SW_PosterSummer Symposium 2015 Final Edit
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Transcript of SW_PosterSummer Symposium 2015 Final Edit
• The addi(on of grape leaves to CaCl2 brined fermenta(ons did not improve the texture of the fermented cucumbers, likely because there was no polygalacturonase in the brine to inhibit.
• There seems to be a synergis(c effect between the highest concentra(on of grape leaf (36g/gal) and ace(c acid (25mM). These treatments were less likely to contain less spoilage metabolites and held a stable pH throughout fermenta(on.
• A grape leaf extract has poten(al to be used as a natural preserva(ve in CaCl2 fermenta(ons. However, the tested concentra(ons of grape leaves contain tannins within the known limit of detec(on, which may contribute an astringent taste.
• PG and yeast and molds were not associated with the soKening of CaCl2 fermented cucumbers, and the soKening mechanism in CaCl2 fermenta(ons is s(ll unknown.
Sean Whitfield1,2, Dr. Suzanne Johanningsmeier1,2, Dr. Ilenys Perez-Diaz1,2 1USDA-ARS Food Science Research Unit, Raleigh, NC; 2Department of Food, Bioprocessing, and Nutrition Sciences
During the 1950s and 1960s, research on the inhibi(on of polygalacturonase (PG), an enzyme that degrades cucumber texture, was conducted with a variety plants. Grape leaves of the Muscadine family, specifically the Scuppernong Variety (GL), were indicated as one of the best contenders to inhibit PG in mul(ple experiments. The inhibitory effects of GL were never inves(gated in cucumber fermenta(ons with 1.1% CaCl2 brine, which has an increased likelihood for texture variability and spoilage compared to tradi(onal NaCl fermenta(ons. HYPOTHESIS STATEMENT Adding GL to fermenta(ons with CaCl2 brines will improve the texture of the cucumbers by inhibi(ng PG
• To determine the impact of ace(c acid and grape leaf (GL) in the reten(on of texture quality of CaCl2 fermented cucumbers. • To inves(gate the effect of ace(c acid on the microbiota of the brine of CaCl2 fermenta(ons
• Gregory Vineyards, for allowing grape leaf samples to be taken from their muscadine cul(vars (275 Bowling Spring Dr, Angier, NC 27501) • Dr. Perez-‐Diaz Lab members for supplies for microbiological analyses.
Cucumber fermenta(on in CaCl2 brines (1.1% CaCl2, 6mM potassium sorbate) has undergone commercial trials to reduce salt waste, but can result in variable texture and increased risk of spoilage. Lab scale fermenta(ons were conducted to determine if ace(c acid and/or grape leaves improve firmness of CaCl2 fermented cucumbers. A full factorial treatment structure in a completely randomized design was applied to the CaCl2 fermented cucumbers for ace(c acid (0, 25 mM) and grape leaf (0, 18, 36 g/gal). A control group fermented in 6% NaCl, 2 mM potassium sorbate, and 25mM ace(c acid was included. Fermenta(ons were inoculated with 106 CFU/ml Lactobacillus Planetarium. Fermenta(on metabolites and pH were analyzed during fermenta(on and storage, and texture analysis was performed on days 28 and 129. The drip plate method was used for microbiological counts of enterobacteriaceae, lac(c acid bacteria , clostridia, yeast and molds on cucumbers, grape leaves, and in fermenta(on brines. It was found that 25mM ace(c acid reduced enterobacteriaceae counts by two orders of magnitude by the second day of fermenta(on, 5.1 ± 0.8 CFU/ml vs 7.8 ± 0.4 CFU/ml for fermenta(ons without ace(c acid (P = 0.0419). No improvement in firmness was observed for cucumbers fermented in CaCl2 brines and grape leaf (P = 0.6522), but CaCl2 fermenta(ons with 36 g/gal grape leaf and 25 mM ace(c acid had less spoilage metabolites (P < 0.05) and had a stable pH during storage.
SPOILAGE METABOLITES
Legend
0
10
20
30
40
50
60
2
3
4
5
6
0 25 50 75 100 125 150
Spoilage M
etab
olite
s (m
M)
Brine pH
Time (Day)
Spoilage of Cucumbers Fermented in CaCl2 (100mM) & AceJc (25mM)
0
10
20
30
40
50
60
2
3
4
5
6
0 25 50 75 100 125 150
Spoilage M
etab
olite
s (m
M)
Brine pH
Time (Day)
Cucumbers Fermented in CaCl2 (100mM), GL (36g/gal), & AceJc (25mM)
0
10
20
30
40
50
60
2
3
4
5
6
0 25 50 75 100 125 150
Spoilage M
etab
olite
s (m
M)
Brine pH
Time (Day)
Spoilage of Cucumbers Fermented in CaCl2
0
10
20
30
40
50
60
2
3
4
5
6
0 25 50 75 100 125 150
Spoilage M
etab
olite
s (m
M)
Brine pH
Time (Day)
Cucumbers Fermented in CaCl2 & GL (36g/gal)
0
10
20
30
40
50
60
2
3
4
5
6
0 25 50 75 100 125 150
Spoilage M
etab
olite
s (m
M)
Brine pH
Time (Day)
NaCl Control
Effect of GL and AceJc Acid on LacJc Acid ProducJon
0 20 40 60 80 100 120 140
0 25 50 75 100 125 150
LacJc Ac
id (m
M)
Time (Day)
NaCl Control CaCl2 (100mM) GL(0g/gal) AceJc (0mM) CaCl2 (100mM) GL (18g/gal) AceJc (0mM) CaCl2 (100mM) GL (36g/gal) AceJc (0mM)
Effect of GL on LacJc Acid ProducJon & RetenJon During Storage
0 20 40 60 80
100 120 140
0 25 50 75 100 125 150
LacJc Ac
id (m
M)
Time (Day)
NaCl Control CaCl2 (100mM) AceJc (0mM) CaCl2 (100mM) AceJc (25mM)
Effect of AceJc Acid on LacJc Acid ProducJon & RetenJon During Storage
MICROBIOLOGY
Legend CaCl2 (100mM) AceJc (0mM) CaCl2 (100mM) AcerJc (25mM) NaCl Control
Effect of AceJc Acid on Enterobacteriaceae Counts
Effect of AceJc Acid on LacJc Acid Bacteria Counts
TEXTURE
Effect of AceJc Acid on Cucumber Firmness
Effect of Grape Leaf and AceJc Acid on Cucumber Firmness
Effect of Grape Leaf on Cucumber Firmness
• No polygalacturonase ac(vity was detected in any treatments throughout fermenta(on and storage.
POLYGALACTURONASE ACTIVITY
pH AceJc Acid Propionic Acid Propanol 1, 2-‐Propanediol
*Potassium Sorbate was effecJve in
inhibiJng yeast and molds during the first 9 days of fermentaJon
LACTIC ACID PRODUCTION Full Factorial Treatment Structure with Complete RandomizaJon
Two Levels of AceJc Acid (0,25mM)
Three Levels of Grape Leaf
(0, 18, 36g/gal)
CaCl2 FermentaJon Treatments: (100mM CaCl2, 6mM Potassium
Sorbate)
NaCl Control (6% NaCl, 2mM Potassium Sorbate, 25mM AceJc Acid)
Two Texture Time Points
28 FermentaJons In Total
Day 28
Day 129
Day 28
Day 129
Two Replicates for Each
Treatment
Two Replicates for Each
Treatment Incubated at 30 °C
Inoculated with 106 CFU/ml Lactobacillus plantarum
HPLC: FermentaJon Metabolites
Microbiological analysis: Drip Plate Method
AsepJc Brine Sampling with Syringe and Septa
Diffusion Plate Assay: PG AcJvity
Firmness of Fermented Cucumber Mesocarp Tissue: Average Peak Puncture Force
Indicators of
Secondary
FermentaJon
0 2 4 6 8
10 12 14
28 129 Average Pe
ak Force (N
)
Time (Day)
NaCl Control CaCl2 (100mM) AceJc (0mM) CaCl2 (100mM) AceJc Acid (25mM)
0 2 4 6 8
10 12 14
28 129 Average Pe
ak Force (N
)
Time (Day)
NaCl Control CaCl2 (100mM) AceJc (0mM) GL(0g/gal) CaCl2 (100mM) AceJc (0mM) GL(18g/gal) CaCl2 (100mM) AceJc (0mM) GL (36g/gal)
0 2 4 6 8 10 12 14
28 129
Average Pe
ak Force (N
)
Time (Day)
NaCl Control CaCl2 (100mM) AceJc Acid (25mM) GL (0g/gal) CaCl2 (100mM) AceJc Acid (25mM) GL (18g/gal) CaCl2 (100mM) AceJc Acid (25mM) GL(36mM)
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
0 1 2 3 4 5 6 7 8 9
MRS
(CFU
/ml)
Time (Day)
0 20 40 60 80
100 120 140
0 20 40 60 80 100 120 140
LacJc Ac
id (m
M)
Time (Day)
NaCl Control CaCl2 (100mM) GL(0g/gal) AceJc (25mM) CaCl2 (100mM) GL (18g/gal) AceJc (25mM) CaCl2 (100mM) GL (36g/gal)
Lactobacillus plantarum on Cucumber Tissue
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
0 1 2 3 4 5 6 7 8 9
VRBG
(CFU
/ml)
Time (Day)
Under Limit of DetecJon by day 5