Effects of sowing date on severity of blight caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> and yield components of five chickpea cultivars grown under two climatic conditions in Tunisia

Five chickpea cultivars, Chitoui, Neyer, Kasseb, Beja 1 and Bouchra, were planted on three sowing dates at two Experimental Stations in Tunisia: Bou Salem in the north and the more southerly Mornag, where the climate is drier. Severity of blight, caused by Ascochyta rabiei, was measured on a 1–9 scale (defined) on vegetative parts and on pods as percent infected and percent infected that were empty. At both locations, disease was essentially absent on plants sown on the third dates but present on plants sown on the two earlier dates. At Bou Salem, disease severity was highest for the second sowing date whereas at Mornag it was highest for the first sowing date; but for each sowing date, disease severity was lower at Mornag than at Bou Salem. Yield components were measured as number of pods per plant, number of seeds per plant, number of seeds per 100 pods, 100 seed weight and weight of seeds per plant. Both disease severity and yield differed significantly among sowing dates (differently at each location) and also among cultivars for each sowing date, these differences depending both on sowing date and location. A lower yield was always associated with a higher disease severity, although the quantitative relationship differed between cultivars and locations. Cultivar Beja 1 had the lowest vegetative disease scores at both locations and both sowing dates 1 and 2. Beja 1 also scored well for all yield components. Plants sown on the third (latest) date gave the highest yields for all cultivars at both locations (except for an unusually high yield of Neyer at Mornag on sowing date 2), in some instances being more than double those from the earlier sowing dates. Thus, in contrast to other studies, late sowing did not result in yield loss.     

Trypsin from the viscera of Bogue (<Emphasis Type="Italic">Boops boops</Emphasis>): isolation and characterisation

Trypsin from the viscera of Bogue (Boops boops) was purified to homogeneity by precipitation with ammonium sulphate, Sephadex G-100 gel filtration and Mono Q-Sepharose anion exchange chromatography, with an 8.5-fold increase in specific activity and 36% recovery. The molecular weight of the purified enzyme was estimated to be 23 kDa by SDS–PAGE and size exclusion chromatography. The purified trypsin appeared as a single band on native-PAGE and zymography staining. The purified enzyme showed esterase-specific activity on N-α-benzoyl-l-arginine ethyl ester (BAEE) and amidase activity on N-α-benzoyl-dl-arginine-p-nitroanilide (BAPNA). The optimum pH and temperature for the enzyme activity, after 10 min incubation, were pH 9.0 and 55°C, respectively, using BAPNA as a substrate. The trypsin kinetic constants K _m and k _cat on BAPNA were 0.13 mM and 1.56 s⁻¹, respectively, while the catalytic efficiency k _cat /K _m was 12 s⁻¹ mM⁻¹. Biochemical characterisation of B. boops trypsin showed that this enzyme can be used as a possible biotechnological tool in the fish processing and food industries.     

A metabolomic approach to the evaluation of the origin of extra virgin olive oil: a convenient statistical treatment of mass spectrometric analytical data

The selection of suitable markers from the secondary metabolism of lipoxygenase, in experimental olive oils produced from drupes harvested in different areas of the Italian Calabria region and of Tunisia, allows an easy discrimination between each cluster of samples. The origin of the foodstuff can be ascertained even when the distances between the production zones are very close to each other as in Calabria. Olive oils produced from irrigated and nonirrigated farms in Tunisia were also clearly distinguishable. The markers were detected by chemical ionization mass spectrometry with an ion trap gas chromatography-mass spectrometry apparatus. The quantitative data of Calabrian olive oil samples were subjected to linear discriminant analysis, whereas the Tunisian data were treated by means of other two statistical tools, i.e., the Kruskal-Wallis test and the Wald-Wolfowitz test.     

Sap flow measurements in young olive trees (Olea europaea L.) cv. Chétoui under Tunisian conditions

Measurements of sap flux were carried out from May 2003 to March 2004 on 6 year-old irrigated olive trees of cultivar Chétoui cultivated at 6 m × 6 m spacing in Mornag (36.5°N, 10.2°E), Northern Tunisia. The aim of the research is to evaluate the sap flux technique for its applicability with young olive trees and to estimate their water consumption under field conditions. Three thermal sensors were implanted in the trunk of three olive trees following to North (N), South-East (SE) and South-West (SW) directions. Data were analyzed following to the procedure of Do and Rocheteau (2002b) that derives from Granier (1985). In this paper, data on probe calibration, wood conductive section estimation and sap flux spatial-variability are presented and discussed. Relationships between sap flux measurements, climate and soil water status have been investigated. Results show that sap flux values vary with sensor position, soil water content and climate demand. Good agreements between sap fluxes and global radiation and reference evapotranspiration measurements were observed. Some variations were recorded under water shortage conditions. Maximum and minimum daily fluxes of 4.5 l and 41.0 l per tree were found in February 2003 and in August 2003, respectively. Maximum transpiration represented only 53% of the crop evapotranspiration as determined by the F.A.O. method.     

Influence of olive maturity stage and geographical origin on some minor components in virgin olive oil of the chemlali variety

Minor compounds such as sterols, aliphatic alcohols, tocopherols, and chlorophylls in virgin olive oil from Chemlali cultivar were analyzed during the maturity process. The study concerns oils from the following three different olive growing areas of Tunisia: Sfax, Sidi Bouzid, and Enfidha. Analytical results showed that both the maturity process and the olive provenances influence the evolution of the content of these compounds.     

Effect of Degree of Hydrolysis and Protease Type on the Antioxidant Activity of Protein Hydrolysates From Cuttlefish (Sepia officinalis) By-Products

We have investigated the antioxidant activities of eight hydrolysates from cuttlefish by-products obtained by treatment with various gastrointestinal proteases (chymotrypsin, trypsin, and crude alkaline enzyme extracts from cuttlefish and sardinelle) and bacterial proteases (Alcalase and crude enzymes from Bacillus pumilus A1, Bacillus mojavensis A21, and Bacillus cereus BG1). The antioxidant activities of the cuttlefish by-products protein hydrolysates (CPHs) were evaluated using various in vitro antioxidant assays, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power, and total antioxidant capacity. All hydrolysates showed different degrees of hydrolysis (DH) and varying degrees of antioxidant activity. Among the different hydrolysates, cuttlefish crude enzyme hydrolysate exhibited the highest antioxidant activity, followed by sardinelle crude enzyme and Alcalase hydrolysates. Further, CPHs with different degrees of hydrolysis were prepared by treatment with proteolytic enzymes from cuttlefish, sardinelle, and B. mojavensis A21. All hydrolysates showed a greater antioxidative activity as indicated by all the methods considered. In addition, antioxidant activity in hydrolysates was positively correlated with the increase of DH. The results of this study indicated that CPHs might be a good candidate for further investigation in developing new antioxidants.     

Golden Grey Mullet (Liza aurata) Alkaline Proteases: Biochemical Characterization,Application in the Shrimp Wastes Deproteinization,Laundry Commercial Detergents,and Preparation of Antioxidant Protein Hydrolysate

Digestive alkaline proteinases from golden grey mullet (Liza aurata) were extracted and characterized. The crude alkaline protease showed optimum activity at pH 8.0 and 60°C, and it was highly stable over a wide range of pH from 4.0 to 10.0, retaining more than 80% activity after incubation for 1 h at 4°C. The alkaline proteases showed extreme stability toward nonionic and anionic surfactants after preincubation for 1 h at 25°C and relative stability toward oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various solid and liquid detergents. Further, proteases from golden grey mullet viscera were found to be effective in the deproteinization of shrimp wastes. The protein removal after 3 h at 45°C with an enzyme/substrate (E/S) ratio of 10 U/mg protein was about 76%. The golden grey mullet proteases were also shown to be efficient in the production of antioxidant protein hydrolysate.     

Isolation and Characteristics of Carboxypeptidase B from Zebra Blenny (Salaria basilisca) Viscera

Carboxypeptidase B (CPB) from zebra blenny (Salaria basilisca) viscera was purified using ammonium sulphate precipitation and Sephadex G-100 gel filtration, with a 28-fold increase in specific activity and 21.72% recovery. The molecular weight of the enzyme was estimated to be 34.5 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature for the enzyme activity were around pH 8.0 and 60°C, respectively, using Hippuryl-l-Arg as a substrate. The enzyme was unstable above 50°C and below pH 5.0. The enzyme was activated by Co²⁺ and Zn²⁺ and inhibited by ethylenediaminetetraacetic acid (EDTA). The N-terminal amino acid sequence of the enzyme was determined as S P S Y T K Y N T. The CPB kinetic constants, K_m and k_cat for Hippuryl-l-Arg, were 0.32 mM and 36.23 s^?1, respectively.     

Improvement of the composition of Tunisian myrtle berries (Myrtus communis L.) alcohol extracts

Different extracts from myrtle berries were obtained using alcohol-water mixtures as an extraction medium in the range of 60-90% (v/v) to study the extraction efficiency in the preparation of myrtle liqueur. Flavonoids and anthocyanins were identified by high-performance liquid chromatography (HPLC) coupled with electrospray mass spectrometry and quantified during the maceration period by HPLC coupled with ultraviolet/visible detection. The antioxidant activity was tested by the 2,2-diphenyl-1-picrylhydrazyl assay. Dry matter, pH, and color parameters (L, a, b) were also analyzed. At the end of the maceration period, EE80 showed better anthocyanins stability and the highest total antioxidant activity (87.5%). These results suggest that the use of ethanol 80% provides the extract with the best characteristics for liqueur preparation. The present study contributes significantly to increase the marketing appeal of myrtle berries.