Determination of moisture content and water activity in algae and fish by thermoanalytical techniques

Abstract

Recebido em 18/12/07; aceito em 25/2/08; publicado na web em 2/4/09The water content in seafoods is very important since it affects their sensorial quality, microbiological stability, physical characteristics and shelf life. In this study, thermoanalytical techniques were employed to develop a simple and accurate method to determine water content (moisture) by thermogravimetry (TG) and water activity from moisture content values and freezing point depression using differential scanning calorimetry (DSC). The precision of the results suggests that TG is a suitable technique to determine moisture content in biological samples. The average water content values for fish samples of Lutjanus synagris and Ocyurus chrysurus species were 76.4 ± 5.7% and 63.3 ± 3.9%, respectively, while that of Ulva lactuca marine algae species was 76.0 ± 4.4%. The method presented here was also successfully applied to determine water activity in two species of fish and six species of marine algae collected in the Atlantic coastal waters of Bahia, in Brazil. Water activity determined in fish samples ranged from 0.946 -0.960 and was consistent with values reported in the literature, i.e., 0.9 -1.0. The water activity values determined in marine algae samples lay within the interval of 0.974 -0.979.

Effects of Smoking and Freezing on the Nutritive Value of African Mud Catfish, Clarias gariepinus Burchell, 1822

“…Fish has the potential to be considered as a balanced food and can therefore be expected to provide relief from malnutrition (Ogundiran, Adewoye, Ayandiran, & Dahunsi, 2014). It also has a high economic value for many countries because it represents the largest share among agribusiness products on the global market (Silva, Silva, Andradel, Veloso, & Santos, 2008). Rahji and Bada (2010) reported that while Nigeria requires about 1.5 million tonnes of fish annually and is expected to meet FAO's recommended minimum fish consumption rate of 12.5 kilograms per head yearly to satisfy basic protein needs, the nation currently imports up to 400,000 tonnes to bridge the fish supply-demand gap.…”

ASI: Hydrothermal extraction and characterization of bio‐crude oils from wet chlorella sorokiniana and dunaliella tertiolecta

“…A further increase in temperature resulted in the decomposition of algal biomass above 450°C, similar trends were reported by da Silva et al . . The other application of TGA is the determination of the ash content of the biomass samples.…”

Биохимический Анализ Некоторых Морских Макроводорослей Побережья Коллама (Индия)

“…Содержание влаги в талломах всех исследованных видов составляло более 70%, что соответствует литературным данным (Murata, Nakazoe, 2001;da Silva et al, 2008;Bruton et al, 2009) (рис. 1).…”

“…1). Специфические уровни влажности водорослей изученных родов были аналогичны уровням влажности, описанным в литературе (da Silva et al, 2008), за исключением рода Sargassum, изученный нами представитель которого (S. tenerrimum), имел более высокие значения этого показателя. Самое высокое содержание влаги было в талломах C. scalpelliformis (87,56%), а наиболее низкое -у U. lactuca (78,27%).…”

“…2-6 риски на ввершиных столбцов -стандартное отклонение Определение содержания воды в морепродуктах чрезвычайно важно, так как вода сильно влияет на их микробиологическую и химическую стабильность, физические свойства и технологические процессы (переработка, хранение и распределение), а также используется для определения их пищевого состава. Эти параметры необходимы для обеспечения сохранности питательных свойств, установления оптимального срока хранения, а также для того, чтобы сделать их доступными потребителю в свежем, замороженном и переработанном состоянии (da Silva et al, 2008).…”