La tercera generación de políticas de desarrollo regional

1

Department of Food Science and Technology, Faculty of Agriculture, University of Peradeniya

2

Biochemistry Division, Tea Research Institute of Sri Lanka, Talawakelle

Tea produced in Sri Lanka, which has been well known as Ceylon Tea, is acclaimed as one of the best teas in the world. The unique characteristics of Ceylon tea, reputed for more than a century, are influenced by climatic conditions of plantations. Tea is the second most popular drink, which represents a major source of dietary polyphenols. The polyphenolic fraction in tea, which represents 30 to 40% (w/w) of solid compounds, serves as dietary antioxidants. Black tea contains significant amounts of flavonols, such as quercetin, myricetin and kaempferol, which are known to possess health promoting properties. However, there is very little work carried out to date to quantify flavonols in Sri Lankan black tea samples. The present study was carried out in this backdrop, with the objective of quantifying total polyphenols and flavonols present in upcountry, low country, mid country and Uva grown black tea.

Samples of (500 g) Broken Orange Peckoe (BOP) tea were obtained from 29 estates belonging to 10 different geographical locations of low country, midcountry, upcountry and Uva regions. Upcountry tea samples were collected from Dimbula, Nuwara Eliya, Bogawanthalawa, Udapusselawa and Agrapatana. Mid country was obtained from Kandy while low country tea was obtained from Ruhuna and Sabaragamuwa sub regions. Uva tea was obtained from Malwatte Valley and Bandarawela. _{All samples were collected}

during December 2010. The total polyphenolic content of tea samples was determined in quadruplicate using ISO 14502-1 method and expressed as percent gallic acid equivalent (GAE) on dry matter basis. Total flavonols and flavones were quantified using four different aluminum chloride methods and results were expressed as both rutin equivalents (RE) and quercetin equivalents (QE). Further, the conditions necessary for hydrolysing and analysing flavonols in tea infusions were optimised and the hydrolysed flavonols were quantified using HPLC.

Total polyphenolic content of black tea samples ranged from 11.66 ± 0.58 to 25.41 ± 0.58% GAE (w/w) on dry matter basis. Up country tea brew contained the highest quantity of total flavanols and flavones (18.82 mg RE/g), while the low country tea contained 11.46 mg RE/g. The flavonols and flavones of upcountry and Uva teas were significantly (P<0.05) different from those of mid and low country. The contents of myricetin, quercetin and kaempferol in black tea ranged from 0.25 ± 0.01 to 6.48 ± 0.39, 0.79 ± 0.06 to 20.60± 0.86, and 0.52 ± 0.02 to 7.42 ± 0.89 mg/g, respectively. These results indicate that tea from different regions, sub regions and estates were significantly (P<0.05) different suggesting that the geographical location and/ or the growing condition has an impact on these contents.

Proceedings of the Peradeniya University Research Sessions, Sri Lanka, Vol. 16, 24th _{November 2011}

41

Optimization of Processing Conditions to Develop Salt Fermented Herring (Amblygaster sirm) by Preserving its Sensory Qualities

K.M.G.R.M. Kariyawasam1, D.S. Ariyarathna2, R.P.N.P. Rajapakse1 and C.K. Illeperuma1

1

Department of Food Science and Technology, Faculty of Agriculture, University of Peradeniya

2

National Aquatic Resources Research and Development Agency, Colombo

Herring (Amblygaster sirm), an underutilised fatty fish, has good potential for developing new food products due to its high Ω-3 fatty acid and vitamin D contents. Salting is a traditional preservation technique, which is practiced to ferment fish to develop different products. However, most such products are poor in sensory attributes compared to fresh fish. Therefore, this study was carried out to identify a new process to develop salt fermented herring while preserving its sensory qualities present in fresh fish. Initially, herrings were salted at three different fish to salt ratios (3:1, 4:1 and 5:1) and stored at 4±1⁰C or ambient temperature (28-30⁰C) up to 48 h under light proof conditions. At 24 h intervals samples were analysed for sensory attributes (colour, odour, texture, taste and overall acceptability) using a 9-point hedonic scale by employing 30 untrained panelists. Herrings treated with 4:1 ratio were significantly (p<0.05) different from the other two treatments with respect to all tested sensory attributes. Moreover, salted herrings (4:1) stored for 48 h had significantly (p<0.05) favourable sensory attributes compared to those salted fish stored for 24 h. Therefore, 4:1 fish to salt ratio was selected for further processing based on sensory attributes and analysed for physico-chemical properties. It was observed that, total volatile basic nitrogen (TVB-N), lipid oxidation and histamine levels were far below the recommended maximum levels. The salted herrings (4:1) were stored in two different brine solutions (75% or saturated) at 4 ±1⁰C or ambient temperature for the fermentation process. At weekly intervals, samples were tested for TVB-N content, histamine content, lipid oxidation and sensory attributes. There were no significant (p>0.05) differences observed in the above parameters under both storage conditions up to one month of storage. The levels of TVB-N, histamine and lipid oxidation gradually increased in salted fish stored in 75% brine solution and sensory attributes became gradually unacceptable, by the seventh week post-storage at both temperatures tested. However, in salted herrings (4:1) stored in saturated brine solution, the above parameters did not change significantly (p>0.05) and remained at acceptable levels. Therefore, results of this study confirm that the salt fermentation of herrings at 4:1 ratio for 48 h followed by storage in saturated brine solution can be used to preserve them at least for three months without affecting their sensory qualities.

Proceedings of the Peradeniya University Research Sessions, Sri Lanka, Vol. 16, 24th _{November 2011}

42

Antioxidant Activity of Different Varieties of Bitter Gourds (Momordica spp.) Cultivated in Sri Lanka