Prediction of critical times for water-extracted avocado oil heated at high temperatures

Vegetable oils are used in various cooking processes. However, when they are heated at high temperature and/or for a long period, chemical reactions can generate damaging substances for the health. The aim of the study was to predict the critical times at high temperatures of avocado oil. A four-level two-variable Central Composite Design was used to model the thermal oxidation of avocado oil extracted using the aqueous method. Temperature (120 – 180 °C) and time (11 – 209 min) were the independent variables. The response variable was the content in total polar compounds (TPC) with an upper limit defined at 25% (w/w). The composition and the oxidative status of fresh avocado oil were also investigated. The results obtained by a multiple regression analysis showed that data can be fitted with a second order polynomial equation (R2 = 0.98, Adj. R2 = 0.97) with all regression coefficients being significant (p < 0.05). The critical heating time ranged from 232 min to 214 min between 120 °C-140 °C and from 188 min to 4 min between 140 °C-180 °C. It was influenced by avocado oil composition. Thus, water-extracted avocado oil is not recommended for frying (140 °C – 180 °C) while it can be used for recipes involving long cooking time at moderate temperature (120 °C-140 °C)

Ginger powder protects soybean oil from oxidative degradations especially vitamin E during intermittent frying of plantain chips

This study aimed at evaluating the potential of ginger powder to improve the oxidativestability of soybean oil during intermittent frying of plantain chips. Plantain slices werefried in soybean oil with and without 15 g/l of ginger powder.The oils sampled during 5days of intermittent frying were analyzed for total polar compounds, conjugamalondialdehyde, vitamin E and fatty acid composition. The results showed that thepresence of ginger limited the oxidative deteriorations. Based on comparison of the resultsof the two types of frying, the formation of total polar compounds, conjugated dienesmalondialdehyde, were reduced respectively by 26.9%, 12.5% and 2.6%while up to 42.4%of vitamin E, and 39 % polyunsaturated fatty acids were preserved. So, the use of gingerpowder during intermittent frying of plantain chips could be an nutritional quality of soybean oils

Composition of raw cow milk and artisanal yoghurt collected in Maroua (Cameroon)

The composition of milk is of most importance to the dairy industry and human health. This study was conducted to provide data on the composition of raw cow milk and artisanal yoghurt collected in Maroua (Cameroon). Milk and yoghurt samples were collected from 11 breeding sites and 12 producers in the city of Maroua, respectively. The following parameters were determined: pH, dry matter, ash, fat, lactose, total protein, non-casein nitrogen (NCN), non-protein nitrogen (NPN), true protein, whey protein, casein, amino acid composition, α-lactalbumin, β-lactoglobulin, αS1-casein, αS2-casein, β- casein, κ-casein and mineral composition. The results showed that, the composition of the milk and yoghurt varied from one sample to another. The chemical composition of some of the milk and yoghurt studied differed from the corresponding samples in previous studies. For example the mean pH of the raw cow milk (6.25) and artisanal yoghurt (3.84) were lower. The mean NPN levels of the cow milk and yoghurt (0.21g/100g) were higher. The mean fat content of milk (4.48 g/100 g) was higher. The protein fraction was lower in yoghurt while Fe, Cu and Mn levels were lower in both cow milk and yoghurt. The data reported in this paper would be helpful in dairy technology and public health.Key words: Composition, cow milk, artisanal yoghurt, Maroua, Cameroon

Prediction of critical times for water-extracted avocado oil heated at high temperatures

Vegetable oils are used in various cooking processes. However, when they are heated at high temperature and/or for a long period, chemical reactions can generate damaging substances for the health. The aim of the study was to predict the critical times at high temperatures of avocado oil. A four-level two-variable Central Composite Design was used to model the thermal oxidation of avocado oil extracted using the aqueous method. Temperature (120 – 180 °C) and time (11 – 209 min) were the independent variables. The response variable was the content in total polar compounds (TPC) with an upper limit defined at 25% (w/w). The composition and the oxidative status of fresh avocado oil were also investigated. The results obtained by a multiple regression analysis showed that data can be fitted with a second order polynomial equation (R2 = 0.98, Adj. R2 = 0.97) with all regression coefficients being significant (p < 0.05). The critical heating time ranged from 232 min to 214 min between 120 °C-140 °C and from 188 min to 4 min between 140 °C-180 °C. It was influenced by avocado oil composition. Thus, water-extracted avocado oil is not recommended for frying (140 °C – 180 °C) while it can be used for recipes involving long cooking time at moderate temperature (120 °C-140 °C)

Measurement of phospholipid oxidation in model membranes by determination of oxygen consumption with a semi-automatic polarographic method

International audienc

Evaluation de l'effet antioxydant de la carnosine vis-a-vis des phospholipides a l'aide de la mesure de la consommation d'oxygene et du test a l'acide thiobarbiturique

National audienc

Effect of ripening on the composition and the suitability for jam processing of different varieties of mango (Mangifera indica)

As part of an effort to solve the problem of post harvest losses of fruits, physicochemical characteristics of four mango varieties (Palmer, Améliorée, Mango and Keitt) were determined at two ripening stages. Their suitability for jam processing was also evaluated based on viscosity measurements. The pulps of pre-ripe mangoes were highly acidic (pH: 3.50 – 3.85), rich in starch (4.4 – 11.1 % w/w) as well as in dry matter. They contained less soluble sugars (4.04 – 7.56 g/100 g) and recorded lower viscosity values than those of the ripe mangoes. The pre-ripe Palmer and Améliorée mango varieties had high dry matter content, while the Mango and Améliorée varieties had higher soluble sugars contents. Due to their higher starch contents, all the jams prepared with pre-ripe mangoes were more viscous than the ripe mango preparations. Ripe Palmer and Améliorée varieties were the best for jam processing, based on their viscosity values. These results could help to improve the quality of mango jams. Key words: Mango, proximate analysis, ripening stage, jam processing. African Journal of Biotechnology Vol.2(9) 2003: 301-30