Sihem Bellagha

Does the spicing step affect the quality and drying behaviour of traditional kaddid, a Tunisian cured meat?

BACKGROUND The effects of spicing on the physicochemical and microbial characteristics and drying behaviour of kaddid, a Tunisian dry-cured meat, were studied. In addition, the quality characteristics of traditional sun-dried kaddid and processed convective-dried kaddid were compared. RESULTS Spicing had no significant effect on the pH and water activity of brined beef meat at 21% (w/w), but it reduced the product water and salt contents. Effects of spicing on brined meat microbial flora were the appearance of sulfito-reducer bacteria, an increase in total mesophilic aerobic flora (+15%) and staphylococci (+26%) and a decrease in faecal coliforms (-23%). The salted beef meat sorption behaviour was affected by spicing. Besides, spicing increased the kaddid drying rate, allowing a significant decrease in the drying process time (-33%). Traditional and processed kaddid presented comparable microbial characteristics. Both drying methods led to a reduction in the number of total mesophilic aerobic flora in unspiced and spiced kaddid and of faecal coliforms in spiced kaddid. CONCLUSION The study showed that spicing, as a step in kaddid meat processing to enhance the final product flavour, caused changes in the salted meat physicochemical and microbial characteristics and accelerated the drying rate. Convective drying at 30 °C is recommended to produce kaddid having the same characteristics as the traditional product.

Ethyl Formate Fumigation of Dry and Semidry Date Fruits: Experimental Kinetics, Modeling, and Lethal Effect on Carob Moth

ABSTRACT Ethyl formate (EF) was studied as a fumigant agent with the objective to replace methyl bromide (MB) for date fruit disinfestations. Date fruits Phoenix dactylifera ‘Deglet Nour’ with different initial moisture content (16% for dry dates, 20% for semidry dates, and a mixture of the two types) were separately fumigated with EF at different concentrations: 28.6, 57.3, 85.9, and 114.6 g/m3 for 2 h. Experimental data of EF sorption during fumigation was successfully fitted to Pelegs model. This model allows the prediction of the effects of date moisture content and EF concentration on sorption behavior. Samples with different moisture content showed similar EF sorption behavior. Dates were artificially infested with carob moth (Ectomyelois ceratoniae (Zeller)) at different life stages. Eggs, third- and fifth-instars, and pupae were exposed to 28.6, 57.3, 85.9, and 114.6 g/m3 EF for 2 h. Among these life stages, fifth-instars were the most resistant to EF fumigation. A 2-h fumigation with 114.6 g/m3EF provided complete control of eggs, third-instars, and pupae of carob moth, and generated 91.6% mortality of fifth-instars. A longer fumigation time or higher EF concentration may provide complete control of all life stages of carob moth.

Effects of cooking and food matrix on estimated mineral bioavailability in Mloukhiya, a Mediterranean dish based on jute leaves and meat

Traditional Mediterranean plant-based dishes could allow tackling malnutrition while preserving the cultural heritage. To determine the effect of the cooking method on mineral bioavailability, the content in minerals and chelators of Mloukhiya, a Mediterranean dish based on jute leaves (Corchorus olitorius) that contains also meat, was monitored during the whole cooking process. Mineral bioaccessibility was assessed by measuring in vitro dialyzability. Model equation was also used to estimate mineral bioavailability. Comparison of Mloukhiya samples collected at different cooking time points showed that the dish total mineral content did not change despite the exchanges between sauce and meat during cooking. However, iron bioavailability decreased, because 58% of heme iron was degraded after 5h of cooking and non-heme iron showed poor bioaccessibility (1.2%), mainly due to its high content of phenolic compounds. The bioaccessibility of other minerals (zinc, calcium, magnesium and potassium) was high, indicating that the food matrix had no or little effect. The mineral bioavailability values predicted by using mathematical models were of the same order of magnitude as the bioaccessibility values.

Impact of initial moisture content levels, freezing rate and instant controlled pressure drop treatment (DIC) on dehydrofreezing process and quality attributes of quince fruits

Abstract Dehydrofreezing process involves water partial removal before freezing. This treatment has been proposed in order to reduce the negative impacts of conventional or even accelerated freezing, especially on the textural quality of high water content fruits and vegetables. Indeed, in such cases, freezing and thawing processes result in severe damage of the integrity of product’s cell structure due to the formation of ice crystals. For this purpose, quince fruits (7 g H2O/g db) were subjected to convective air drying of 40 °C and 3m/s to reach different water content levels of 2, 1, and 0.3 g H2O/g db. Freezing profiles obtained at various freezing rates (V1, V2, and V3) for different water contents allowed the main freezing characteristics such as the Initial Freezing Temperature (IFT), the Practical Freezing time (PFt), and the Specific Freezing time (SFt) to be assessed. The impact of freezing rate was important on PFt and SFt, and more pronounced for high water contents (W between 7 and 2 g H2O/g db (dry basis)). Furthermore, IFT decreased sharply when initial sample water content decreased. Indeed, it started at −0.8 °C for W = 7g H2O/g db, while it reached a value of −8.2 °C for samples of W = 1g H2O/g db. Since convective air drying normally triggers shrinkage which causes a detrimental deformation of fruit structures, instant controlled pressure drop (DIC) treatment was used to improve the texture and enhance the whole dehydrofreezing performance and the final frozen-thawed product quality. Moreover, DIC implied a slight increase of PFt compared to untreated ones. On the other hand, quality attributes were estimated through the assessment of thawed water exudate (TWE g H2O/100 g db), color and texture (maximum puncture force as index of firmness): freezing rate and water content had great impacts on TWE. Hence, the lower the water content, the weaker the TWE. Furthermore, the TWE of the pre-dried quince (0.3 g H2O/g db) had higher value for DIC-textured samples than for the un-treated ones. Indeed, DIC-texturing leads to a well-controlled structure expansion of the cell wall. These textural changes resulted in more lixiviation of residual water. Consequently, water becomes more available, hence more releasable after thawing. Finally, the partial removal of water by air drying before freezing remarkably reduced the negative impact of freezing/thawing processes on final quince color. Decisively, the firmness of quince fruit increased with the decrease of water content level. Abbreviations: DMC: Dry Matter Concentration (%); DIC: Instant controlled pressure drop; W: Water content dry basis (g H2O/g db); IFT: Initial Freezing Temperature (°C); PFt: Practical Freezing time (min); SFt: Specific Freezing time (min); TWE: Thawed Water Exudate (g H2O/100 g db); L, a, and b: Color coordinates; (L): The degrees of lightness; (a) and (–a): The redness (a) or greenness (−a), respectively; (b) and (−b): The yellowness (b) or blueness (−b), respectively; ΔE*ab: Total color difference; L0, a0, and b0: Color coordinates of fresh or dried quince samples; SD: Standard Deviation; ANOVA: Analysis of variances; LSD: Least Significant Differences; cp: Specific Heat of the product depending on composition (dry material and water content)(KJ/kg K); cpd: Specific Heat of the dry material (KJ/kg K); cpW: Specific Heat of water (KJ/kg K); V1: Freezing rate without insulation; V2: Freezing rate with a food stretch film insulation with thickness e2 = 3 mm and thermal conductivity λ2 = 0.17 W/m K; V3: Freezing rate with a versatile flexible insulation (Armacell) with thickness e3 = 13mm and weak thermal conductivity λ3 = 0.036 W/m K; vd: Volume of dry material of quince sample (mm3); vH2O: Volume of quince sample water (mm3); vt: Total volume of quince sample (mm3); e0: Quince sample thickness (mm); e2: Insulation thickness in the case V2; = 3 mm; ; e3: Insulation thickness in the case V3; = 13 mm; ; λ0: Quince sample conductivity (W/m K); λ2: Insulation conductivity in the case V2; = 0.17 W/m K; ; λ3: Insulation conductivity in the case V3; = 0.036 W/m K; λd: Conductivity of quince sample dry material (W/m K); λH2O: Conductivity of water (W/m K); λequiv: Equivalent conductivity of quince sample versus water content (W/m K); mi and mf: Weights of the frozen and thawed samples, respectively