shelf-life stability of oat groats processed with superheated steam d. head 1, s. cenkowski 1, s....
TRANSCRIPT
SHELF-LIFE STABILITY OF OAT GROATS
PROCESSED WITH SUPERHEATED STEAM D. Head1, S. Cenkowski1, S. Arntfield2 K. Henderson3
1Biosystems Engineering, UofM, Winnipeg, MB 2Food Science, UofM, Winnipeg, MB 3Can-Oat Milling, Portage la Prairie, MB
Presentated at the CSBE/SCGAB 2008 Annual Conference Vancouver, BC, July 13 - 16, 2008
Oats are heat processed
• to enhance stability (high lipid content, 5-7%)• to develop characteristic flavour
Routine industrial process includes:
•Roasting, steaming and drying to
inactivate the fat splitting enzymes
Roasting at 88-115C for 90-104 min (up to 80% inactivation)then steaming at 100-104C for 8-10 min
Grain is dried and…processed toCommercial products (flour, bran, rolled oats)
Limiting factors for storage and handling
• Degradation of lipids via enzymatic hydrolysis followed by oxidation leading to rancidity and off-flavours development
• Prevention:– Hydro-thermal inactivation of the lipolytic enzymes– The kiln drying operation is difficult to control, lengthy and
not energy efficient– Risk of grain cross-contamination with microorganisms
present in the air used for cooling of the grain after kiln drying
• Superheated steam drying and processing is an attractive technology offering variety of advantages over the kiln drying
Objective
• to determine the shelf-life stability of oat groats processed with the optimum superheated steam
parameters and stored at 21C
Optimum SS processing conditions were established in previous studies:
• steam temperature of 110C• steam velocity of 1 m/s• processing time of 10 and 14 min
Materials and methods
• Groats standard kilned at a commercial plant A and B• SS processed groats at 110C at 1m/s for 10 and 14 min
(SS10 and SS14)• Storage at 21C for 6 months+ and measured:
– Moisture content– Pasting viscosity at 64C (Rapid Visco Analyzer)– Hexanal and free fatty acids content– Sensory evaluation (flavour: oaty, toasted, raw, bitter, rancid)– Color determination (L, a, b values)
Results
3000
4000
5000
6000
7000
0 30 60 90 120 150 180 210 240 270 300 330 360 390
Storage Time (days)
Fin
al V
isco
sity
at 6
4o C (
cP)
Plant APlant B
SS10SS14
Fig. 1 Storage time effect on the final viscosity (at 64C (commercial plant A & B) or processed with superheated steam (SS)
Storage at 21CCommercial plants
110C, 10min and 14 min
Plant A
Plant B
0
2
4
6
8
10
12
0 30 60 90 120 150 180 210 240 270 300 330 360 390
Storage Time (days)
Moi
stur
e C
onte
nt (
% w
b)
Plant A
Plant B
SS10
SS14
Fig. 2 Moisture content of oat groats processed commercially (Plant A and B) or with SS at 110C and 1 m/s for 10 and 14 min.
Storage at 21C
Commercial plants
110C, 10min and 14 min
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 30 60 90 120 150 180 210 240 270 300 330 360
Storage Time (days)
Fre
e F
atty
Aci
ds (
g/10
0g f
at)
Plant APlant BSS10SS14
Storage at 21C
Fig. 3 The effect of storage time on free fatty acids content of oat groats processed commercially or with superheated steam (SS) at 110C
Commercial plants
110C, 10min and 14 min
0
1
2
3
4
5
6
7
8
9
0 30 60 90 120 150 180 210 240 270 300 330 360
Storage Time (days)
Hex
anal
(pp
m)
Plant APlant BSS10SS14
Fig. 4 The effect of storage time on level of hexanal released from oat groats processed commercially (Plant A and B) or with superheated steam (SS) at 110C
Commercial plants
110C, 10min and 14 min
Storage at 21C
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420
Storage Time (days)
Sen
sory
Scr
ore
(0-1
0)
Plant APlant BSS10SS14
Oaty Flavour
Storage at 21C
Fig. 5 The effect of storage time on intensity of oaty flavour of oat groats processed commercially or with superheated steam (SS) at 110C
Commercial plants
110C, 10min and 14 min
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420
Storage Time (days)
Sen
sory
Sco
re (
0-10
)
Plant APlant B
SS10SS14
Toasted Flavour Commercial plants
110C, 10min and 14 minStorage at 21C
Fig. 6 The effect of storage time on intensity of toasted flavour of oat groats processed commercially or with superheated steam (SS) at 110C
0.0
0.4
0.8
1.2
1.6
2.0
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420
Storage Time (days)
Sen
sory
Sco
re (
0-10
)
Plant APlant BSS10SS14
Rancid Flavour Commercial plants
110C, 10min and 14 min
Storage at 21C
Fig. 9 The effect of storage time on intensity of rancid flavour of oat groats processed commercially or with superheated steam (SS) at 110C
45
48
51
54
57
60
0 30 60 90 120 150 180
Storage Time (days)
L v
alue
Plant A Plant B SS10 SS14
Fig.10 The effect of storage time on L value (lightness) of oat groats processed commercially or with superheated steam (SS) at 110C
Commercial plants 110C, 10min and 14 min
Storage at 21C
Summary
• The shelf-life stability of oat groats processed with superheated steam at 110C for 10 and 14 min, and stored at 21C was acceptable and exceeded the intended storage time period of 6 months