Rosa M. Raybaudi-Massilia

Antimicrobial Activity of Essential Oils on Salmonella Enteritidis, Escherichia coli, and Listeria innocua in Fruit Juices

The antimicrobial properties of essential oils (EOs) and their derivatives have been known for years. However, the information published about the minimal effective concentration of EOs against microorganisms in fruit juices is scarce. In this study, both MIC and MBC of six EOs (lemongrass, cinnamon, geraniol, palmarosa, or benzaldehyde) against Salmonella Enteritidis, Escherichia coli, and Listeria innocua were determined by the agar and broth dilution methods, respectively. All of the six EOs inhibited the microbial (Salmonella Enteritidis, E. coli, and L. innocua) growth at a concentration from 1 microl/ ml (MIC). These studies led to choosing the three most effective EOs. Lemongrass, cinnamon, and geraniol were found to be most effective in inhibiting the growth of the microorganisms and thus were used for the MBC analysis. On this last point, significant differences (P < 0.05) among EOs, their concentrations, and culture media (apple, pear, and melon juices, or tryptone soy broth medium) were found after comparing the results on MBC for each microorganism. A concentration of 2 microl/ml from lemongrass, cinnamon, or geraniol was enough to inactivate Salmonella Enteritidis, E. coli, and L. innocua in apple and pear juices. However, in melon juice and tryptone soy broth medium, concentrations of 8 and 10 microl/ml from cinnamon, respectively, or 6 microl/ml from geraniol were necessary to eliminate the three microorganisms, whereas lemongrass required only 5 micro/ml to inactivate them. These results suggest that EOs represent a good alternative to eliminate microorganisms that can be a hazard for the consumer in unpasteurized fruit juices. The present study contributes to the knowledge of MBC of EOs against pathogenic bacteria on fruit juices.

Combination of high-intensity pulsed electric fields with natural antimicrobials to inactivate pathogenic microorganisms and extend the shelf-life of melon and watermelon juices

The effect of high-intensity pulsed electric field (HIPEF) combined with citric acid (0.5-2.0%, w/v) or cinnamon bark oil (0.05-0.30%, w/v) against populations of Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogenes in melon and watermelon juices were evaluated. Microbiological shelf-life and sensory attributes were also determined. Populations of E. coli O157:H7, S. Enteritidis and L. monocytogenes were reduced by more than 5.0log(10)CFU/ml in HIPEF-processed melon (35kV/cm for 1709 micros at 193Hz and 4 micros pulse duration) and watermelon (35kV/cm for 1682 micros at 193Hz and 4 micros pulse duration) juices containing 2.0% and 1.5% of citric acid, respectively, or 0.2% of cinnamon bark oil. In addition, these treatments were also able to inactivate mesophilic, psychrophilic and, molds and yeasts populations, leading to a shelf-life of more than 91 days in both juices stored at 5 degrees C. Hence, the microbiological quality and safety of these fruit juices by combining HIPEF and citric acid or cinnamon bark oil were ensured. However, the taste and odor in those HIPEF-treated melon and watermelon juices containing antimicrobials were significantly affected. Therefore, further studies are needed to decrease the impact on the sensory attributes by using antimicrobials.

Comparative Study on Essential Oils Incorporated into an Alginate-Based Edible Coating To Assure the Safety and Quality of Fresh-Cut Fuji Apples

Cinnamon, clove, and lemongrass essential oils (EOs) and their active compounds cinnamaldehyde, eugenol, and citral, respectively, were investigated for their effectiveness as antimicrobial agents in an alginate-based edible coating (EC) on fresh-cut Fuji apples. This EC also contained malic acid, N-acetyl-L-cysteine, glutathione, and calcium lactate as quality stabilizing compounds. The EC applied on apple pieces effectively maintained the physicochemical characteristics of the apple pieces for more than 30 days, decreased the respiration rate, reduced the Escherichia coli O157:H7 population by about 1.23 log CFU/g at day 0, and extended the microbiological shelf life by at least 19 days. The addition of EOs at 0.7% (vol/vol) or their active compounds at 0.5% (vol/vol) into the EC increased its antimicrobial effect, reduced the E. coli O157:H7 population by more than 4 log CFU/g, and extended the microbiological shelf life by more than 30 days. However, those concentrations of EOs affected the physicochemical characteristics of fresh-cut apples and thus limited their shelf life from 7 to 21 days. Lemongrass and cinnamon EOs (0.7%), citral (0.5%), and cinnamaldehyde (0.5%) were the most effective compounds for extending microbiological shelf life, whereas lemongrass, cinnamon, and clove EOs at 0.3% (vol/vol) best maintained the physicochemical characteristics of the product. Apple pieces with EC at day 0 and with EC with or without lemongrass EO at 0.7% at day 15 were preferred by the panelists. ECs containing natural antimicrobials and quality stabilizing compounds may be useful for extending the shelf life of fresh-cut fruits.

Effects of Pulsed Electric Fields on Pathogenic Microorganisms of Major Concern in Fluid Foods: A Review

Pathogenic microorganisms such as Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni have been implicated in foodborne diseases and outbreaks worldwide. These bacteria have been associated with the consumption of fresh fruit juices, milk, and dairy products, which are foodstuff, highly demanded by consumers in retails and supermarkets. Nowadays, consumers require high quality, fresh-like, and safe foods. Pulsed electric field (PEF) is a non-thermal preservation method, able to inactivate pathogenic microorganisms without significant loss of the organoleptic and nutritional properties of food. The PEF treatment effectiveness to destroy bacteria such as Listeria innocua, E. coli, Salmonella Typhimurium, E. coli O157:H7 and E. coli 8739 at pasteurization levels (≥ 5.0 log10 cycles) in some fluid foods was reported. However, data on the inactivation of some microorganisms such as Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni in fluid foods by PEF processing is very limited. Therefore, future works should be focused toward the inactivation of these pathogenic bacteria in real foods.

Inactivation of Salmonella enterica Ser. Enteritidis in Tomato Juice by Combining of High-Intensity Pulsed Electric Fields with Natural Antimicrobials

The effect of high-intensity pulsed electric field (HIPEF) treatment (35kV/cm, 4 mus pulse length in bipolar mode without exceeding 38 degrees C) as influenced by treatment time (200, 600, and 1000 micros) and pulse frequency (100, 150, and 200 Hz) for inactivating Salmonella enterica ser. Enteritidis inoculated in tomato juice was evaluated. Similarly, the effect of combining HIPEF treatment with citric acid (0.5%, 1.0%, 1.5%, and 2.0%[wt/vol]) or cinnamon bark oil (0.05%, 0.10%, 0.2%, and 0.3%[vol/vol]) as natural antimicrobials against S. Enteritidis in tomato juice was also studied. Higher treatment time and lower pulse frequency produced the greater microbial inactivation. Maximum inactivation of S. Enteritidis (4.184 log(10) units) in tomato juice by HIPEF was achieved when 1000 micros and 100 Hz of treatment time and pulse frequency, respectively, were applied. However, a greater microbial inactivation was found when S. Enteritidis was previously exposed to citric acid or cinnamon bark oil for 1 h in tomato juice. Synergistic effects were observed in HIPEF and natural antimicrobials. Nevertheless, combinations of HIPEF treatment with 2.0% of citric acid or 0.1% of cinnamon bark oil were needed for inactivating S. Enteritidis by more than 5.0 log(10) units (5.08 and 6.04 log(10) reductions, respectively). Therefore, combinations of HIPEF with organic acids or essential oils seem to be a promising method to achieve the pasteurization in these kinds of products.

Polysaccharides as Carriers and Protectors of Additives and Bioactive Compounds in Foods

© 2012 Raybaudi-Massilia and Mosqueda-Melgar, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Polysaccharides as Carriers and Protectors of Additives and Bioactive Compounds in Foods