The Effect of Low Levels of Antioxidants on the Swelling and Solubility of Cassava Starch

The addition of low levels of sodium sulphite had a dramatic effect on the structure of cassava (Manihot esculenta Crantz) starch pasted at 95°C. Inclusion of 100 ppm sulphite promoted granule disintegration resulting in a reduction in measured swelling volume to nearly 10% of its value in the absence of sulphite and release of almost all the carbohydrates from the starch granule. It is suggested that sulphite addition promotes oxidative reductive depolymerization (ORD) of the polysaccharides since its effect on the granules is prevented when lower levels (around 20 ppm) of the polar antioxidant propyl gallate are added. Possible practical applications of the results and implications for the understanding of starch granule structure are discussed.     

The Effect of Low Levels of Sulphite on the Swelling and Solubility of Starches

The effect of low levels of sulphite on the swelling volume and release of polysaccharide from a range of starches pasted at 95°C and 121°C has been investigated. In all cases the addition of 0.01% sulphite enhanced the release of polysaccharide on heating at 95°C and for potato, cassava and sago starches the measured volume showed a marked reduction. In the case of rice and wheat starches, sulphite only had a large effect on the swollen volume at pasting temperatures of 121°C, whereas, even at this temperature, maize was little affected. The addition of the polar antioxidant propyl gallate completely nullified the sulphite effect, with the exception of potato starch, suggesting that sulphite could act by promoting oxidative reductive de-polymerisation of the polysaccharide. The effect of 0.01% sodium chloride was also investigated. It was found to have a similar effect to sulphite in the case of potato starch but did not influence the swelling volume or solubility of the other starches.     

Design and simulation of a novel solar photovoltaic system assisted single-slope solar still distillation unit

Water is an essential component of our lives. Conventional seawater desalination, based on fossil fuel energy, is primary in meeting freshwater demands. Thus, solar desalination still emerged as an alternative technology that employs environmentally friendly renewable energy. Here, we aim to design and simulate a novel hybrid solar photovoltaic (PV) system coupled with a single-slope solar still unit for freshwater production. Various design techniques were utilized to fine-tune the model towards producing 3–4.6 kg/m² · day of distillate water, thereby calculating the design aspects such as tank size, energy, and cost. The results revealed that a conventional solar desalination system had 22% lower efficiency than the proposed novel still distillation unit assisted with a solar PV system (connected to a heating element). The maximum efficiency of 45% has been recorded at the peak solar insolation due to the combination of the solar PV system. According to our design constraints, only a 3 m² basin area was required to achieve a productivity of ${\mathit{P}}_{\mathit{st}}$ = 1–5 kg/day. Design analysis showed that the total capital cost of a conventional still can be significantly reduced from 2600 to 1500 $/unit with PV system integration at the specified productivity and optimal solar radiation of ~17 MJ/m² · day at peak time (02.00 PM). This work paves the way towards maximizing solar energy utilization from PV integration with solar desalination to achieve high freshwater productivity in single-basin solar still systems.