. Sediment bioassays, using Chironomus tentans, were conducted immediately and at periodic intervals for up to 4 months. Though the levels of cadmium in the bulk sediment samples from different stored periods were not significantly different, different toxicity levels to C. tentans were observed. The toxicity was significantly different between subsequent storage times. There was a significant decrease in the bioaccumulation factor (BAF) values with extended storage times, indicating a reduction in the bioavailability of cadmium. This study suggests that the storage of spiked sediment used in sediment toxicity study can influence the results.

Influence of fungal pathogens and environmental conditions on disease severity, flower fall and desiccation of harvested Geraldton waxflower 1. Studies with model packages

Summary. Flowering sprigs of Geraldton waxflower (Chamelaucium uncinatum Schauer cv. ‘Alba’) inoculated with Botrytis cinerea, Alternaria alternata or left uninoculated (control treatment) were kept in sealed plastic containers (model packages). Three relative humidity treatments (75, 90 or 100%) by 4 temperature treatments [5, 10, 20 or 5/20° C (alternated daily)] were maintained. An additional treatment of ethylene absorbent (Purafil) sachets in the model packages was included. Disease severity, flower fall and desiccation were monitored over 22 days. Both disease severity and flower fall were reduced in treatments with no inoculum, at lower temperatures (5, 10 and 5/20°C) and under reduced relative humidities (75 and 90%). However, desiccation was a problem at 75 and 90% relative humidity and at 20 and 5/20°C. Ethylene scrubbing at 100% relative humidity did not significantly reduce disease severity or flower fall. Considered collectively, our results show that postharvest disease severity, flower fall and desiccation can be minimised by keeping waxflower at ≤10˚C and ≥90% relative humidity.

Packaging to reduce water loss can delay ripening of mango (Mangifera indica L. cv. ‘Kensington Pride’) fruit

Summary. Water loss and premature ripening during postharvest handling reduce the market quality of mango fruit. Towards investigating the use of moisture barrier liners for mango fruit trays, relationships between in-package relative humidity and weight loss and ripening of ‘Kensington Pride’ fruit were studied. Individual fruit were held at 20°C in sealed plastic containers (small 1.2 L buckets). The lid of each container had a single circular hole. Holes were of various sizes, ranging from 5 to 135 mm diameter. Ripening mature green fruit held at the lowest relative humidity of 57% (135 mm diameter hole) lost weight at a significantly (P£0.05) greater rate (10 mg/g initial FW. day) than fruit at higher relative humidities of 59 (open air), 60 (95 mm diameter hole), 61 (55 mm diameter hole), 71 (35 mm diameter hole), 74 (25 mm diameter hole) and 83% (25 mm diameter hole plus free water). These fruit at higher relative humidities lost weight at rates ranging between 9 and 4 mg/g initial FW. day. Fruit softening and skin colouring rates were similar across all relative humidities. In a second experiment, mango fruit were allowed to ripen in containers with smaller holes, ranging from 5 to 95 mm diameter, in their lids. Fruit at the lowest relative humidity (60%, 95 mm diameter hole) lost weight at a significantly (P≤0.05) greater rate (9 mg/g initial FW. day) than fruit from other treatments. Furthermore, these fruit ripened about 2 days sooner than fruit at higher relative humidities: 85 (25 mm diameter hole), 88 (15 mm diameter hole), 91 (10 mm diameter hole) and 93% (5 mm diameter hole). Fruit at the higher relative humidities lost weight at rates between 6 and 2 mg/g initial FW. day, and ripened in 6 to 12 days. Thus, hole size can be varied in order to control in-package relative humidity and regulate mango fruit weight loss and ripening. Australian Journal of Experimental Agriculture, 1997, 37, 463–7 463

Powder state alanine ⧸ESR dosimeter for measuring the absorbed dose of electron beam

This paper describes the application of powder state alanine/ESR dosimeter for measurement of the absorbed dose of electron beam, for transfer the dose standards and for quality controls of the products processed by electron beam irradiation. The dosimeter is a sealed plastic container containing pre-treated alanine powder. Spectra of the internal standard and the alanine sample are measured simultaneously by using dual - cavity of a ESR spectrometer. The internal standard is a CuCl 2. 2H 2O monocrystal which gives stable ESR signals. A diamond sample is regard as working standard. With these two standards, the measurement accuracy can be improved apparently. The standard dose value is determined with a electron beam calorimeter made in our laboratory for dose calibration purpose. The advantages and the dosimetry characteristics of the application of powder state alanine/ESR dosimeters are discussed. This method is proved accurate and easy to use. In the region of 10-10 4Gy, the dose response show a linear relationship and the precision is better than ± 2%.

Cardiovascular changes after closure of uterine circulation during pregnancy

To assess the effects of the presence of the uteroplacental circulation on the systemic arterial pressure, blood volume, and cardiac output during pregnancy, we measured those variables and plasma renin activity (PRA) during a 30-min period before and after occlusion of the uterine circulation. After uterine vascular occlusion, pregnant rabbits (n = 7) experienced a drop in mean arterial pressure of 8.7%, heart rate of 9.5%, cardiac output of 30.2%, and hematocrit of 18.2% (each with P less than 0.05). Stroke volume decreased an average of 29.7%; however, it did not reach significance. PRA and venous pressure did not change significantly from the control period (P greater than 0.1). Nonpregnant rabbits did not experience changes in arterial or venous pressures, hematocrit, heart rate, cardiac output, or PRA after closure of the uterine circulation. To exclude the possibility that the findings were secondary to the release of toxic products to the peritoneal cavity by the ischemic pregnant uterus, we also studied the effect of closure of the uterine circulation in five anesthetized pregnant guinea pigs. These animals' uteri were exteriorized and maintained in a sealed plastic container during the experiment. In these animals, arterial pressure decreased 15.6% by 10 min (P less than 0.05). The finding of a significant decrease in arterial pressure and heart rate is compatible with the idea that the uterine circulation produces a substance with a short half-life that has a significant direct effect on the heart and/or systemic vascular tone.

Theoretical aspects of the design of a passive radon dosemeter

Some mathematical aspects of the development and design of a passive radon dosemeter are considered. In particular, a mathematical model is presented that is concerned with the gaseous diffusion of radon into a confined region bounded by a plastic material of known diffusion coefficient. The relationship between the time-integrated radon concentrations, inside and outside a sealed plastic container are derived. Estimates of the exposure of people to radon can be made using the time integrated radon concentration inside a calibrated container containing a CR-39 etched-track device. As a consequence of the analysis, it is possible to design a passive radon dosemeter that will be accurate, resistant to moisture and whose response will be independent of rapid variations in radon concentration. The possibility of using a container of this type for the measurement of diffusion coefficients is discussed.

Mass-rearing Technique for Aleochara bilineata (Coleoptera: Staphylinidae)

Mass-rearing techniques for economic production and storage of large numbers of Aleochara bilineata (Gyllenhal) (AB) for laboratory use and field studies are described. AB adults caged in plastic containers holding 1 cm of moist sand at 14°C, in darkness, readily accepted onion maggot (OM), Delia antique (Meigen), larvae as their food source. AB eggs collected from oviposition cages were distributed around OM pupae scattered over the surface of moist sand in similar tightly sealed plastic containers. At 22°C and a photoperiod of LD 16:8, with 1:1 AB egg: OM pupa, the mean parasitism rate was 71%; larvae reared under these conditions did not enter diapause. At 14°C, in darkness, using 1.25:1 AB eggs: OM pupa reared under diapause-inducing conditions, the mean parasitism rate was 74%, and >95% of the first-instar AB entered diapause. A minimum of 8 weeks at 1°C aws necessary to fulfill diapause requirements; diapausing larvae could be held at this temperature for as long as 6 months with no decrease in survival rate. Five hours of labor per week were required to produce ca. 10,000 AB adults per week.

Toxin Production in Hard‐Cooked Eggs Experimentally Inoculated with Clostridium botulinurn

ABSTRACTHard‐cooked eggs were cooled for 30 min in water containing concentrations of spores of Clostridium botulinum ranging from 101 to 104 spores per mL. The eggs were then air dried and incubated either aerobically, anaerobically, or in sealed plastic containers and checked daily for toxin production using the mouse bioassay. Toxin was detected inside the eggs within 2 to 7 days depending on the method of incubation. Sensory changes in toxic eggs were also recorded, and although the proteolytic strains usually produced unacceptable odors and/or appearances, these dhanges were not always detected.

Conservation of wilted herbage ensiled in sealed plastic containers, with and without the addition of urea, and its intake by sheep

AbstractTimothy‐meadow fescue grass was wilted to 27.7–33.9% dry matter content and two silos were filled with the wilted material alone and two with the wilted herbage to which urea, at a level of 1.38% of the dry matter ensiled, was added. The mean dry matter loss from the control silages was 16.7% and from the urea‐treated silages 11.4%. No urea could be detected in the silage made from the urea‐treated herbage. There was no evidence for any major differences in the fermentation pathways between the control and urea‐treated silage. Voluntary intake of control and urea‐treated silage by sheep was similar (1.7 times the maintenance metabolisable energy requirement) so that nitrogen intake was higher when the urea‐silage was fed. No toxic effects of the treated silage were observed when assessed by blood urea and ammonia levels.

Protection of Stored Woolens from Insect Damage

Various control techniques were evaluated as methods of protecting stored woolens. The use of tightly sealed plastic containers us barriers prevented larvae of the black carpet beetle ( Attagenus piceus (Oliv.)) and larvae of the webbing clothes moth ( Tineola bisselliella (Hum.)) from attacking stored woolens. Formalin and paradichlorobenzene (PDB) fumigants were effective against clothes moth adults, but both were ineffective against the carpet beetle larvae. The residual spray technique, employing 5% DDT, 5% methoxychlor, 1.25% lindane, 2% chlordane, 0.5% dieldrin, or 0.5% Diazinon, did not give satisfactory kill of the carpet beetle larvae. The hazards involved in using DDT, chlordane and other impregnants were considered. For the homemaker, the barrier technique using tightly scaled plastic containers is recommended as an easy and effective control measure.