Other - Abstracts
Abstracts
R. Dias, S. Navarro, and Miriam Rindner
Analyses of imported and locally produced durable food products were undertaken to determine the presence of insects. Results were grouped according to product: manufactured products, coffee-tea, oil seeds, nuts, cereal grains, dried fruit, legume seeds and spices. Insect species found in the samples were grouped according to country of origin. The survey covered entomological analyses undertaken from 1986 to 1990. Results showed that highest levels of infestation were in the legume seeds (60%). Frequency of occurrence of the different stored product insect species was also listed (in Hebrew).
R. Dias, Miriam Rindner, S. Navarro, and E. Donahaye
A rapid flotation method was developed to determine the presence of insect fragments in dried vegetables in accordance with Israeli standards. Dried peppers, broccoli and a dried vegetable mix were used to compare recovery of insects and insect fragments (Oryzaephilus surinamensis and Stegobium paniceum) between the rapid flotation method, the visual method and the AOAC flotation method. A significantly higher recovery rate was recorded by the rapid flotation method for broccoli while for the other vegetables no significant difference was recorded between the three methods. (in Hebrew).
A.Varnava, S. Navarro, and E. Donahaye
A method for the bulk storage of barley in the open air under Mediterranean conditions was developed. A large (75 x 25m) concrete platform with low walls was filled with barley and covered with a PVC overliner and a polyethylene underliner. The barley formed a pile of 4,018 tonnes with a peak 7 m high and was stored for 34 months under hermetic seal. Periodic monitoring was carried out to determine temperature fluctuations, intergranular gas composition, insect infestation, and grain quality parameters. Ambient temperatures were shown to create temperature gradients in the upper layers, and moisture migration occurred towards the peak of the grain bulk. However, the resulting spoilage by moulds was limited to 0.22% weight loss on an annual basis. An additional 0.12% loss due to insect damage, and spillage resulted in an annual storage loss of 0.34%. Possible solutions to this problem were discussed. The platform successfully protected the grain against insect, bird, and rodent attack and provided safe storage during the rainy season. At the end of storage, the PVC overliner which had been used continuously since 1988 remained with low gas-permeability, retained its mechanical characteristics and was suitable for reuse.
G. C. Sabio, S. Navarro, E. Donahaye, F. M. Caliboso, M. Rindner and R. Dias
The feasibility of the sealed storage technology for storing bagged corn grains with up to 14% moisture content outdoor, was investigated in the Philippines. The essential advantage of this storage technique lies in the generation of an oxygen-depleted and carbon dioxide enriched intergranular atmosphere storage ecosystem that arrests insect development. The structures used were weld-mesh walled plastic silos with a capacity of 40 tonnes and frameless flexible envelopes (Volcani cubes) of 20 tonnes. A total of 11 trials consisting of 9 gas-tight sealed storage and 2 conventional storage as control, were conducted for periods of up to 6 months. Results showed no significant increase in population density of insects in the gas-tight sealed corn stacks whereas in the control, insect population increased considerably. Insect density in sealed storage was maintained below the threshold of economic damage without the use of pesticides. Comparative average weight loss due to insect activity after about 3 months of storage was 0.3% in sealed stacks and 5.3% in the control.
M. Calderon, E. Donahaye, S. Navarro, and R. Davis
A polyvinyl chloride silo, equipped with an aeration system, was used in the arid, semi-desert region of southern Israel, to store 548 metric tonnes of locally grown wheat over a 30 months period. Grain temperature, moisture content, atmospheric gases, and insect infestations were recorded periodically, as well as the ambient temperature and the relative humidity. The grain was cooled by aeration during the winters of 1983-1985. The silo was sealed hermetically during summers. Aeration cooled the grain to temperatures below 17degC. The highest CO2 and the lowest O2 during hermetic storage were 10.6% and 5.8% respectively. A relatively high initial insect infestation was suppressed and subsequent localized infestation by the lesser grain borer, Rhyzopertha dominica, was dealt with by a spot fumigation using phosphine.
The overall, annual loss of grain calculated from the samples taken during loading and unloading was 0.24%. Observations were also made on water condensation, microflora, and rodents.
B. YAKOBSON. S. NAVARRO, E.J. DONAHAYE, A. AZRIELI, Y. SLAVEZKY AND H. EFRATI
The building structure of bee hives is based on the wax cells produced by the bees themselves. The most important of the species that attack beeswax is Galleria mellonella (L.), the greater wax moth, and protection of stored combs from this insect is of high priority, especially in hot climates.
A new approach to control of this pest has been to replace the traditionally used chemical insecticides, such as EDB, by environmentally sound methods. We propose the use of controlled atmosphere methodology with CO2 for insect control and subsequent protection of honey supers during storage. The results of field tests using mixtures of CO2 in air at initial concentrations ranging from 96 to 63%, for prolonged exposure periods, are presented. The tests were undertaken using 12-m3 plastic enclosures and specially sealed 34 m3 20-foot freight containers. Both methods enabled complete control of the wax moths and subsequent protection from reinfestation. The rigid structure of the containers had the inherent advantage of giving better protection from rodents and pilfering. However, each container requires specific sealing procedures followed by sealing tests. The plastic enclosures, found to be suitable for smaller enterprises, had the advantage of ease of portability and installation at the storage site. Their structural seals were checked during manufacture. So far they have been under continual use for 5 years.
Filipinas M. Caliboso, S. Navarro, D.G. Alvinda, E.J. Donahaye and Glory C. Sabio
Due to high temperature and relative humidity in the Philippines, significant losses occur in stored paddy as a result of mold contamination, a loss exacerbated when grains are not properly or uniformly dried before storage. This led to the investigation of the effect of hermetic storage using gastight flexible liners on population changes of fungi in dry paddy (below 14% moisture content) and of the growth of mold in paddy with intermediate moisture content (18%) when the paddy is stored outdoors.
The concept of gastight storage was tested using especially designed enclosures and employing heavy duty flexible liners developed in Israel. Field evaluations showed that insect infestation was controlled in bagged paddy, with the added benefit that mold growth was controlled. Following one-and-a-half to six months in storage, most fungi generally did not develop. This may be attributed to the effect of the modified atmosphere generated inside the gastight liners. Higher fungal counts were noted at the periphery and top grain layers in the gastight enclosures. Further observations revealed that the proliferation and prevalence of mold species was affected by both storage time and the modified atmosphere present inside the gastight liners.
G. C. Sabio, S. Navarro, E. Donahaye, F.M. Caliboso, M. Rindner and R. Dias
The feasibility of the sealed storage technology for storing bagged corn grains with up to 14% moisture content outdoor, was investigated in the Philippines. The essential advantage of this storage technique lies in the generation of an oxygen-depleted and carbon dioxide enriched intergranular atmosphere storage ecosystem that arrests insect development. The structures used were weld-mesh walled plastic silos with a capacity of 40 tonnes and frameless flexible envelopes (Volcani Cubes) of 20 tonnes. A total of 11 trials consisting of 9 gastight sealed storage and 2 conventional storage as control, were conducted for periods of up to 6 months. Results showed no significant increase in population density of insects in the gastight sealed corn stacks whereas in the control, insect population increased considerably. Insect density in sealed storage was maintained below the threshold of economic damage without the use of pesticides. Comparative average weight loss due to insect activity after about 3 months of storage was 0.3% in sealed stacks and 5.3% in the control.
M. Calderon, E. Donahaye, S. Navarro and R. Davis
A PVC silo, equipped with an aeration system, was used in the arid, semi-desert region of southern Israel, to store 548 tonnes of locally grown wheat over a 30-month period. Grain temperature, moisture content, atmospheric gases, and insect infestation were recorded periodica11y, as well as the ambient temperature and relative humidity.
The grain was cooled by aeration during the winters of 1983-1985. The silo was sealed hermetically during the summers. Aeration cooled the grain to temperatures below 17°C. The highest CO2 and the lowest O2 1evels recorded during sealed storage were 10.6 and 5.8%, respectively.
A relatively high initial insect infestation was suppressed, and subsequent localized infestation by the grain borer, Rhyzopertha dominica, was delt with by a spot fumigation using phosphine.
The overall annual loss of grain, calculated from samples taken during loading and unloading, was 0.24%. Observations were also made on water condensation, microflora and rodents.
R. Dias, S. Navarro and M. Rindner
Analyses of imported and locally produced durable food products were undetaken to determine the presence of insects. Results were grouped accordmg to product manufactured products, coffee and tea, oil seeds, nuts, cereal grains, dried fruit, legume seeds, and spices. Insect species found in the samples were grouped according to country of origin. The survey covered entomological analyses undertaken from 1986 to 1990. The results showed that the highest levels of infestation were in the legume seeds (60%). Frequencies of occurrence of the various stored-product insect species were also determined.
R. Dias, M. Rindner, S. Navarro and E. Donahaye
A rapid flotation method was developed to determine the presence of insect fragments in dried vegetables, in accordance with Israeli standards. Dried peppers, broccoli and a dried vegetable mix were used to compare the recoveries of insects and insect fragments (Oryzoephilus surinamensis and Stegobium paniceum) by the rapid flotation method, the visual method and the AOAC flotation method. A significantly higher recovery rate was recorded by the rapid flotation method for broccoli while for the other vegetables no significant difference was recorded among the three methods.
M. Rindner, E. Donahaye, S. Navarro, Y. Blauschild and A. Azrieli
Respiration rates of paddy rice (var. Tebonnet) were examined at moisture contents ranging from 12.5 to 15.5% and at temperatures of 26, 30, and 35°C. To facilitate the prediction of safe storage periods, graphs were drawn to express the influence of grain moisture content and temperature on the storage times required to produce a grain dry-weight loss of 0.5%. Microfloral counts at the end of 3 months storage indicated pronounced microfloral development at moisture contents of 14.5 and 15.5%. Equilibrium moisture content curves drawn for the three storage temperatures indicated that the critical moisture content was about 14.5%, equivalent to 75% relative humidity in air.
M. Calderon and S. Navarro
T. castaneum adults were exposed to atmospheres containing O2 concentrations of 2%-5% supplemented with 5%-35% CO2 at 26¡ and 30¡ for 24-120 hr at 57% relative humidity. Mortality of insects at the given O2 concentrations was higher when the level of the added CO2 was increased, the temperature was higher and the exposure time was extended. A significant interaction was found between the levels of O2 and CO2 tested, indicating the clear synergistic effect of these two gases on the mortality of test insects.
Calderon. M. and Navarro, S.
Tribolium castaneum and Rhyzopertha dominica adults and eggs were exposed to atmospheres containing 2-8% O2, supplemented with 5%-30% CO2 at 26°C and 55% R.H. for 24-144 h. Eggs of both species were more susceptible than their adult stage to low O2 concentrations per se as well as to the O2 and CO2 mixtures tested. R. dominica eggs were more tolerant than T. castaneum eggs to the above treatments.
Addition of CO2 to low O2 atmospheres resulted in a synergistic effect on adult mortality of both species, while there was only an additive effect on the eggs exposed to the same treatments.
These results provide additional information to be considered in the use of controlled atmospheres for grain storage.
M. Calderon, S. Navarro and E. Donahaye
The effect of low pressure (10-12 mm to 16-20 mm mercury) on the mortality of six species of common stored-product insects was examined in steel containers of 20 l capacity filled with grain, which were held under low pressure for periods of 1-7 hr and 1-5 days at temperatures of 18±1°C and 25±1°C. The susceptibility of adults and larvae of the species tested to the above treatment is given below: the most susceptible to low pressure were, Ephestia cautella (Wlk.) adults, followed by Oryzaephilus surinamensis (L.) adults, Tribolium castaneum (Herbst.) adults, Callosobruchus maculatus (F.) adults, T. castaneum larvae, Trogoderma granarium Everts larvae, Sitophilus oryzae (L.) adults, Callosobruchus maculatus larvae, S. oryzae larvae. In all species, 100 per cent mortality of both larvae and adults was obtained after 120 hr, except in the case of C. maculatus larvae and S. oryzae larvae.
The results so far obtained indicate the possibility of using low pressure for the control of stored-product insects in grain, in particular where infestation is caused by the more susceptible insects to the above treatment.
R. Dias, S. Navarro, E. Donahaye, Miriam Rindner, A. Azrieli and D. Hovevey-Zion
Stored-product insects develop in a wide range of durable agricultural products including processed commodities. Information on the relative frequency of occurrence of stored-product insects in these commodities provides an index to the sanitary conditions prevailing during processing, and also emphasizes the need for increased quality inspection of imported commodities so as to minimize the risks of introducing quarantine pests. The presence of insects was examined in 2,332 food samples taken mostly by the Israel Health Authorities over 9 years between January 1991 and December 1999. A total of 2,078 of these samples were taken at random from commodities imported into Israel, while 254 samples were taken from locally grown, processed and marketed products suspected of infestation during the same period of time. The results showed that the most infested commodity imported to Israel was coffee; the most commonly occurring species was Rhyzopertha dominica; commodities imported from African countries were the most commonly infested. This survey provided updated information on the occurrence of insect species in imported commodities and in locally manufactured and processed foods. It also focused on the need for sanitary measures to be taken on imported and locally processed food.
1. Tunc and S. Navarro
Tribolium castaneum eggs were exposed to modified atmospheres for 0-96 hr at 26°C. The effect on egg mortality was determined by exposure to low oxygen atmospheres at three different relative humidities, and also at four different carbon dioxide concentrations at 50% relative humidity. Relative humidity had only a limited effect on survival of eggs exposed to low oxygen concentrations. Complete mortality was observed in atmospheres of 2% and 4% oxygen in nitrogen with relative humidities of 20%, 50% and 95%. While at 6% oxygen, only at 20% relative humidity was complete mortality obtained over the 96 hr exposure period. At 40% carbon dioxide and 50% relative humidity, at all tested concentrations of oxygen (4% to 15%), complete mortality was obtained.
P. Williams, W. Minett, S. Navarro and T.G. Amos
A bolted galvanized iron silo (21.5 t) was sealed using a polyvinyl resin formulation (1624 White) sprayed onto joints from the inside. Gastightness was assessed by pressure decay and static pressure tests. The silo was loaded with wheat into which cages of insect-infested wheat, thermocouples and gas sampling lines, were introduced. Oxygen levels were reduced to < 1% by purging with nitrogen, and similar levels were then maintained by a slow nitrogen bleed for 35 days, after which the silo was emptied. Al1 adult insects were dead but, as expected, some immatures survived since the maintenance period was too short to ensure complete kill at the observed grain temperatures (generally < 1 5°C). The silo was reloaded, resealed and tested again for leaks. Some leaks were found and sealed with silicon rubber; Gastightness was not as good as before, though the silo would still be suitable for fumigation. Further sealing would be required however, if nitrogen were to be used efficiently (maintenance rate of 0.2 m3t-1 day-1).
Sealing achieved was sufficient to permit use of nitrogen or fumigants but sealants cost $132 and labour a minimum of $280, representing an overall cost of $19.1 6 t-1. This would still be cheaper than buying a new silo of suitably gastight construction at a cost of at least $28 t-1.
(=Australian $$).
A. Friedlander and S. Navarro
Exposure of Ephestia cautella pupae to hypercarbic atmospheres causes an accumulation of sorbitol in the tissues. This accumulation is maximal at 80% CO2 and decreases at higher concentrations. The reason for this paradoxical behavior is the inhibition by carbon dioxide of the reduction of glyceraldehyde catalyzed by aldose reductase. This inhibition is competitive and is overcome by accumulation of the substrate. It is suggested that the sorbitol pathway might be a bypass of phosphofructokinase, although its efficiency is questionable.
A. Friedlander and S. Navarro
The triglyceride content of Ephestia cautella pupae exposed to increased carbon dioxide atmospheres at low relative humidity was not markedly affected. There was a significant increase in weight loss of pupae exposed to low relative humidity. Results indicate that for E. cautella, metabolic water formation by fat utilization can hardly regulate water exigencies for the pupae and cannot fully compensate for water losses in high carbon dioxide atmospheres.
A. Friedlander, S. Navarro and Don L. Silhacek
1. The effect of carbon dioxide on the main NADPH-producing systems in Ephestia cautella pupae, namely the 'malic' enzyme and 6-phosphogluconic acid dehydrogenase, a key enzyme in the hexose monophosphate pathway. was investigated. Both systems were found to be sensitive to carbon dioxide.
2. At high levels of CO2 the 'malic' enzyme becomes fully reversible, the reaction being driven towards pyruvate production by coupling the 'malic' enzyme to the ubiquitous lactic acid dehydrogenase.
3. 6-Phosphogluconic acid dehydrogenase is largely inhibited at high levels of CO2.
4. The combined effect results in NADPH production becoming dependent on available malate.
A. Friedlander and S. Navarro
Ephestia cautella pupae, 0-24 hr old, were exposed for 24 hr to a controlled atmosphere, either high in carbon dioxide or low in oxygen at 26°C. Tissue levels of glycogen, trehalose, glucose, alpha-glycerophosphate, glycerol, lactate, alanine, ATP, ADP, AMP, citrate and malate were determined in exposed pupae. Hypercarbia tended to increase the consumption of glycogen but had no clear effect on trehalose consumption. Glucose levels were similar to insects exposed to normal and to hypercarbic atmospheres but significantly higher in insects exposed to hypoxia. Alpha-glycerphosphate, glycerol, lactate and alanine levels were high in 0-24 hr old pupae but fell after 24 hr exposure to normal of hypoxic atmospheres. The levels of these metabolites fell less when nitrogen was replaced by carbon dioxide. Hypercarbia reduced the total amount of adenine nucleotides and the energy charge. However, 1% oxygen in nitrogen markedly affected the ATP level. Citrate was reduced in hypercarbia and in hypoxia, whereas malate was reduced by hypercarbia but increased in hypoxia.
Miriam Rindner, S. Navarro, E. Donahaye, R. Dias A. Azrieli and Glory Sabio
Under present agreements of the Montreal protocol, methyl bromide (MB) phase-out for developed countries will take place by 2005. Although there is a large number of suggested potential alternatives to MB for disinfestation of durable commodities, development of most of these alternatives is likely to be costly. Furthermore, any alternative must compare favorably with the rapid kill achieved by MB which is its major advantage over other treatments.
The combined factors of MB phase-out, the gradual development of insect resistance to fumigants and the undesirable effects of fumigant residues in food, have led to the idea of using carbon dioxide enriched controlled atmospheres. The objective of this investigation was to develop an alternative control treatment based on a combination of heat and CO2.
CO2 concentration and temperature levels were investigated using diapausing larvae of Trogoderma granarium as test insects. The influence of CO2 at 45°C on reducing the exposure time expressed as LT95 (hours to obtain 95% mortality) values for T. granarium showed that by increasing the CO2 concentration to 90% the exposure time decreased to about 7.8 hours. These results demonstrate the potential use of CO2 in combination with heat as an alternative control method to MB. Our findings show that by increasing the CO2 concentration to 90% and raising the temperature to 45°C the exposure time can be decreased to about 8 hours.
J. Larry Zettler and Shlomo Navarro
We investigated the possibility that California prunes stored in modified atmospheres will tolerate higher water activity (aw) levels than those required at normal atmospheres and that the naturally occurring microfloral infection level on the prunes may generate the modified atmospheres that inhibit mold activity in airtight conditions. Dry prunes were moisturized to a range from 18 to 38% moisture content to acquire samples with water activities ranging from 0.575 to 0.858 aw. In unsealed conditions at 35oC, there was a level of naturally occurring microorganisms (aerobic plate count, yeast count and mold count) that generally increased above water activity of 0.70. However, incubating these samples in a sealed container for 35 days at 35°C indicated that the naturally occurring microorganisms remained unchanged throughout the range of water activities. Microfloral respiration as a function of temperature was determined by incubating similarly moisturized prune samples at 25°, 30° and 35°C and then measuring the declining O2 concentrations through time. Results showed that the higher the water activity and the higher the temperature, the more intense the O2 consumption by the product. A nearly linear relationship was observed between O2 depletion and time. Anaerobic conditions were reached in less than 2 days at 25°C only at 0.858 aw the highest water activity tested. At higher temperatures, anaerobic conditions were achieved at water activities of 0.824 and above. These results indicate that at aerobic conditions microorganisms can flourish and cause deterioration on prunes if the water activity of the fruit is above 0.7 (moisture content of 24.6%). However, under sealed conditions, prunes can tolerate a higher water activity without microorganism growth and deterioration of the fruit.
Chuwit Sukprakarn, Kanjana Bhudhasamai, Bussara Chankaewmanee
Trials on the preservation of corn seed quality under airtight storage conditions were carried out in the Rachasima province of Thailand during 1996-7. Sacks of corn for seed purposes (var. Suwan No.1), were stored in sealed PVC sheeting, 0.8 mm. thick and tailored to a shape known as the Volcani cube, with a volume of 15 m3 and a storage capacity of approximately 10 tonnes. Two cubes were loaded with grain and placed outdoors for 3 and 9 months respectively and observations were made at 2 week intervals to monitor temperature, relative humidity and seed moisture content inside the cubes. At the end of the respective storage periods, the cubes were opened to enable evaluation of numbers of insects, grain damage by insects, mould infection, percentage germination and, moisture contents of the corn seed. The results of both trials indicated that the cubes could preserve corn seed quality. At the end of the trials, insect damage and live insects were not observed. Also the levels of mould infection had only slightly increased and a low level of aflatoxin was revealed only in the second trial. Seed moisture contents, germination percentages, temperature and relative humidities within the cubes before and after treatment showed only slightly differences and the seed was still in good condition.
Alvindia, D.G., Caliboso, F.M., Sabio, G.C. and Regpala, A.R.
Field trials were carried out in the Philippines for outdoor storage of maize sealed in flexible liners. Two storage atmospheres were evaluated: carbon dioxide (CO2)-enriched and hermetic storage.
Tests were carried out to determine insect infestation, moisture content, microbial infection, weight loss, grain quality and seed germination.
Insect infestation was completely prevented in the CO2 enriched cubes while few live insects were noted in the hermetic cubes. Insect-damaged kernels and weight loss were minimised. Grain moisture content remained stable after three months although mould growth was noted at the top surface of the stacks. Grain quality was preserved and seed germination was not affected.
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