Response surface methodology was used to optimize the fermentation conditions for the total phenolics content and antioxidant activity of black tea (Camellia sinensis). Fresh tea leaves were fermented following a rotatable central composite design of eleven experiments replicated thrice. The minimum and maximum fermentation time and temperature were respectively of 1 - 3 h and 30 - 40 °C. The results demonstrated that fermentation time and temperature significantly affect the total phenolics content and antioxidant activity of black tea. The optimum fermentation conditions for the present study were at 36 °C for 35 min which the values for total phenolics content and total antioxidant activity were 38.99 g GAE/100 g dw and 19.74 mg VitC Eq/100 g dw, respectively. Antioxidant activity was strongly correlated with total phenolics content of black tea.
Aims: Ginger (Zingiber officinale) is one of the most popular and widely used spice, known for its health benefits. This study aimed at assessing the potential impact of a Handcrafted dryer (HCD) on the quality of ginger in comparison to the most common drying methods.
Methodology: Fresh ginger originating from 2 regions were dried using the following techniques: HCD; Air Drying (AD); Ventilator Oven (VO) at 50°C, 60°C and 80°C; Freeze Drying (FD) and Microwave drying (MD) at 700 and 900 W) methods. Dried products were ground and infused in hot water and the total flavonoid contents, and antioxidant potential through different mechanisms (DPPH radical, FRAP and TAC assays) as well as the sensory properties of the infusions were assessed.
Results: TFC of the samples significantly varied with regard to the origin of the Ginger. Infusions deriving from the dried ginger from HCD and VO at 80°C exhibited the highest TPC, TFC and antioxidant activities. While the rise of temperature with VO led to an increase of TPC, it was rather a decrease that was observed with the rise of microwave power level but which did not have a significative effect on the antioxidant potential. No significant difference was noticed in the acceptance of infusions by consumers except MD samples, which received the lowest score by panelists.
Conclusion: Heat-based processes appears to be useful in the optimization of the nutritional value of dried ginger, and HCD appropriate for farmers as it is easy and not expensive to put into practice.
Palm wine is the commonest name of the beverage obtained from fermented palm sap, the exudate from tapped unopened spathe of oil palm tree (Elaeis guineensis). This refreshing wine of West and Central Africa is very sweet but within 24 hours the concentration of sucrose falls to less than 50% the initial amounts due to a rapid sugar fermentation by microorganisms. In Cameroon, Central Africa, traditional attempts to preserve palm wine imply the introduction of natural preservatives mostly barks and leaves from edible or medicinal plants. The leaves of Cymbopogon citratus, Pimenta racemosa, Vernonia amygdalina, Ocimum basilicum and the barks and the leaves of Garcinia lucida and of Adansonia digitata commonly used in palm wine preservation were analyzed for their chemical composition. The results showed that lipid, protein, ash, crude fiber, total sugars and vitamin C contents were respectively from 15.70 ± 1.13 to 23.57 ± 1.80%, from 8.38 ± 0.38 to 43.81 ± 3.69%, from 1.14 ± 0.17 to 10.06 ± 0.39%, from 11.74 ± 1.11 to 48.42 ± 0.55%, and from 1.49 ± 0.02 to 22.56 ± 0.59% and from 55.76 ± 3.15 to 175.71 ± 2.09 μg /100 g dw. The phyto-chemicals levels were respectively from 1.37 ± 0.22 to 3.61 ± 0.6 % for total alkaloids, 2.66 ± 0.12 to 4.80 ± 0.24 % for total phenolics and 0.57 ± 0.09 to 1.88 ± 0.09 mg /100 g dw for total saponins. Concerning anti-nutrients, the oxalates levels were higher than the threshold value (250 mg/100 g) reported as safety limit. Despise the proven antimicrobial benefits of alkaloids, saponins and phenolics found in those leaves and barks, caution shall be paid during their use due to their high oxalates levels.
The present study was conducted to determine the influence of cooking methods on the nutritional potential of Telfairia occidentalis leaves. Standard methods were used for the analysis of nutrient and anti-nutrient contents. The analyses were carried out in triplicate and the results showed that raw T. occidentalis leaves contain interesting levels of crude fibre (25.3 g), carbohydrates (24.3 g), protein (24 g), fat (8.2 g) and ash (8.3 g). The descending order of mineral content obtained in this study is as follows: K> Ca>Mg>P>Fe>Mn>Na>Zn>Cu. The boiled samples without kanwa (rock salt) had the highest contents of crude fibre, calcium, zinc and copper. However, these leaves contained antinutrients such as oxalates (31.3 mg), phytates (1.3 mg), saponins (23.6 mg). These antinutrients were considerably reduced by cooking. In the boiled samples without kanwa (rock salt), we observed the highest reduction rates: 70.4% for oxalates and 53.8% for phytates. It would therefore be very beneficial to consume Telfairia occidentalis leaves boiled without kanwa (rock salt).
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