**5. Potential application of herbal extracts in foods**

The microbiological safety in ready to eat products is a cause of big concern not only for the consumers and food industries but also for the regulatory agencies. It can be said that the food industry faces a constant problem in providing the food where there are no food-borne pathogens present [3, 4]. The number of documented outbreaks of food-borne diseases has increased in the last decade with *Salmonella* spp., *L. monocytogenes*, and *E. coli* being responsible for the largest number of outbreaks and deaths [5]. The different diseases, caused by foodrelated pathogenic bacteria, such as listeriosis, hemorrhagic colitis, campylobacteriosis, and salmonellosis, are still reported. For example, in meat and meat products, spoilage bacteria could shorten the shelf life by causing off-odors, discoloration, gas production, etc. Recently, we have trend in reducing the level of synthetic antimicrobial agents, as well as salt levels, in ready meals because of the proven development of hypertension and increased risk of cardiovascular disease. In recent years, consumers prefer fewer chemicals and more natural foods. Therefore, there is growing interest in using natural antimicrobial compounds, includ‐ ing extracts of herbs and spices, as salt replacers or alternatives to synthetic compounds for food preservation [119].

As already emphasized, in addition to providing flavor and fragrance, spices and herbs also have antimicrobial potential and thus can be used for preventing food deterioration and shelf life extension. It was found that, however, well herbal extracts perform in antibacterial assays in vitro, generally, a higher concentration is required to obtain the same efficacy in foods. [120]. The basic properties of the food (fat/protein/water content, antioxidants, preservatives, pH, salt, and other additives) are the most relevant in this respect, although, the extrinsic elements (temperature, packaging in vacuum/gas/air, and characteristics of microorganisms) can also influence bacterial sensitivity [20, 121].

Utilization of packaging materials containing these herbal extracts as antimicrobial com‐ pounds is also becoming an attractive option in the food industry. If herbal extracts were to be more widely applied as antibacterials in foods, the organoleptic impact would be important.

#### **5.1. Meat, meat products, and fish dishes**

Activity of oregano, thyme, basil, marjoram, lemongrass, ginger, and clove EOs against bacterial strains inoculated experimentally in irradiated minced meat and against natural microbiota found in minced meat samples was tested [122]. MIC90% values ranged from 0.05%v/ v (lemongrass oil) to 0.46%v/v (marjoram oil) to Gram-positive bacteria and from 0.10%v/v (clove oil) to 0.56%v/v (ginger oil) to Gram-negative strains.

Eugenol and coriander, clove, oregano, and thyme oils were found to be in inhibiting *L. monocytogenes, Aeromonas hydrophila*, and autochthonous spoilage flora in meat products, sometimes causing a marked initial reduction in the number of recoverable cells [123] whereas mustard, cilantro, mint, and sage oils were less effective or ineffective [124].

Carvacrol vapor antimicrobial activity was established against *S. enteritidis* on pieces of raw chicken [125]. The effectiveness of oils and vapors of lemon, sweet orange, and bergamot against *L. monocytogenes*, *S. aureus*, *B. cereus*, *E. coli* O157, and *Campylobacter jejuni* was inves‐ tigated on chicken [126]. The results indicate that bergamot was the most inhibitory EO due to high content of citral and linalool.

The antimicrobial effect of extracts from *S. officinalis* L. and berries of *Schinus molle* L. against *Salmonella anatum* or *S. enteritidis* inoculated on minced beef meat was studied [127]. It was found that use of 0.1% or 1.5% *S. officinalis* with 6% or 4% NaCl or 0.1% or 1.5% *S. molle* with 4% or 8% NaCl could effectively eliminate *S. anatum* from refrigerated raw beef.

Effectiveness of eight EOs as antimicrobial agents for fish preservation on 18 genera of bacteria, which included some important food pathogen and spoilage bacteria, was investigated. Clove EO showed the highest inhibitory effect, followed by rosemary and lavender [128]. It was found that citrus EO incorporated into different edible biopolymer film has the potential to preserve fish fillets [129]. Also, using EO in a coating for shrimps appears effective in inhibiting the respective natural spoilage flora [130].

The antimicrobial effect of nine EOs on *Photobacterium phosphoreum* on the shelf life of modified atmosphere-packed cod fillets was determined. The antimicrobial effect of EO was studied in a liquid medium and in product storage trials. Oils of oregano and cinnamon had strongest antimicrobial activity, followed by lemongrass, thyme, clove, bay, marjoram, sage, and basil oils, whereas oregano oil (0.05%, v/w) reduced the growth of *P. phosphoreum* in naturally contaminated cod fillets and extended shelf life from 11–12 days to 21–26 days at 2°C [131].

#### **5.2. Fruit and vegetable**

The shelf life of unpasteurized fruit juices is limited by microbial enzymatic spoilage; more‐ over, these products could be contaminated by some pathogens. Some EOs could be used to prevent this kind of problem. Lemongrass and geraniol have been found effective against *E. coli*, *Salmonella* sp., and *Listeria* spp. in apple, pear, and melon juices [47, 132].

Carvacrol and cinnamaldehyde were very effective at reducing the viable count of the natural flora on kiwifruit but less effective on honeydew melon. It is possible that this difference is due to difference in pH between the fruits: the lower the pH, the more effective EOs and their components generally are [20, 133].

The antimicrobial activity of basil, caraway, fennel, lemon balm, marjoram, nutmeg, oregano, parsley, rosemary, sage, and thyme EO against food-borne pathogens and key spoilage bacteria pertinent to ready-to-eat vegetables was evaluated [134]. On a carrot model product, basil, lemon balm, marjoram, oregano, and thyme EOs were deemed organoleptically accept‐ able, but only oregano and marjoram EOs were deemed acceptable for lettuce. It was found that selected EOs may be useful as natural and safe additives for promoting the safety and quality of ready-to-eat vegetables [135]

Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs using food model media based on lettuce, meat and milk [136]. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars.

The antimicrobial potential of oregano EO on *S. typhimurium* ATCC 13311 on tomatoes was tested. Tomatoes treated with 100 ppm oregano oil resulted in 2.78 log reduction, after 20 min [137]. Oregano oil was effective at inhibiting *E. coli* O157:H7 and reducing final populations in eggplant salad compared to the untreated control. Also, it was found that, in vegetable dishes, the antimicrobial activity of oil decrease in storage temperature and/or a decrease in the pH increases [138].

#### **5.3. Cereals and dairy products**

Nielsen *et al*. [139] found that cinnamon, mustard, garlic and clove EO have strong effect in active packaging to prevent bread from fungal contamination. Although oregano oleoresin weakly prevent the growth of most important spoilage fungi of bread, vanilla EO had no preventative effect against these fungi [139].

It was found that sage oil was ineffective against *B. cereus* in rice was while carvacrol was very effective at extending the *B. cereus* lag phase, reducing the final population compared to a control [20, 140, 141].

Orange, lemon, grapefruit, madrine, terpeneless lime, orange, D-limonene, terpineol, and geraniol were tested against *Salmonella, E. coli, S. aureus*, and *Pseudomonas* spp. in different types of milk. Terpineol was the most effective oil in vitro, thus it was used in combination with orange oil for a validation in milk [142]. For mint oil, it was found that it is effective against *S. enteritidis* in cucumber salad and low-fat yoghurt [143].
