quality assessment of high and normal oleic acid peanut
TRANSCRIPT
Quality Assessment of Various Peanut Butters 1
Quality Assessment of High and Normal Oleic Acid Peanut Butters by Sensory and
Volatile Flavor Compound Analysis
Stephen Koltun
Advisor: Paul J. Sarnoski
University of Florida
Institute of Food and Agricultural Sciences
Department of Food Science and Human Nutrition
Gainesville, Florida, 32611
Quality Assessment of Various Peanut Butters 2
Abstract
Two peanut genotypes (Florunner and Tufrunner) were analyzed using gas
chromatography-mass spectrometry (GC-MS) to determine variations in lipid oxidation,
as well as the pyrazine compounds that correlate highly with roasted flavor and aroma.
Compounds were measured using headspace solid-phase microextraction (SPME) after
peanuts were roasted and made into three peanut butters (normal oleic, high oleic
without skin, high oleic with skin) according to the Standard of Identity for peanut butter.
Peanut butters were stored at 40 ˚C for accelerated shelf life testing (ASLT) and three
sensory panels were conducted at various times (initial, 56 days, 98 days) in order to
assess 8 characteristics (oxidized aroma, sweetness, bitterness, saltiness, brown color,
texture, flavor, overall acceptability). Results showed that high oleic varieties had a
slower rate of lipid oxidation when compared to the normal oleic variety. Sensory panel
results indicated that high oleic with skin peanut butter was the most favored of the
three experimental varieties and was comparable to commercial brand peanut butters.
The inclusion of peanut skins is also known to have health benefits due to their
concentration of phenolics and dietary fiber.
Keywords: gas chromatography-mass spectrometry (GC-MS), lipid oxidation, solid-
phase microextraction (SPME), peanut butter, oleic acid, accelerated shelf life testing
(ASLT)
Quality Assessment of Various Peanut Butters 3
Introduction
Peanuts (Arachis hypogaea) are a popular legume that originated in South
America. They are grown around the world, with the United States being the fourth
largest producer (USDA-FAS 2016). Peanuts are sensitive to soil and climate
conditions, so they are mainly grown in three major areas: the Southeast (Alabama,
Florida, Georgia, Mississippi, South Carolina), the Southwest (New Mexico, Oklahoma,
Texas), and Virginia and North Carolina, with Georgia being the largest peanut-
producing state (USDA-NASS 2016).
In the United States, production of peanuts is estimated to be at 6.21 billion
pounds (USDA-NASS 2016). There are four major cultivar groups that are the most
popular in the United States: Runner, Spanish, Valencia, and Virginia. Runner peanuts
are most commonly used in peanut butter and salted nuts due to good flavor, better
roasting characteristics, and higher yield compared to Spanish types.
Peanut butter processing consists of several steps: cleaning, shelling, roasting,
cooling, blanching, grinding, and packaging. After cleaning and shelling, peanuts are dry
roasted using either the batch or continuous method. The batch method is more
common, which involves heating batches of peanuts to 160 ˚C for 40 to 60 min. A
photometer is used to indicate when desired doneness is achieved, as well as ensure a
uniform product has been produced. The peanuts are transferred to a perforated metal
cylinder where they are cooled using a large volume of air. At this point a manufacturer
can decide to remove the skins by either heat or water blanching. Heat blanching is
more common and it uses heat, agitation, and gentle rubbing to separate the skins from
the peanuts. The product goes through an inspection process that removes any
Quality Assessment of Various Peanut Butters 4
unwanted particles, including but not limited to: scorched or rotten peanuts, light
peanuts, discolored peanuts, and foreign contaminants like metal. The peanut butter is
made by two grinding operations. The peanuts are first reduced to a rough, medium
grind and then to a fine, smooth texture. At this point, additives like salt, sugar, and
stabilizers are fed into the peanut butter to add flavor, improve consistency, and
lengthen shelf life. The stabilized peanut butter is finally vacuum packaged or flushed
with inert gas in order to reduce oxidation (Considine 1982).
Of all the processing steps, the only critical control point that can kill potential
microorganisms is roasting. That means that the peanut butter is susceptible to
pathogenic bacteria, mainly Salmonella spp., in all subsequent unit operations.
Salmonella tennessee, Salmonella typhimurium, and Salmonella bredeney outbreaks
have occurred in peanut butter in 2007, 2008, and 2012 respectively (Sheth et al. 2011;
CDC 2009, CDC 2012). In response to these various outbreaks, research has been
conducted in order to eliminate the bacteria in the final product without affecting the
overall quality.
There has been a shift in consumer demand towards natural foods with fewer
preservatives and additives, but partially hydrogenated oils (PHOs) have been used in
the peanut butter industry to improve consistency in peanut butter products. The U.S.
Food and Drug Administration (FDA) has issued a recent ordinance that states PHOs
are no longer recognized as GRAS, or generally recognized as safe, for human
consumption (2015). This research focuses on high oleic peanuts that will be made into
a shelf stable peanut butter. The peanut butter that does not use any PHOs may be
used as a viable alternative to combat the ever-changing food laws.
Quality Assessment of Various Peanut Butters 5
Lipid Oxidation in Peanuts and Peanut Products
Oxidative rancidity is the result of chemical reactions involving oxygen and a
lipid. Lipid oxidation is referred to as autoxidation because it is an autocatalytic reaction,
which the reaction rate increases as the reaction proceeds. It results in off flavors, color
change, degradation of nutrients, and possibly toxicity. The rate of oxidation is affected
by fatty acid composition, degree of unsaturation, presence of pro- and antioxidants,
partial pressure O2, storage conditions, water activity, and pH (Choe and Min 2006).
There are three steps of autoxidation: initiation, propagation, and termination.
During initiation, a hydrogen atom is abstracted from the fatty acid by an initiator and a
fatty acid free radical is formed. In propagation, a peroxyl free radical is formed in the
presence of oxygen which leads to the formation of a hydroperoxide in the presence of
another fatty acid. This reaction repeats rapidly. Termination happens with the reaction
between two radicals (Frankel 2005). Hydroperoxides (primary products) can be very
unstable and decompose to form secondary oxidation products, which include: acids,
alcohols, aldehydes, carbonyls, and ketones. These secondary products are
responsible for the rancid odor and flavor of oxidized fat.
There are various methods to prevent and/or retard lipid oxidation, the most
obvious being the removal of oxygen by using vacuum or modified atmosphere
packaging. Removing or decreasing oxygen in the system means the lipid molecules
cannot be oxidatively deteriorated. Other important methods are avoiding high
temperatures, using less unsaturated fatty acids or using more saturated fatty acids,
and incorporating the use of antioxidants. Autoxidation can also be retarded by reducing
light and by removing catalysts (e.g. metals).
Quality Assessment of Various Peanut Butters 6
High-Oleic Peanuts
Peanuts mainly consist of oleic and linoleic acid. Oleic acid is a monounsaturated
fatty acid with one double bond (C18:1), while linoleic acid is a polyunsaturated fatty
acid with two double bonds (C18:2) (Caballero 2016). Peanuts usually contain about
52% oleic acid, but there are peanuts known as high oleic peanuts that contain about
80% oleic acid (Derbyshire 2014). The fatty acid composition of high and normal oleic
acid peanuts is otherwise relatively similar, except for differences in palmitic acid
(C16:0) and linoleic acid (C18:2) (Braddock 1994). High oleic peanuts also have a lower
sugar content and increased thermal stability when compared to normal oleic peanuts
(Chung et al. 2002; Derbyshire 2014). Due to an increased thermal stability, high oleic
peanuts produce less undesirable flavor characteristics such as painty, cardboard, and
oxidized (Nepote et al. 2008).
The high oleic trait is genetically controlled by two recessive genes: AhFAD2A
and AhFAD2B. The AhFAD2A gene is more common in Runner and Virginia peanuts,
but it is not present in Spanish peanuts. These high oleic peanut cultivars have been
developed with a variety of techniques, including conventional breeding (SunOleic97R,
Tamrun OL01, Georgia04S), chemical mutagenesis (Flavorunner 458), and gamma
irradiation (Georgia-02C) (Benkeblia 2011).
Oleic content is measured using gas chromatography (GC), capillary
electrophoresis, near-infrared reflectance spectroscopy (NIRS), and real-time PCR (RT-
PCR). GC and capillary electrophoresis are able to determine the oleic acid to linoleic
acid (O/L) ratio, the only difference being that GC uses large sample sizes and capillary
electrophoresis uses a smaller sample size. NIRS and RT-PCR are both non-
Quality Assessment of Various Peanut Butters 7
destructive tests, but these tests are only able to determine whether or not a peanut
sample is high in oleic acid and not the overall O/L ratio (Chamberlin et al. 2014).
Materials and Methods
Sample Preparation and Storage
Two peanut genotypes were analyzed; Florunner, a normal-oleic variety; and
Tufrunner, a high-oleic variety. Peanut yield, shelling, and grading data were obtained
from the University of Florida North Florida Research and Education Center (NFREC) at
Marianna, Florida and sound, mature seed samples (medium and above grade size)
were sent to the University of Florida, Gainesville, for further analysis. Peanut seeds
were stored at -20 ˚C in nitrogen-flushed, sealed plastic Hefty One-Zip Slider© (Lake
Forest, Ill., U.S.A.) freezer bags.
Peanut Roasting
Frozen, unroasted, shelled peanuts were allowed to equilibrate to room
temperature for approximately two hours before roasting. Roaster heating was set to
reach a temperature of 250 ˚C. The Pyrex forced air convection oven (Suppentown
International, City of Industry, CA) was fitted with a thermocouple in the center in order
to ensure that the air temperature was adequate. Each peanut variety was then roasted
in a stainless steel basket in approximately 400 g batches, and stirred three times, for
approximately 8 min for normal-oleic peanuts and 10 min for high-oleic peanuts until
color and odor reached an acceptable roasting level, as determined by Baker et al.
(2003). Peanut batches were removed from the roaster by transferring to a stainless
steel bowl and agitated manually using cotton examination gloves covered by nitrile
Quality Assessment of Various Peanut Butters 8
gloves to partially remove the skins in a sanitary manner and protect the investigator
from potential burns. Further agitation was required to remove all skins by manually
scraping against a metal sieve (6.5 mm).
Peanuts were transferred to a kitchen blender (Ninja Kitchen System, Newton,
MA) where salt, sugar, and peanut skins were added depending on the batch. In order
to keep with the Standard of Identity for Peanut Butter (U.S. CFR 21), 1.6 g of salt and
10.4 g of sugar were added per 100 g of peanuts. For the high oleic peanuts with skins,
6.82 g of peanut skins were added per 100 g of peanuts. The mixture was then
homogenized for approximately 15 min or until there were no noticeable granules of
significant size.
The homogenized peanut paste was then transferred to an induction-heated
kitchen mixer (Kenwood, Upper Saddle River, NJ), fitted with a U-shaped Teflon
attachment to scrape the peanut mixture at 140 ˚C for another 15 min, which should
have been an adequate to pasteurize the product (71.7 ˚C/161 ˚F for 15 sec). The
resulting peanut butter samples were immediately poured into sterile, 4-ounce sample
specimen cups and stored at 45 ˚C for accelerated shelf life testing (ASLT).
Sensory Analysis
A 10-person (4 male, 6 female) sensory panel consisting of students and staff of
the Food Science and Human Nutrition Department were used to evaluate the peanut
butters. Six different peanut butters were tested (three experimental varieties and three
commercial brands): Florunner, unblanched Tufrunner, blanched Tufrunner, unblanched
Trader Joe’s, Skippy Natural, and Peter Pan. Sensory attributes rated were oxidized
aroma, sweetness, bitterness, saltiness, brown color, texture, flavor, and overall
Quality Assessment of Various Peanut Butters 9
acceptability. Oxidized aroma, sweetness, bitterness, saltiness, and brown color were
rated for intensity on a 150 mm line scale with predetermined anchors for each attribute
(Gills and Resurreccion 1999). The six peanut butters were also ranked for texture,
flavor, and overall acceptability. On the test day, all stored peanut butters were
equilibrated to room temperature and mixed to mimic typical use conditions before
sensory evaluation. Panelists were given approximately 10 g of peanut butter per
sample and told to evaluate all intensity attributes before moving on to ranking the
peanut butters.
Solid-Phase Microextraction (SPME)
Peanut butter samples were transferred to 40-mL vials fitted with
polytetrafluoroethylene (PTFE) septa caps (Fisher Scientific, Pittsburgh, Pa., U.S.A.),
enough to fill half of the vial. Vials were shaken for 1 min and allowed to settle, while
sealed, then heated to 60 ˚C for 15 min. The 50/30 µm
divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) SPME fiber (Agilent
Technologies, Santa Clara, Ca., U.S.A.) was then inserted into the vial via the septa,
exposing the fiber to the headspace of the roasted peanut butter sample for 15 min to
obtain headspace/fiber equilibrium (Baker et al. 2003). Samples were then analyzed by
gas chromatography-mass spectrometry (GC-MS) using a 5975 MSD (Agilent
Technologies, Santa Clara, Ca., U.S.A.) and a ZB-WAXplus column with 30 m length,
0.25 mm I.D., and 0.25 µm film thickness (Phenomenex, Torrance, Ca., U.S.A.). Volatile
compounds were separated using temperature programming. Thermal desorption for 3
min in the injection port was required in order to remove all compounds from the fiber.
Quality Assessment of Various Peanut Butters 10
Statistical Analysis
Statistical Analysis Software (SAS 9.4) was used for statistical analysis of
sensory panel data. Two-way Analysis of Variance (α = 0.05) was used to determine
significant effects of treatment on attribute intensities (Table 1). Duncan’s multiple range
test was performed in order to separate means based on significance for oxidized,
sweetness, bitterness, saltiness, and brown color. Friedman’s analysis (α = 0.05) was
used to determine significant effects of treatment on attribute rankings (Table 2). Least
significant difference (LSD) was performed in order to separate rank totals based on
significance for texture, flavor, and overall acceptability.
Results
Sensory Analysis
There was a total of 8 variables used in the sensory panel to quantify the
characteristics of six different peanut butters (three experimental varieties and three
commercial brands) and they are summarized in Tables 1 and 2. During the initial
sensory test, all six peanut butters had relatively low oxidized values and no significant
differences were found. As time went on, the sensory tests after 56 and 98 days
showed a significantly greater level of oxidation for the normal oleic peanut butter when
compared to the high oleic peanut butters. Three tastes: sweetness, bitterness, and
saltiness were rated by sensory analysis. All three of these attributes were rated lower
for all of the experimental peanut butters as time went on. There was a significant
difference among the peanut butters in terms of brown color. The high oleic with skin
variation was significantly darker in brown color than all other peanut butters. Brown
Quality Assessment of Various Peanut Butters 11
color was relatively unaffected by time for every peanut butter variety. Panelists were
required to rank the peanut butters against each other for texture, flavor, and overall
acceptability. For each of these attributes, the high oleic with skin variation was
significantly more favorably ranked than the other two experimental peanut butters and
this peanut butter even ranked significantly higher than some of the commercial brands.
Solid-Phase Microextraction (SPME)
Samples were analyzed using GC-MS. Chromatogram peak areas for
compounds of interest were converted to percentages and are summarized in Tables 3,
4, and 5 for normal oleic, high oleic without skin, and high oleic with skin, respectively.
The normal oleic peanut butter showed a greater rate of oxidation when compared to
the high oleic peanut butters due to a drastically higher concentration of oxidation
products. Over the course of the study, the normal oleic variety saw a 1975% increase
in pentanal, 2334% increase in hexanal, and 2277% increase in 1-pentanol. The high
oleic varieties started showing signs of oxidation at the 56 day mark, characterized by
the presence of hexanal.
Pyrazine compounds are responsible for a range of sensory responses. In all
three of the experimental varieties, these compounds are found during the initial
analysis and have a negative correlation with regard to time. Some of these pyrazine
compounds degraded so much that they were not found during the final analyses.
These pyrazine compounds are detected in the high oleic varieties for a longer period of
time when compared to the normal oleic variety. In the normal oleic peanut butter,
compounds such as trimethylpyrazine and 2,5-dimethylpyrazine are no longer found in
Quality Assessment of Various Peanut Butters 12
the sample at the 56 day mark. However, the high oleic peanut butters retained most of
their pyrazine compounds up until the 98 day mark.
Discussion
Being one of the most important attributes of this study, rancidity in peanuts is
described as the aroma associated with oxidized, stale peanuts. Peanut butter oxidation
showed a clear, positive correlation with regard to time. This is due to the nature of the
study as the accelerated shelf life testing requires the peanut butter be subjected to
harsh environmental conditions like increased storage temperatures, which increases
the rate of oxidation. Sweetness is the taste associated with sucrose solutions,
bitterness is the taste associated with caffeine solutions, and saltiness is the degree of
the taste sensation associated with sodium chloride solutions (Gills and Resurreccion
1999). The decrease in these attributes over time are most likely due to the respective
compounds being lost in the sample as thermal degradation and oil separation
occurred. Brown color was the only visual attribute that was examined over time and it
is the intensity or strength of brown color from light to dark brown. Brown color of the
experimental varieties was comparable to that of the three commercial brands. The high
oleic experimental peanut butters with skins had some negative feedback due to the
added skins, but panelists indicated that it was minor. Panelists were required to rank
the peanut butters against each other instead of on an individual basis to give the
researchers an idea of how the peanut butters would compare if released in the market.
Results indicated that the high oleic with skin variation was the most favorable of the
three experimental varieties and was comparable to the commercial brands.
Quality Assessment of Various Peanut Butters 13
The other part of the experiment was to use GC-MS to quantify the compounds
in the experimental peanut butters as the samples underwent lipid oxidation over time.
As previously discussed, hydroperoxides (primary products of lipid oxidation) can
undergo further oxidation to form a variety of volatile and nonvolatile secondary
products when exposed to elevated temperatures (Frankel 2005). Compounds of
interest for this study included alkanes, alkenes, alcohols, aldehydes, and pyrazines.
While pyrazines are not a product of oxidation, these compounds are associated with
roasted aromas in peanuts and are prone to degradation over time. A summary of these
sensory responses to pyrazines is given in Table 6 (Braddock 1994).
The compounds in the peanut butters fluctuated in concentration throughout the
study, but most of them show a clear positive or negative trend. Any deviations from this
could be due to the nature of the technique used to measure oxidation. At different
points during oxidation, production of different compounds may be more or less
favorable. This may have been the reason why fluctuations in compound amount were
seen at different points in time. Overall you see that the high oleic experimental varieties
have a longer induction period, which is defined as the length of time before rapid
acceleration of lipid oxidation occurs.
Overall, the GC-MS data agreed with the results from the sensory panel. The
normal oleic peanut butter had higher scores for oxidation throughout the study, which
correlates to the amount of oxidation products that are present in the sample. The
overall decrease in flavor and aroma sensation for the three peanut butters is attributed
to the decrease in pyrazine compounds. Sweetness, roasted, caramel, and nutty are
just a few of the attributes that pyrazine compounds are directly responsible for.
Quality Assessment of Various Peanut Butters 14
The aim of this study was to determine whether or not a high oleic acid peanut
could be a viable alternative to the normal oleic acid peanut that is currently used for
peanut butter commercially. According to sensory panel data, consumers rated high
oleic with skin peanut butter the highest of all three experimental varieties and it was
ranked equally or higher than some commercial brands. According to GC-MS data, both
of the high oleic peanut butters showed less lipid oxidation than the control. The use of
high oleic peanuts could combat the dangers of microorganisms like Salmonella as
these peanuts can be heated to higher temperatures for longer periods of time without
creating off-flavors as a result of extensive heating. There was little difference between
the two high oleic peanut butters in regard to overall oxidation products, so future
research might benefit from increasing the amount of peanut skin added to each batch.
The nutritional implications of peanut skin also needs to be further researched in order
to be able to market to the health-conscious consumer.
Conclusion
Peanut butter is prone to lipid oxidation because of its unsaturated bonds. High
oleic peanuts are more oxidatively stable compared to normal oleic peanuts due to the
oleic acid to linoleic acid (O/L) ratio. High oleic peanuts can also be heated to higher
temperatures for longer periods of time without negatively affecting the quality of the
peanut butter. Peanut skin has a high polyphenol content, which directly correlates to its
ability to act as an antioxidant and possibly an antimicrobial, as well as other health
promoting compounds. This research demonstrates the ability of high oleic peanut
butter to withstand higher temperature. A peanut butter with high oleic peanuts and
Quality Assessment of Various Peanut Butters 15
peanut skins is able to be heated enough to potentially destroy microbes, mainly
Salmonella spp., without adverse effects on quality and can also lead to a longer shelf
life without the use of additives.
Quality Assessment of Various Peanut Butters 16
Literature Cited
Baker GL, Cornell JA, Gorbet DW, O’Keefe SF, Sims CA, & Talcott ST. 2003.
Determination of pyrazine and flavor variations in peanut genotypes during
roasting. Journal of Food Science, 68(1):394-400.
Caballero B. 2016. Encyclopedia of food and health. Oxford: Academic Press, an
imprint of Elsevier.
Braddock, JC. 1994. Stability of volatile flavors and aromas of peanuts with high and
normal oleic acid content. M.S. Thesis, University of Florida.
CDC. 2009, May 11. Multistate outbreak of Salmonella typhimurium infections linked to
peanut butter, 2009-2009 (Final Update). Available from:
http://www.cdc.gov/salmonella/2009/peanut-butter-2008-2009.html. Accessed
2016 November 1.
CDC. 2012, November 30. Multistate outbreak of Salmonella bredeney infections linked
to peanut butter manufactured by Sunland, Inc. (Final Update). Available from:
http://www.cdc.gov/salmonella/bredeney-09-12/. Accessed 2016 November 1.
Chamberlin KD, Barkley NA, Tillman BL, Dillwith JW, Madden R, Payton ME, & Bennett
RS. 2014. A comparison of methods used to determine the oleic/linoleic acid
ratio in cultivated peanut (Arachis hypogaea L.). Agricultural
Sciences, 05(03):227-237.
Choe E, Min DB. 2006. Mechanisms and factors for edible oil oxidation. Comprehensive
Reviews in Food Science and Food Safety, 5(4): 169-186.
Quality Assessment of Various Peanut Butters 17
Chung S, Maleki S, Champagne ET, Buhr KL, & Gorbet DW. 2002. High-oleic peanuts
are not different from normal peanuts in allergenic properties. Journal of
Agricultural and Food Chemistry, 50(4): 878-882.
Considine DM. 1982. Foods and food production encyclopedia. New York: Van
Nostrand Reinhold.
Derbyshire EJ. 2014. A review of the nutritional composition, organoleptic
characteristics and biological effects of the high-oleic peanut. International
Journal of Food Sciences & Nutrition, 65(7):781-790.
FDA. 2015. FDA cuts trans fat in processed foods. Available from:
http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm372915.htm.
Accessed 2016 June 5.
Frankel EN. 2005. Lipid Oxidation (Second Edition). Woodhead Publishing.
Gills LA, Resurreccion AVA. 1999. Sensory and physical properties of peanut butter
treated with palm oil and hydrogenated vegetable oil to prevent oil separation.
Journal of Food Science, 65(1):173-180.
Sheth AN, Hoekstra M, Patel N, Ewald G, Lord C, Clarke C, . . . Lynch M. 2011, August
1. A national outbreak of Salmonella serotype tennessee infections from
contaminated peanut butter: A new food vehicle for salmonellosis in the United
States. Clinical Infectious Diseases, 53(4):356-362.
USDA-NASS. 2016. Crop production annual summary. Available from:
http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1
047. Accessed 2016 November 1.
Quality Assessment of Various Peanut Butters 18
USDA-FAS. 2016, June. United States world agricultural service production. Available
from: http://apps.fas.usda.gov/psdonline/circulars/production.pdf. Accessed 2016
November 1.
Quality Assessment of Various Peanut Butters 19
Tables and Figures
Table 1. Sensory Attribute Intensities of Stored Roasted Peanut Products
Sample
Oxidized Sweetness Bitterness Saltiness Brown Color
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
Trader Joe’s
Unblanched
25.2
a
25.9
b
26.6
c
20.4
b
17.4
c
20.6
b
25.8
a
41.7
a
34.6
a
49.4
a
41.6
a
32.4
a
79.2
b
85.7
b
76.4
b
High Oleic
w/o Skin
26.3
a
21.2
b
25.1
c
42.9
a
53.4
a
47.7
a
19.7
a
12.3
b
25.4
a
50.1
a
35.3
a
35.9
a
61.8
c
25.9
e
60.7
c
Skippy
Natural
34.2
a
15.2
b
29.9
bc
34.5
ab
32.3
b
44.3
a
19.5
a
20.6
b
20.1
a
44.7
a
41.2
a
32.6
a
70.8
bc
58.4
cd
59.6
c
Normal Oleic 34.0
a
45.8
a
68.4
a
43.5
a
38.7
ab
33.1
ab
15.4
a
24.0
b
32.0
a
46.3
a
36.1
a
50.1
a
30.4
d
44.4
d
30.4
d
Peter Pan 31.2
a
23.6
b
18.6
c
39.9
a
39.3
ab
26.3
b
24.8
a
17.8
b
19.4
a
40.9
a
43.7
a
34.6
a
70.8
bc
69.0
c
63.7
c
High Oleic
w/ Skin
27.3
a
27.0
b
49.9
ab
51.2
a
47.1
ab
32.9
ab
19.1
a
17.8
b
35.4
a
55.4
a
39.4
a
35.0
a
107.2
a
102.3
a
109.3
a
*Intensities based on 0 to 150 scale, mean separation performed with Duncan’s multiple
range test
Table 2. Ranking Sums of Stored Roasted Peanuts from a Sensory Panel
Sample
Texture Flavor Overall
Acceptability
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
0
Day
56
Day
98
Day
Trader Joe’s
Unblanched
36
ab
29
a
19
bc
20
a
21
a
15
cd
21
d
26
a
16
cd
Quality Assessment of Various Peanut Butters 20
High Oleic w/o
Skin
32
abc
26
a
20
bc
37
a
28
a
26
abcd
37
abcd
27
a
25
abcd
Skippy Natural 48
a
37
a
35
a
44
a
33
a
31
ab
44
ab
41
a
30
abc
Normal Oleic 17
c
29
a
16
c
32
a
29
a
13
d
22
d
25
a
13
d
Peter Pan 48
a
36
a
33
ab
37
a
37
a
29
abc
47
a
35
a
31
ab
High Oleic w/ Skin 29
bc
32
a
24
abc
40
a
41
a
33
a
39
abc
35
a
32
a
*Rankings based on 0 (lowest possible ranking) to 6 (highest possible ranking) scale,
rank total separation performed with least significant difference (LSD) test
Table 3. Percentage Change of Compounds in Normal Oleic Peanut Butter
Compound 56 Day 98 Day
Pentanal 148% 1975%
Hexanal 722% 2334%
1-Methyl-1H-pyrrole -50% -37%
1-Pentanol 690% 2277%
Methylpyrazine -30% ---
Octanal --- -54%
1-Hexanol -32% -2%
2-Ethyl-6-methylpyrazine -25% -35%
Quality Assessment of Various Peanut Butters 21
Nonanal -27% -55%
3-Ethyl-2,5-dimethylpyrazine 13% -3%
Benzaldehyde 33% 12%
1-Octanol 63% ---
*Percent changes are all relative to the first time compound was found in sample (i.e.
0%). A “---“ indicates compound was not found in the sample
Table 4. Percentage Change of Compounds in High Oleic Peanut Butter without Skins
Compound 14 Day 28 Day 56 Day 70 Day 98 Day
2-Methyl-2-propanol 0% 3% 72% 8% ---
2-Methylbutanal 9% 47% --- 62% ---
3-Methylbutanal -18% 20% 3% 68% -84%
Hexanal --- --- 0% -73% -13%
1-Methyl-1H-pyrrole -33% -45% -60% -21% -5%
Methylpyrazine --- --- --- -62% ---
2,5-Dimethylpyrazine -69% -57% -93% -57% ---
2-Ethyl-5-methylpyrazine --- -45% --- -46% ---
Nonanal 34% -11% -18% -19% -46%
Trimethylpyrazine -50% -42% --- -38% -78%
3-Ethyl-2,5-dimethylpyrazine -48% --- --- -45% -45%
Benzaldehyde 24% 18% 10% 104% 206%
* Percent changes are all relative to the first time compound was found in sample (i.e.
0%). A “---“ indicates compound was not found in the sample
Quality Assessment of Various Peanut Butters 22
Table 5. Percentage Change of Compounds in High Oleic Peanut Butter with Skin
Compound 14 Day 28 Day 56 Day 70 Day 98 Day
2-Methylbutanal -24% -39% -34% -1% ---
3-Methylbutanal -30% -49% -36% -9% ---
Hexanal --- --- 0% 24% -22%
1-Methyl-1H-pyrrole -39% -34% -58% -9% -68%
Methylpyrazine --- --- -67% 29% ---
2,5-Dimethylpyrazine -67% -2% -58% 21% ---
2-Ethyl-5-methylpyrazine --- 31% -39% --- ---
Nonanal 151% 208% --- 304% -76%
Trimethylpyrazine -37% 57% -22% 122% -70%
3-Ethyl-2,5-dimethylpyrazine -25% 67% -24% 140% -37%
Benzaldehyde -21% 98% 72% 150% 33%
* Percent changes are all relative to the first time compound was found in sample (i.e.
0%). A “---“ indicates compound was not found in the sample
Table 6. Volatile Compounds Identified in Roasted High and Normal Oleic Acid Peanuts
Compound Sensory Response
Acetic acid bread dough, yeasty
Methylpyrazine grilled chicken, savory
2,5-Dimethylpyrazine malty, chocolate
Ethylpyrazine toasted, dark roasted
Quality Assessment of Various Peanut Butters 23
2,3-Dimethylpyrazine roasted
Benzaldehyde ---
2-Ethyl-5-methylpyrazine nutty, roasted
2-Ethyl-3-methylpyrazine roasted
Benzeneacetaldehyde floral, sweet, caramel
3-Ethyl-2,5-dimethylpyrazine roasted, slightly sweet
2,3-Dihydrobenzofuran rubbery, harsh
Benzothiazole harsh, rubbery, burnt
3-Methylpyridine intense, peanut butter, roasted
*Adapted from Braddock (1994)