Now showing items 1-6 of 6

    • Article

      Agar production from Gracilariopsis heteroclada (Gracilariales, Rhodophyta) grown at different salinity levels 

      AQ Hurtado-Ponce - Botanica Marina, 1994 - Walter de Gruyter
      Gracilariopsis heteroclada grown in fiber glass tanks at four salinity levels was treated with three different concentrations of aqueous NaOH. Yield, gel strength, gelling and melting temperatures of the extracted agar were determined. Plants grown at salinities of 24 and 32 ppt and treated with 3% NaOH produced the strongest gel (850 g cm-2) and weakest gel (300 g cm-2), respectively. Statistically significant differences in gel strength, dynamic gelling and melting temperatures were observed between the various treatments. The interactive effect of salinity and NaOH was significant in gel strength, gelling and melting temperatures of the gel from G. heteroclada.
    • Article

      Agar yield and gel strength of Gracilaria heteroclada collected from Iloilo, Central Philippines 

      MRJ Luhan - Botanica Marina, 1992 - Walter de Gruyter
      Seasonality of yield and gel strength of agar from Gracilaria heteroclada was determined. Gel strength was high (510-794 gm cm-2) during early dry season (October-March) and low (43-101 gm cm-2) during the wet season (May-August). A negative correlation exist (P ≤ 0.05) between agar yield and gel-strength.
    • Article

      Effects of gel depth and gel surface area on agar gel strength 

      TR de Castro - The Philippine Scientist, 1993 - San Carlos Publications, University of San Carlos
      Agar is a high priced phycocolloid extracted from red seaweeds (Rhodophyta) called agarophytes. It is a mixture of polysaccharides whose basic monomer is galactose (Armisen and Galatas 1987). Agar has many uses in the food and pharmaceutical industry, and the measure of its commercial value is based on its physical properties. One of the most important physical properties of commercial agar products is its gel strength (Chandrkrachang and Chinadit 1988). Gel strength is the force required to rupture the gel and it is measured through the use of gel testers available in the market, such as the Nikkan-sui, Rowerbal, and the Marine Colloids gel testers. Each instrument has built-in specifications for optimum use and results. Standard procedures used in the preparation of 1.5% agar gels for gel strength determination usually require 1.5 g of sample. Replication of samples in laboratory testing is however standard requirement and replication is constrained when sample extracts are scarce.

      This paper discusses the effects on gel strength of different gel depths and gel surface areas. It aims to identify the minimum size of vessel and depth of gel that will give optimum results using a Marine Colloids Model GT-2 gel tester.
    • Article

      Evaluation of agar from three species of Gracilaria from Panay and Guimaras islands 

      TR de Castro - The Philippine Scientist, 1993 - San Carlos Publications, University of San Carlos
      Agar from three species of Gracilaria, G. changii G. coronopifolia, and Gracilariopsis heteroclada, collected form Panay and Guimaras islands was evaluated. Each species was pretreated with NaOH solution before extraction. Highest agar yields were obtained following alkaline pretreatment at the lowest concentration (1% NaOH) for all species. Highest gel strengths were obtained at different alkaline pretreatment conditions: 644 ± 3.4 g cm-2 at 3 % NaOH for 60 min for G. changii, 641 ± 11.9 g cm-2 at 5 % NaOH for 30 min for G. heteroclada, and 170 g cm-2 at 5 % NaOH for 30 min G. coronopifolia. Agar gelling temperatures ranged from 38.5-40ºC and agar melting temperature ranged from 80.5-85 ºC. Specific viscosity was highest for agar from G. changii at 18 cps. Moisture and ash contents ranged from 8.04-15.20 % and 4.32-4.98%, respectively. Based on the result for this study, G. heteroclada and G. changii are two species which merit further studies for their prospective commercial value to the different industries using agar.
    • Article

      Influence of extraction time on the rheological properties of agar from some Gracilaria species from the Philippines 

      AQ Hurtado-Ponce - Botanica Marina, 1992 - Walter de Gruyter
      The influence of extraction time on the clean anhydrous yield, rheological properties, dynamic gelling and melting temperatures of 1.5% agar from six species of Gracilaria and one species of Gracilariopsis collected from the Philippines was determined. The lowest agar yield was measured from Gracilaria 'verrucosa' (10.1%) even after 120 minutes extraction while the highest yields were recorded from G. coronopifolia both after 30 (23.5%) and 60-minute extraction times (26.1%) and G. eucheumoides after 120-minute extraction time (27.3%). A 60-minute extraction of G. heteroclada produced gels with the highest breaking strength (1013 g), the maximum cohesiveness (7.4 mm), the greatest breaking energy (7481 g mm), and the greatest stiffness (137.3 g/mm -1). Gracilaria blodgettii gave the weakest gel tested. Dynamic gelling temperature was lowest for G. blodgettii at 60 min (28 °C) and highest for G. edulis at 120 minutes of extraction (46.3 °C). Melting temperature was lowest at 30 min extraction for G. salicornia (58.0 °C) and highest at 30 minutes for G. edulis (95.0 °C).

      A strong interactive effect of species, extraction time, and rheological properties was observed, but there was no interaction observed among the species, extraction time and temperatures. Each species showed good rheological properties at a specific extraction time.
    • Article

      Rheological properties of agar from Gracilariopsis heteroclada (Zhang et Xia) Zhang et Xia (Gracilariales, Rhodophyta) treated with powdered commercial lime and aqueous alkaline solution 

      AQ Hurtado-Ponce - Botanica Marina, 1992 - Walter de Gruyter
      Rheological properties were measured for 1.5% agar gels from Gracilariopsis heteroclada pre-treated with powdered commercial lime (CaCO3) during sun drying, and a combination of two alkaline solutions during water-bath heating in the laboratory. All samples were subjected to a one or three hours of heating prior to extraction.

      Slightly higher agar yield were obtained from samples treated with lime while drying (2.9-4.5%) than from seaweed (2.1-3.8%) treated with alkaline solutions in the laboratory. Better rheological (breaking strength,cohesiveness, breaking energy, and rigidity) and physical properties (dynamic gelling and melting temperatures) were obtained from laboratory treated seaweed after a 3-hour treatment.

      No effect of collection site, alkali treatment and treatment time on the yield of agar, was observed. However, significant (P ≤ 0.01) effects were recorded for collection site, alkali treatment and treatment time both on rheological properties and on gelling and melting temperatures.