Effect of Exogenous Lipase on Dough Lipids During Mixing of Wheat Flours

In control dough, endogenous wheat lipase was inactive, because the triacylglycerol (TAG), 1,2-diacylglycerol (DAG_1,2), and 1,3-diacylglycerol (DAG_1,3) fractions of nonpolar lipids were not affected by mixing. Conversely, the free fatty acid (FFA) and monoacylglycerol (MAG) fractions decreased, mainly due to the oxidation of polyunsaturated fatty acids (PUFA) catalyzed by wheat lipoxygenase. Addition of exogenous lipase to flour (15 lipase units [LU] per gram of dry matter) resulted in substantial modification of nonpolar lipids during dough mixing. Due to the 1,3 specificity of the lipase used in this experiment, the TAG and DAG_1,3 fractions decreased, whereas the MAG and FFA fractions increased. The DAG_1,2 fraction increased at the beginning of mixing and decreased after 40 min of mixing. Moreover, part of the PUFA released by lipase activity was oxidized by wheat lipoxygenase, resulting in major losses of PUFA. Conversely, the net content of the saturated and monounsaturated fatty acids (SMUFA) remained constant, because the free SMUFA content increased primarily at the expense of the esterified forms. For a constant mixing time of 20 min, increasing the amount of lipase added to dough (from 2.5 to 25 LU/g of dry matter) resulted in a linear decrease in the TAG fraction and a linear increase in the SMUFA content in the FFA fraction. At the same time, the PUFA content of the FFA fraction increased only for additions of lipase to flour of >5 LU/g of dry matter, due to partial oxidation by wheat lipoxygenase.     

BANAD: A farm model for ex ante assessment of agro-ecological innovations and its application to banana farms in Guadeloupe

The ex ante assessment of innovative agro-ecological innovations is a key step in the development of more sustainable crop management systems. To this end, models are useful tools because they make it possible to rapidly assess numerous innovations in different contexts. Whereas many farm optimisation models focusing on the farmer’s strategic decision to adopt new crop management systems have been published, little attention has been given to the ex ante modelling of the dynamic operational impacts of innovation adoption at the farm level. BANAD, a mechanistic model for such applications, is proposed. It allows the ex ante assessment of innovative management systems including new agro-ecological techniques, while taking into account different farming contexts and policy and market conditions. It includes three components: (i) a crop management system model, (ii) a crop model (SIMBA) and (iii) a farming system model. Our results applied to the ex ante assessment of six innovative banana management systems for three contrasted farm types in Guadeloupe showed that the impacts of agro-ecological innovations, which include rotations, improved fallow, intercropping, pest-resistant cultivar, and an integrated organic system, can vary considerably according to (i) the farm type in which the innovation is integrated, (ii) the nature of the agro-ecological innovations, and (iii) the criteria considered and the temporal horizon of the assessment. Innovative intercropping systems that were effective at the field level in terms of the yield improvement and decreased pesticide use could be problematic at the farm level because they increased the workload and decreased income. The adoption of rotations or improved fallow seemed to be relevant for smallholders but could induce a critical period of 1.5-2.5 years during which income decreased drastically. Under certain conditions of markets and subsidies, very environmentally friendly innovations that are less productive can however be economically effective.     

Effects of Mixing Conditions and Wheat Flour Dough Composition on Lipid Hydrolysis and Oxidation Levels in the Presence of Exogenous Lipase

The lipid profiles of wheat flour doughs containing exogenous lipase were studied under different mixing conditions using a microscale mixer. An experimental design comparing the effects of dough water content (52–68%), the speed of mixing (50–100 rpm), and the mixer temperature (18–32°C) showed that the hydrolysis levels were positively influenced by temperature and speed of mixing and negatively influenced by water content. The positive effect of temperature was enhanced both by highspeed mixing and low water content. The lipid oxidation levels were positively influenced by the speed of mixing and negatively influenced by the water content. The positive effect of temperature on the oxidation levels was less important. A series of experiments conducted with different types of industrial and semi-industrial mixers with equal concentrations of lipase added to the dough showed large differences among the rates of lipid hydrolysis and oxidation. However, the mixing conditions proposed by bakers to obtain doughs with similar handling properties led to similar dough lipid profiles. Sodium chloride did not change the lipid profile when added to dough. Conversely, calcium chloride promoted a large increase of lipid hydrolysis and oxidation due to its activation of lipase activity. Addition of yeast increased the lipid hydrolysis and slightly decreased lipid oxidation.     

Influence of temperature on historic and future population fitness of the western spruce budworm,Choristoneura occidentalis

Abstract

Climate change affects the geographic range and outbreak behavior of forest insects. Both the range and dynamics of insect populations are linked to physiological responses to abiotic conditions and trophic interactions via their effects on individual fitness. We develop a process-based simulation model of population fitness for the western spruce budworm, Choristoneura occidentalis (Freeman) to examine the effects of temperature on historical range and observed outbreak behavior in the complex topography western North America. Model predictions are consistent with observed changes in the distribution and frequency of this insect’s outbreaks over the past 100?years. These changing patterns are the result of several direct and indirect responses of the insect to temperature. Overwintering survival is negatively affected by warming and determines its southern and lower-elevation limit. Ability to complete its life cycle before killing frosts limits its range to the north and at higher elevations. Interactions affecting synchrony between the insect’s feeding life stages and host foliage development also determines fitness and will increase the area favoring fitness of western spruce budworm in the future, especially in western Canada where host trees extend much farther north than the insect currently does.     

Sediment source fingerprinting: benchmarking recent outputs,remaining challenges and emerging themes

Journal of Soils and Sediments - This review of sediment source fingerprinting assesses the current state-of-the-art, remaining challenges and emerging themes. It combines inputs from international...     

Effects of Different Dietary Lipid Sources on the Survival, Growth, and Fatty Acid Composition of South American Catfish, Pseudoplatystoma fasciatum, Surubim, Juveniles

The present study examines the effect of four semi‐purified diets (casein–gelatin based) where the source of fatty acids was free (esterified) oleic acid and linoleic acid (LA) (LOA diet), linseed and olive oil (predominantly LA and linolenic acid) (LO diet), cod liver oil (rich in highly unsaturated fatty acids) (CLO diet), and soybean lecithin (phospholipids; mostly LA) (LE diet) on the growth of juvenile South American catfish (surubim, Pseudoplatystoma fasciatum, Pimelodidae) (0.98 ± 0.04 g individual weight). Fish were fed at a restricted–readjusted feeding rate for 8 wk. At the end of the experiment, LE‐diet‐fed fish grew significantly larger than those of the other three groups (P < 0.05). Considerable cannibalism was observed in all the treatments. It is suggested that the quantitative growth performance may possibly change under other conditions, with less or no cannibalism. Survival did not differ significantly among the fish fed four different diets. Muscle and liver lipid contents did not vary among dietary treatments (P > 0.05), but whole‐body lipid concentrations were affected by dietary treatments. Fish fed LE diet contained significantly lower lipid level than those fed three other diets (P < 0.05). Muscle and liver fatty acid profiles reflected dietary fatty acid composition. Arachidonic acid level was significantly higher in muscle and liver of fish fed LOA and LE diets than in those fed LO and CLO diets. The results suggest that the efficiency of elongation and desaturation of 18C fatty acids depends on the dietary lipid source, and South American catfish has considerable capacity to transform linoleate to arachidonate.     

Phytoplankton biomass and environmental factors over a gradient of clear to turbid peri‐urban ponds

• 1. Small lakes and ponds with high nutrient loadings can be clear, turbid or intermediate, with low, high and intermediate phytoplankton biomass, respectively.
• 2. A combination of biotic and abiotic factors, such as hydraulic retention time, presence of submerged vegetation, depth, top‐down phytoplankton control, and cascading effects of fish community structure, play an important role in phytoplankton biomass control when nutrients are not limiting. Different combinations of these factors lead to different levels of phytoplankton biomass.
• 3. Identification of the main factors controlling phytoplankton biomass in a particular pond or a small lake is essential for choosing an appropriate management strategy for the maintenance of a desired ecosystem state.
• 4. When a pond or a small lake ecosystem is impaired by eutrophication, a considerable degree of its ecological quality can be restored through the modification of some environmental factors when a sufficient reduction in nutrient input is not feasible.

Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of coffee husk and cocoa pods biochar on phosphorus fixation and release processes in acid soils from West Cameroon

Acid soil in West Cameroon has limited phosphorus (P) availability which limits plant growth. This is mainly because of low pH, high levels of exchangeable aluminium (Al) and iron (Fe) and fixation of P. In this study, acid soils, sampled in Bafang, were amended with biochar produced from coffee husks (CH) and cocoa pod husks (CP) at two different temperatures (350 and 550 °C) in other to evaluate the effect on the physicochemical properties of the acid soil and the effect on P sorption and desorption. The soil was amended with biochar at a rate of 0, 20, 40 and 80 g/kg and incubated for 7 and 60 days. Physicochemical properties of all soil–biochar samples were determined followed by sorption experiments and data fitted in the Langmuir and Freundlich isotherm models in other to evaluate soil P sorption capacity and its affinity to soil amended with biochar. Moreover, desorption studies were done to evaluate the availability of P in soil amended with biochar after sorption. The outcomes of this study reveal an increase in soil pH, electrical conductivity (EC), available P, soil organic carbon and a drastic decrease in exchangeable Al and Fe. The point of zero charge of biochar-amended soil was higher than the control and increased with amendment rate. The experimental data of the sorption of P on soils and soil–biochar samples fits into Langmuir and Freundlich models (R² > 0.9) suggesting that the P adsorption is controlled by both model mechanisms. Soil–biochar mixture results in a decrease in the sorption capacity as compared with the control and the decrease was predominant with increasing amendment rate. At amendment rates of 20, 40 and 80 g/kg after 7 days of incubation, $Q_{\max }$ for SCH350 were 2267, 2048 and 1823 mg/kg which increased to 2407, 2112 and 1990 mg/kg after 60 days of incubation. This tendency was observed for all biochar inputs with respect to the increase in incubation days. Furthermore, desorption of P from soil–biochar mixtures was enhanced with biochar added at greater rate and produced at higher temperature. The desorption percentage was increased by more than around 10% for all biochar types from 20 mg/kg to 80 mg/kg amendment. Thus, biochar addition to acid soils reduces P fixation to acid soil and improves P desorption to soil solution, thereby providing more available P in the soil solution and better conditions for plant growth.