Effect of vacuum-steam-vacuum treatment on microbial quality of whole and fresh-cut cantaloupe.

Minimally processed fruits and vegetables have a limited shelf life because of deterioration caused by spoilage microflora and physiological processes. Cutting may increase microbial spoilage of fruits through transfer of microflora on the outer surfaces to the interior tissue. The objectives of this study were to use the vacuum-steam-vacuum (VSV) process to reduce indigenous spoilage microflora on the surface of cantaloupes and to investigate the effects of such treatments on transfer of spoilage microflora from the cantaloupe surface to the fresh-cut melon during rind removal and cutting. Whole cantaloupes were treated in the VSV processor, and fresh-cut pieces prepared from treated and control samples were stored at 5 and 10 degrees C for up to 9 days. Presence and growth of mesophilic bacteria, yeasts and molds, and Pseudomonas spp. were determined in fresh-cut samples during storage. Texture and color (CIE L*, a*, and b*) also were measured during storage. VSV treatment resulted in a 1.0-log reduction of aerobic mesophilic bacteria, a 2.0-log reduction of yeasts and molds, and a 1.5-log reduction of Pseudomonas spp. on cantaloupe surfaces. VSV treatment significantly reduced transfer of yeasts and molds and Pseudomonas spp. from whole cantaloupe surface to fresh-cut pieces during preparation (P < 0.05). Texture and color of the fresh-cut pieces prepared from the VSV-treated whole melons were similar to those of the controls. The results of this study indicate that the use of the VSV process to reduce the surface populations of yeasts and molds and Pseudomonas spp. on whole cantaloupes will reduce subsequent transfer of these microbes to fresh-cut pieces and enhance the microbial quality of the fresh-cut product.

Development of a continuous process to make casein films.

A semicontinuous pilot plant process was developed to make films from calcium caseinate plasticized with glycerol. Calcium caseinate/glycerol solutions were wetted and spread on polyethylene or Mylar belts and were readily removed after forming films. A Meier rod was used to spread the solution onto the belt. Feed rates were 3.3 and 5 g/cm. The resulting films using the polyethylene belt had a tensile strength of 5 MPa and 30% elongation with thickness of 0.14 mm. When the glycerol concentration was adjusted, the process produced films with properties similar to those previously reported for a batch process. It is anticipated that this process will apply to other proteins.

A novel nonchemical method for quarantine treatment of fruits: California red scale on citrus.

A process for removing or killing California red scale, Aonidiella aurantii (Maskell), from citrus fruit as a postharvest treatment was evaluated. The process subjects the fruit to vacuum, steam, and vacuum that physically removes red scale from the fruit and kills those scales that are not removed from the fruit. Different numbers of cycles and steam temperatures were compared for efficacy in removing scale from lemons or killing those that remained. Multiple (two to three) cycles removed up to 96% of first molt scales on the fruit, but they were much less effective in removing other stages, especially those that had advanced beyond the second instar. However, it was extremely effective in killing the scales remaining on the fruit. Although this process does not eliminate cosmetic damage caused by scale presence, it might be used in combination with high-pressure washers currently used in packing houses to allow importers and exporters to meet the most stringent quarantine requirements. Because of its killing power, this technique should be tried on other insects and commodities to see whether it can be substituted for certain uses of methyl bromide.

Drying kinetics of calcium caseinate.

Drying is a major component of the cost of making caseinate-based films. We determined the drying curves for making calcium caseinate/glycerol films at low and high relative humidity at 21-34 degrees C. The drying curves exhibited a very long constant rate period followed by a single falling rate period. Much of the drying was in the constant rate period and preceded the actual film formation. Normally, calcium caseinate solutions are dried from about 5% solids, but it was possible to start with a more concentrated solution, 10% solids, to avoid much of the constant rate period. The resulting films were equal to those prepared starting at high initial moisture. An estimate of the drying costs indicated it is much cheaper to start with the more concentrated solutions.

Use of vacuum-steam-vacuum and ionizing radiation to eliminate Listeria innocua from ham.

Listeria spp. are a frequent postprocess contaminant of ready-to-eat (RTE) meat products, including ham. Vacuum-steam-vacuum (VSV) technology has been used successfully to eliminate Listeria innocua from hot dogs. Ionizing radiation can eliminate Listeria spp. from RTE meats. However, the excessive application of either technology can cause changes in product quality, including structural changes, changes in cure color (redness), and lipid oxidation. In this study, two cycles of VSV were combined with 2.0 kGy of ionizing radiation to obtain 4.40- and 4.85-log10 reductions of L. innocua on ham meat and skin, respectively. The use of both treatments resulted in an additive, as opposed to synergistic, reduction of L. innocua on ham. The combination treatment did not cause statistically significant changes in product structure, color (redness), or lipid oxidation.