Exploring the synergistic effects of essential oil and plant extract combinations to extend the shelf life and the sensory acceptance of meat products: multi-antioxidant systems.

To develop multi-antioxidant systems for the preservation of meat products, mixtures of essential oils or plant extracts were investigated for their antioxidant interactions. The combinatorial study revealed that the chemical diversity of both major and minor components of these ingredients contributed to the antioxidant interactions. A shift from antagonistic or additive interaction to synergistic one was achieved by modulating the ratio of mono-components of multi-antioxidant systems. Mixtures containing oregano/thyme (25/50 of IC50), thyme/clove (25/100) and thyme/cinnamon (50/25) oils as well as cranberry/rosemary (25/25), cranberry/green tea (25/25), cranberry/apple (25/25), rosemary/apple (50/25) and grapeseed/cranberry (50/50) extracts have shown synergistic antioxidant effects. Among the investigated systems, thyme/clove oils and oregano/thyme oils/grape-seed extract systems have extended, in situ, the shelf-life of chicken and ground pork products stored at 4 °C by 2 to 4 folds. The sensory acceptability of treated samples was rated to be moderately better than control. This study lays the ground for the development of efficient natural multi-antioxidant systems. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05653-4.

The prebiotics (Fructo-oligosaccharides and Xylo-oligosaccharides) modulate the probiotic properties of Lactiplantibacillus and Levilactobacillus strains isolated from traditional fermented olive.

This study aimed to examine the influence of two prebiotics, fructo-oligosaccharides (FOS) and xylo-oligosaccharides (XOS), on probiotic properties (resistance to low pH and bile salt, hydrophobicity and auto-aggregation), metabolites production, and antimicrobial activity of probiotic Lactiplantibacillus (L. pentosus S42 and L. plantarum S61) and Levilactobacillus (L. brevis S27) strains isolated from fermented olive. The results demonstrated the ability of strains to ferment XOS more than FOS as a sole carbon source, resulting in pH reduction. The prebiotics (FOS and XOS) significantly increased (p < 0.05) their survival in gastro-intestinal conditions (low pH and 0.3% of bile salts), as well as their hydrophobicity, auto-aggregation and production of proteins, compared to glucose (control). The major organic acids produced by Lactiplantibacillus and Levilactobacillus strains, were oxalic, malic and lactic acids from FOS, XOS and glucose, respectively. No antimicrobial activity was observed from cell-free supernatant (CFS) of Lactiplantibacillus and Levilactobacillus strains obtained from FOS. In the presence of XOS the organic acids, produced by Lactiplantibacillus and Levilactobacillus strains, were more diverse with high contents, and exhibited higher antifungal and antibacterial activities, more than that of FOS and glucose. The combination of L. plantarum S61 and XOS demonstrated the highest inhibition zones ranges of 20.7-22.2 mm against pathogenic bacteria and 29.2-30 mm against yeasts. This combination can be used in production of antifungal preservatives and pharmaceuticals, against pathogenic and spoilage yeasts.

Correlation between chemical composition and antimicrobial properties of essential oils against most common food pathogens and spoilers: In-vitro efficacy and predictive modelling.

Using disk diffusion assay and broth microdilution, we evaluated the antimicrobial activity of 38 commercially available essential oils (EOs) against 24 food pathogens and spoilers. These including E. coli O157: H7 (3 types), Listeria (3 types), Bacillus (2 types), Salmonella enterica (2 types), Staphylococcus aureus (3 types), Clostridium tyrobutiricum, Pseudomonas aeruginosa, Brochotrix thermosphacta, Campylobacter jejuni, Carnobacterium divergens, Aspergillus (2 types), and Penicillium (4 types). Correlation between EOs' chemical composition and antimicrobial properties was studied using R software. Moreover, statistical models representing the relationship were generated using Design Expert®. The predictive models identified the chemical attributes of EOs that drive their antimicrobial properties while providing an understanding of their interactions. Thyme (Aldrich, Novotaste), cinnamon (Aliksir, BSA), garlic (Novotaste), Mexican garlic blend N & A (Novotaste), and oregano (BSA) were the strongest antimicrobial. The most sensitive pathogens were P. solitum (MIC of 19.53 ppm) and L. monocytogenes (MIC of 39 ppm). The correlation analysis showed that phenols and aldehydes had the strongest positive effects on the antimicrobial properties followed by the sulfur containing compounds and the esters; while the effects of monoterpenes and ketones were negative. Different sensitivity of food pathogens to chemical families was observed. For instance, phenols and aldehydes exhibited a linear inhibitory effect on L. monocytogenes (LM1045, MIC), while sesquiterpene and ester showed a significant effect on S. aureus (ATCC 6538, MIC). The developed predictive models are expected to predict the antimicrobial properties based on the chemical families of essential oils.

Barley protein concentrates: Extraction, structural and functional properties.

Protein concentrates were prepared from defatted barley (Hordeum vulgare L.) flour using alkaline and enzymatic treatments. Milder enzymatic treatments included (i) a bi-enzymatic method involving the use of starch-hydrolyzing enzymes, and (ii) a tri-enzymatic method using the former bi-enzymatic treatment followed by digestion with glucanase. The concentrate obtained through alkaline extraction (AI-BP) was comprised mainly of low molecular weight fractions of proteins. Bi-enzymatic treatment produced a protein concentrate with the highest protein content (49.0%), while those obtained by the tri-enzymatic treatment followed by an isoelectric precipitation step (TEI-BP) gave the highest protein recovery yield (78.3%). In both of the latter concentrates, 35 kDa B-hordeins were the major protein fraction. Divergence in secondary/tertiary structure elements (AI-BP; TEI-BP) was obtained and attributed to the difference in the protein profiles. Further characterization of protein concentrates indicated that they exhibit pseudoplastic behavior. Emulsifying capacity of concentrates was comparable to that of whey protein isolate.

Optimization of enzymatic production of prebiotic galacto/galacto(arabino)-oligosaccharides and oligomers from potato rhamnogalacturonan I.

A bi-enzymatic system using two multi-enzymatic preparations (Depol 670L and Gamanase 1.5L) was investigated for the production of prebiotic galacto/galacto(arabino)-oligosaccharides and oligomers with well-defined degree of polymerisation (DP) from potato galactan-rich rhamnogalacturonan I. Depending on the reaction condition, yields of low (DP of 2-6) and high-MW oligosaccharides (DP of 7-12) and oligomers (DP of 13-70) varied between 0.1-13.9, 0.0-37.5 and 0.0-75.7%, respectively. Substrate concentration and Depol 670L/Gamanase 1.5L ratio were identified as the most significant linear terms in oligosaccharide and oligomer yield models, respectively. Moreover, interaction between reaction time and substrate concentration had a significant effect on the yield of oligosaccharides, while interaction between reaction time and Depol 670L/Gamanase 1.5L ratio affected significantly the yield of oligomers. Higher yields of both oligosaccharides and oligomers were obtained when equal amount of Depol 670L and Gamanase 1.5L was used in combination. The DP and the monosaccharide composition of the generated galacto/galacto(arabino)-oligosaccharides and oligomers were confirmed.

Production of exopolysaccharides by selected Bacillus strains: Optimization of media composition to maximize the yield and structural characterization.

Selected Bacillus strains were investigated for the production of exopolysaccharides (EPS) by fermentation in three different culture media: (i) mineral base-medium with added yeast extract (M1), (ii) succinate-containing mineral base-medium with added yeast extract (M2) and (iii) tryptone and yeast extract-containing base-medium (M3). Modest EPS yield of 6.7g/L was recorded for Bacillus amyloliquefaciens 23350 grown on M1, where the EPS produced was characterized by a low MW (<5kDa) and of being mainly glucans. The most significant yield (48.57g/L) was obtained with Bacillus licheniformis 14580 in M2; the EPS produced was 5-30kDa in size and characterized by an exceptionally heterogeneous monosaccharide profile with galactose, fructose and glucose as the predominating monomers. The use of M1 medium for the growth of B. licheniformis 14580 resulted in low yield; however, the obtained heteropolymers EPS were characterized by a higher MW 30-100kDa. The effect of the concentrations of yeast extract, sodium succinate and sucrose on the EPS production by B. licheniformis 14580 were studied using response surface methodology analysis. Greater EPS yields were achieved with increased concentrations of sodium succinate and sucrose and with decreased concentrations of yeast extract in the mineral media.

Digestibility and prebiotic properties of potato rhamnogalacturonan I polysaccharide and its galactose-rich oligosaccharides/oligomers.

Galactose-rich oligosaccharides/oligomers (oligo-RG I) were produced by the enzymatic treatment of potato galactan-rich rhamnogalacturonan I (RG I) with endo-ß-1,4-galactanase and Depol 670L multi-enzymatic preparation. The digestibility study revealed that 81.6 and 79.3% of RG I and its corresponding oligomers remained unhydrolyzed, respectively. The prebiotic properties of RG I and its hydrolysates were investigated using a continuous culture system inoculated with immobilized fecal microbiota. Both RG I and oligo-RG I have stimulated the growth of Bifidobacterium spp. and Lactobacillus spp., with oligo-RG I hydrolysates being more selectively fermented by these beneficial bacteria. Furthermore, none of RG I nor its hydrolysates increased the populations of Bacteroidetes and Clostridium leptum. Total amounts of short chain fatty acids, generated upon the fermentation of oligo-RG I, were higher than those obtained with its parent RG I and the positive control (fructooligosaccharides). The overall study contributes to the understandings of the prebiotic properties of potato RG I and its corresponding oligosaccharides/oligomers.

Enzymatic generation of galactose-rich oligosaccharides/oligomers from potato rhamnogalacturonan I pectic polysaccharides.

Potato pulp by-product rich in galactan-rich rhamnogalacturonan I (RG I) was investigated as a new source of oligosaccharides with potential prebiotic properties. The efficiency of selected monocomponent enzymes and multi-enzymatic preparations to generate oligosaccharides/oligomers from potato RG I was evaluated. These overall results of yield were dependent on the activity profile of the multi-enzymatic preparations. Highest oligo-RG I yield of 93.9% was achieved using multi-enzymatic preparation (Depol 670L) with higher hydrolytic activity toward side chains of RG I as compared to its backbone. Main oligo-RG I products were oligosaccharides with DP of 2-12 (79.8-100%), while the oligomers with DP of 13-70 comprised smaller proportion (0.0-20.2%). Galactose (58.9-91.2%, w/w) was the main monosaccharide of oligo-RG I, while arabinose represented 0.0-12.1%. An understanding of the relationship between the activity profile of multi-enzymatic preparations and the yield/DP of oligo-RG I was achieved. This is expected to provide the capability to generate galacto- and galacto(arabino) oligosaccharides and their corresponding oligomers from an abundant by-product.

Microwave-assisted alkaline extraction of galactan-rich rhamnogalacturonan I from potato cell wall by-product.

Galactan-rich rhamnogalacturonan I (RG I), exhibiting promising health benefits, is the most abundant polysaccharide in potato pulp by-product. In the present study, the microwave-assisted alkaline extraction of galactan-rich RG I was investigated. Solid/liquid ratio was identified as the most significant parameter affecting linearly yield and galactose/rhamnose contents. Microwave power and solid/liquid ratio exhibited a significant adverse interactive effect on the yield. Galactose content of extracted polysaccharides can be modulated by compromising between KOH concentration and extraction time, which exhibited adverse interaction. Optimum conditions were identified using the established predicted models and consisted of treatment of potato cell wall at solid/liquid ratio of 2.9% (w/v) with 1.5M KOH under microwave power of 36.0 W for 2.0 min. Yield of intact galactan-rich RG I of 21.6% and productivity of 192.0 g/Lh were achieved. The functional properties of RG I-rich polysaccharides were comparable or superior to potato galactan and oranges homogalacturonan.

Extraction and structural characterisation of rhamnogalacturonan I-type pectic polysaccharides from potato cell wall.

Cell wall material from potato pulp by-product was used for the extraction of galactan-rich rhamnogalacturonan I (RG-I) type pectic polysaccharides using alkaline (NaOH and KOH) and enzymatic (endopolygalacturonase from Aspergillus niger) methods. The extraction yield increased as the concentration of alkaline solution was increased from 0.5 M (22-24%) to 2 M (53-56%). The yield of 38% obtained upon the enzymatic treatment was similar to those observed with 1M alkaline solutions. The results reveal the high debranching of arabinan side chains of RG I as compared to the galactan ones under harsh alkaline conditions. The molecular weight distribution shows that the enzymatic extraction led to the highest proportion of high-molecular weight polysaccharides (>500 kDa; 62.2%). According to monosaccharide pattern, the weak acidic fractions of high alkaline (1-2 M)-based polysaccharide extracts was the most enriched with galactan-rich RG I. Using milder conditions (enzyme and weak alkaline), two RG I populations with low and high linked homogalacturonan fragments were recovered in the weak and strong acidic fractions, respectively. The structure of galactan-rich RG I was confirmed by H(1) NMR spectroscopy analysis.