Arianna Roda

Improved processing methods to reduce the total cyanide content of cassava roots from Burundi

The identification of highly effective procedures that reduce the cyanogens contained in cassava roots which require no sophisticated equipment, and can readily be adopted by subsistence farmers is of tremendous importance. This study, which used cassava root samples collected in Burundi, included fermentation tests using both selected and native cultures at different temperatures for variable times. Moreover, drying procedures with and without fermentation were carried out. A factorial analysis of variance (ANOVA) showed that the detoxification was mainly affected by fermentation length and by the initial cyanogens content of the roots. When fermentation lasted 48 h and the initial cyanide level was lower than 300 mg/kg dry weight (d.w.), the detoxification was also found to vary based on the microorganism inoculated; Saccharomyces cerevisiae demonstrated the greatest effectiveness. In terms of drying conditions, a temperature of 60°C, even for a shorter duration of time (8 h), lowered the initial cyanide level by more than 90%. Finally, when dehydration followed fermentation, the pressed pulp showed a substantial reduction in cyanide content. By means of this last procedure, safe cassava was produced according to FAO/WHO amendments (10 mg HCN equivalent per kilogram flour), if the initial cyanide level of roots did not exceed 200 mg/kg d.w. Actually, the initial maximum total cyanide content was confirmed to be fundamental in order to obtain safe products in relation to processing method adopted. Keywords : Cassava, cyanide, detoxification, drying, fermentation. African Journal of Biotechnology Vol. 12(19), pp. 2685-2691

Vinegar Production from Pineapple Wastes –preliminary Saccharification Trials

This study is located in the within of a research devoted at processing wastes both in developing and in developed Countries, so reducing both environmental pollution and seasonal fruit losses. In particular, the full work intended to completely process pineapple wastes into vinegar which may be then used as dressing, food preservative, and disinfectant. The preliminary trials presented here deepened the first process step (i.e. the saccharification) and looked into the feasibility of producing the greatest yield of reducing sugars from peels and core of pineapples. Wastes were cut into thin strips, chopped in a mixer, and divided into samples of peel and core to which distilled water was added. For enhancing reducing sugar yield, physical treatments were arranged to disaggregate the fibrous structure followed by enzyme treatments to breakdown cellulose polymers and to hydrolyse sucrose. The optimal time-temperature conditions of each process step were searched for gaining the highest reducing sugars yield at the end of the saccharification. Cellulolytic enzymes were tested for 4-8-18-24 h at 30-40-50 °C, invertase addition was arranged, and amylolytic enzymes were evaluated. All determinations were done in duplicate and a factorial ANOVA with Tukey’s test at p ≤ 0.05 was used to measure the significance of the differences among treatments. The conditions allowing the greatest reducing sugar yield were: the addition to 100 g of waste fresh weight (fw) of 0.025 mL of thermostable α-amylase before a 10 min treatment at 143.27 kPa followed by 24 h-50 °C incubation with 0.05 g pectinase/kgfw, 6 g cellulase/kgfw, 1 g hemicellulase/kgfw, and 0.05 % glucoamylase and pullulanase (Venzyme/kgfw). Then, samples were incubated with 0.05 g invertase/kgfw for 3 h at 50 °C. Under these conditions, more than 100 g of reducing sugars per kg of fresh peels and about 330 g of reducing sugars per kg of fresh core were obtained.

Metabolite profiling and volatiles of pineapple wine and vinegar obtained from pineapple waste

Vinegar is an inexpensive commodity, and economic considerations require that a relatively low-cost raw material be used for its production. An investigation into the use of a new, alternative substrate - pineapple waste - is described. This approach enables the utilization of the pineapples (Ananas comosus) peels and core, which are usually discarded during the processing or consumption of the fruit. Using physical and enzymatic treatments, the waste was saccharified, and the resulting substrate was fermented with Saccharomyces cerevisiae for 7-10days under aerobic conditions at 25°C. This resulted in an alcohol yield of approximately 7%. The alcoholic medium was then used as a seed broth for acetic fermentation using Acetobacter aceti as the inoculum for approximately 30days at 32°C to obtain 5% acetic acid. Samples were analyzed at the beginning and end of the acetification cycle to assess the volatile and fixed compounds by GC-MS and UHPLC-QTOF-MS. The metabolomic analysis indicated that l-lysine, mellein, and gallic acid were significantly more concentrated in the pineapple vinegar than in the original wine. Higher alcohols, aldehydes, and ketones characterized the aroma of the final pineapple vinegar, whilst off-flavors were significantly reduced relative to the initial wine. This study is the first to highlight the metabolite profile of fruit vinegar with a slight floral aroma profile derived from pineapple waste. The potential to efficiently reduce the post-harvest losses of pineapple fruits by re-using them for products with added food values is also demonstrated.

Process development for maltodextrins and glucose syrup from cassava

The objective of this study was to produce maltodextrins (MD) and glucose syrup (GS) throughout a smallscale process from the direct conversion of cassava roots collected in Burundi and previously detoxified. The detoxified cassava slices were blended with water at ratios of 1:1.0; 1:1.3; 1:1.6. Then, the cassava mash was undergone previously to gelatinization and then to liquefaction experiments aimed at obtaining MD with a Dextrose Equivalent (DE) value < 20. The doses of 0.013, 0.016, 0.019, 0.025, and 0.075 % (venzyme/wfresh mash) thermostable α-amylase (Liquezyme-X) were investigated to be added to cassava mash at pH 6.5 before and after 10 min - 90 °C step at atmospheric pressure (patm) or 143.27 kPa (110 °C) allowing the starch gelatinization. Then liquefaction times of 10, 15, 20, 30, 40, 45, 60, 90 and 120 min were tested. The saccharification step followed the liquefaction in order to obtain a GS with DE close to 99. The hydrolyzed cassava mash from liquefaction experiments was added at pH 5.4 and 60°C with 0.019 % (venzyme/wfresh mash) glucoamylase (Dextrozyme GA) and pullulanase (Dextrozyme GX) testing 1, 2, 4, 6, 18, 24, and 48 h incubation times. All experiments were done in duplicate and analysis of variance (ANOVA) with Tukey’s test at p≤0.05 was used to measure the effect of changing variables among treatments. Correlation Pearson’s test were applied to measure the strength of the interactions between the variables. Results showed that the 10 min-143.27 kPa (on lab-scale) and the 12 min-145÷152 kPa (on small-scale) burst of starch granules in 1:1.6 cassava: water mash with 0.013 % (venzyme/wfresh mash) thermostable αamylase at pH 6.5 followed by 15 min-90 °C liquefaction phase at patm allowed at obtaining MD with DE value < 20. In order to gain a GS having a DE value close to 99, a 4 h-60 °C saccharification phase at pH 5.4 with 0.019 % (venzyme/wfresh mash) glucoamylase and pullulanase should be carried out. Finally, highly significant correlations were found out between the water amount in the cassava mash, the concentration of the α-amylase enzyme, and the liquefaction time. This type of process had the advantage to be simple and practical, with reduced working times and enzyme doses, so to be popularizing especially in developing Countries. Further investigations are needed on some energy intensive operations, as like as pH adjustment, pressure increasing, and heating.

Mild Process for Dehydrated Food-grade Crude Papain Powder from Papaya Fresh Pulp: Lab-scale and Pilot Plant Experiments

Proteases are protein digesting biocatalysts long time used in the food industry. Although many authors reported the crystallization of papain and chymopapain from papaya latex, the powder of crude papain had the largest application as food supplements due to its highly positive effect on the degradation of casein and whey proteins from cows milk in the stomach of infants. As the industrial preparative procedures have not been extensively applied, this study aims at producing dehydrated crude papain from fresh papaya pulp, planning lab-scale trials, followed by process development toward the pilot industrial-scale. In the lab-scale experiments, the enzyme activity (EA), expressed as protease unit (PU) /g, were evaluated on pulp and papain standard before and after a 2 h thermal treatment at 70 °C, 90 °C, and 120 °C, and the thermal behavior was monitored by means of differential scanning calorimeter (DSC). The process development toward the pilot-scaling optimized: the homogenization of the fresh pulp, followed by its filtration at high pressure (HP) in order to obtain the vegetation water and the pre-dehydrated pulp which was then oven dried varying the time-temperature conditions (4 h-80 °C; 2 h-120 °C; 30 min-150 °C). Proceeding at higher temperatures for a shorter time allowed obtaining commodity-related and technologically valid products. In the final pilot-scale step, filtration was done with vertical HP filter press, and final dehydration was performed with 2-step turbo-drying: the first aimed to concentrate with 2 min air flow (500 m 3 /h) at 200 °C, the second aimed to dry with 10 min air flow (500 m 3 /h) at 120 °C. The resulting dehydrated pulp was grinded with ball-mill to obtain a stable powder. Starting from 90±2 % pulp moisture, the two turbo-drying steps lowered the water content from 75±4 % to 50±2 % and from 50±2 % to 8±1 %, respectively. The enzyme release from the final powder highlighted an EA of the food-grade crude papain powder extract of 28 PU/g. The thermal steps provided with turbo-driers permitted to maintain a fraction of sugars and pectin acting as a protective structure, so increasing the digestion effects provided by papain. Vegetation waters were ultra-filtered allowing at obtaining a concentrated pectin suspension and rich in nutrient waters which can be reused along the food chain. Further efforts should be made to implement this procedure as potential alternative for the dehydrated crude papain production, deepening the impact of process variables on this matter.

Effect of Technological Treatments and Polysaccharide Ingredients on Oxidative Stability of Innovative Freeze-dried Walnut Products

Many confectionery companies employ semi-finished lipid products, such as nut pastes, as an ingredient for the preparation of several foods. Nevertheless, during the storage, nut pastes have some drawbacks due both to the onset of rancidity, both to the separation between oil and semi-solid phase. The development of stable semi-finished walnut products in form of powder would allow to extend the walnut use in various preparations by increasing their convenience. As is well known, walnuts are highly nutritious fruits with well evidenced health benefits. In spite of natural antioxidant content walnut kernels are rich in polyunsaturated fatty acids and vulnerable to oxidation. In order to preserve thermo sensitive substances, a freeze-drying (lyophilizing) technique was developed by addition of polysaccharide matrices (including dietary fiber) in a walnut paste obtained by roasted kernels. This study aims to provide information on the impact of technological treatments and ingredient combinations on oxidative stability of freeze-dried walnut products. In preliminary tests, kernels were roasted at 110 °C for 5 min, 10 min, and 15 min. Residual moisture, pH and total acidity, peroxide value, and polyphenol contents were measured, as quality evaluation, in order to select the optimum operating conditions for the paste preparation. Optimal paste was obtained by milling 10 min roasted kernels, as it ensured a low residual humidity without affecting peroxides and polyphenols. Water and different combinations of maltodextrins DE12, tragacanth gum, and barley betaglucan were added to optimal walnut paste by creating emulsions which were then lyophilized. Quality evaluation was carried out on samples before and after freeze-drying treatment, and on freeze-dried products after 7 day, 60 °C storage. The formulation, containing maltodextrin and tragacanth gum, supplemented with betaglucans (at a ratio of 1:100 with the optimal walnut paste), showed no differences in the values of pH, acidity and polyphenols measured throughout treatment. All of the samples kept peroxide values < 10 meqO2/Kg expressed on dry matter. In particular, the addition of betaglucans gave the lyophilized samples a firm texture, without altering the oxidative chemical-physical parameters.