Transcript Eurocaft poster Berlin - Organic Eprints

Growth inhibition of moulds by natural
pesticides derived from olive oil residues
Eleonora Winkelhausen1 Robert Pospiech2 and Günther Laufenberg2
1
Faculty of Technology and Metallurgy, University “Sts. Cyril and Methodius”, Rudjer Boskovich 16, 1000 Skopje, Republic of Macedonia;
[email protected]
2 Department of Food Technology, University Bonn, Römerstr.164, D-53117 Bonn, Germany; [email protected]
INTRODUCTION
Synthetic crop protection agents play an essential role in the protection of plants or harvested
fruits against microorganisms. They are effective and economically advantageous but, by
modern standards, they lack selectivity and applied at high rates they are threat to human health
and environment. Complying with the growing public awareness of these hazards, increasing
emphasis is placed upon the search for novel, natural products with pesticidal activity. Phenolic
compounds, present in the olive fruit, definitely belong to this group.
Olive press cake, representing 40 % of the original olive weight
used for oil production, contain 0.3 % phenolics, representing an
abundant and cheap source of natural antimicrobial compounds.
The major phenolic compound in unripe olive fruits Olea europaea is
the secoiridoid Oleuropein being responsible for their bitterness.
Therefore olives are often pickled debittering the flavor.
MATERIALS AND METHODS
Micro organisms used
Alternaria solani (tomatoes, potatoes, red peppers)
Botrytis cinerea (grapes, berry-fruits, some vegetable)
Fusarium culmorum (cereal grains, production of mycotoxins)
Extraction of the phenolic compounds
The extraction of the olive press cake was performed in a stirred-tank batch extractor at
750 rev min-1. The residual oil and pigments were removed with hexane (ratio 1:4 w/v).
The polyphenols were then extracted using a mixture of water and ethanol (1:1, v/v).
Solid-liquid ratio was 1:6 (w/v). The extract was filtered (0.45 m) and concentrated by a
rotary-evaporator at 30oC. Phenols were determined spectrophotometrically at 720 nm
using Folin- Ciocalteu reagent.
Assay of the antifungal activity
Media
Malt extract, 30 g/L, meatpeptone extract, 3 g/L with or without
agar, 20 g/L
The fungi were grown on media containing 0, 0.1 and 0.2 % (w/v) phenolic extract and
0.2 % (w/v) Euparen MW G (Bayer), a commercial agrochemical. The cultivation was
carried out in Erlenmeyer flasks on a rotary shaker (125 rev min-1) at 25°C. At defined
time intervals, the content of the entire flask was vacuum filtered (0.45 m). The filtrate
was used for pH and redox potential measurements, while the cell residue was washed
and dried for cell mass determination.
Olive oil residue
Olive press cake, collected during 2002/2003 harvest season from
Kalamata organic cultivars in Greece was dried at 60oC, packed in
vacuumed plastic bags and stored at 4oC until used.
RESULTS
A. solani
F. culmorum
B. cinerea
7
7
pH
6
6
6
5
pH
pH
7
5
5
10
4
4
8
-1
Biomass concentration (g l )
8
-1
Biomass concentration (g l )
Biomass concentration (g l-1)
3
6
4
2
0
0
24
48
72
96
120
144
168
2
1
0
0
24
48
72
96
120
144
168
6
4
2
0
0
Time (h)
24
48
72
96
120
144
168
Time (h)
Time (h)
Fig. 1. Effect of the natural and commercial antifungal compounds. Phenolic
compounds: 0 (), 0.1 (), 0.2 % (w/v) (▲), Euparen MW G 0.2 % (w/v) ()
a
c
Fig .2. Growth of A. solani on medium with 0, 0.1
and 0.2 % (w/v) phenolic compounds
Table 1. Influence of the phenolic compounds and Euparen
MW G on the mycelial growth rate of the fungi after 180 h.
-1
-1
Mycelial growth rate (g l d )
b
Fungus
Fig. 3. Morphology of the F. culmorum mycelium observed on a light microscope.
Growth on a medium without (a) and with phenolic extract (b, c).
Phenolic compounds
(% w/v)
Euparen MW G
0
0.1
0.2
0.2
A. solani
1.022
0.370
0.242
0.156
B. cinerea
0.256
0.098
0.076
0.061
F. culmorum
0.633
0.301
0.152
0.112
CONCLUSIONS
18th congress of
chemists and
technologists of
Macedonia
23.-25.09.04
The presence of phenolic extract in the medium that normally supports the growth of the fungi, inhibited the growth of all three
fungi, with higher phenol concentration (0.2 % w/v) being more effective.
The medium with Euparen influenced the growth of all three fungi in the same manner. Although with reduced rate, they grew till fifth
day when their growth slightly declined. In media containing phenolic compounds, the growth was delayed and slow, but did not decline.
The results indicated the presence of antifungal activity in the phenolic extract and hence the possibility of its application as an
antimicrobial agent.
Further studies should focus on optimizing the inhibitory concentration and conditions. Attention should be paid to the mechanism
of the antifungal action.