Effect of plasticizer type and amount on hydroxypropyl methylcellulose-beeswax edible film properties and postharvest quality of coated plums (cv. Angeleno).
The effect of the composition of hydroxypropyl methylcellulose (HPMC)-beeswax (BW) edible coatings on stand-alone film properties and on postharvest quality of coated 'Angeleno' plums was studied. Glycerol (G) and mannitol (M) were tested as plasticizers at two different plasticizer/HPMC ratios (100:1 and 300:1 molar basis). BW content was 20 or 40% (dry basis). An increase in G content increased film flexibility and vapor permeability (WVP), whereas an increase in M content enhanced film brittleness without affecting WVP. An increase in BW content reduced film flexibility and reduced WVP of only G-plasticized films. Coatings reduced plum softening and bleeding, but were not effective in reducing plum weight loss. At low plasticizer content, coatings reduced texture loss effectively. Low BW also lowered plum bleeding. Plasticizer type affected only ethanol and acetaldehyde contents without affecting the remaining quality parameters. Therefore, HPMC-BW coatings have the potential to extend the shelf life of plums. However, this effect depends on coating composition. Differences between coating and film performance indicate that data from stand-alone films may be used as a preliminary screening, but coating performance should be analyzed on coated fruit.
Preparation and Characterization of Composites Based on Polylactic Acid and Beeswax with Improved Water Vapor Barrier Properties.
UNLABELLED
Beeswax and a plasticizer (ATBC) were added to polylactic acid (PLA) films in order to enhance the water vapor barrier properties of the films. Beeswax improved the barrier properties; the water vapor permeability in the composite containing 1% beeswax was 58% lower than that of the neat PLA. Fourier transform infrared spectroscopy and X-ray diffraction analysis revealed that the incorporation of beeswax and ATBC had so little effect on the PLA structure. In addition, the structure of PLA did not vary substantially with the additions. The surfaces of the composites were examined by using field emission scanning electron microscopy. Differential scanning calorimetry results showed that the degree of crystallinity of the PLA films increased with the addition of beeswax and ATBC. However, the tensile strength and elongation at break of the composites containing beeswax were up to approximately 50% lower than those of the neat PLA. Although further study is needed to improve the mechanical properties, the aforementioned results showed that the PLA barrier properties can be improved by the incorporation of a small amount of beeswax and ATBC.


PRACTICAL APPLICATION
The results of this study can be applied for the preparation of PLA composite films with improved barrier properties. Such biodegradable films are extremely useful for applications in the food packaging industry.
Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.
Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.