Essential oils from oregano and thyme were applied for 24 h as fumigants against the mycelia and spores of Aspergillus flavus , Aspergillus niger and Aspergillus ochraceus , as well as against natural microflora of wheat grains. The minimal inhibitory concentration (MIC) of oregano oil needed to inhibit the mycelial growth of the fungi was 2.0 μl/L, while spores were eradicated following exposure to 2.0 to 2.5 μl/L. The thyme essential oil was less efficient in controlling mycelia and growth was observed even following exposure to 4.0 μl/L. However, the thyme essential oil was fungitoxic to spores (MIC = 3.0 μl/L). In another set of trials the efficacy of the oils and two of their constituents (carvacrol and thymol) in controlling natural microflora of surface-sterilized wheat grain was studied. Of the four materials investigated, only oregano essential oil exhibited fungicidal activity and, following 24 h exposure to 20 μl/L, a significant reduction in the percent of infested grain was observed even after 5 days of incubation on potato dextrose agar. A reduction in the germinability of the grains was evident following exposure to the materials tested. When the fungicidal activity of oregano essential oil was evaluated using grains with different moisture contents (MC), data revealed that the better inhibitory effect was achieved in grain with a high MC. The findings emphasize the toxicity of oregano and thyme essential oils as fumigants against fungi attacking stored grain and strengthen the possibility of using them as an alternative to chemicals for preserving stored grains.

SummaryThe effects of short heat (boiling temperature) treatments, consisting of ‘blanching’ in concentrated sucrose (70%) solution (I), or plain water (11); or osmotic dehydration in cold (room temperature) (111) or hot (boiling) sucrose (70%) solution (IV); and a combination of (111) following (I) or (11), on the drying behaviour of papaya, dehydrated to the intermediate moisture (IM) range, were studied. Significant increases were observed in the dry matter content of papaya treated as above (I, 111, IV or 111 following T or IT), with the obvious increase in the expected production yields and probable reduction of the heat energy needed for the drying process.The drying behaviour of papaya as a raw material for IM products, during and after the above treatments, as well as following hot‐air, (cabinet) or direct‐sun drying, was studied. The drying time needed for cabinet or solar drying following osmotic treatments of papaya was considerably shortened, and therefore a significant saving in the heat energy needed for drying is to be expected. The optimal treatments to achieve a considerable shortening in the drying time, without affecting negatively the quality of the 1M papaya, seemed to be syrup ‘dipping’, or a combination of water or syrup blanching and cold osmotic dehydration.The above methods can be applied in both small, non‐sophisticated fruit dehydration plants (mainly solar drying), or in larger and more sophisticated ones (mainly forced hot‐air drying).

Summary Freezing (‐ 40°C) a cell suspension of Salmonella gallinarum at a cooling rate of 18°C per min and an initial cell concentration of 37 × 10 7 cells/ml resulted in a recovery more than five times that obtained from a lower cooling rate (0.5°C per min). Decreasing the initial cell concentration to 12 × 10 3 cells/ml at the higher cooling rate resulted in an increase of only twice the recovery of the lower rate. The percentage recovery from the higher cell concentration was greater than from the lower concentration, only at the higher cooling rate. The apparent recovery of Salmonella gallinarum on a selective medium immediately after freezing, was only 60% of that on a nonselective medium, and decreased to 5% after 1 week of storage at ‐ 20°C.

Summary The viable counts of total aerobic mesophiles and psychrophiles, coliforms, coagulase‐positive staphylococci and salmonellae in green beans were greatly reduced by blanching in the course of their preparation for freezing. The increase in bactcrial numbers between blanching and freezing appears to be caused by contamination from the conveyor belt and from the hands of employees. Salmonellae, detected in small numbers prior to blanching, were not recovered after blanching. Freezing at a rate of 4–5°C per min, had only a slight destructive effect on the various bacterial groups studied. A significant reduction in counts, especially of coliforms and staphylococci, occurred after 4 weeks of frozen storage. Aerobacter aerogenes was the main coliform organism recovered from the frozen green beans.

S ummary : Oleuropein, the bitter principle of green olives, is surface active; this and its effect on cell membranes, as demonstrated with human erythrocytes, seems to be the basis of its antimicrobial activity. Oleuropein effected a significant leakage of glutamate, potassium and inorganic phosphate from Lactobacillus plantarum. Oleuropein had no effect on the rate of glycolysis when added to resting cells of L. plantarum but it caused a decrease in the ATP content of the cells.

Summary.Treatment of green olives for 2 min with dilute hot alkali before brining increased the release of sugars, B complex vitamins, amino acids and phenolic compounds, and enhanced the establishment of lactic acid bacteria in the brine. Two components of the ethyl acetate extract of green olives, which showed an antibacterial activity, were isolated and identified as the glycoside oleuropein and its phenolic aglycone. The inhibition of Lactobacillus plantarum by the ethyl acetate extract or by oleuropein was augmented by reducing the concentration of organic nitrogenous compounds, increasing the NaCl concentration in the assay medium and decreasing the inoculum size. Besides its activity towards various bacteria, oleuropein inhibited the growth of Geotrichum candidum Link, Rhizopus sp. and Rhizoctonia solani Kühn. On the basis of these findings, an explanation for some problems in the lactic fermentation of green olives is suggested.

SUMMARYThe marked enhancement of lactic fermentation rates of intact Merhavia and Manzanillo green olives in brine following pretreatment with hot alkali results mainly from the destruction of an antilactic factor by the alkali. The press juice of Manzanillo green olives contains an ether‐extractable, hot alkali labile factor which temporarily inhibits acid production by Lactobacillus plantarum in APT broth. A rapid method for the detection of the antilactic factor is described. The antilactic factor present in intact green olives may not be the same as that in the press juice.