INTRODUCTION RESULTS RESULTS: 45 C Storage Study …
1
Using Steam Treatment to Enhance Storage Stability of Grains from Perennial Intermediate Wheatgrass Amy Mathiowetz , Catrin Tyl , and Baraem Ismail Department of Food Science and Nutrition, University of Minnesota, Twin Cities, 1334 Eckles Avenue, St. Paul, MN 55108 MATERIALS AND METHODS • IWG exhibits a higher protein content than HRW (Table 1). • IWG has a higher lipase activity than HRW, while HRW exhibits greater lipoxygenase activity (Table 2). These enzymes contribute to hydrolytic and oxidative rancidity, respectively, and can be problematic over storage. • However, IWG boasts superior antioxidant activities (as measured by DPPH and LMB assays), attributed to their greater antioxidant content, specifically hydroxycinnamic acids (Table 3), which may help to delay oxidation over storage, contributing to longer shelf life. • DPPH measures radical scavenging activity by electron transfer, whereas LMB measures antioxidant capacity by electron transfer and the ability of antioxidants to reduce hydroperoxides by hydrogen atom transfer 14 . Moreover, LMB demonstrates particularly high correlations (Table 4) with hydroxycinnamic acids, the antioxidants that have been demonstrated as some of the most active in wheat species 15,16 . • The following steam treatment conditions were considered optimal in terms of minimal antioxidant degradation and maximum enzyme inactivation and were adopted for the remainder of the storage study: 100°C, 90-95%RH, 60 minutes. • Steamed and not steamed samples of IWG and HRW stored for varying lengths of time at 45°C and 0.43 a w have been analyzed for peroxide value (an indicator of primary oxidation), free fatty acids (an indicator of hydrolytic rancidity) and lipase activity up to five weeks. • HRW that was not steamed reached peak hydroperoxide formation at four weeks, while steamed HRW and IWG (both steamed and not steamed) have considerably less hydroperoxide formation at four weeks (Figure 2), indicating less oxidation.\ • The steamed grains have less hydroperoxide formation than the grains that were not steam treated. Additionally, it is to be expected that HRW showed higher peroxide values overall, as HRW has a higher lipoxygenase content, as previously noted. • Aside from steamed IWG, samples have shown minimal change in free fatty acid status over time (Figure 3), which may be explained by the higher lipase activity of IWG (Figure 4). 1. Glover JD, Reganold JP, Bell LW, Borevitz J, Brummer EC, Buckler ES, Cox CM, Cox TS, Crews TE, Culman SW, Dehaan LR, Eriksson D, Gill BS, Holland J, Ho F, Hulke BS, Ibrahim AMH, Jackson W, Jones SS, Murray SC, Paterson AH, Ploschuk E, Sacks EJ, Snapp S, Tao D, Van Tassel DL, Wade LJ, Wyse DL, Xu Y. 2010. Science. 328(5986):1638-1639. 2. Rose DJ, Ogden LV, Dunn ML, Pike OA. 2008. Cereal Chem. 85:218-223. 3. De Almeida JL, Pareyt B, Gerits LR, Delcour JA. 2013. Cereal Chem. 91(4): 321-326. 4. Meera MS, Bhashyam MK, Ali SZ. 2011. Food Science and Technology. 44(10):2199-2204. 5. Ekstrand B, Gangby I, Akesson G, Stollman U, Lingnert H, Dahl S. 1993 Journal of Cereal Science. 17(3):247-254. 6. Guo W, Beta T. 2015. Food Research International 51:518-525. 7. Lindenmeier M, Alexander B, Somoza V. 2007. Molecular Nutrition and Food Research. 51(12): 1441- 1446. 8. Bright D, Stewart GG, Patino H. 1999. J. Am. Soc. Brew. Chem. 57(4): 133-137. 9. Abdel-Aal ESM, Young JC, Rabalski I, Hucl P, Fregeau-Reid J. 2007. Journal of Agricultural and Food Chemistry 55:787-794. 10. Vaidyanathan S and Bunzel M. 2012. Cereal Chem. 89(5): 247-254. 11. Li Y and Schwarz PB. 2012. . Am. Soc. Brew. Chem. 70(4): 287-289. 12. Timabud T, Sanitchon J, Pongdontri P. 2013. Food Chemistry 141:2405-2411. 13. Rose DJ and Pike OA. 2006. Journal of the American Oil Chemists’ Society 83:415-419. 14. Huang DJ, Ou BX, Prior RI. 2005. Journal of Agricultural and Food Chemistry 53 (6): 1841-1856. 15. Verma B, Hucl P, Chibbar RN. 2009. Food Chemistry 116:947-954. 16. Tyl CE and Bunzel M. 2012. Journal of Agricultural and Food Chemistry 60:731-739. REFERENCES RESULTS: 45°C Storage Study This project was supported by grants from the Minnesota Department of Agriculture and the Forever Green Initiative, as well as funds gifted by the Land Institute. Intermediate wheatgrass was supplied by Department of Agronomy and Plant Genetics at the University of Minnesota. ACKNOWLEDGEMENTS • Thinopyrum intermedium, or intermediate wheatgrass (IWG), is a novel perennial crop with grains that have a competitive nutritional profile and advantageous environmental attributes. • With strong agronomic and industrial appeal, IWG has potential to be marketed on a larger scale; however, such an effort requires more information about the grain, including its shelf life. • Heat treatment has been shown to be an effective means of elongating storage life of grains by inactivating problematic enzymes responsible for hydrolytic and oxidative rancidity, namely lipase and lipoxygenase respectively. Preliminary studies indicated that these enzymes could be more problematic in IWG than in wheat. • IWG and hard red wheat (HRW) control were subjected to six treatments consisting of two steam treatments (present/absent) and three incubation temperatures (4°C, 23°C, and 45°C). Antioxidant activity pre- and post-steam treatment was analyzed using 1,1-Diphenyl-2-picryl- hydrazyl (DPPH) radical scavenging and leucomethylene blue (LMB) assays. Lipoxygenase activity was measured by the ferrous oxidation- xylenol orange (FOX) assay, and lipase activity was determined spectrophotometrically. • Throughout storage, samples were analyzed for indicators of hydrolytic and oxidative rancidity, including free fatty acids, hydroperoxides, malondialdehydes, and hexanal. • Lipoxygenase activity in IWG subjected to 60 min of steam treatment significantly decreased after two weeks of accelerated storage (P<0.05). The antioxidant activity was not significantly affected (P>0.1). Also, compared to our HRW control, IWG has a higher content of ferulic acid, an active antioxidant commonly found in wheat. • The interruption of enzymatic activity by steam treatment coupled with the preservation of antioxidants could help prolong the shelf life of IWG, ultimately protecting its properties and rendering it marketable. INTRODUCTION Samples: • IWG (Rosemount, August 2015) • HRW (St. Paul and Lamberton, July 2015) Steam Treatment • Half of samples subjected to steam in proofing oven • 100°C at 95%RH Storage Conditions • aw = 0.43 • Groats stored in open petri dishes in dessicators • Dark environment • Temp variable: 4, 25, 45°C Milling • Samples pulled for analysis at various time points and milled • UDI Cyclone Sample Mill with 0.5 mm screen size Moisture • Moisture content of milled samples analyzed by infrared method • Ohaus MB45 Chemical Analysis • Antioxidant activity and content • Enzymatic activity • Products of oxidative and hydrolytic rancidity • Functionality Figure 4. Comparison of lipase activity over storage at 45°C (a w =0.43) in steam treated and non-steam treated intermediate wheatgrass (IWG) and hard red wheat (HRW) Analysis Method Antioxidant Activity • DPPH (2,2-diphenyl-1-picryl-hydrazyl) Radical Scavenging Assay 6 • Leucomethylene Blue Assay 7,8 Antioxidant Content • Carotenoids by RP-HPLC on a C30 column with PDA detection 9 • Hydroxycinnamic acids by RP-HPLC on a C18 column with PDA detection 10 Enzymatic Activity • Lipoxygenase activity by ferrous oxidation xylenol orange (FOX) 11,12 • Lipase activity per method described by Rose and Pike (2006) 13 Hydrolytic Rancidity • Free fatty acids (AOAC Method 940.28) Oxidative Rancidity • Peroxide value (primary oxidation) (AOAC Method 965.33) • Hexanal quantification (secondary oxidation) by GC-FID Proximate Analysis • Fat content by Mojonnier method (Adapted from AOAC 922.06) • Ash content by dry-ashing (AOAC Method 923.03) • Moisture by vacuum oven (AACCI Method 44-40.01) • Protein content by Dumas method (AOAC 990.03) RESULTS Constituent HRW IWG Avg. Percent ± SD* Protein 13.3 ± 0.172 15.7 ± 0.012 Fat 3.61 ± 0.492 5.07 ± 0.035 Ash 1.54 ± 0.069 2.14 ± 0.064 Moisture 9.66 ± 0.428 7.15 ± 0.049 Carbohydrate (by difference) 71.9 ± 1.161 69.9 ± 0.160 Table 1. Macronutrient composition of intermediate wheatgrass (IWG) and hard red wheat (HRW) *Standard deviation Table 3. Comparison of hydroxycinnamic acid content prior to steam treatment in intermediate wheatgrass (IWG) milled using two different methods and ball-milled hard red wheat (HRW) Sample µg FAᵃ/g flour ± SD* μg pCAᵇ/g flour ± SD* µg SAᵈ/g flour ± SD* IWG UDI-milled 813 ± 73.7 20.4 ± 3.60 76.4 ± 5.19 IWG Ball-milled 838 ± 83.8 23.5 ± 3.13 71.6 ± 4.42 HRW Ball-milled 506 ± 54.1 7.00 ± 1.72 50.0 ± 5.61 ᵃFerulic acid, ᵇpCoumaric acid, ᵈSinapic acid, *Standard deviation Measured Variable HRW IWG Avg. Results ± SD* Lipoxygenase activity (U/g) 2.83 ± 0.330 1.60 ± 0.155 Lipase activity (U/g) 1.84 ± 0.178 2.79 ± 0.489 Antioxidant activity by DPPHᵃ (acetone extraction) (µmoles TEᵇ/g) 28.1 ± 1.60 61.3 ± 3.69 Antioxidant activity by DPPH (alkaline hydrolysis with ethyl ether extraction) (μmoles TE/g) 34.9 ± 3.82 51.7 ± 2.57 Antioxidant activity by LMBᵉ mmoles (TE/g) 0.589 ± 0.002 0.765 ± 0.002 ᵃ2,2-diphenyl-1-picryl-hydrazyl, ᵇTrolox equivalents, ᵉLeucomethylene blue, *Standard deviation Table 2. Comparison of enzymatic activities and antioxidant activities in intermediate wheatgrass (IWG) and hard red wheat (HRW) prior to steam treatment Assay Ferulic acid Sinapic acid pCoumaric acid Correlation coefficient DPPHᵃ Radical Scavenging Assay 0.686 0.701 0.703 LMBᵇ Antioxidant Activity Assay 0.981 0.94 0.97 Table 4. Correlations between hydroxycinnamic acid antioxidant content and antioxidant activity by DPPH and LMB antioxidant activity assays ᵃ2,2-diphenyl-1-picryl-hydrazyl, ᵇLeucomethylene blue Figure 1. Lipoxygenase activity measured by the FOX assay over time at 60°C in samples steam- treated for various lengths of time Figure 2. Comparison of primary oxidation as indicated by peroxide value over storage at 45°C (a w =0.43) in steam treated and non-steam treated intermediate wheatgrass (IWG) and hard red wheat (HRW) Figure 3. Comparison of hydrolytic rancidity as indicated by percent free fatty acids over storage at 45°C (a w =0.43) in steam treated and non-steam treated intermediate wheatgrass (IWG) and hard red wheat (HRW) 0 0.5 1 1.5 2 2.5 3 3.5 4 0 5 10 15 20 25 30 35 40 Lipase Activity U/g (Dry Basis) Time (days) IWG steamed IWG not steamed HRW steamed HRW not steamed • A steam treatment length of 60 minutes significantly decreased the lipoxygenase activity of IWG after two weeks of accelerated storage (P<0.05), as shown in Figure 1. At this same treatment length, antioxidant activity of steamed-treated IWG as measured by leucomethylene blue and DPPH assays was not significantly decreased as compared to samples that were not steam treated (P>0.1). • Storage studies are currently underway at 4°C, 25°C, and 45°C. In addition to measuring the parameters shown here, samples are also currently being analyzed for lipoxygenase activity, antioxidant activity, antioxidant content, and hexanal. As samples are stored at controlled relative humidity (a w =0.43), moisture levels remain constant, at approximately 10%, over storage. • Future work will focus on storage of flour, as opposed to storage of whole groats, under the same conditions. • Functionality testing, including loaf volume, starch pasting properties, and dough strength will be tested over time in stored IWG and HRW samples, steam treated and not steam treated, as well as in samples stored as flour and whole groats. • The effect of steam treatment on storage stability and functionality of IWG will influence future processing conditions of the grain. DISCUSSION FUTURE WORK & IMPLICATIONS 3 4 5 6 7 8 9 DAY 0 DAY 3 DAY 6 DAY 9 DAY 12 LOX activity/g (dry basis) Days of Storage at 60°C 0min 30min 60min 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 0 5 10 15 20 25 30 35 40 45 mEq hydroxyperoxides/kg sample Time (days) IWG steamed IWG not steamed HRW steamed HRW not steamed 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0 5 10 15 20 25 30 35 40 45 %Free Fatty Acid (Expressed as % Oleic Acid) in 100g Flour DB Time (days) IWG steamed IWG not steamed HRW steamed HRW not steamed
Transcript of INTRODUCTION RESULTS RESULTS: 45 C Storage Study …
Using Steam Treatment to Enhance Storage Stability of Grains from Perennial Intermediate Wheatgrass
Amy Mathiowetz, Catrin Tyl, and Baraem Ismail
Department of Food Science and Nutrition, University of Minnesota, Twin Cities, 1334 Eckles Avenue, St. Paul, MN 55108
MATERIALS AND METHODS
• IWG exhibits a higher protein content than HRW (Table 1).
• IWG has a higher lipase activity than HRW, while HRW exhibits greater lipoxygenaseactivity (Table 2). These enzymes contribute to hydrolytic and oxidative rancidity,respectively, and can be problematic over storage.
• However, IWG boasts superior antioxidant activities (as measured by DPPH andLMB assays), attributed to their greater antioxidant content, specificallyhydroxycinnamic acids (Table 3), which may help to delay oxidation over storage,contributing to longer shelf life.
• DPPH measures radical scavenging activity by electron transfer, whereas LMBmeasures antioxidant capacity by electron transfer and the ability of antioxidantsto reduce hydroperoxides by hydrogen atom transfer 14. Moreover, LMBdemonstrates particularly high correlations (Table 4) with hydroxycinnamic acids,the antioxidants that have been demonstrated as some of the most active in wheatspecies15,16 .
• The following steam treatment conditions were considered optimal in terms ofminimal antioxidant degradation and maximum enzyme inactivation and wereadopted for the remainder of the storage study: 100°C, 90-95%RH, 60 minutes.
• Steamed and not steamed samples of IWG and HRW stored for varying lengths oftime at 45°C and 0.43 aw have been analyzed for peroxide value (an indicator ofprimary oxidation), free fatty acids (an indicator of hydrolytic rancidity) and lipaseactivity up to five weeks.
• HRW that was not steamed reached peak hydroperoxide formation at four weeks,while steamed HRW and IWG (both steamed and not steamed) have considerablyless hydroperoxide formation at four weeks (Figure 2), indicating less oxidation.\
• The steamed grains have less hydroperoxide formation than the grains that werenot steam treated. Additionally, it is to be expected that HRW showed higherperoxide values overall, as HRW has a higher lipoxygenase content, as previouslynoted.
• Aside from steamed IWG, samples have shown minimal change in free fatty acidstatus over time (Figure 3), which may be explained by the higher lipase activity ofIWG (Figure 4).
1. Glover JD, Reganold JP, Bell LW, Borevitz J, Brummer EC, Buckler ES, Cox CM, Cox TS, Crews TE, Culman SW, Dehaan LR, Eriksson D, Gill BS, Holland J, Ho F, Hulke BS, Ibrahim AMH, Jackson W, Jones SS, Murray SC, Paterson AH, Ploschuk E, Sacks EJ, Snapp S, Tao D, Van Tassel DL,
Wade LJ, Wyse DL, Xu Y. 2010. Science. 328(5986):1638-1639.2. Rose DJ, Ogden LV, Dunn ML, Pike OA. 2008. Cereal Chem. 85:218-223.3. De Almeida JL, Pareyt B, Gerits LR, Delcour JA. 2013. Cereal Chem. 91(4): 321-326.4. Meera MS, Bhashyam MK, Ali SZ. 2011. Food Science and Technology. 44(10):2199-2204.5. Ekstrand B, Gangby I, Akesson G, Stollman U, Lingnert H, Dahl S. 1993 Journal of Cereal
Science. 17(3):247-254.6. Guo W, Beta T. 2015. Food Research International 51:518-525.7. Lindenmeier M, Alexander B, Somoza V. 2007. Molecular Nutrition and Food Research. 51(12): 1441-
1446.8. Bright D, Stewart GG, Patino H. 1999. J. Am. Soc. Brew. Chem. 57(4): 133-137.9. Abdel-Aal ESM, Young JC, Rabalski I, Hucl P, Fregeau-Reid J. 2007. Journal of Agricultural and Food
Chemistry 55:787-794.10. Vaidyanathan S and Bunzel M. 2012. Cereal Chem. 89(5): 247-254.11. Li Y and Schwarz PB. 2012. . Am. Soc. Brew. Chem. 70(4): 287-289. 12. Timabud T, Sanitchon J, Pongdontri P. 2013. Food Chemistry 141:2405-2411. 13. Rose DJ and Pike OA. 2006. Journal of the American Oil Chemists’ Society 83:415-419.14. Huang DJ, Ou BX, Prior RI. 2005. Journal of Agricultural and Food Chemistry 53 (6): 1841-1856.15. Verma B, Hucl P, Chibbar RN. 2009. Food Chemistry 116:947-954.16. Tyl CE and Bunzel M. 2012. Journal of Agricultural and Food Chemistry 60:731-739.
REFERENCES
Before Thermal Treatment After Thermal Treatment
After Thermal
Treatment
mA
u
mA
u
mA
u
Minutes
Minutes
Minutes
Min MGin
MGinGin
Gin
P34min
At
256nm
At
323nm
RESULTS: 45°C Storage Study
This project was supported by grants from the Minnesota Department of Agricultureand the Forever Green Initiative, as well as funds gifted by the Land Institute.Intermediate wheatgrass was supplied by Department of Agronomy and PlantGenetics at the University of Minnesota.
ACKNOWLEDGEMENTS
• Thinopyrum intermedium, or intermediate wheatgrass (IWG), is a novel perennial crop with grains that have a competitive nutritional profile and advantageous environmental attributes.
• With strong agronomic and industrial appeal, IWG has potential to be marketed on a larger scale; however, such an effort requires more information about the grain, including its shelf life.
• Heat treatment has been shown to be an effective means of elongating storage life of grains by inactivating problematic enzymes responsible for hydrolytic and oxidative rancidity, namely lipase and lipoxygenase respectively. Preliminary studies indicated that these enzymes could be more problematic in IWG than in wheat.
• IWG and hard red wheat (HRW) control were subjected to six treatments consisting of two steam treatments (present/absent) and three incubation temperatures (4°C, 23°C, and 45°C). Antioxidant activity pre-and post-steam treatment was analyzed using 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging and leucomethylene blue (LMB) assays. Lipoxygenase activity was measured by the ferrous oxidation-xylenol orange (FOX) assay, and lipase activity was determined spectrophotometrically.
• Throughout storage, samples were analyzed for indicators of hydrolytic and oxidative rancidity, including free fatty acids, hydroperoxides, malondialdehydes, and hexanal.
• Lipoxygenase activity in IWG subjected to 60 min of steam treatment significantly decreased after two weeks of accelerated storage (P<0.05). The antioxidant activity was not significantly affected (P>0.1). Also, compared to our HRW control, IWG has a higher content of ferulic acid, an active antioxidant commonly found in wheat.
• The interruption of enzymatic activity by steam treatment coupled with the preservation of antioxidants could help prolong the shelf life of IWG, ultimately protecting its properties and rendering it marketable.
INTRODUCTION
Samples:
• IWG (Rosemount, August 2015)
• HRW (St. Paul and Lamberton, July 2015)
Steam Treatment
• Half of samples subjected to steam in proofing oven
• 100°C at 95%RH
Storage Conditions
• aw = 0.43
• Groats stored in open petri dishes in dessicators
• Dark environment
• Temp variable: 4, 25, 45°C
Milling
• Samples pulled for analysis at various time points and milled
• UDI Cyclone Sample Mill with 0.5 mm screen size
Moisture
• Moisture content of milled samples analyzed by infrared method
• Ohaus MB45
Chemical Analysis
• Antioxidant activity and content
• Enzymatic activity
• Products of oxidative and hydrolytic rancidity
• Functionality
Figure 4. Comparison of lipase activity over storage at 45°C (aw=0.43) in steamtreated and non-steam treated intermediate wheatgrass (IWG) and hard red wheat(HRW)
Analysis Method
Antioxidant Activity
• DPPH (2,2-diphenyl-1-picryl-hydrazyl) Radical Scavenging Assay6
• Leucomethylene Blue Assay7,8
Antioxidant Content
• Carotenoids by RP-HPLC on a C30 column with PDA detection9
• Hydroxycinnamic acids by RP-HPLC on a C18 column with PDA detection10
Enzymatic Activity • Lipoxygenase activity by ferrous oxidation xylenol orange (FOX)11,12
• Lipase activity per method described by Rose and Pike (2006)13
HydrolyticRancidity
• Free fatty acids (AOAC Method 940.28)
OxidativeRancidity
• Peroxide value (primary oxidation) (AOAC Method 965.33)• Hexanal quantification (secondary oxidation) by GC-FID
ProximateAnalysis
• Fat content by Mojonnier method (Adapted from AOAC 922.06)• Ash content by dry-ashing (AOAC Method 923.03)• Moisture by vacuum oven (AACCI Method 44-40.01)• Protein content by Dumas method (AOAC 990.03)
RESULTS
Constituent HRW IWG
Avg. Percent ± SD*
Protein 13.3 ± 0.172 15.7 ± 0.012
Fat 3.61 ± 0.492 5.07 ± 0.035
Ash 1.54 ± 0.069 2.14 ± 0.064
Moisture 9.66 ± 0.428 7.15 ± 0.049
Carbohydrate (by difference) 71.9 ± 1.161 69.9 ± 0.160
Table 1. Macronutrient composition of intermediate wheatgrass (IWG)and hard red wheat (HRW)
*Standard deviation
Table 3. Comparison of hydroxycinnamic acid content prior to steam treatment inintermediate wheatgrass (IWG) milled using two different methods and ball-milled hardred wheat (HRW)
Sample µg FAᵃ/g flour ± SD* µg pCAᵇ/g flour ± SD* µg SAᵈ/g flour ± SD*
IWG UDI-milled 813 ± 73.7 20.4 ± 3.60 76.4 ± 5.19
IWG Ball-milled 838 ± 83.8 23.5 ± 3.13 71.6 ± 4.42
HRW Ball-milled 506 ± 54.1 7.00 ± 1.72 50.0 ± 5.61
ᵃFerulic acid, ᵇpCoumaric acid, ᵈSinapic acid, *Standard deviation
Measured Variable HRW IWG
Avg. Results ± SD*
Lipoxygenase activity (U/g) 2.83 ± 0.330 1.60 ± 0.155
Lipase activity (U/g) 1.84 ± 0.178 2.79 ± 0.489
Antioxidant activity by DPPHᵃ (acetone extraction) (µmoles TEᵇ/g) 28.1 ± 1.60 61.3 ± 3.69
Antioxidant activity by DPPH (alkaline hydrolysis with ethyl ether extraction) (µmoles TE/g) 34.9 ± 3.82 51.7 ± 2.57
Antioxidant activity by LMBᵉ mmoles (TE/g) 0.589 ± 0.002 0.765 ± 0.002
ᵃ2,2-diphenyl-1-picryl-hydrazyl, ᵇTrolox equivalents, ᵉLeucomethylene blue, *Standard deviation
Table 2. Comparison of enzymatic activities and antioxidant activities in intermediatewheatgrass (IWG) and hard red wheat (HRW) prior to steam treatment
Assay Ferulic acid Sinapic acid pCoumaric acid
Correlation coefficient
DPPHᵃ Radical Scavenging Assay 0.686 0.701 0.703
LMBᵇ Antioxidant Activity Assay 0.981 0.94 0.97
Table 4. Correlations between hydroxycinnamic acid antioxidant content andantioxidant activity by DPPH and LMB antioxidant activity assays
ᵃ2,2-diphenyl-1-picryl-hydrazyl, ᵇLeucomethylene blue
Figure 1. Lipoxygenase activity measured by the FOX assay over time at 60°C in samples steam-treated for various lengths of time
Figure 2. Comparison of primary oxidation as indicated by peroxide value overstorage at 45°C (aw=0.43) in steam treated and non-steam treated intermediatewheatgrass (IWG) and hard red wheat (HRW)
Figure 3. Comparison of hydrolytic rancidity as indicated by percent free fatty acidsover storage at 45°C (aw=0.43) in steam treated and non-steam treatedintermediate wheatgrass (IWG) and hard red wheat (HRW)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20 25 30 35 40
Lip
ase
Act
ivit
y U
/g (
Dry
Bas
is)
Time (days)
IWG steamed IWG not steamed HRW steamed HRW not steamed
• A steam treatment length of 60 minutes significantly decreased the lipoxygenase activity of IWG after two weeks of accelerated storage (P<0.05), as shown in Figure 1. At this same treatment length, antioxidant activity of steamed-treated IWG as measured by leucomethylene blue and DPPH assays was not significantly decreased as compared to samples that were not steam treated (P>0.1).
• Storage studies are currently underway at 4°C, 25°C, and 45°C. In addition tomeasuring the parameters shown here, samples are also currently beinganalyzed for lipoxygenase activity, antioxidant activity, antioxidant content,and hexanal. As samples are stored at controlled relative humidity (aw=0.43),moisture levels remain constant, at approximately 10%, over storage.
• Future work will focus on storage of flour, as opposed to storage of whole groats,under the same conditions.
• Functionality testing, including loaf volume, starch pasting properties, and doughstrength will be tested over time in stored IWG and HRW samples, steam treatedand not steam treated, as well as in samples stored as flour and whole groats.
• The effect of steam treatment on storage stability and functionality of IWG willinfluence future processing conditions of the grain.
DISCUSSION
FUTURE WORK &
IMPLICATIONS
3
4
5
6
7
8
9
DAY 0 DAY 3 DAY 6 DAY 9 DAY 12
LOX
act
ivit
y/g
(dry
bas
is)
Days of Storage at 60°C
0min
30min
60min
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
0 5 10 15 20 25 30 35 40 45
mEq
hyd
roxy
pe
roxi
de
s/kg
sam
ple
Time (days)
IWG steamed IWG not steamed HRW steamed HRW not steamed
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 5 10 15 20 25 30 35 40 45
%Fr
ee
Fat
ty A
cid
(Ex
pre
sse
d a
s %
Ole
ic
Aci
d)
in 1
00
g Fl
ou
r D
B
Time (days)
IWG steamed IWG not steamed HRW steamed HRW not steamed
