Species diversity of benthic diatoms and its relation to environmental variables in Ton Ngachang Waterfall, Songkhla province

The species diversity of benthic diatoms and its relation to environmental variables were studied in Ton Ngachang Waterfall, Songkhla province. Epilithic and epipsammic diatoms were sampled at 5 stations from upstream (station 1, 2 and 3) to downstream (station 4 and 5) in summer (April 2004 and February 2005), early rainy season (June and August 2004) and rainy season (November and December 2004). A total number of 15 genera, 49 species and 8 families in order Pennales were found. Achnanthes was the dominant genus throughout the study period with 8 species. A principal components analysis (PCA) on relative abundance revealed that Achnanthes minutissimaK˙˙ utzing and A. lanceolata (Brebission) Grunow were the most abundant species of epilithic diatoms and epipsammic diatoms respectively, whereas species richness on both substrata were not significant different (P>0.05). Analysis of variance (ANOVA) indicated that the numbers of benthic diatom species between upstream and downstream were not significant different (P>0.05), while there was statistical significance (P<0.05) among the seasons in epilithic diatoms. Multivariate analysis of variance (MANOVA) on physico-chemical factors showed that nitrate, ortho-phosphate, silicate, BOD, conductivity and TSS were significant different (P<0.05) between seasons. Canonical correspondence analysis (CCA) ordination indicated that nitrate, silicate, BOD, pH, conductivity, temperature and velocity were correlated with the benthic diatom abundance

Measurement of mango firmness by non-destructive limited compression technique

Thai mango 'Nam Dok Mai Si-Thong' has an attractive golden yellow skin colour even in immature fruit, not ready for consumption. Firmness becomes an important quality attribute to assess the ripening stage of the fruit during storage. In this study, the possibility of a non-destructive method using a texture analyser for assessing the firmness behaviour during storage was investigated in three different experiments for (1) probe selection, (2) distance selection using the selected probe and (3) evaluation of the selected probe and distance on mango quality. The results revealed that an aluminium flat probe with 35 mm diameter is a suitable probe for measurement. Limited distance compression at 1 mm was selected since that combination did not leave any compression marks on the fully ripened mangoes. Evaluation of mango quality attributes obtained by this technique could be used to assess non-destructively the firmness behaviour of the mango fruit during storage. The technique can be used to monitor the firmness of mango fruit on an individual basis, using the same fruit in successive assessments. Non-linear indexed regression can be applied to extract information on the behaviour and variation of firmness of individual mangoes. Obtained explained parts (R2 adj) frequently are well over 90%.</p

Optimization of ingredient and processing levels for the production of coconut yogurt using response surface methodology

In this study, response surface methodology (RSM) was employed to optimize the ingredient formulation and processing parameters of coconut milk yogurt production such as temperature, time, and amount of starter culture on the sensory evaluation responses. Besides, the physicochemical properties such as pH, titratable acidity, and viscosity of the yogurt were also analysed. The analyses show that the coconut yogurts have a pH from 4. 01 to 5. 79, acidity from 0. 461 to 2. 079 (%), and viscosity from 433 to 21,833 cp during the optimization process. From the analysis of variance, the R2 of all response variables is more than 0. 73 that indicates that a high proportion of variability was explained by the model. Based on the response surface 3D plot of the sensory evaluation, the optimum acceptability of the coconut yogurt processing parameter are at temperature of 37oC, 8 h of the fermentation duration, and 3%(w/w) of the starter culture