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 Table of Contents  
Year : 2020  |  Volume : 4  |  Issue : 1  |  Page : 26-30

In vitro antibacterial traits of the commonly used food preservatives and spices in their crude forms

Department of Microbiology, School of Life Sciences (SLS), Independent University, Bangladesh (IUB), Dhaka, Bangladesh

Date of Submission23-Sep-2019
Date of Acceptance18-Nov-2019
Date of Web Publication17-Mar-2020

Correspondence Address:
Dr. Rashed Noor
School of Life Sciences (SLS), Independent University, Bangladesh (IUB), Plot 16, Block B, Aftabuddin Ahmed Road, Bashundhara, Dhaka 1229
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/bbrj.bbrj_132_19

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Introduction: Preservatives or chemical additives are frequently used in various food items with the principal objective of preventing the food spoilage caused by adulteration, chemical changes, and due to microbial contamination. The current study attempted to detect the in vitro antibacterial activities of the crude forms of common food additives/preservatives. Methods: A total of seven locally available samples (four preservatives and three different spices) were collected from the super shops within Bashundhara Area, Dhaka. The antibacterial traits of the collected samples were examined by the Kirby–Bauer (agar well diffusion) method. The test bacterial strains used in this study were Escherichia coli, Salmonella species, Staphylococcus aureus, Pseudomonas aeruginosa, and Pseudomonas fluorescens. Results: Except the crude granular spices (turmeric powder, chili powder, and the tasting salt), the other three food additive samples (tomato sauce, honey, and vinegar) were found to be nearly effective in eliminating the bacterial growth, while soy sauce did not exhibit notable antibacterial activity. Conclusion: The investigation showed that the liquid food additives were effectively capable of abolishing bacterial growth whereas the crude samples didn't impart the anti-bacterial activity.

Keywords: Antibacterial activity, food preservatives, food quality, spices

How to cite this article:
Maniha SM, Tabassum T, Tabassum T, Tabassum N, Noor R. In vitro antibacterial traits of the commonly used food preservatives and spices in their crude forms. Biomed Biotechnol Res J 2020;4:26-30

How to cite this URL:
Maniha SM, Tabassum T, Tabassum T, Tabassum N, Noor R. In vitro antibacterial traits of the commonly used food preservatives and spices in their crude forms. Biomed Biotechnol Res J [serial online] 2020 [cited 2022 Oct 5];4:26-30. Available from: https://www.bmbtrj.org/text.asp?2020/4/1/26/280857

  Introduction Top

In general, preservatives refer to a broad variety of compounds which are supposed to retard bacterial growth within foods and pharmaceutical products. Preservatives can be originated naturally or can be synthetically manufactured, with the motto of preventing the growth of pathogenic microorganisms. Indeed, the cases of foodborne infections, intoxications, and the toxicoinfections are very common around all parts of the world.[1],[2],[3] Maintenance of food safety is now a globally burning issue to maintain the mass public health because lots of cases regarding foodborne illness have been reported so far due to microbiological contamination, i.e., access of a range of microorganisms, including Staphylococcus spp., Pseudomonas spp., Acinetobacter spp., Streptococcus spp., Bacillus spp., Listeria spp.,  Brucella More Details spp., Campylobacter spp., Arcobacter spp., and Cronobacter spp. into different food items.[1],[2],[3] Foodborne disease outbreaks due to the proliferation of the enteric bacteria, Vibrio spp., and Aeromonas spp. are so common around the world, especially in densely populated poor countries where people are lacking knowledge on hygiene and on food microbiology.[1],[4]

Usage of different types of preservatives is very common almost in all countries, which are actually natural or synthetic substances and are targeted to affix the food items (i.e., fruits, fruit juices, vegetables, and processed foods) with the aim of enhancing the overall microbiological quality (due to the possible antibacterial traits of the preservatives) of foods as well as their shelf lives.[5] As stated above, preservatives can kill the invading bacteria, fungi, and molds within the food items; thus, they help out the food to remain fresh and potent for a longer period of time. In addition, the food preservatives/additives can also be used to retain the stable color, flavor, and texture of the foods. Food additives, food preservatives, and food spices have long been known to enhance the taste of food as well as to some extent quality of foods due to their antibacterial properties, antioxidative properties, and the antienzymatic properties.[5],[6],[7],[8],[9],[10],[11],[12] The choice of using different preservatives is really a good remedy to eradicate foodborne diseases.[4],[13],[14],[15],[16] Synthetic preservatives such as sodium benzoate and sodium nitrate have long been used in food preparation because they are effective in small amounts. Earliest and commonly used preservatives include the concentrated sugars, salts, pickling with salt, vinegars, lemon juice, and mustard oil.[5] Spices are widely known as the flavor and aroma enhancers of foods along with the stabilizing impact together with the antibacterial activities.[17],[18],[19],[20] Their medicinal as well the antioxidative properties on food-spoilage microorganisms are well known.[9],[10],[11],[12],[16],[18],[20]

Previously, we worked with some preservative samples including sodium sulfite, sodium benzoate, acetic acid, citric acid, vinegar, honey, and turmeric powders to examine their antibacterial activities against an array of bacteria; we found sodium sulfite and citric acid to be the most effective preservative.[5] Sulfites, used as a food preservative or enhancer, are typically used in the forms of potassium bisulfite or potassium metabisulfite, sodium bisulfite, sodium metabisulfite, or sodium sulfite. Acidic environment is quite detrimental for the bacterial growth; hence, a range of bacteria is unable to in presence of citric acid, which is frequently added to jams and jellies, the candy products, in the canned foods, and even to the meat products as an effective preservative. The potential antibacterial activity of these two preservatives further led us to study with the other commonly used food additives. Therefore, the current study further attempted to examine the antibacterial effectiveness of seven popular items of preservatives (of which honey and the turmeric powder were examined previously) against potentially harmful bacterial strains.

  Materials and Methods Top

Study area and sampling

A total of seven types of locally used food additives and spices were chosen for this study. The finished product packs of tomato sauce, turmeric powder, tasting salt, chili powder, honey, vinegar, and soy sauce (with the appropriate labels of dates of manufacturing and the dates of expiry on the corresponding packs) were collected from the super shops within Bashundhara residential area, Dhaka, during mid-August. The samples were collected as previously described [5] and were quickly transported to the Microbiology Laboratory of School of Life Sciences, Independent University, Bangladesh, for further analysis.

Assay of in vitro antibacterial activity

The traditional approach of the agar well diffusion technique (Kirby–Bauer disk diffusion method) was applied for the measurement of the antibacterial activity of the collected samples.[21],[22],[23],[24],[25] Lawns of five test bacterial suspensions ( Escherichia More Details coli,  Salmonella More Details species, Staphylococcus aureus, Pseudomonas aeruginosa, and Pseudomonas fluorescens cultures) were prepared using the log phase cells (the culture turbidity was compared to the 0.5 McFarland standard equivalent to 105 cells/mL) on the Mueller–Hinton agar (MHA).[5],[21],[22],[23],[24],[25] Simultaneously, wells were prepared with a borer on the MHA and approximately 10 mg/mL of the crude samples were introduced into the corresponding wells. Buffered Peptone water was used as negative controls while the antibiotic disks of gentamicin (10 μg) were used as positive control.[5],[25] Plates were then incubated at 37°C for 15 h followed by the observation for the appearance of zones of inhibitions. The zones were measured very carefully with the help of electronic slide calipers in the millimeter (mm) scale; the results were recorded as sensitive (S), resistant (R), or intermediate resistant (I).[21],[24],[25] Experiments were performed five times, and the results were found to be reproducible. The inferential statistics was conducted as shown by the mean and range in [Table 1].
Table 1: Antibacterial activities of the food preservatives and spices

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  Results and Discussion Top

As stated earlier, the applications of diverse categories of preservatives are widespread over the world.[5],[6],[7],[8],[9],[10],[11],[12] Tomato sauce is very popular, which is used to augment the taste of varieties of main foods. However, though, in the current study, tomato sauce was analyzed for the measurement of antibacterial trait, the major component preservative of tomato sauce is the sodium benzoate, which is known to increase the shelf life.[5] The test bacterial strains of E. coli, S. aureus, and P. fluorescens were found to be susceptible to tomato sauce, whereas Salmonella and P. aeruginosa appeared to be resistant [Table 1] and [Figure 1], [Figure 2]. Therefore, even sodium benzoate was not directly examined (because that is not used directly as the additive), the antibacterial trait of its commercial form in the food item, i.e., the tomato sauce was found to be 60% satisfactory in its antibacterial potential.
Figure 1: Antibacterial activities against enteric bacteria and staphylococci. Agar well diffusion (Kirby–Bauer disk diffusion method) was used for this study as described in Materials and Methods. Lawns of Escherichia coli, Salmonella species, and Staphylococcus aureus were prepared on the Mueller–Hinton agar. Approximately 10 mg/mL of the crude samples was introduced into the wells made on the MHA. Plates were incubated at 37°C for 15 h and the zones of inhibitions were observed in the millimeter (mm) scale. Results were recorded as sensitive (S), resistant (R), or intermediate resistant (I). Experiments were performed five times and the results were found to be reproducible

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Figure 2: Antibacterial activities of Pseudomonas spp. As described in Figure 1, lawns of Pseudomonas aeruginosa and Pseudomonas fluorescens were prepared on the MHA; around 10 mg/mL of the crude samples were introduced into the wells made on the corresponding plates, followed by incubation at 37°C for 15 h. Zones of inhibitions were observed and the results were recorded as S, R, or I as described in Materials and Methods. Experiments were performed five times and the results were found to be reproducible

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Spices are generally known to be used as food supplements color producers along with improving the tastes of the food items. However, from the scientific point of view, their antiseptic properties, anticancer traits, the wound healing potential, and finally the antibacterial characteristics are also well known.[16],[19] In this regard, the present study dealt with two common spices: turmeric powder and chili powder to examine their antibacterial properties. The tasting salt, monosodium glutamate, was also included in the current examination. However, unfortunately, the crude granular samples of turmeric powder, tasting salts, and chili powder were found to be absolutely ineffective against all the five test strains. Such resistance of the bacterial strains against these three crude samples was possibly due to the lack of diffusion through the MHA and perhaps due to the defective diffusion coefficient.[24] Nevertheless, possible methods of employing methanol and ethanol extracts of the corresponding samples may unravel their antibacterial activities against the test organisms.[6] Such suggestive prediction is supported by several earlier evidences.[9],[10],[18],[19],[20] There is a point to ponder that even the extraction methods are expected to reveal the antibacterial traits of these three food additives; however, these are used in such raw forms to the foods inclusive of the cooking process. Therefore, the current data reveals the true scenario of these three samples regarding the antibacterial activities; certainly, these negative data would be significant to compare with their extracts onward.

Another health beneficiary food as well as food additive is honey, which has appeared to be most popular since the ancient times.[5] Honey is actually a good candidate to be a preservative because its high concentration of sugar is supposed to efflux water out of the microbial cells, causing their ultimate destruction and thereby preventing foods from microbial spoilage. In the current study, except Salmonella species, S. aureus, P. aeruginosa, and P. fluorescens were found to be extremely resistant against honey, whereas E. coli was found to be intermediate resistant (I) against this sample [Table 1] and [Figure 1], [Figure 2]. Indeed, honey is known to combat bacteria with its antibacterial activity, and hence its use in the treatment of infection and diseases is not unknown. A very recent study has found an amazing increment in the antibacterial activity trait of honey.[26] Another sample used in the current study was vinegar that is known to consist of acetic acid which perfectly suited to preserve foods since most of the food spoilage microorganisms cannot survive in the acid environment like the citrus ones. In the current study, vinegar was found to be effective against Salmonella spp., P. aeruginosa, and P. fluorescens, whereas E. coli and S. aureus were found to be resistant against this sample [Table 1] and [Figure 1], [Figure 2]. Therefore, vinegar was found to possess the antibacterial activity at least with 60% effectiveness in the current study. The last sample used in this very study was the soy sauce whose antibacterial properties are known to be generated from its contents, i.e., salt and acid alcohol.[5] In case of soy sauce used in the current study, all the test strains exhibited resistance against this preservative; however, a small zone of inhibition of around 10 mm was noticed against P. fluorescens. However, as stated above, the methanol and ethanol extracts of this sample could be more effective in inhibiting bacterial growth, hence demanding further experiments.

  Conclusion Top

The findings of the present study evidently suggest that the common food additives are quite potential in eliminating bacterial growth to some extent. However, regarding the spice samples used in this study, it is assumed that the methanol and ethanol extracts could show potential antibacterial activities.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1]


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