Mold used as starter cultures in foods and their properties

1. Molds used as
starter cultures
in foods and
their properties
M. ANZA Adamou

2. Introduction
– Microorganisms are often considered by the general
public to be pathogens. The anticipation is that in food,
they are often responsible for alterations of our
products. However bacteria, yeasts, as well as molds are
useful and necessary for the manufacture of certain
foods. This presentation will present molds and their use
in food.

3. Molds
– Molds are heterotrophic filamentous fungi, they are non-
photosynthetic and immobile eukaryotes. They are called
multicellular but the notion is rather vague since it is a structure
often mycelian and coenocytic (cells fused to several nuclei). The
structure of the wall differs according to the species, the
cytoplasm contains ribosomes, mitochondria, an endoplasmic
reticulum and one or more nuclei. The hyphe is the structural
element of molds, the filaments of which constitute a network
called mycelium (Cassandre et al., 2014)

4. Molds on culture medium and
microscopic view

5. The development of molds
 Lifestyle of molds
– Molds must draw from the environment the water, nutrients and
minerals necessary for the synthesis of their own matter. They absorb
them through the wall of their vegetative apparatus. They are said to be
absorbotrophic. Different ways of life exist: symbiosis with plants,
parasites of animals or plants, some also develop on organic waste or
contaminate food products (this third category constitutes the
saprophytes).

6. The development of molds
 Development conditions
– The source of carbon and energy from molds comes from organic carbon
molecules, in addition, for the development of mold, there must be a
sufficient quantity of oxygen, a temperature between 5 and 25 ° C (a
development is possible between 0 And 60 ° C, but outside the optimum
temperatures it will be slower), sufficient moisture (Cassandre et al.,
2014).

7. The development of molds
 Growth and multiplication
– Sexual or asexual reproduction is done by spores, tiny living particles,
dehydrated cells with reduced metabolism, surrounded by thick protective walls
that isolate them from the environment. They are produced in large numbers,
and can survive for a long time (several months or even several years). They are
deposited and will germinate when conditions (mainly moisture conditions)
become favorable. The germination of the spores is at the origin of the
vegetative form of the molds; In fact, the development of these includes a
vegetative phase, growth and nutrition, and almost simultaneously, a
reproductive phase during which the formation of the spores takes place.

8. Mold in the food industry
– The molds are often endowed with important lytic properties (cellulolytic,
pectinolytic, amylolytic, proteolytic ...) which make them dangerous
degradation agents but also sometimes useful allies (in particular in the refining
of cheeses or the production of enzymes) (Cassandre, Sophie et al. 2014).
– Except for a few exceptions (such as bovine rennet used in cheese factories or
papain extracted from a tropical fruit and used in the preparation of beer), the
enzymes used in the food industry are of microbial origin. Indeed,
microorganisms allow an abundant and rapid production, without seasonal
constraints and their enzymatic arsenal is very diversified (Infos Nutrition).

9. Mold in the food industry
– In cheese dairy, the two main species of Penicillum used for their technological
characteristics are P. camemberti and P. roqueforti. They are used respectively
for Camembert cheeses and blue cheeses. Penicillium camemberti is a
filamentous mold that gives the soft cheeses and the flowery rind their uniform
white and fluffy appearance. It is considered to be the domesticated form of P.
commune. It is known synonymous P. candidum, P. rogeri, P. album and P.
caseicolum (Abbas & Dobson, 2011a).
– Penicillium camemberti is classified in the reign of Fungi, in the division of
Ascomycota, class Eurotiomycetes, order Eurotiales, family Trichocomaceae,
genus Penicillium and species camemberti (Lessard, 2014).

10. Mold in the food industry
– The optimum growth temperature range is 20–25 C, with growth being
recorded at 5 C but not at 37 C. With respect to pH, growth can take place in
the pH range of 3.5–6.5. Penicillium camemberti has similar water activity
(Aw) limits for growth as P. roqueforti with an optimum aw value of 0.998 for
growth at 25 C and an ability to grow in the aw range from 0.91 to 0.94. Thus,
from a pH standpoint, P. camemberti is ideal as a starter culture given that
the pH of Camembert and related types of cheese reaches about 4.6 during
the first 24 h and eventually following maturation increases to around 5.5 in
the center of the cheese and around 7.0 in the outer part of the cheese
(Abbas & Dobson, 2011a; Frisvad, 2014)

11. Mold in the food industry
– Penicillium roqueforti is a psychrophile and grows vigorously at
temperatures as low as 4 C, but not above 35 C. It is tolerant to both acid
and alkaline conditions and can grow in the pH range of 3–10. Many P.
roqueforti strains are known to be very tolerant to weak acid
preservatives, being able to grow in the presence of 0.5% acetic acid.
This property can be used to selectively grow P. roqueforti as other
Penicillium species are unable to grow under these conditions.
Penicillium roqueforti is also resistant to sorbate (Abbas & Dobson,
2011b).

12. Mold in the food industry
– Although it is found almost exclusively in the cheese environment, this
mold is also used in the production of fermented sausages. Penicillium
strains used as refining ferment are usually inoculated directly into the
milk as spores. Since their activity depends on their physiological state
(including germination, growth and sporulation rates), conidia are
rehydrated and activated before being seeded. The physiological state is
therefore determinant for the implantation kinetics of P. camemberti
and to ensure that the properties of the inoculum used are reproducible
in order to obtain constant cheeses from one production to another
(Lessard, 2014)

13. Mold in the food industry
– Air-dried fermented meat sausages (salami or saucisson) are, mostly in
southern Europe, often fermented with P. nalgiovense, or more rarely
with Penicillium chrysogenum. These mold fermented sausages are very
popular in countries like Italy, Romania, Hungary, Switzerland, Spain, and
France, and about 60–100% of all dry sausages are mold fermented.
Mold fermented dry sausages are also produced in Germany, Bulgaria,
Belgium, and Austria, but are less common in these countries. Other
countries in northern Europe are slowly beginning to appreciate the
unique flavor of these fermented products (Frisvad, 2014).

14. Mold in the food industry
– Parma ham (Italy), Serrano ham (Spain), Südtiroler Bauernspeck (Germany),
Bindenfleisch, Bündnerfleisch (Switzerland), and country-cured hams (United
States) are often overgrown with Eurotium and Penicillium species. These raw
hams are often initially prepared by rubbing their surfaces with a mixture of
salt, nitrate, and carbohydrates. After a cool soak treatment, they are ripened
for a period of 5–10 months. Some of the same species that can grow on dry
sausages can also grow on dry-cured ham, including the ochratoxigenic species
P. nordicum and Penicillium verrucosum. Often the Eurotia and Penicillia will
grow heavily on these hams, and this fungal layer is removed by brushing,
trimming, or washing. The most common Penicillia are P. expansum, P.
commune, P. olsonii, P. nordicum, and P. polonicum, and all these Penicillia are
potentially toxigenic (Frisvad, 2014)

15. Mold in the food industry
– Some species from Aspergillus like A. oryzae or A. niger are also used specially
for the production of enzymes in food products.
– A. oryzae is isolated from soils and plants, particularly rice. A. oryzae is named
after its occurrence in nature and cultivation industrially on rice, Oryza sativa. A.
oryzae has an optimal growth temperature of 32–36 °C (±1 °C) and is unable to
grow above 44 °C. It has an optimal growth pH of 5–6 and can germinate at pH
2–8. It has been reported that A. oryzae could grow in corn flour with a water
content of about 16%. It generally can grow on media with a water activity (aw)
above 0.8, but it rarely grows below 0.8 (Gomi, 2014).

16. References
– Abbas, A., & Dobson, A. D. W. (2011a). Yeasts and Molds | Penicillium camemberti A2 - Fuquay, John W
Encyclopedia of Dairy Sciences (Second Edition) (pp. 776-779). San Diego: Academic Press.
– Abbas, A., & Dobson, A. D. W. (2011b). Yeasts and Molds | Penicillium roqueforti A2 - Fuquay, John W Encyclopedia
of Dairy Sciences (Second Edition) (pp. 772-775). San Diego: Academic Press.
– Cassandre, A. d. P., Sophie, B., Marine, B., Florine, C., Paolo, C., Bénédicte, O., . . . Laura, W. (2014). Les
microorganismes dans lalimentation. Professional project.
– Frisvad, J. C. (2014). PENICILLIUM | Penicillium/Penicillia in Food Production. 14-18. doi:10.1016/b978-0-12-
384730-0.00249-4
– Gomi, K. (2014). ASPERGILLUS | Aspergillus oryzae. 92-96. doi:10.1016/b978-0-12-384730-0.00011-2
– Infos Nutrition. Les Enzymes dans l'industrie alimentaire(On line). http://www.guide-des-
aliments.com/dietetique/Information/Micro-organismes/CR-Enzymes-industrielles.html Consulted the
13/12/2016
– Lessard, M.-H. (2014). Le suivi de la croissance et de l’activité spécifique des mycètes pendant l’affinage du
Camembert. (Philosophiae Doctor (Ph.D.)), Université LAVAL.