Complete Factorial Design Research Articles

Investigation of color and turbidity in the clarification of sugarcane juice by ozone

AbstractThe sugar‐energy industries are highlighted in Brazil for exercising fundamental roles in the economy, being responsible for the production of products and by‐products considered essential in the daily life of a society, such as sugar, alcohol and energy. One of the processes used in the production of sugar is the clarification of sugar by sulfur. Due to the high toxicity of sulfur and its derivatives, harmful to both the human and the environment, there is a great and constant concern in reducing the consumption and emissions of these compounds. Seeking a method of clarification of sugarcane juice that uses less harmful clarifying agents and provides less loss of sugars, the present work investigated how ozonation affects certain parameters of the sugarcane juice, which are turbidity and color (International Commission for Uniform Methods of Sugar Analysis). In the experiment, the samples were divided into two lots and submitted to ozonation with ozone generation rates of 13, 17, and 21 mg O3/min, temperatures of 30, 60, and 90 °C and duration of 0, 30, and 60 min. A complete factorial design with three factors was used, in three equidistant levels (33), totaling 27 samples for each lot. The experiments were performed randomly, submitted to analysis of variance using the STATISTICA software. The results presented in this work are better than those obtained in real situations and similar to others in experimental situation by ozonation; when compared with traditional methods of clarification, our results are at least equal to them.Practical applicationsA method of obtaining better quality sugar is presented from the point of view of clarification. This method does not use chemical agents harmful to human health and the environment.

Effect of vaccine storage temperatures and dose rate on antibody responses to foot and mouth disease vaccination in Cambodia.

A field study investigated the effects of foot and mouth disease vaccine storage temperature for 7 days (frozen, refrigerated or held at ambient temperature) and dose (half or full dose) on the serological response to vaccination. It utilised a complete factorial design replicated on 18 smallholder cattle farms in three villages in Pursat province, Cambodia. Antibody responses from the 108 cattle involved were assessed by serological examination of blood samples collected at primary vaccination (day 0), at booster vaccination (day 30) and finally at 60 days post primary vaccination. Vaccination responses to the inactivated vaccine were assessed by testing for antibodies directed against FMD structural proteins in a liquid‐phase blocking ELISA (LPBE test) and differentiated from responses to natural infection by examining antibody titres against non‐structural viral proteins (NSPE test). LPBE results indicated that the mean log10 LPBE antibody titres of all experimental cattle increased from below protective levels at day 0 to protective levels at 30 days post primary vaccination, and increased further at 60 days post primary vaccination. Storage at ambient temperature for 1 week had no effect on antibody response to vaccination. However, freezing the vaccine for a week or use of a half dose resulted in significant reduction in titres at day 60 (P = 0.04 and P = 0.02, respectively). The results of this study reinforce the need to store FMD vaccines within the range recommended by the manufacturers and to adhere to the specified dosage instructions.

Earthworm abundance response to conservation agriculture practices in organic arable farming under Mediterranean climate

Earthworms are one of the most important soil macrofaunal groups, and they play a major role in agricultural ecosystems. Agricultural practices, such as reduced tillage, the use of green manures and organic fertilization, can be beneficial for earthworm populations in agricultural systems. However, under a Mediterranean climate, not much is known regarding their response to agricultural management. The aim of this study was to analyse the effects of tillage type, organic fertilization, and green manures on the density and biomass of earthworms in organic arable dryland. The trial was conducted in a four-year crop rotation with a complete factorial design that combined tillage system (mouldboard ploughing vs. chisel), fertilization (composted farmyard manure vs. no fertilizer) and green manures (green manures vs. no green manures). Earthworms were assessed in each plot by the extraction of all individuals in three soil areas of 33cm×33cm that were excavated to a depth of 25cm. Only five earthworm species were found in this trial, and the earthworm community was dominated by such endogeic ecotypes as Aporrectodea rosea and Allolobophora georgii, and the anecic ecotype Aporrectodea trapezoides. Endogeic species can benefit from soil inversion because of the incorporation of organic matter, but the anecic ones can be negatively affected by it. The results show that plots with farmyard manure had higher density and biomass of earthworms. We observed that the type of tillage significantly affected earthworm populations: plots that had been ploughed with mouldboard ploughing (soil inversion) the year prior to sampling presented more juveniles. The biomass of earthworms was significantly lower in plots with green manures and chiselling. Our results indicated that the combination of chiselling and green manures were not optimal for earthworm populations, but organic fertilization played a considerably more important role and enhanced their abundances.

New insights on abatement of organic matter and reduction of toxicity from landfill leachate treated by the electrocoagulation process

In this work, new insights on organic matter (OM) removal performance along with the assessment of the toxicity of landfill leachate (LL) treated by Electrocoagulation (EC) method were investigated. In the context of response surface methodology (RSM), the optimal EC experimental conditions were sought by applying a 33 complete factorial design, regarding pH, current density and electrolysis time as operational parameters. The sum of dissolved organic and inorganic carbon, namely as dissolved total carbon (DTC), was chosen as a global response parameter. Other EC experiments were performed, keeping fixed pH and current density at local optimal values and varying the electrolysis time. Determination of the median lethal concentration (LC50) from bioassays based on Artemia salina and Lactuca sativa indicators was performed. A second-order polynomial function was statistically validated with good predictions of the DTC data, indicating best removals by setting values of pH, current density, and electrolysis time at 5, 128.57 Am−2 and 120min, respectively. Additionally, removals above 90% were achieved for color, turbidity, iron concentration and dissolved inorganic carbon, whereas reductions on related-to-organic matter parameter values were around 60%. Although the EC treatment reduced the LL effluent toxicity, as verified by toxicity bioassays, 90min treatment times showed best results on LC50, but higher toxicity was persistent in electrolysis times below 40min. Thus, a second stage of treatment based on a biological process could be suitably included in order to abate recalcitrant OM and decrease remaining toxicity in a more efficient integrated treatment system.

Preference and perception of fat in salty and sweet foods

IntroductionHigher liking for fat is a risk factor for obesity. Fat in food is often combined with a sweet or salty taste. This study aims to investigate the role of fat on pleasantness and perception in both a salty and a sweet liquid food product. MethodsIn a complete factorial design, 47 participants (23 males) tasted creamy tomato soup and custard in four fat concentrations (0, 7.5, 15, 30%), combined with four salt concentrations (0.04, 0.35, 0.7, 1.5%) in soup, and four sugar concentrations (0.56, 4.5, 9, 18%) in custard. Participants rated pleasantness, saltiness intensity, sweetness intensity and fattiness intensity. The preferred fat concentrations were determined by hedonic ranking. ResultsFat and salt separately affected pleasantness in soup (P < .01). Fat, sugar and their interaction affected pleasantness in custard (P < .001). Sugar and salt were a stronger influencer of pleasantness than fat. Preference for fat in soup was variable, whereas the highest concentration of 30% fat was preferred in custard (P < .001). Ratings of fattiness intensity were more responsive to fat concentrations in soup than in custard (P-interaction fat × food base <.001). ConclusionSalt and sugar are stronger influencers on food liking than fat. Across foods, there is no consistent effect of fat on perception or on liking, therefore the attractiveness of fat in foods cannot be generalised. The attraction to high fat levels in custard, while hardly perceiving differences in fat concentrations, remains unclear and needs further investigation.

Capsaicinoid microencapsulation of chili pepper fruit (C. annuum) oleoresin by complex coacervation

A complex coacervation method was used to achieve the microencapsulation of capsaicinoids of chili pepper oleoresin (CJO) using maltodextrin (MDx) and skim milk powder. Conditions were set for two variables and adjusted to a complete factorial design (23). The recovery time of CJO was reduced to 2 h using acetone as the extraction solvent, and the best interaction of CJO-MDx was observed. However, a synergistic effect was reached using complex coacervation (recovery of 63% of CJO). Spherical microcapsules with high levels of pungency (approximately 320,000 Scoville Heat Units) were obtained. The physicochemical properties of the powder with the best characteristics were humidity, 5.40%; bulk density, 0.50 g cm−3; and yield, 3.55%. The interaction between centrifugal disk spin velocity and temperature was found to be the most significant. The interactions among the parameters have statistical significance but do not have any important physical significance. In conclusion, the complex coacervation permits the microencapsulation of capsaicinoids in high levels, with good physicochemical characteristics and high levels of pungency.

Statistical analysis of the factors that influenced the mechanical properties improvement of cassava starch films

In order to obtain cassava starch films with improved mechanical properties in relation to the synthetic polymer in the packaging production, a complete factorial design 23 was carried out in order to investigate which factor significantly influences the tensile strength of the biofilm. The factors to be investigated were cassava starch, glycerol and modified clay contents. Modified bentonite clay was used as a filling material of the biofilm. Glycerol was the plasticizer used to thermoplastify cassava starch. The factorial analysis suggested a regression model capable of predicting the optimal mechanical property of the cassava starch film from the maximization of the tensile strength. The reliability of the regression model was tested by the correlation established with the experimental data through the following statistical analyse: Pareto graph. The modified clay was the factor of greater statistical significance on the observed response variable, being the factor that contributed most to the improvement of the mechanical property of the starch film. The factorial experiments showed that the interaction of glycerol with both modified clay and cassava starch was significant for the reduction of biofilm ductility. Modified clay and cassava starch contributed to the maximization of biofilm ductility, while glycerol contributed to the minimization.

Optimization of factors to obtain cassava starch films with improved mechanical properties

In this study, was investigated the optimization of the factors that significantly influenced the mechanical property improvement of cassava starch films through complete factorial design 23. The factors to be analyzed were cassava starch, glycerol and modified clay contents. A regression model was proposed by the factorial analysis, aiming to estimate the condition of the individual factors investigated in the optimum state of the mechanical properties of the biofilm, using the following statistical tool: desirability function and response surface. The response variable that delimits the improvement of the mechanical property of the biofilm is the tensile strength, such improvement is obtained by maximizing the response variable. The factorial analysis showed that the best combination of factor configurations to reach the best response was found to be: with 5g of cassava starch, 10% of glycerol and 5% of modified clay, both percentages in relation to the dry mass of starch used. In addition, the starch biofilm showing the lowest response contained 2g of cassava starch, 0% of modified clay and 30% of glycerol, and was consequently considered the worst biofilm.

Potensi Limbah Abu Layang (Coal Fly Ash) Sebagai Koagulan Cair Dalam Pengolahan Air Gambut

Coal Fly Ash is waste of coal combustion which is included in toxic and hazardous material (B3). This study aims to find the optimum conditions of liquid coagulant manufacturing process from coal fly ash. The process of making liquid coagulant from coal fly ash is a modification of Park method (1997) to make coagulant from clay, because it has the same composition. The optimum conditions were obtained at 2500C, 60 minutes, 1: 5 ratio and 2M H2SO4 concentration. Furthermore, liquid coagulant at optimum condition was carried out effectiveness test in peat water treatment, the research was done by using randomized complete factorial design (RAL) with 9 treatment combinations and 3 replications, analyzed in the laboratory and analyzed of variance (ANOVA). Parameters measured were color, pH, turbidity, TDS, TSS. The results showed that the difference of coagulant dosage gave significant effect on color, pH, TDS, and turbidity parameters, but no significant effect on TSS parameter. The difference of stirring time significant effect on pH and turbidity parameter while for color, TDS, and TSS parameter no significant effect.

Complete factorial design to adjust pH and sugar concentrations in the inoculum phase of Ralstonia solanacearum to optimize P(3HB) production.

Poly(3-hydroxybutyrate) (P(3HB)) is a biodegradable plastic biopolymer that accumulates as lipophilic inclusions in the cytoplasm of some microorganisms. The biotechnological process by which P(3HB) is synthesized occurs in two phases. The first phase involves cell growth in a complex culture medium, while the second phase involves polymer accumulation in the presence of excess carbon sources. As such, the efficiency of the second phase depends on the first phase. The aim of this study was to evaluate culture media with different concentrations of sucrose and glucose and different pH values in the inoculum phase of Ralstonia solanacearum RS with the intention of identifying methods by which the biomass yield could be increased, subsequently enhancing the yield of P(3HB). The culture medium was formulated according to the experimental planning type of central composite rotational design 22. The independent variables were pH and sugar concentration (sucrose and glucose), and the dependent variables were OD600nm, dry cell weight (DCW), and P(3HB) yield. The highest cell growth, estimated by the OD600nm (20.6) and DCW (5.35) values, was obtained when sucrose was used in the culture medium at a concentration above 35 g.L-1 in combination with an acidic pH. High polymer (45%) accumulation was also achieved under these conditions. Using glucose, the best results for OD600nm (12.5) and DCW (2.74) were also obtained at acidic pH but with a sugar concentration at the minimum values evaluated. Due to the significant accumulation of polymer in the cells that were still in the growth phase, the accumulating microorganism P(3HB) Ralstonia solanacearum RS can be classified as having type II metabolism in relation to the polymer accumulation phase, which is different from other Ralstonia spp. studied until this time.

Interrill soil erosion processes on steep slopes

To date interrill erosion processes are not fully understood under different rainfall and soil conditions. The objectives are to 1) identify the interrill erosion regime and limiting process under the study condition, 2) characterize the interactive effects of rainfall intensity and flow depth on sediment transport competency and mode, and 3) develop a lumped interrill erosion model. A loess loam soil with 39% sand and 45% silt was packed to flumes and exposed to simulated rainfall. A complete factorial design with three factors was used, which included rainfall intensity (48, 62, 102, 149, and 170mmh−1), slope gradient (17.6, 26.8, 36.4, 46.6, and 57.7%), and slope length (0.4, 0.8, 1.2, 1.6, and 2m). Rain splash, sediment discharge in runoff, and flow velocity were measured. Results showed that rainfall intensity played a dual role not only in detaching soil materials but also in enhancing sediment transport. Sediment transport was the process limiting interrill erosion rate under the study condition. Two major sediment transport modes were identified: rainfall-driven rolling/creeping and flow-driven rolling/sliding. The relative importance of each mode was largely determined by flow depth. The competence of the flow in transporting sediment decreased downslope as flow depth increased due to increased dissipation of raindrop energy. The optimal mean flow depth for the maximal interrill erosion rates was <0.1mm, which is much shallower than the widely reported 2mm. Slope length was negatively related to interrill erosion rate. The negative correlation seemed stronger for heavier rains, indicating the cushioning effects of flow depth. Lumped interrill erosion models, developed from short slopes, are likely to overestimate erosion rates. Given transport as the limiting process, the so called erodibility value, estimated with those models, is indeed sediment transportability under the study condition. The effects of slope length on interrill erosion regimes need to be studied further under a wider range of conditions.

Desirability function for optimization of Dilute Acid pretreatment of sugarcane straw for ethanol production and preliminary economic analysis based in three fermentation configurations

Sugarcane straw is a lignocellulosic residue accumulated during the harvest of sugarcane and is a potential feedstock for second generation biofuel. This work covers the optimization of pretreatment step in the ethanol production using a complete factorial design (23), where the analyzed factors were temperature, acid concentration and time in the Dilute Acid pretreatment. Desirability function was applied in this stage to maximize sugar yields and minimize inhibitor concentrations, resulting in overall sugars yield ∼60% and furfural concentration of 0.5g/L. An enzymatic hydrolysis stage was done to increase sugar release. The fermentation stage was studied through three different configurations, such as Separate Hydrolysis and Fermentation (SHF), Simultaneous Saccharification and Fermentation (SSF) and Presaccharification and Simultaneous Saccharification and Fermentation (PSSF). The most promising alternative turned out to be PSSF due its higher ethanol concentration, with a value of 14.8g/100g dry weight (DW) biomass, equivalent to 187L/tonne DW using C6-sugars. The economic analysis revealed that the integration between enzymatic hydrolysis and fermentation in the ethanol production affected the total capital cost. The cost of raw materials (sugarcane straw and enzymes) had the most significant impact on the total production cost and accounted between 35.66 and 25.88% of the total cost of the ethanol plant from sugarcane straw.

Changes in antioxidant system and oxidative stress under water stress in four cucumber cultivars

Enzymatic and non-enzymatic systems play an important role in the survival of plants, especially under moisture stress. Therefore, responses of four cucumber (Cucumis sativus L.) cultivars, i.e., Esfahani, Super pretty, Superps and Bonanza, subjected to different moisture stress levels, viz., 100 (control), 75, 50 and 25% field capacity, were investigated in the greenhouse to evaluate their antioxidant enzyme activities. Contents of proline, hydrogen peroxide, α-tocopherol, electrolyte leakage, activities of catalase (CAT), and peroxidase (POX), lipid peroxidation in terms of malondialdehyde (MDA) content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity were measured. The experiment was arranged in complete factorial design with five replications. The activities of antioxidant enzymes CAT and POX and DPPH scavenging activity, contents of α-tocopherol, proline, electrolyte leakage as well as lipid peroxidation significantly increased in all the cultivars under increasing moisture stress levels as compared with their controls. Percent increase in antioxidant enzymes activity, α-tocopherol and proline accumulation were highest, while MDA content and electrolyte leakage were lowest in the moisture stress tolerant cultivar Bonanza under moisture stress. Hence, it may be concluded that the moisture stress tolerance of the cucumber cultivars is due to the activity of enzymatic antioxidants and contents of non-enzymatic antioxidants, and proline accumulation.

Mycorrhizal colonisation of cotton in soils differing in sodicity

Despite the reported importance of mycorrhizal symbioses for early growth and nutrient acquisition of cotton, little is known about how sodicity affects this relationship. Changes in mycorrhizal colonisation and nutrient uptake of cotton in a range of naturally non-sodic (exchangeable sodium percentages (ESP)<6) and low-sodic soils (ESP 6–10), from cotton production areas in southern Queensland and northern New South Wales, with different ESP (ranged between 1.4 and 9.8) was investigated in a glasshouse experiment. The experiment was a complete factorial design with 11 recently-collected soils and two mycorrhizae treatments (either inoculated with fresh “live” mycorrhizal inoculum or without inoculum). Linear mixed model analysis showed minimal effects of sodicity, when ESP was less than 10, on mycorrhizal colonisation, associated plant growth and nutrient uptake. Principle component and regression analysis showed that other sources of variation including soil pH and soil P content, rather than sodicity, might drive cotton colonisation in Vertosols with low to moderate ESP. The colonisation percentage was positively linearly correlated with P, Mg, and Zn uptake of cotton plants. Further investigation into mycorrhizal spore density and species diversity under sodic soil conditions is warranted.

RESPON PUPUK DAUN NPK TERHADAP PERTUMBUHAN Nepenthes ventrata DAN Nepenthes neglecta

Leaf NPK fertilizer experiments on pitcher plant (Nepenthes neglecta and ventrata) conducted in May 2008 to March 2009 in a greenhouse, Botany Division, Research Center for Biology-LIPI, Cibinong Science Center, Cibinong. The objective is to study the effect of leaves NPK fertilizer on the growth of the two Nepenthes species tested. Experiments using Random Complete Factorial Design with two factors, namely the two Nepenthes species and threedoses of fertilizer each treatment repeated six times. Growth parameters measured include; long shoot leaves, plant height, number of leaves, number of mature pitchers and growth pitchers. Results showed that the dose of NPK fertilizer provided (2 and 4 ml / lt) have no effect on plant height and number of leaves, but little effect on the number of mature pitchers thanthe control plants. The statistical tests also showed no interaction between the two Nepenthes species with a given dose of fertilizer on the growth of plants. Minimum-maximum temperature recorded in the greenhouse during the experiment was 22.20C and 38.50C. Meanwhile, air humidity between 43,6-64,7%.Key words: Leaf NPK fertilizer, plant growth, pitcher plant

Optimization of Culture Conditions for Growth Associated with Cr(VI) Removal by Wickerhamomyces anomalus M10

Chromate-resistant microorganisms with the ability of reducing toxic Cr(VI) to less toxic Cr(III), are candidates for bioremediation. An alternative culture medium to reduce Cr(VI) using Wickerhamomyces anomalus M10 was optimized. Using the Plackett-Burman design, it was determined that sucrose, K2HPO4 and inoculum size had significant effects on chromate removal (i.e., reduction) at 24h. Concentrations of these significant factors were adjusted using a complete factorial design. In this case, only the K2HPO4 effect was significant at 12h of culture, with greater Cr(VI) removal at low concentration (1.2gL-1). The optimum medium was validated at the fermenter scale level. Optimal culture conditions for complete removal of Cr(VI) (1mM) were 400rpm agitation and air flow of 1vvm. Moreover, W. anomalus M10 completely removed consecutively added pulses of Cr(VI) (1mM). These results show interesting characteristics from the standpoint of biotechnology because the development of a future remediation process using W. anomalus M10 can represent an efficient and highly profitable technology for removing the toxic form of Cr.

Identifying nitrogen-use efficient soft red winter wheat lines in high and low nitrogen environments

Nitrogen use efficiency (NUE) is of great interest to wheat (Triticum aestivum L.) breeders because it addresses the daunting prospect of feeding the burgeoning population under the constraints of limited land resources and a warming climate. In this study, we evaluated a 56 entry panel of SRW breeding lines and cultivars from the eastern US wheat region in 2014 for NUE and related traits. The 56-entry block was grown at Lexington and Princeton, KY at two N rates (0 and 112kgha−1) in a complete factorial design. We measured normalized difference vegetative index (NDVI), biomass, harvest index, N harvest index, N uptake efficiency, N utilization efficiency, post-anthesis N uptake, N remobilization efficiency and overall NUE. Breeders usually apply high rates of N fertilizer to their plots in order to maximize genetic yield potential. Our study indicates that without screening breeding lines in low N environments concurrently, it will not be possible to identify high NUE genotypes. Post-anthesis N uptake, was highly correlated with yield (r=0.79) under high N, but heritability of this trait was close to zero. Heritability of NUE, on the other hand was moderately high (h2=0.65). Five breeding lines ranked within the top 10 for NUE in both low and high N environments. NDVI was found to be both heritable and highly correlated with yield across N environments (R2=0.78). Genome wide association studies of NUE and related traits revealed QTL associated with NUE (chromosome 2B), uptake efficiency (chromosome1B) and utilization efficiency (chromosomes 1A and 3A). In accord with other studies, these QTL are of small effect and will likely only be useful in genomic selection as opposed to marker-assisted selection.

A new multiresponse optimization approach in combination with a D-Optimal experimental design for the determination of biogenic amines in fish by HPLC-FLD

A new strategy to approach multiresponse optimization in conjunction to a D-optimal design for simultaneously optimizing a large number of experimental factors is proposed. The procedure is applied to the determination of biogenic amines (histamine, putrescine, cadaverine, tyramine, tryptamine, 2-phenylethylamine, spermine and spermidine) in swordfish by HPLC-FLD after extraction with an acid and subsequent derivatization with dansyl chloride. Firstly, the extraction from a solid matrix and the derivatization of the extract are optimized. Ten experimental factors involved in both stages are studied, seven of them at two levels and the remaining at three levels; the use of a D-optimal design leads to optimize the ten experimental variables, significantly reducing by a factor of 67 the experimental effort needed but guaranteeing the quality of the estimates. A model with 19 coefficients, which includes those corresponding to the main effects and two possible interactions, is fitted to the peak area of each amine. Then, the validated models are used to predict the response (peak area) of the 3456 experiments of the complete factorial design. The variability among peak areas ranges from 13.5 for 2-phenylethylamine to 122.5 for spermine, which shows, to a certain extent, the high and different effect of the pretreatment on the responses. Then the percentiles are calculated from the peak areas of each amine. As the experimental conditions are in conflict, the optimal solution for the multiresponse optimization is chosen from among those which have all the responses greater than a certain percentile for all the amines. The developed procedure reaches decision limits down to 2.5 μg L−1 for cadaverine or 497 μg L−1 for histamine in solvent and 0.07 mg kg−1 and 14.81 mg kg−1 in fish (probability of false positive equal to 0.05), respectively.

Optimization of Growth and Bacteriocin Activity of the Food Bioprotective Carnobacterium divergens V41 in an Animal Origin Protein Free Medium

Optimization of Carnobacterium divergens V41 growth and bacteriocin activity in a culture medium deprived of animal protein, needs for food bioprotection, was performed by using a statistical approach. In a screening experiment, twelve factors (pH, temperature, carbohydrates, NaCl, yeast extract, soy peptone, sodium acetate, ammonium citrate, magnesium sulphate, manganese sulphate, ascorbic acid and thiamine) were tested for their influence on the maximal growth and bacteriocin activity using a two-level incomplete factorial design with 192 experiments performed in microtiter plate wells. Based on results, a basic medium was developed and three variables (pH, temperature and carbohydrates concentration) were selected for a scale-up study in bioreactor. A 23 complete factorial design was performed, allowing the estimation of linear effects of factors and all the first order interactions. The best conditions for the cell production were obtained with a temperature of 15°C and a carbohydrates concentration of 20 g/l whatever the pH (in the range 6.5-8), and the best conditions for bacteriocin activity were obtained at 15°C and pH 6.5 whatever the carbohydrates concentration (in the range 2-20 g/l). The predicted final count of C. divergens V41 and the bacteriocin activity under the optimized conditions (15°C, pH 6.5, 20 g/l carbohydrates) were 2.4 x 1010 CFU/ml and 819200 AU/ml respectively. C. divergens V41 cells cultivated in the optimized conditions were able to grow in cold-smoked salmon and totally inhibited the growth of Listeria monocytogenes (< 50 CFU g-1) during five weeks of vacuum storage at 4° and 8°C.

Tensile Properties of AA6156-T4 Friction Stir Welded Joints in As-Welded and Post-Weld Aged Condition

The effect of the T62 post-weld heat treatment on the tensile strength of AA6156-T4 friction stir welded joints is studied. To this aim, the 0.2% proof stress and the tensile strength of as-welded and post-weld treated joints as function of the rotating and welding speed was analyzed performing a complete factorial design with three levels for each studied parameter. Statistical analyses were carried out to establish empirical models of the tensile properties of the joints as a function of the studied welding parameters. The obtained models were validated through statistical tools such as Mallow's CP, S, R2 and R2(adj). The developed regression models can be effectively used to predict the mechanical proprieties of the joints at 95% confidence level.