Antimicrobial properties of commercial annatto extracts against selected pathogenic, lactic acid, and spoilage microorganisms

Study on synergistic effects of curcumin and bixin against foodborne pathogens

Various studies have shown that natural colorants, in addition to their coloring attributes, have valuable biological effects such as antioxidant, anti-inflammation, and anticarcinogenic properties. Moreover, their use as a food colorant can restrict the potential disadvantages of synthetic additives and turn foods into functional products. In this study, in vitro antimicrobial activities of two natural colorants of bixin and curcumin against some important foodborne pathogens: Staphylococcus aureus (S. aureus), Listeria innocua (L. innocua), and Escherichia coli (E. coli) were investigated by disk diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration values were determined by agar dilution and broth microdilution methods. The synergistic activity of the colorants against selected microorganisms was assayed by the checkerboard microdilution method. The results showed that the inhibitory effects of bixin against S. aureus were more pronounced than E. coli and L. innocua. The lowest concentration of curcumin (0.6 mg/mL) in the disk diffusion method was not inhibited by any tested bacteria. However, it was effective at the higher concentrations against three microorganisms, but its diameter of inhibition zones was lower than gentamicin in all concentrations. Synergetic effects were observed by curcumin and bixin combination against S. aureus (FICI ≤ 0.5), but they act as an antagonist against E. coli and L. innocua. The results of the synergy test were confirmed by the isobologram curves.

Plants: A natural solution to enhance raw milk cheese preservation?

Plants have been traditionnally used for centuries in cheese manufacturing, either for their aromatic properties or as technological auxiliaries (e.g. milk-clotting enzyme preparations, cheese wrappers). Some of these plants are known to have antimicrobial and/or antioxidant properties and could also act as natural preservatives for raw milk and derived dairy products. This review examined the traditional uses of plants in dairy processing, and then focuses on known antimicrobial and antioxidant properties of their extracts (e.g. maceration, decoction, essential oil). Known effects of theses plants on technological flora (starter cultures and microorganisms implicated in cheese ripening) were also summarized, and the potential for plant extracts used in combination with hurdle technologies was explored. Then, legal restriction and bioactivity variations from a culture media to a food matrix was reviewed: non-toxic bioactive molecules found in plants, extract preparation modes suitable with foodgrade processing restrictions, the role of the food matrix as a hindrance to the efficiency of bioactive compounds, and a review of food legislation. Finally, some commercial plant extracts for milk preservation were discussed.

Bostrycin production by agro-industrial residues and its potential for food processing

Bostrycin, a red antibacterial agent produced by Nigrospora sp. no. 407, is considered for meat processing. To optimize production, the culture conditions of submerged fermentation (SmF) and solid-state fermentation (SSF) were investigated. The optimal SmF conditions were a medium containing 1.0% cane molasses and incubation at 30 °C and 150 rpm for 6 days. In SSF, other than bostrycin, less pigment was produced and the optimal ratio of bagasse to water was 1:2 for 10 days. The production and recovery rate of bostrycin by SmF were 120 mg/L and 40%, respectively. Bostrycin exhibited thermostable, pH-dependent color change and dose-dependent antibacterial activity against Clostridium botulinum. Bostrycin-modified meat turned strong red for at least 24 h and could not be removed by washing; bostrycin maintained its antibacterial activity with a bacteriostasis rate of 91% on Staphylcoccus aureus. This is an easy and inexpensive means of acquiring bostrycin from molasses and sugarcane.

Some biological activities of pigments extracted from Micrococcus roseus (PTCC 1411) and Rhodotorula glutinis (PTCC 5257)

The importance of replacing synthetic pigments with natural types is increasing day by day in the food industry due to the harmful effects of some synthetic pigments. Microorganisms are a major source of natural pigments, which nowadays have attracted the attention of researchers. In this study, carotenoid pigments were produced by Micrococcus roseus and Rhodotorula glutinis, and some of their biological properties such as antimicrobial, antioxidant, anticancer, and anti-inflammatory activities were evaluated. Given the results, bacteria, especially gram-positive bacteria, had higher sensitivity to the pigments extracted from M. roseus (PEM) and R. glutinis (PER) compared to molds so that Bacillus cereus and Alternaria citri had the highest and the lowest sensitivity, respectively. PER showed a higher antioxidant activity compared with PEM in the various methods of measuring antioxidant activity. In vitro and in vivo anti-tumor-promoting activities of PER were measured significantly more than PEM (P <0.05). Both pigment extracts remarkably inhibited the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation, so that ID₅₀ (50% inhibitory dose) of PEM and PER were 0.22 and 0.09 mg/ear, respectively.

Alternatives to Antibiotics to Prevent Necrotic Enteritis in Broiler Chickens: A Microbiologist's Perspective

Since the 2006 European ban on the use of antibiotics as growth promoters in animal feed, numerous studies have been published describing alternative strategies to prevent diseases in animals. A particular focus has been on prevention of necrotic enteritis in poultry caused by Clostridium perfringens by the use of microbes or microbe-derived products. Microbes produce a plethora of molecules with antimicrobial properties and they can also have beneficial effects through interactions with their host. Here we review recent developments in novel preventive treatments against C. perfringens-induced necrotic enteritis in broiler chickens that employ yeasts, bacteria and bacteriophages or secondary metabolites and other microbial products in disease control.

Gum arabic and Fe²⁺ synergistically improve the heat and acid stability of norbixin at pH 3.0-5.0

Thermal and acid stabilities of norbixin are challenges for its application as a food colorant. In this work, gum arabic and Fe(2+) were studied for the possibility to improve the thermal and acid stabilities of norbixin. Norbixin was dissolved at 0.004% w/v in deionized water with and without 0.2% w/v gum arabic and/or 0.15 mM ferrous chloride, adjusted to pH 3.0-5.0, and heated at 90 or 126 °C for 30 min. Before heating, norbixin precipitated at pH 3.0-4.0, which was prevented by gum arabic. The thermal stability of norbixin was improved by the combination of gum arabic and Fe(2+). Fluorescence analyses indicated the complex formation between norbixin and gum arabic with and without Fe(2+). Particle size and atomic force microscopy results suggested Fe(2+) and gum arabic synergistically prevented the aggregation of norbixin at acidic pH and during heating. It was hypothesized that the core of gum arabic-norbixin complexes was strengthened by Fe(2+) to enable the synergy.

Effect of date palm coproducts and annatto extract on lipid oxidation and microbial quality in a pork liver pâté

Dates are an interesting source of bioactive compounds, and coproducts from the date industry are of potential use in the manufacturing of meat products. In the present research, spreadable pork liver pâtés were made using fresh date coproducts (2.5% and 7.5%) as a potential functional ingredient and an ethanolic annatto extract (128 mg/kg) as colorant. The effect of these 2 ingredients on the lipid oxidation and microbial quality of the pâtés was assessed during 21 d of storage. The pâtés containing 7.5% date paste were seen to have the highest content of phenolic compounds during storage. The combination of 2.5% date paste and annatto protected pâtés against lipid oxidation throughout the 21 d of storage, thiobarbituric acid-reactive substances values being 0.47 mg MDA/kg at the end of this period, while other combinations increased oxidation compared to the control pâté. The control and those made with 2.5% date paste alone showed the highest counts of mesophilic aerobic bacteria, while the addition of annatto and/or 7.5% date paste reduced this count. The results suggest that a combination of both ingredients is necessary to reduce oxidation and microbial growth, but whereas the concentration of 2.5% is more appropriate to reduce oxidation, the combination with 7.5% date paste reduces the microbial counts. Both ingredients could have an opportunity of valorization in the meat industry for improving the quality.

Nitrite-free Asian hot dog sausages reformulated with nitrite replacers

This research deals with the application of a global strategy designed to produce a nitrite-free Asian hot dog. Different ingredients such as annatto, cochineal, orange dietary fibre, vitamins E and C, lactate and celery were combined in order to study the appearance (colour), lipid oxidation stability and microbial stability of the nitrite-free formulations. The control sample contained much more (P < 0.05) residual nitrite (88.7 mg/kg) than the samples without added nitrite (23-24 mg/kg). Generally, no formulation-dependent variations were observed in fat and water binding properties. Control sample had the highest L* and a* values, while the product with annatto (RA) had the lowest a* values. Lipid oxidation levels were similar irrespective of formulation. The hot dog reformulated with cochineal (RC) scored higher for overall acceptability than RA, mainly due to its colour.

Use of essential oils to inhibit alicyclobacillus acidoterrestris: a short overview of the literature

Essential oils (EOs) are promising and friendly antimicrobials for the prolongation of the shelf life of many foods. They have been extensively used to inhibit spoiling and pathogenic microorganisms of many kinds of products like fruit juices and acidic drinks. Therefore, they could be used successfully to control the germination of spores of Alicyclobacillus acidoterrestris, that finds in these products an optimal environment for growth. This paper reports a brief overview of the literature available, focusing on the effects of EOs toward alicyclobacilli.

Digestive stability and transport of norbixin, a 24-carbon carotenoid, across monolayers of Caco-2 cells

Annatto is a natural pigment widely used in the food industry to add yellow to red colors to dairy and cereal products. Here, the in vitro bioaccessibility and potential bioavailability of norbixin, the abundant 24-carbon carotenoid in annatto, were investigated. Norbixin added to milk was highly stable during simulated digestion, and bile salts enhanced partitioning of this carotenoid in the aqueous fraction during the small intestinal phase of digestion. Apical uptake of norbixin by Caco-2 cells was proportional to the concentration in apical medium, but cellular content increased only slightly after 60 min. Transport of norbixin to the basolateral compartment was maximum at 120 min. Both all-trans and cis isomers of norbixin were present in cells and basolateral medium. The results suggest that ingested norbixin is stable during gastric and small intestinal phases of digestion and that both cis and all-trans isomers are bioavailable.

Bioautography and chemical characterization of antimicrobial compound(s) in commercial water-soluble annatto extracts

Annatto preparations based on extracts of the seed of tropical bush Bixa orellana L consist of carotenoid-type pigments. Previous reports indicate that commercial annatto extracts have biological activities against microorganisms of significance to food fermentation, preservation, and safety. The objective of this study was to separate and identify the compound(s) responsible for the antimicrobial activity of annatto preparations. Commercial water-soluble annatto extracts were screened by thin-layer chromatography and bioautography followed by liquid chromatography/photodiode array/mass spectrometry (LC/PDA/MS) analysis of active fractions. Bioautography revealed two fractions with antimicrobial activity against Staphylococcus aureus. LC/PDA/MS analysis of both fractions revealed 9'-cis-norbixin (UV(max) 460 and 489 nm) and all-trans-norbixin (UV(max) 287, 470, and 494 nm) as the major components. Structure confirmation was achieved by (1)H NMR spectroscopy. Results indicate that 9'-cis-norbixin and all-trans-norbixin are responsible for the antimicrobial properties of annatto.