PhD Vermeiren Lieve Compleet - Hogeschool Gent

More documents

Recommendations

Info

1.4.3. The genus Pediococcus This genus is characterised by tetrad formation and a spherical shape, pseudocatalase production and salt tolerance. The pediococci have a homofermentative metabolism and produce DL- or L(+)-lactic acid from glucose according to the Embden-Meyerhof pathway. Pediococci occur on plant materials, in various food products and as spoilage agents in alcoholic beverages such as beer. Pediococcus pentosaceus and Pediococcus acidilactici are important starter cultures for fermented sausage production (Stiles & Holzapfel, 1997). 1.4.4. The genus Lactobacillus 1.4.4.1. Habitat The lactobacilli grow in and are associated with many different habitats, e.g. plants, soil, water, sewage and manure, cereal products, silage, milk and dairy products, meat, fish and vegetable products. They are involved in spoilage of several food products and occur in the respiratory, intestinal and genital tracts of humans and animals (Stiles & Holzapfel, 1997). 1.4.4.2. Cell morphology and growth conditions Lactobacilli meet the general definition for LAB. Their cells vary from long and slender, sometimes bent rods to short, often coryneform coccobacilli and chain formation is common. The lactobacilli are strictly fermentative and have complex nutritional requirements for amino acids, peptides, nucleic acid derivatives, vitamins, salts, fatty acids or fatty acid esters and fermentable carbohydrates. Their growth temperature ranges from 2 to 53-55°C. Most lactobacilli grow best at mesophilic temperatures with an upper limit of around 40°C. Some grow also below 15°C and some psychrophilic strains even below 5°C (as low as 2°C). The so-called thermophilic lactobacilli may have an upper limit of 55°C. Lactobacilli are generally aciduric or acidophilic, they grow best in slightly acidic media with an initial pH of 6.4 to 4.5 and growth ceases when pH 4.0 to 3.6 is reached, depending on the species and strain. Although most strains are fairly aerotolerant, optimum growth is achieved under microaerophilic or anaerobic conditions (Kandler & Weiss, 1986; Carr et al., 2002). Chapter 1 – Antagonistic micro-organisms for biopreservation of food products 5
1.4.4.3. Classification Although earlier subdivisions exist, the classical division of the lactobacilli is based on their fermentation characteristics: (1) obligately homofermentative; (2) facultatively heterofermentative and (3) obligately heterofermentative (Kandler & Weiss, 1986; Stiles & Holzapfel, 1997). The obligately homofermentative lactobacilli (group 1) possess aldolase but no phophoketolase (Kandler & Weiss, 1986) and degrade hexoses almost exclusively to lactic acid by the Embden-Meyerhof pathway and do not ferment pentoses or gluconate (Vandamme et al., 1996). Some important food associated species of this group are Lactobacillus acidophilus, Lactobacillus delbrueckii and Lactobacillus helveticus (Stiles & Holzapfel, 1997). The facultatively heterofermentative lactobacilli (group 2) ferment hexoses almost exclusively to DL-lactic acid by the Embden-Meyerhof pathway or to lactic acid, acetic acid, ethanol and formic acid under glucose limitation. Pentoses are fermented to lactic acid and acetic acid via an inducible pentose phosphoketolase (Kandler & Weiss, 1986; Vandamme et al., 1996). They may produce gas from gluconate but not from glucose. Important food-associated species in this group are Lactobacillus casei, Lactobacillus plantarum, Lactobacillus sakei and Lactobacillus curvatus (Stiles & Holzapfel, 1997). The obligately heterofermentative lactobacilli (group 3) lack aldolase and ferment hexoses to DL-lactic acid, acetic acid, ethanol and CO2 via the 6-phosphogluconate pathway. Pentoses are fermented to lactic acid and acetic acid. In general, a pentose phosphoketolase is involved in both pathways (Kandler & Weiss, 1986; Vandamme et al., 1996). The production of gas from glucose is a characteristic feature of these bacteria. The most important food-associated species of this group are Lactobacillus sanfranciscensis involved in the production of sourdough bread, Lactobacillus reuteri of interest because of its antimicrobial metabolite reuterin and Lactobacillus brevis causing spoilage in citrus fruits, beer, wine and some meat products (Stiles & Holzapfel, 1997). The past two decades, a whole range of taxonomic reassignments occurred within the genus Lactobacillus, based almost exclusively on the results of rRNA-sequencing or DNA-DNA hybridisations. The large number of nomenclature revisions is a striking indication of the discrepancies between the results obtained by former traditional phenotypic tests (classical Chapter 1 – Antagonistic micro-organisms for biopreservation of food products 6
Page 1: Hogeschool Gent Biopreservation of
Page 4 and 5: ir. Lieve Vermeiren Biopreservation
Page 6 and 7: Woord vooraf Proefbuizen, labojasse
Page 8: Table of contents
Page 11 and 12: 3.4. EFFECT OF PROTECTIVE LAB ON TH
Page 13 and 14: 1. INTRODUCTION....................
Page 15 and 16: 2.8. STATISTICAL ANALYSES 189 3. RE
Page 18 and 19: Introduction and objectives In rece
Page 20 and 21: • Sub-objective 5 Chapter 5 aimed
Page 22: Summary
Page 25 and 26: Chapter 3 presented a systematic st
Page 27 and 28: 10A and an atmosphere containing 50
Page 30: Samenvatting
Page 33 and 34: werden deze stammen beschouwd als m
Page 35 and 36: ewaartemperatuur (4°C versus 7°C)
Page 37 and 38: In-vitro testen toonden aan dat de
Page 40 and 41: Chapter 1 Antagonistic micro-organi
Page 42 and 43: esides lactic acid, including carbo
Page 46 and 47: taxonomy) and the present phylogene
Page 48 and 49: 1.5.1. Fermentation end-products 1.
Page 50 and 51: The ability of lactic acid to rotat
Page 52 and 53: 1.5.2. Bacteriocins Bacteriocins, p
Page 54 and 55: molecule inserts into the membrane
Page 56 and 57: 1.5.3. Other antagonistic systems 1
Page 58 and 59: explains why CMP, immediately after
Page 60 and 61: Weissella Weissella viridiscens has
Page 62 and 63: 2.3.3.3. Discolouration Green disco
Page 64 and 65: eported an incidence of L. monocyto
Page 66 and 67: The use of micro-organisms or their
Page 68 and 69: 3.2.2. Organic acids In general, re
Page 70 and 71: Furthermore, protective LAB can be
Page 72 and 73: Fish, fish products and seafood Spo
Page 74 and 75: Table 1.3. Effect of (non-)bacterio
Page 76 and 77: performance as a biopreservative in
Page 78 and 79: Table 1.6. Studies on the effect of
Page 80 and 81: prevent them from growth of food bo
Page 82 and 83: The application of the host-specifi
Page 84 and 85: Multiplicity of infection (MOI) Pha
Page 86 and 87: using Leuc. carnosum 4010 in frankf
Page 88 and 89: activity of LAB in general, this se
Page 90 and 91: effect (Gram et al., 2002). Several
Page 92 and 93: for one or more of these vitamins o
Page 94 and 95:
clinical cases, patients were immun
Page 96 and 97:
different degrees and classify them
Page 98:
this way an equal distribution over
Page 102 and 103:
Chapter 2 Evaluation of meat born l
Page 104 and 105:
temperatures, the characterisation
Page 106 and 107:
dextranicum LMG 6908 T , Leuc. carn
Page 108 and 109:
2.6. Behaviour of 12 selected putat
Page 110 and 111:
considered as unacceptable. Finally
Page 112 and 113:
From the 74 remaining strains, only
Page 114 and 115:
Among the isolates, 76% (28/37) was
Page 116 and 117:
Within the group of isolated strain
Page 118 and 119:
with fast growth rates at low tempe
Page 120 and 121:
pH 6.3 6.2 6.1 6.0 5.9 5.8 5.7 0 5
Page 122 and 123:
34th day of the storage period, alt
Page 124 and 125:
Table 2.5. Summary of the LAB-count
Page 126:
Chapter 3 In-vitro and in-situ grow
Page 129 and 130:
1. Introduction A considerable part
Page 131 and 132:
7°C and revived by transferring a
Page 133 and 134:
The sensory quality of cooked ham s
Page 135 and 136:
lesser extent compared to the LAB s
Page 137 and 138:
LC2 and LM3 not significantly decre
Page 139 and 140:
Sensory rejection was mainly based
Page 141 and 142:
log10(cfu/g), respectively. It migh
Page 144:
Chapter 4 Co-culture experiments de
Page 147 and 148:
1. Introduction Interest in the rol
Page 149 and 150:
growth characteristics, antibacteri
Page 151 and 152:
1 g/l Peptone (Oxoid)) was prepared
Page 153 and 154:
were sensitive to 8/11 tested antib
Page 155 and 156:
Log10(cfu/g) Log10(cfu/g) 9 8 7 6 5
Page 157 and 158:
On the other hand, no significant (
Page 159 and 160:
Table 4.3. Evolution of the glucose
Page 161 and 162:
Log10(cfu/g) Log10(cfu/g) 9 8 7 6 5
Page 163 and 164:
day 28 in the HG-product. However,
Page 165 and 166:
glucose. Buchanan & Bagi (1997) als
Page 168:
Chapter 5 The interaction of the no
Page 171 and 172:
1. Introduction Several authors hav
Page 173 and 174:
(3) an interaction study at 7°C be
Page 175 and 176:
3. Results and discussion The chemi
Page 177 and 178:
Log10(cfu/g) 9 8 7 6 5 4 3 2 1 0 0
Page 179 and 180:
Clearly, the growth of L. sakei 10A
Page 181 and 182:
Table 5.2. Evolution of the pH of t
Page 184:
Chapter 6 The sensory acceptability
Page 187 and 188:
1. Introduction During the last dec
Page 189 and 190:
mixture of Leuc. mesenteroides LM2
Page 191 and 192:
to a sensory panel of 18 non-traine
Page 193 and 194:
inoculation, 200 g portions of prod
Page 195 and 196:
Buffering capacity (mmol lactic aci
Page 197 and 198:
where LAB-growth results in sensory
Page 199 and 200:
3.2.1. Antagonistic activity of L.
Page 201 and 202:
In all five products, L. sakei 10A
Page 203 and 204:
the glucose consumption in 10A-samp
Page 205 and 206:
In general, CMP with such low pH-va
Page 207 and 208:
3.3. Discussion 3.3.1. Antagonistic
Page 209 and 210:
that cooked ring sausages were deem
Page 212:
Chapter 7 The contribution of lacti
Page 215 and 216:
1. Introduction The last two decade
Page 217 and 218:
Table 7.1. Composition of the diffe
Page 219 and 220:
In all three experiments, growth of
Page 221 and 222:
2.5.2. Challenge experiment in CFS
Page 223 and 224:
3. Results and discussion 3.1. Co-c
Page 225 and 226:
However, cell numbers were analysed
Page 227 and 228:
Log10(cfu/ml) or pH Log10(cfu/ml) o
Page 229 and 230:
Log10(cfu/ml) Log10(cfu/ml) 10 9 8
Page 231 and 232:
Log10(cfu/ml) Log10(cfu/ml) 9 8 7 6
Page 233 and 234:
that case the pH of the CFS would h
Page 235 and 236:
Log10(cfu/ml) Log10(cfu/ml) 9 8 7 6
Page 237 and 238:
these experiments when there was st
Page 240:
Chapter 8 Treatment with bacterioph
Page 243 and 244:
1. Introduction Listeria monocytoge
Page 245 and 246:
(7°C and 30°C). Experiments were
Page 247 and 248:
L. monocytogenes cocktail, 100 µl
Page 249 and 250:
3. Results and discussion 3.1. Effe
Page 251 and 252:
susceptibility of the genus Listeri
Page 253 and 254:
end-point for the microbial shelf-l
Page 255 and 256:
therefore, be sufficient to control
Page 257 and 258:
contaminated cooked meat products,
Page 260 and 261:
General discussion, conclusions and
Page 262 and 263:
possible that the bacteriocin was n
Page 264 and 265:
manufactured cooked meat products (
Page 266 and 267:
deviations can be prevented and led
Page 268:
List of abbreviations
Page 271 and 272:
pfu plaque forming unit PPS Pepton
Page 274 and 275:
References 1. Aasen, I.M., Markusse
Page 276 and 277:
26. Berry, E.D., Liewen, M.B., Mand
Page 278 and 279:
50. Buncic, S., Avery, S.M. & Moorh
Page 280 and 281:
75. Devlieghere, F., Debevere, J. &
Page 282 and 283:
99. Foegeding, P.M., Thomas, A.B.,
Page 284 and 285:
125. Hudson, J.A., Billington, C.,
Page 286 and 287:
150. Korkeala, H., Alanko, T., Mäk
Page 288 and 289:
174. Marceau, A., Zagorec, M. & Cha
Page 290 and 291:
nonbacteriocinogenic Carnobacterium
Page 292 and 293:
style green olive fermentations. Ap
Page 294 and 295:
253. Stratford, M. (2000). Traditio
Page 296:
277. Vitas, A.I. & Garcia-Jalon, V.
Page 300 and 301:
Curriculum vitae Curriculum vitae L
Page 302 and 303:
of Listeria monocytogenes by the no
Page 304 and 305:
2. ILSI Europe 2nd International Sy
Page 306:
13. EFSA Colloquium On Microorganis
show all

PhD Vermeiren Lieve Compleet - Hogeschool Gent

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?