**5. Significance of the metabolites of LAB**

156 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

The economic losses and the health hazards of the mycotoxins produced by spoilage fungi are the main concerns of the food industry (Gray & Bemiller, 2003). According to Gerez et al., (2009) the spoilage of bakery products by fungi is more common in countries with a high humidity and temperature. Pitt and Hocking (1999) estimated that about 5-10% of food production is spoiled by the growth of yeast and fungi in food materials. Similarly, in Western Europe, the growth of the spoilage fungi of bread is estimated to reach more than 200 million Euros per year (Legan, 1993; Schnürer & Magnusson, 2005). The history conditions of the food can be a major factor in determining any fungal spoilage - for example, stored and processed foods are more sensitive to spoilage when compared with fresh and prepared foods. *Aspergillus* and *Penicillium* species are the most common spoilage fungi for many foods and feeds while *Fusarium* species are reported to attack the cereal

The most widespread species of fungi that contaminate bakery products belong to the genera *Aspergillus*, *Penicillium*, *Eurotium* (Abellana et al., 1997; Guynot et al., 2005), *Monilia*, *Mucor*, *Endomyces*, *Cladosporium*, *Fusarium* and *Rhizopus* (Lavermicocca et al., 2000, 2003). In addition, fungi may be responsible for off-flavours, the production of mycotoxins and allergenic compounds. There are more than 400 known mycotoxins produced by different fungi (Filtenborg et al., 1996). Mycotoxigenic fungi such as *Aspergillus*, *Fusarium* and *Penicillium* are serious hazards for human health. The six classes of mycotoxins frequently encountered in different food systems are: aflatoxins, fumonisins, ochratoxins, patulin,

**4. Common techniques to control spoilage fungi in bakery products** 

Two types of techniques/factors are commonly used to control spoilage fungi: physical ones such as drying, freeze drying, cold storage, modified atmosphere storage, irradiation, the pasteurization of packaged bread and heat treatment; and chemical ones, in general based on the use of organic acids such as propionic acid and its salts (Farkas, 2001; Legan, 1993). Heat treatment is one of the most important physical factors in controlling fungi growth and mycotoxin production, as mycotoxins are destroyed by heat, although the effectiveness of destruction is affected by the food matrix and the composition of the mycotoxin (Scott, 1984). Mycotoxins have different heat stability - for example, ochratoxin A is highly stable even at 200 ºC (Trivedi et al., 1992), aflatoxins are destroyed only at temperatures of approximately 250 ºC (Levi, 1980), while zearalenone and fumonisin require high temperatures between 150-200 ºC to be efficiently destroyed (Bennett et al., 1980). Microwaves are effective in destroying mycotoxins - the aflatoxin in peanuts is reported to be destroyed using microwaves at a power level of 1.6 kW for 16 min and at 3.2 kW for 5 min (Luter et al., 1982). Among the physical methods, a modified atmosphere and gamma irradiation are preferred to the chemical methods and they have been used successfully in

**3. Spoilage fungi in food** 

grains in the field (Samson et al., 2000).

trichothecenes and zearalenone (Dalié et al., 2009).

grain storage (Shapira & Paster, 2000).

LAB are well known for their antifungal activity, which is related to the production of a variety of compounds including acids, alcohols, carbon dioxide, diacetyl, hydrogen peroxide, phenyllactic acid, bacteriocins and cycle peptides (Gerez et al., 2009; Lavermicocca et al., 2000; Magnusson et al., 2003; Prema et al., 2008). These compounds were added to several foods in order to conserve them from food-borne and spoilage microorganisms. Organic acids are the main product of LAB in the fermentation systems of the raw materials. The main acids produced by LAB are lactic acid and acetic acid, besides certain other acids depending upon the strain of LAB (El-Ziney, 1998). These acids will be diffused through the membrane of the target organisms in their hydrophobic un-dissociated form and then used to reduce the cytoplasmic pH and stop metabolic activities (Piard & Desmazeaud, 1991). Other factors that contribute to the preservative action of the acids are the sole effect of pH, the extent of the dissociation of the acid and the specific effect of the molecule itself on the microorganisms (Axelsson, 1998).

Bacteriocins exhibit good potential for use in the food industry and as bio-preservation agents (Ennahar et al., 1999). Bacteriocins are small, ribosomally synthesized, antimicrobial peptides or proteins that display inhibition activity toward related species, with no reports about fungal inhibition (Cotter & Ross, 2005). The notable property of LAB supernatant is the heat stability of the antifungal compounds present in it. This will promote the use of LAB supernatant and/or antifungal compounds in heat-treated foods. The supernatant of certain LAB observed to be active within a wide range of pH, starting from as low as 3 and up to 9 depending upon the strain (Muhialdin et al., 2011b). This could be considered as a major factor whereby LAB are used in food preservation when compared with the chemical preservative which are usually active at low pH between 3 and 4.5. Additionally, LAB have a broad spectrum of antifungal activity against several food spoilage and mycotoxin-producing fungi while commercial preservatives are usually used to control only one or few fungi.

Lactic Acid Bacteria in Biopreservation and the Enhancement of the Functional Quality of Bread 159

*P. pentosaceus P. expansum* Rouse et al. (2008)

*Rhizopus oryzae, A. niger, A. flavus, Penicillium* sp and *F. oxysporum* 

*L. reuteri* 1100 *F. graminearum* Gerez et al. (2009)

ATCC 22546

*A. niger* and *A.* 

*A. niger* FST 4.21, *A. fumigatus* J9, *F. culmorum* TMW 4.0754 *P. expansum* FST 4.22 and *P. roqueforti* FST 4.11

*Botrytis cinerea, Glomerella cingulate,* 

*Phytophthora drechsleri Tucker, P.* 

*citrinum, P. digitatum* and *F. oxysporum* 

*oryzae*

*Penicillium roqueforti* DPPMAF1 Ogunbanwo et al.

Yang & Chang

Muhialdin et al.

Ryan et al. (2011)

Wang et al. (2012)

(2011a)

Rizzello et al. (2011)

(2008)

(2010)

Broad spectrum Coda et al. (2011)

**Compound Producer Inhibited fungi References** 

*L. fermentum* and *Leuconostoc mesenteroides* 

(cyclo(Leu–Leu)) *L. plantarum* AF1 *Aspergillus flavus* 

*L. plantarum*  LB1 and *L. rossiae*

*P. pentosaceus* Te010, *L. pentosus* G004, and *L. paracasi* D5

*L. amylovorus* DSM

LB5

(S1A7)

19280

*L. plantarum*  IMAU10014

**7. Method for determining antifungal activity** 

**Table 1.** Antifungal compounds produced by lactic acid bacteria and their target fungi

Rapid, reliable and sensitive methods for the detection of the antifungal activity of LAB becomes essential in the search for new replacements for chemical preservatives with

Mixture of peptides *L. plantarum* 1A7

Possibly protein-like *L. fermentum* Te007,

Possibly cyclic dipeptide

diacetyl and hydrogen peroxide

Acetic acid, phenyllactic acid

Four peptides and organic acid mixture

nine carboxylic acids, two

nucleosides, sodium decanoate and five cyclic dipeptides

3-phenyllactic acid and Benzene acetic acid, 2- propenyl

potential industrial applications.

ester
