Good Hygiene Practices along the coffee chain

Fungal Overview

Module 1.1

Slide 2 Module 1.1 – Fungal Overview

Background: yeasts and moulds (fungi) in food

Eukaryotic cell structure More complex than prokaryotic

(bacteria) Yeasts

Unicellular (3 – 5μm) Can divide rapidly (but slower than

bacteria - 2-3h) Moulds

Tubular cells (30 - 100μm) (hyphae) Grow by apical extension (can grow very

long - filamentous fungi) Reproduce by sexual and asexual

production of spores Adapted to lower moisture conditions

than most bacteria

Slide 3 Module 1.1 – Fungal Overview

Background: fungi in food

‘Useful’ fungi Edible mushrooms Used in processing / preservation

Spoilage fungi Can grow on foods with lower available water

than most bacteria (some as low as aw = 0.65) Typically spoil semi-moist foods – cheeses,

cured meats, bread, cakes, fruit preserves etc Cereals, grains, nuts, coffee, cocoa that are

incorrectly stored (damp, moist conditions) – huge food and feed losses annually

Toxigenic fungi

Slide 4 Module 1.1 – Fungal Overview

Toxigenic fungi: Overview of mycotoxins

Fungal metabolites When ingested, inhaled or absorbed through skin cause lowered

performance, sickness or death in man or animals, including birds. Acute effects

• Headache, fever, nausea, diarrhœa, vomiting, weakness, tremors, convulsions

• In some cases death Chronic or long-term effects

• Cancer• Genetic or birth defects

Over 200 kinds of mycotoxin, produced by about 150 different fungi

Certain crops are commonly associated with certain mycotoxins Ecological associations of mould with crop plants Certain post-harvest conditions can favour certain moulds

Slide 5 Module 1.1 – Fungal Overview

Mycotoxins of major significance

Mould species Mycotoxins

Aspergillus parasiticus Aflatoxins B1, B2, G1, G2

Aspergillus flavus Aflatoxins B1, B2

Fusarium sporotrichiodes

T-2 toxin

Fusarium graminearum Deoxynivalenol,

Zearalenone

Fusarium moniliforme Fumonisin B1

Penicillium verrucosum Ochratoxin A

Aspergillus ochraceus Ochratoxin A

Penicillium expansum Patulin

Slide 6 Module 1.1 – Fungal Overview

Aflatoxins

Commonly associated with maize, groundnuts, tree nuts, spices, dried fruit etc.

Carry-over from animal feed to foods of animal origin for humans: e.g. Aflatoxin M1 in milk

International guidelines exist for prevention and control

CZ

CBS

CYA

Slide 7 Module 1.1 – Fungal Overview

Other important mycotoxins

Trichothecenes – Fusarium spp Associated with a variety of cereals and wet harvest

conditions Zearalenone – Fusarium spp

Associated with maize grown in temperate climates Fumonisins – Fusarium spp

Primarily associated with maize Patulin - Penicillium spp, Aspergillus spp

Associated with apple products Ochratoxin – Aspergillus spp, Penicillium spp

Associated with cereals, wine, grape juice, dried fruit, coffee and cocoa

Slide 8 Module 1.1 – Fungal Overview

OTA contamination in coffee

OTA long known as a renal toxin and carcinogen which is also teratogenic (produces birth defects)

Evidence of genotoxicity published in the early 1990’s - if true, categorizes OTA with aflatoxin

Studies in Europe on dietary exposure concluded the most significant sources are grain and grain products; beer; wine; dried fruit; coffee

Several countries have already adopted maximum levels of contamination in coffee

Some importers have rejected contaminated batches EU harmonised limits for roasted and soluble coffees - in

force from January 2005

Slide 9 Module 1.1 – Fungal Overview

OTA producers in coffee

OTA producers in coffee: Aspergillus ochraceus (and related) Aspergillus carbonarius Aspergillus niger complex

Elsewhere: Penicillium verrucosum Penicillium nordicum

These organisms interact with other coffee-associated organisms, and not just Coffee Berry Borer (CBB) and Colletotrichum etc. The fungi include:

Fusarium stilboides Candida edax Cryptococcus album

Additional context are the conditions man’s activities impose in the orchard and during processing and trading

•Cladosporium spp. •Penicillium brevicompactum•Auriobasidium pululans•Eurotium repens

A. Colonies of A. flavus from Aspergillus flavus group. B. & C. Typical colonies of Penicillium spp.

AC

B

Slide 10 Module 1.1 – Fungal Overview

Conditions for activity of OTA producers

Not all isolates of a species that is known to produce a mycotoxin will do so:

A. niger complex 5% usually weak A. carbonarius 80% often strong A. ochraceus and similar 80% often strong

The range of conditions over which a mycotoxin producer can grow is broader than those over which it can produce mycotoxin:

A. niger complex: Aw and temperature limits n.a. A. carbonarius: Aw limits 0.92 and 0.85 temperature limits 35˚C

and 37˚C A. ochraceus: Aw limits 0.82 and 0.78 temperature limits 40˚C and

42˚C The interaction of physiological and ecological properties is too

complex - thus laboratory studies are only indicative At this stage of our understanding, only field studies can clarify the

limiting conditions for OTA contamination in coffee production

Slide 11 Module 1.1 – Fungal Overview

Effect of pH and Aw on mould growth

XH

Xerophile

pH 3.0 4.0 5.0 7.0Aw0.99+

0.98

0.94

0.905

Hydrophile

pH 3.0 4.0 5.0 7.0Aw0.99+

0.98

0.94

0.905

Mesophile

pH 3.0 4.0 5.0 7.0Aw0.99+

0.98

0.94

0.905

Slide 12 Module 1.1 – Fungal Overview

Factors controlling mould growth

Initial contamination? Oxygen / gaseous environment? Nutrients? Temperature? Water activity?

What is it? How do we measure it?

Aw =

Slide 13 Module 1.1 – Fungal Overview

Moisture content (m.c.) and Aw

m.c. describes the sample; Aw predicts microbial growth potential

In commerce, m.c. is measured but the microbial stability is only predicted by Aw so we need to inter-convert

So we need to understand the precision of this inter-conversion

10 20 30 40 50 60

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

mc

aw

Cherry robusta

+++

Slide 14 Module 1.1 – Fungal Overview

Evaluating moisture in commodities

Chemical methods Oven method

Temperature? Time? Air circulation? Vacuum?

Electrical methods Capacitance Conductance

Other gravimetric methods Empirical / traditional sensory methods

Moisture content - dry or wet basis?

Slide 15 Module 1.1 – Fungal Overview

Evaluating moisture in commodities

Internal equilibration? Equilibration with chamber air?

Water activity

Slide 16 Module 1.1 – Fungal Overview

Precision and accuracy of measurement

Uniformity of commodity

Sampling Calibration

Methodology Frequency Quality of standards

Instrument stability Robustness Kind of use

‘EDABO’ distillation method of moisture determination developed in

Brazil

SINAR moisture meter

One type of low-cost moisture meter

investigated under the ‘global coffee

project’

Slide 17 Module 1.1 – Fungal Overview

Moisture and Aw in complex systems

The husk is more hygroscopic than the bean - it forms a barrier that slows water loss during drying and slows water ingress during re-wetting.

From the perspective of mould growth, the significance of a given moisture content of bean and cherry is quite different.

y = -0.0585x2 + 3.7691x + 30.236R2 = 0.9774

y = -0.0459x2 + 3.2896x + 26.158R2 = 0.979

40

50

60

70

80

90

100

0 10 20 30 40 50

m.c. (db)

e.r

.h.

bean

husk

hsk

bn

BEAN LIMIT- -HUSK LIMIT

OTA prod limit