Category Archives: Volume 22 No. 1 & No. 2 (2000)

Effects of temperature on drying rates and sensory qualities of sweetened maturing coconut meat (coco-crisps)


Author(s): Lemuel M. Diamante1, Jesebel P. Rosillo1 and Remberto Patindol2

Abstract

This study was conducted to determine the effect of temperature on the drying rates and sensory qualities of sweetened maturing coconut meat called coco-crisps at ambient humidity, constant air velocity and tray density.
The drying of sweetened maturing coconut meat at different temperatures (62-90°C) using an air velocity of 0.25 m/s and a tray density of one layer deep consisted of a constant rate period (CRP) and two stages of the falling rate period (FRP). The CRP drying rates and FRP drying coefficient in both stages increased with temperature. The first stage FRP was faster than the second stage. The activation energy for drying of the product in the first stage FRP was 18.65 KJ/mole and was in the same range as other biological products like casein curd, potatoes and sugar beets. The activation energy for drying of the product in the second stage FRP was about three times higher than in the first stage FRP.
The color acceptability of the product dried down to a moisture content of 3% (dry basis) using drying temperatures of 64 and 80°C were not significantly different from each other and were better than the product dried at 96°C. The samples dried at 64 and 80°C remained white in color while the one dried at 96°C turned light brown in color However, the product dried at 96°C was better than the other two products based on texture and overall acceptability.

Keywords : constant rate period. drying temperature. drying rates. falling rate period. sensory qualities. sweetened coconut meat.

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Soil biological parameters as indicators of sustainability of natural and agricultural land use systems


Author(s): M.S. Nagaraja1 and V.R. Ramakrishna Parama2

Abstract

Evaluating the sustainability of any land use system poses challenging methodological questions. The study conducted at the University of Agricultural Sciences, Bangalore, India revealed that management practices under different land use systems have altered soil functions and processes. The biological changes observed in man-made systems relative to the natural systems are important indicators of the impacts of management practices. Strategies based on these biological indicators and correlating them with productivity of an ecosystem would be a tool to evaluate sustainability of the land use systems. The natural systems such as grasslands and mixed forests, gay higher soil microbial biomass and enzyme activities (dehydrogenase, acid phosphatase and urease) than the agricultural systems. The results suggest that biomass turnover and disturbance through cultivation, pesticides, fire, etc. determine the nature and degree of biological activity in an ecosystem. Microbial biomass and enzyme activity can be used as indicators to evaluate land use system sustainability.

Keywords : land use systems. soil biological parameters. soil enzymes. soil microbial biomass. sustainability.

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Nutrient status of soils in the rain forest of Mt. Pangasugan, Leyte, Philippines


Author(s): Sabine Zikeli1, Victor B. Asio2 and Reinhold Jahn1

Abstract

Soils under rain forests are until now poorly understood. This study was conducted to determine if nutrient status is a limiting factor in the rain forest soils of Mt. Pangasugan in Leyte, Philippines. Four sampling sites at varying elevations in a representative catena were studied. In each site, three soil profiles representing the upper, middle and lower slopes were sampled. Soil samples were analyzed for OM, N, P, K, Ca and Mg. Results showed that, except phosphorus, the nutrients are not limiting in the rain forest soils studied. Phosphorus appears limiting despite the fact that some amount of it is brought into the ecosystem by rain. Results also showed a generally high spatial variability of the nutrient status of the soils in the study site.

Keywords : Andosols. Alisols. catena. nutrient status. rain forest. tropical soil.

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Surface charge characteristics of selected Philippine soils


Author: Anabella B. Tulin

Abstract

The surface charge characteristics of selected Philippine soils, namely: Andisols, Alfisols, Ultisols and Vertisols were studied in relation to the nature of their colloidal components and other soil chemical and mineralogical properties. Sixteen soil samples representing the A and B horizons of 8 soil profiles sampled in different provinces were used in this study. Based on clay mineralogy, the Andisols and Ultisols were dominated by variable charge colloids while the Alfisols and the Vertisols consisted mainly of permanent charge colloids. The magnitudes of increase in negative charge and decrease in positive charge with an increase in pH were indicative of predominant variable charge behavior even for montmorillonitic and/or vermiculitic soils (Vertisols). The KCI adsorption method of determining negative and positive charges was inapplicable to illitic soils. Because of these observations, zero point of charge (ZPC) of tropical soils require careful interpretation. Generally, ZPC values varied among soil orders, with the Vertisols and the Alfisols exhibiting lower ZPC values (from < 2.0 to 5.3) as compared to the Ultisols and the Andisols (from 2.5 to 8.5). Variations in ZPC values among soil orders were attributed to differences in mineralogy, clay free oxides and organic matter contents.

Keywords : permanent charge colloids. Philippine soils, surface charge. variable charge colloids, zero point of charge.

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External morphology of eri (Samia cynthia ricini Boisduval) egg during embryonic development


Author(s): D.N.R. Reddy and K.C. Narayanaswamy

Abstract

This study was conducted to gain better understanding of the features of eri (Samia cynthia ricini Boisduval) egg during progressive embryonic development. The eri egg is oval, flat and broader at the anterior region. The follicular imprints are evenly distributed over the chorion. The creamy white egg colour changed to grayish bluish on the eighth day. The length and width of egg changed on the eighth day after oviposition. The egg mean length was positively related with its width (r=0.9938). Except for an increase on the third day, there was a gradual reduction in egg weight through progressive embryonic development.

Keywords : egg morphology. embryonic development. eri silkworm.

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Botanical control of golden kuhol (Pomacea canaliculata Lamarck) using asyang [Mikania cordata (Burm. F.) B.L. Robinson]


Author(s): Lualhati M. Noriel1, Josef Margraf2, Flora Mia V. Duatin1 and Marilyn P. Guzman1

Abstract

This study was conducted to determine the molluscicidal effect of asyang (Mikania cordata) extract against golden kuhol (Pomacea canaliculata) under laboratory condition and to evaluate its potential for the control of golden kuhol in the field.
Leachates from 24 and 48 hrs soaking of fresh asyang samples caused 23.4% and 27.2% snail mortality, respectively, one day after treatment. Percent mortality, as increased to 33.67% and 56.93% for the 24 and 48-hr treatments, respectively, two days after treatment.
The effect of asyang on the population density of golden kuhol was comparable to that of the molluscicide Bayluscide at the recommended rate Reduction in the number of damaged rice hills in asyang-treated plots was also noted. Rice plants grown in asyang-treated plots were healthier and heavier than those grown in the control plots.

Keywords : asyang. botanicals. golden kuhol.

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Microorganisms asssociated with postharvest spoilage of yams


Author(s): R.C. Ray, M. Nedunzhiyan and C. Balagopalan

Abstract

This study isolated the microorganisms causing major spoilage of yams collected during a two-year period from various markets in Orissa, India. Seven fungal and two bacterial species (Erwinia sp. and Serratia sp.) were isolated from rotted yam tubers. Aspergillus awamori, A. versicolor, Botryodiplodia theobromae, Fusarium solani, Penicillium decumbens and P. purpurogenum caused primal), dry rot while Rhizopus oryzae and Serratia sp. caused primary soft rot. Erwinia sp. was responsible for the secondary soft rot. The nature of the fungal rot was dependent on secondary infection by Erwinia: soft or wet rot when there was secondary infection by Erwinia sp, and dry rot when there was none.

Keywords : microorganisms. spoilage. tropics. yams.

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Distribution, transmission and disease characterization of sweetpotato feathery mottle virus


Author(s): Manuel K. Palomar, E.B. Barsalote and H.S.V. Colis

Abstract

Sweetpotato feathery mottle virus (SPFMV) disease was observed in the sweetpotato fields of the Visayas State College of Agriculture and adjacent barangays with infection ranging from 2.8 to 21.0%. Likewise, in the the germplasm collection of the Philippine Root Crop Research and Training Center, 21.0% of the 1,124 sweetpotato accessions were infected with SPFMV, 8.0% of which were severely infected. Transmission studies showed that SPFMV was mechanically and biologically transmissible but not seedbome. SPFMV was mechanically transmitted to true seedlings (2-5 leaf stage) but not to vegetative cuttings and tuber sprouts. It was also non-persistently transmitted by the melon aphid (Aphis gossypii Glover). The acquisition feeding and inoculation feeding periods of the aphid were 56 sec and 15-60 sec, respectively. Serial transmission trials revealed that the insect could transmit the disease up to 5 plants after a single acquisition feeding only. There were two stains of SPFMV based on disease symptoms in sweetpotato and in reaction to certain host plants. Both strains showed similar transmissibility and physical properties in vitro.

Keywords : disease characterization. survey. sweetpotato feathery mottle disease. transmission.

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An aquatic wild plant as a keystone species in a traditional Philippine rice growing system: its agroecological implications


Author(s): Konrad Martin and Joachim Sauerborn

Abstract

In the province of Ifugao, Northern Luzon, Philippines rice cultivation on irrigated terraces has been practiced since centuries ago. The traditional system is characterized by one harvest per year from permanently flooded fields.The macrophyte Najas graminea Del. is the most abundant submerged wild plant in this agroecosystem. It is argued that this plant can be seen as a keystone species, because of its crucial role in maintaining the organization and diversity of the aquatic community which also has impacts on the terrestrial community of the agroecosystem. This conclusion was drawn from two aspects studied: (1) The food web of the aquatic community depends on the presence of N. graminea since it provides Aufwuchs and detritus, on the surfaces of its leaves, to primary consumers such as crustaceans, the larvae of Ephemeroptera and Chironomidae, and Gastropoda which in turn serve as prey for a number of predators, mainly the larvae of Odonata, certain Coleoptera and Diplonychus rusticus (Fabricius). (2) The golden snail Pomacea canaliculata (Lamarck), a recent invader into Southeast Asian rice fields from tropical America and a serious pest of rice seedlings in modem production systems, caused no appreciable damage in the Ifugao rice terraces so far. The most probable explanation for that is the presence of a high biomass of wild aquatic plants mainly N. graminea and the floating fern Azolla pinnata R. Br. which serve as alternative food sources for P. canaliculata when the rice plants are most vulnerable to its attacks. Comparison of snail fauna in different fields before and seven years after the invasion of P. canaliculata showed that it had no clear negative impacts on the native species. Possible future impacts of the species on the agroecosystem are discussed.

Keywords : agroecosystem. aquatic fauna. food web. golden snail. Ifugao rice terraces. Najas graminea. Pornacea canaliculata.

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