Optimization of Extraction Parameters and Characterization of Tunisian Date Extract: A Scientific Approach Toward Their Utilization.

The response surface methodology (RSM) was used in order to select the extraction conditions of extract from Kentichi date powder; a by-product of the date-processing process. Powder/solvent ratio, extraction temperature, and extraction time all had an impact on sugar yield, and these model factors have quadratic effects influencing sugar yield. Optimal extraction was obtained with 300 g/L powder/solvent ratio, 32.7 °C extraction temperature, and 2.1 h extraction time. Under these conditions, Kentichi date powder's (KDP) sugar yield was 77.1%, which was close to the predicted value of the model (80.50%). The results of Kentichi date powder extract (KDPE) showed that the total sugar content is 160.09 g/L. However, the protein content is 10.31 g/L with a majority of the essential amino acids (essentially glutamic acid (28.39 mg/L) and aspartic acid (9.65 mg/L)). The determination of antioxidant activity of KDPE showed a high activity (DPPH IC50 = 4.8 mg/mL, ABTS IC50 = 3 mg/mL, FRAP = 4.70 µmol AAE/mL and, TAA = 18.04 µmol Fe(II)/mL). The results show also that the freeze-drying technique has a lot of potential for producing powder from KDPE with many desirable properties. The findings indicate that KDPE with a high nutritional value could be used as a component for the formulation of functional foods. Supplementary Information: The online version contains supplementary material available at 10.1007/s12355-022-01223-2.

Bioprocess development and preservation of functional food from tomato seed isolate fermented by kefir culture mixture.

The aim of this work was to explore the use of protein isolate from tomato seed enriched with the sucrose and the ascorbic acid as a medium for the growth of kefir mixture culture to develop a new non-dairy functional food. Unstructured mathematical and logistic models were proposed to describe cell growth, kefiran production, nutriment consumption and antioxidant activity. It was found that the maximal cell mass in the culture reached 8.38 g L-1 after 24 h of fermentation. A significant amount of kefiran was also produced (0.65 g L-1). The kefir culture growth significantly decreased protein content and enhanced the antioxidant activity during varied fermentation through the production of bio active peptides. After 24 h of fermentation, IC50 value for protein isolate was estimated to be about 10.48 µg mL-1. The proposed models adequately described the changes during fermentation and as observed as a promising approach for the formulation of tomato seed-based functional foods. The preservation of the isolate was also investigated through a spray-drying process. The effect of spray-drying on the viability of lactic acid bacteria and stability of protein content and the antioxidant activity of the powder was also carried out. Results showed that the spray-drying method has great potential for the synthesis of powder from the fermented isolate that are rich in desirable properties. However, it was appropriate to preserve the powder for 10 days at 37 °C for the preservation of protein functionality.

Involvement of antioxidant activity of Lactobacillus plantarum on functional properties of olive phenolic compounds.

Eight lactic acid bacteria strains isolated from traditional fermented foods were investigated for their antioxidant activity against DPPH free radicals, ß-carotene bleaching assay and linoleic acid test. L. plantarum LAB 1 at a dose of 8.2 10(9) CFU/ml showed the highest DPPH scavenging activity, with inhibition rate of 57.07 ± 0.57 % and an antioxidant activity (TAA = 43.47 ± 0.663 % and AAC = 172.65 ± 5.57), which increase with cell concentrations. When L. plantarum LAB 1 was administered to oxidative enzymes, residual activities decreased significantly with cell concentrations. The use of L. plantarum LAB 1 on olives process, favours the increase of the antioxidant activity (24 %). HPLC results showed a significant increase of orthodiphenols (74 %). Viable cells of strain were implicated directly on minimum media growth with 500 mg/l of olive phenolic compounds. Results showed an increase in their antioxidant activity. CG-SM analysis, identify the presence of compounds with higher antioxidant activity as vinyl phenol and hydroxytyrosol.

Impact of Lactococcus lactis spp. lactis Bio Adhesion on Pathogenic Bacillus cereus Biofilm on Silicone Flowing System.

Bacillus cereus is a food pathogen that can attach on most of the surfaces and form biofilms, which facilitate the persistence and resistance toward antimicrobials. The aims of this study were (i) to characterize the structural dynamics of B. cereus sessile growth in two nutritional environments (with or without a nutrient flow), and (ii) to evaluate the impact of bio adhesion of Lactococcus lactis on B. cereus biofilm. Significantly greater biofilm volume and thickness were observed under dynamic conditions than under static conditions after 48 h and B. cereus biofilm was highly organized. The variation of physico-chemical characteristics of silicone by B. cereus bio adhesion favours the adhesion of hydrophilic Lc. lactis on the surface adhered by biofilm. Lc. lactis was able to adhere to silicone surface and produce biofilm obviously exhibited a significant reduction of B. cereus adhered cells up to nine orders of magnitude after 48 h of contact with competitive activity for nutrient and oxygen. This study constitutes a step ahead in developing strategies to prevent microbial colonization of silicone with lactococcal protective biofilm.

Kinetic analysis and mathematical modeling of growth parameters of Lactobacillus plantarum in protein-rich isolates from tomato seed.

The aim of the present study was to evaluate the applicability of using protein-rich isolates from tomato seed as a sole source of nutrition for the growth of lactic acid bacteria. Unstructured mathematical and logistic models were proposed to describe growth, pH drop, lactic acid production and nutriment consumption by Lactobacillus plantarum in whole and defatted isolates in order to compare their suitability for the production of a fermented beverage. These media have considerable good quantities of nutriment that allowed the growth of L. plantarum, after which the cell numbers begin to decline. The maximum biomass was observed in defatted isolate (1.42 g L-1) followed by the whole isolate (1.24 g L-1). The lactic acid increased by about 5.5 and 6.5 times respectively in whole and defatted protein isolates. However, significant nutriment consumption occurred during the growth phase as well as stationary phase. A reduction of 61.90% and 95.88% in sugar content, as well as 21.91% and 16.93% reduction in protein content were observed respectively in whole and defatted isolates. In most cases, the proposed models adequately describe the biochemical changes taking place during fermentation and are a promising approach for the formulation of tomato seed-based functional foods.

Removal of aflatoxin B1 and inhibition of Aspergillus flavus growth by the use of Lactobacillus plantarum on olives.

Olives can be contaminated with a wide variety of molds (Aspergillus and/or Penicillium) that can be occurring naturally on fresh and processed olives and could support mycotoxin production. The aim of this work was to investigate aflatoxin B1 (AFB1) production by fungi and its bioaccumulation in olives during storage and to study the impact of the application of Lactobacillus plantarum on the inhibition of mold development and production of AFB1. Two different treatments were applied: (i) olives with natural microflora and (ii) olives inoculated with Aspergillus flavus after elimination of natural microflora. AFB1 has been extracted from olives and quantitated by high-performance liquid chromatography using a fluorescence detector. Results showed the absence of this metabolite in the olives for the season 2008 to 2009. In 2009 to 2010, AFB1 was detected at the level of 11 µg/kg. The application of L. plantarum during the storage of olives favors the reduction of the level of AFB1 to 5.9 µg/kg correlated with a decrease in the amount of molds (86.3%). The images obtained by environmental scanning electron microscopy showed that L. plantarum was able to adhere to the olive surface and probably produce a biofilm that inhibits the multiplication of yeast and fungi by oxygen competition. Results showed an increase of antioxidant activity and amount of total phenolic compounds of olives, respectively, by 24 and 8.6%. In many olives contaminated with A. flavus, AFB1 was present at an initial level of 5.15 µg/kg and increased to 6.55 µg/kg after 8 days of storage. The biological detoxification of AFB1 in olives by L. plantarum is confirmed by the reduction of the level of AFB1 to 2.12 µg/kg on day 0 and its absence after 4 days of storage.