Growth inhibition effect of fruit juices and pomace extracts on the enteric pathogens Campylobacter jejuni and Salmonella ser. Typhimurium
L Galgóczy, T Hevér, L Orosz, J Krisch, C Vágvölgyi, M Tölgyesi, T Papp
antibacterial activity, campylobacter, fruit pomace, juice, salmonella
L Galgóczy, T Hevér, L Orosz, J Krisch, C Vágvölgyi, M Tölgyesi, T Papp. Growth inhibition effect of fruit juices and pomace extracts on the enteric pathogens Campylobacter jejuni and Salmonella ser. Typhimurium. The Internet Journal of Microbiology. 2008 Volume 7 Number 1.
The antibacterial effect of fruit juices and pomace extracts from 13 wild and cultivated fruits (
Bacteria of the genus
In spite of the use of traditional and modern methods in food safety techniques (
Plants have a natural defense mechanism against microbial infections. Antimicrobial peptides, lectins, phenolic compounds, terpenoids, essential oils and various other compounds are likely to be involved in this phenomenon (Cowan 1999). Raw and processed fruits, as well as waste products remaining after processing (peel, seeds, stems, flesh) are good sources of these ingredients. In previous
In the present study, the
Materials And Methods
Bacterial isolates and their maintenance
Clinical isolates of
Fruits and extraction methods
Fruits investigated were cherry (
Determination of antibacterial effect by broth microdilution method
Results And Discussion
The tested strains were sensitive to most juices or extracts (Table 1). Mainly the anthocyanin-rich and acidic fruits had strong antibacterial activity. The dark coloured
Antibacterial activity of berry juices and extracts from whole fruits has been intensively studied in the recent years but little attention was paid to the by-products of juice making. Inhibitory effect of raspberry juice was demonstrated against
Fruits from the family
Mulberry juices showed no effect on the growth of the bacteria but the pomace extracts inhibited the growth of
The inhibitory potential of fruit juices and pomace extracts seen at acidic pH was in most cases lost at pH 7. Water extracts from sour cherry and raspberry as well as methanol extracts from jostaberry, however, revealed a good inhibition effect with MIC values of 8.95, 1.82 and 7.37 mg/ml, respectively (Table 2). These inhibitions are thus independent of the low pH and could be attributed e.g. to anthocyanins and ellagitanins, as demonstrated in case of some other coloured fruits and vegetables (Harborne and Williams 2000; Lee
The low pH of fruit juices is caused by weak organic and phenolic acids. In their undissociated forms (mainly at pH 3 to 5) they can interact with the cell membrane and penetrate into the cell causing the acidification of the cytoplasm. The effect of acidity can also be mediated by the pH-dependent dissociation of other antibacterial molecules and compounds (Burt 2004). The juices and extracts in our tests had a pH range 2.8-5.5 (Table 3), accompanied with the highest antibacterial activities. However, as shown by Table 2, some extracts had strong inhibitory effect on pH 7, too.
A number of factors can influence the antimicrobial activity of plant extracts, including growth conditions, seasonal variations and extraction methodology. The components dissolved in aqueous and alcoholic extraction are partly dissimilar. Water extract contains the majority of anthocyanins, tannins, starches, saponins, polypeptides and lectins present, while methanol extracts, in addition, polyphenols, lactones, flavones, and phenons (Cowan 1999). Ryan
Gram-negative and Gram-positive organisms show different sensitivity to antibacterial agents because the former possess an outer membrane surrounding the cell wall (Ratledge and Wilkinson 1988) restricting the diffusion of hydrophobic compounds. Essential oils (Burt 2004), and other oily substances such as guava and neem extracts (Mahfuzul Hoque
The fruits and berries investigated in our study were good growth inhibitors of both Gram-negative bacteria used in our study, but
All the same, the observed inhibitory potential of the investigated fruit juices and pomace extracts on bacterial growth may be utilized in the development of functional foods and natural food preservatives. The by-products of juice industry may represent an economically interesting source for the extraction of active compounds.
This work was supported in part by the Hungarian grant ETT 214/2006.