1. Effect of natural plant extracts on the antioxidant, microbial and quality characteristics of table olives F. Kalomiri1, M. Alexandraki2, F. Karamitsiou2, E. Gogou1, A. Ntzimani1, D. Tsimogiannis1, P. Taoukis1 1National Technical University of Athens, School of Chemical Engineering, Greece, 2Konstantopoulos S.A.-"OLymp", Katerini, Greece
Introduction
Changes in lifestyle are connected to dietary habits and determine consumer demand for novel functional foods, which are based on traditional healthy foods. Olives and olive based products are considered to be among the most prominent products in the Mediterranean diet.
Nowadays, there has also been noted an increased interest in extracts and essential oils from various plant origins as potential antimicrobial, antioxidant, and antiproliferative agents (Argyropoulou et al., 2014). Additionally, the world demand for dittany’s essential oil and especially its main compound, carvacrol is also increasing (Lemonis et al., 2013).
This trend can be mainly attributed to the recent negative consumer perception against artificial food additives and the demand for novel functional foods with possible health benefits (Γαρδέλη, 2009). Many of the spices commonly used in food not only improve palatability and flavor but also assist in the preservation of the food itself. (Liolios, 2010.).
Table 2: Total viable counts in black and green table olives.
Table 1: Samples coding used in the sudy.
Samples code
Information
BL-C-K1
Black olives (cv. Konservolea) free of extracts
BL-C-K1-D
Black olives (cv. Konservolea) enriched with dittany extract
BL-C-K1-G
Black olives (cv. Konservolea) enriched with ginger extract
BL-C-K1-R
Black olives (cv. Konservolea) enriched with rosemary extract
GR-C
Green olives (cv. Chalikidiki) free of extracts
GR-C-D
Green olives (cv. Chalikidiki) enriched with dittany extract
GR-C-G
Green olives (cv. Chalikidiki) enriched with ginger extract
GR-C-R
Green olives (cv. Chalikidiki) enriched with rosemary extract
Samples code
0 days
9.2 months
BL-C
<1 log cfu/ml
1.60
BL-C-D
2.22
BL-C-G
2.74
BL-C-R
2.23
GR-C
2.26
GR-C-D
1.70
GR-C-G
1.18
GR-C-R
< 1logcfu/ml
Total phenolic content (expressed as galic acid concentration) was found to be approximately 20% and 29% higher in black olives (Fig. 1) enriched with dittany and ginger extracts, respectively, when compared to the control samples.
In the case of green olives (Fig. 2), the addition of dittany and rosemary extracts led to the enhancement of phenolic content in comparison to the control ones. The increase of phenolic content in the case of green olives was approximately 8 and 10%, due to the addition of dittany and rosemary extract, respectively.
Limited information is available concerning the incorporation of herbs extracts or essential oils in table olives.
The objective of this study was to evaluate the effect of natural herbs extracts and essential oils on microbial, nutritional and quality attributes of black and green table olives.
Figure 1: The phenolic content in black olives stored at 25 oC.
Figure 2: The phenolic content in green olives stored at 25 oC.
Materials & Methods
Herbs used in the present study were rosemary, dittany and ginger.
Rosemary
Dittany
Ginger
As far as the organoleptic characteristics are concerned, no significant changes were observed in the kinesthetic characteristics (hardness, fibrousness and crunchiness) during the products’ shelf-life test.
Among the different extracts tested the addition of rosemary extract in both black and green olives, led to a final product with an acceptable and improved flavour with a lower perception of saltiness.
Extracts and essential oils were extracted by selected herbs; rosemary, dittany and ginger by solvent extraction and steam distillation, respectively.
Conclusions
The addition of the selected extracts, especially rosemary extract, in both black and green table olives resulted to microbiologically stable final products. Additionally, dittany, rosemary and ginger extracts enhanced the final content of total phenols and therefore can be regarded as promising candidates for natural plant sources of antioxidants, which can give an added nutritional value and play a beneficial role with regards human health.
Essential oils (10 ppm) and antioxidant extracts ( ppm) were used to enrich low salt storage brine (3% NaCl). Black (cv. Konservolea) and green (cv. Chalkidiki) table olives free of extracts (control samples) and extracts enriched samples were pasteurized, packaged and finally stored at controlled temperature of 25°C.
During the shelf-life test selected quality indicators including microbial growth, total phenolic content and sensory attributes (hardness, fibrousness, crunchiness, odour, colour, flavour and taste) were determined at different time intervals.
References
Argyropoulou, C., Papadatou, M., Grigoriadou, C., Maloupa, E. and Skaltsa, H. (2014). Evaluation of the Essential Oil Content of Cretan Dittany Cultivated in Northern Greece. Medicinal & Aromatic Plants, 3(2), 1-4.
Lemonis, I., Tsimogiannis, D., Louli, V., Voutsas, E., Oreopoulou, V. and Magoulas, K. (2013). Extraction of Dittany (Origanum dictamnus) using supercritical CO2 and liquid solvent. The Journal of Supercritical Fluids, 76,
Liolios, C.C. (2010). Dittany of Crete: A botanical and ethnopharmacological review. Journal of Ethnopharmacology, 131(2),
Γαρδέλη Χρυσαυγή (2009), Μελέτη χημικής σύστασης αιθέριων ελαίων ορισμένων αρωματικών φυτών της ελληνικής χλωρίδας, Γεωπονικό Πανεπιστήμιο Αθηνών.
Results & Discussion
During the first 9 months of storage, total viable count (TVC), lactic acid bacteria (LAB) and yeasts/ moulds remained below the detection limit (< 1 log cfu/ml) for all tested samples.
Only after 10 months of storage, TVCs in the control samples were approximately 2.26 log(cfu/ml) while in the extracts enriched samples, and most effectively in the case of rosemary, a suppression of TVC growth was observed, as the microbial counts remained below the detection limit.
The microbial growth inhibition can be attributed to the reported antimicrobial activity of herbs essential oils.
Acknowledgements
This work was co-financed by the European Union (European Regional Development Fund– ERDF) and Greek national funds through the Operational Program "Competitiveness and Entrepreneurship" of the National Strategic Reference Framework (NSRF) - Research Funding Program.