xt72rb6vz71c https://exploreuk.uky.edu/dips/xt72rb6vz71c/data/mets.xml   Kentucky Agricultural Experiment Station. 1965 journals 155 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.155 text Progress report (Kentucky Agricultural Experiment Station) n.155 1965 2014 true xt72rb6vz71c section xt72rb6vz71c I D   ‘ D   ",‘-   { i:A;,5; ~ r E ‘ ` l D Y     I    '_ `   i i »  i r   » ,
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By Dudley C, M¤rtin··Doris A. Tichenor·Deon E. Knovel V
1 `   Pro ress Re ort
. UNIVERSITY OF KENTUCKY • AGRICULTURAL zxrznimzm STATION 9 155 P
Department of Horticulture ond School of Home Economics -——--— Lexington i _

 
 QUALITY EVALUATION OF FROZEN VEGETABLES
II. §_L¤_e_g Corn
By Dudley C. Martin, Doris A Tichenor and Dean E. Knavel
Sweet corn, a favorite vegetable of Kentuckians, is extensively grown in
home gardens and for sale on local fresh markets. When harvested at optimum
maturity and properly processed. sweet corn is an excellent frozen vegetable.
These studies were designed to evaluate freezing quality in sweet corn
selections and varieties grown on the Kentucky Agricultural Experiment Station
Farm near Lexington.
· EXPERIMENTAL METHODS
Results of experiments conducted during two years are·summarized in this
report. Varieties included in the 1959 series of trials were Aristogold Bantam
Evergreen, 25778, Sure crop 25776, Florigold - 107, 27802, R-8, NK-1304,
Golden Security, Victory Golden, Carmelcross, North Star, Sixty pak, and Asgrow
Golden-22. The varieties studied in 1960 were Golden Security, 25776, 27802,
Iochief, Evertender-C, Staygold, Valleygold, and Gold Cup. 1 The corn was husked
and cleaned. blanched for 4% minutes in boiling water, and cooled for an equivalent
time in ice water. Kernels were cut from the ears and packed in §—pint polyethylene-
lined bags which were heat—sealed All samples were quick—frozen at -350 F and
then transferred to 00 F storage
The sweet corn varieties were evaluated immediately after processing and
also 3, 6, and 9 months later by a trained 12—member student taste panel. Samples
were cooked for 10 minutes iné cup boiling water and served hot. Panelists
evaluated the first series of samples for flavor, color. odor, and texture. Samples .
in the second series were evaluated only for fl avor. color, and texture because
odor scores were found to be very similar for all samples tested in the first series.
A Bausch and Lomb Spectronic 20 colorimeter with reflectance attachment
was used to measure color of the corn. Duplicate readings were taken on uncooked
corn in the first series and on both cooked and uncooked corn in the second series.
Dominant wavelength. purity. and brightness were calculated from the readings.
Dominant wavelength is essentially a hue measurement. With respect to sweet corn, .
higher dominant wavelengths indicate hues approaching yellow—orange from the
- yellow area of the spectrum. Purity represents the amount of the dominant hue
present in the sample. Brightness is a measure of the amount of white light reflected
by the sample--higher brightness values indicate lighter yellow.
Pericarp was determined by an adaptation of the Showalter2 method. . A 50-
gram sample was blended for 3 minutes and then washed through a 30—mesh monel
metal screen. Material retained on the screen was dried, weighed, and calculated
as percent pericarp. Shear press measurements were made on the second set of
sweet corn varieties studied. Eighty grams of thawed. uncooked corn was placed in
the standard cell of· the L. E. E. —Kramer Shear Press. and the pounds of force re-
quired to shear through this sample were recorded
1For production performance and seed source< of these varieties. see Kentucky Agricultursil Experiment
Station Progress Report 117, "Periorni mee of \/i·;i·i.mir Varieties in Kentucl-xy 1959-1961, " by D. E. Knavel.
2RObCi-t K, Show.ilt·.·i· "M wsnring the Pericarp Content of Sweet Corn. " _l};ogeegLng§_@ the Association
of SOL1[l1€l"]'11XgI`LCi1JEl.1_I;L1l_\N_Ol'ljQ§; Vol. 57, 1960 `

 -4-
Percent moisture was obtained by drying duplicate 25—gram samples in a
900 C oven overnight. Sugar analyses were made using the Shaffer—Somogyi
methodg as modified by R K. Showalter, University of Florida.
RESULTS AND DISCUSSION
Sensory gualities: Tables I and 2 show results of taste panel evaluation of
sweet corn. Asgrow Golden-22 was outstanding for flavor among the first group of
varieties tested (Table I) followed by Golden Security, Sure crop, 27802, and
Sixty pak. However. analysis of variance revealed more flavor difference due to
time periods than to varieties. indicating that the varietal differences were too
small to be consistently observed by the panelists. Color of all the varieties was
( acceptable, as shown by color scores ranging from 8.0 to 9. 0, and the panelists ·
were uniformly agreed on the varieties having the best color. Analysis of variance
on the color scores revealed very highly significant differences for varieties but _
no significant differences for time periods. Sixty pak and 27802 were judged as
having the best color of the varieties included in the trials. Odor scores were
very similar for all varieties. ranging from 8.0 to 8.6 on the 10—point scale.
Asgrow Golden-22 had a significantly higher texture score than the other varieties.
When flavor, color, odor. and texture ratings for all time periods were .
combined and compared, Sixty pak. 27802. and Asgrow Golden—22 were considered
most desirable in sensory aspects.
The second set of experiments included eight varieties (Table 2) and panelists
were asked to rate only flavor. color and texture. omitting odor. There were no .
significant flavor differences among the varieties. but Evertender—C and Gold Cup
had significantly higher color scores than the others.
Combined averages for flavor. color, and texture scores for all time
periods revealed that seven of the eight varieties were within a range of 0.2 on
the l0—point scale. Only Staygold was below the range of the others, owing to its
low color score.
Color; Dominant wavelength purity. and brightness for all the varieties
tested are shown in Tables 3 4 and 5. With storage periods combined, dominant
wavelengths of all varieties included in both experiments were between 573.1 and _
575.1 mu. Although this is ¤""“’ Fivzllly a very short range, the color differences (
were readily distinguished bv the panel. There was no difference in the range of
dominant wavelength for cooked and uncooked sweet corn.
Values for percent purity were between 39. 8 and 48. 8 for cooked and un-
cooked samples in both experiments In general. there was a tendency for samples
of higher purity to be assigned higher <-olor scores. Brightness values were be-
tween 42. 4% and 49. 5% and were significantly different for varieties, both cooked
and uncooked.
Of the three color dimensions measured in the experiments——dominant .
wavelength. percent purity. and brightness--dominant wavelength appeared to be
most closely related to color scores assigned by the panel. Dominant wavelengths
Sl`. .·\. Sli.il't`er and M. Somogyi, "Copper iodometric Reagents for Sugar Determination. " lournal Biol.
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of the uncooked sweet corn were significantly and positively correlated with color (
scores for both sets of corn samples (Figs. l and 2). The three varieties included
in both experiments--Golden Security, 25776, and 27802—··had nearly identical I
dominant wavelengths indicating a high degree of color uniformity between crops.
Among these three varieties. 27802 had the highest dominant wavelength and the E
highest panel color score in both experiments.
Percent purity of cooked and uncooked corn was significantly correlated with
color scores for the second series of experiments (r=. 787 and .777). Brightness
of cooked sweet corn was negatively related to flavor and texture scores.
Pericarp; Analysis of variance revealed significant differences in pericarp
content among the eight sweet corn varieties included in the second experiment.
Gold Cup and Evertender-C were highest in pericarp {Table 6) and had the lowest
overall texture score of the samples tested. Also·—these two varieties received the V
highest color scores of the eight There was a significant positive correlation
(r = .802) between pericarp content and color score. The bright yellow color desired
by the panelists as well as increased pericarp developed with advancing maturity.
The more mature samples however were well within acceptable limits for pericarp
content. Staygold had significantly less pericarp than the other varieties and also V
the lowest color score of the eight. It was noted at the time of processing that Stay-
gold was slightly undermature
Shea; Results of shear press determinations on the second set of sweet
corn varieties are shown in Table 7. Valleygold. the variety with the highest texture (
score, had the lowest shear value The correlation between texture and shear was
significant and negative (r i - 705)
iVloisture_;_ The second set of sweet corn samples. with storage periods
combined, ranged from 74.9 to 82 8 percent moisture (Table 8) . Staygold was
significantly higher in moisture content than the other varieties. No significant ·
variation due to length of storage was found
Sugar Con‘Len_t_ The eight varieties in the second set of samples were analyzed
for total sugar and reducing sugars after one month of frozen storage and again after
7; months (Table 9) There were highly significant differences for total sugar
content among the varieties tested. with Staygold having the highest total sugar ·
(4. 02 percent) and Evertender-C the lowest (2. 67 percent). Differences between the
two storage periods were not significant Reducing sugar content generally followed
the total sugar pattern. ln all varieties the reducing sugars amounted to 20-28 · I
percent of the total sugar ‘
Alcohol In_s_oluble Sohggg Table 9 also shows the alcohol-insoluble solids
(AIS) in sweet corn after 7§ months’ frozen storage. The values ranged from 11.3
percent of the fresh weight (Staygold) to 18. 8 per cent (Gold Cup). The percent AIS was
positively correlated with pericarp measurements (r s .854) and negatively corre-
lated with moisture (r -. 857):ind reducing sugar content (r : -.785). Increased G
pericarp and AIS. together with lower moisture content. are to be expected with
advancing maturity of sweet corn. However. the AIS content was positively corre-
lated (r i .83l) with tot ¤‘ t isie panel score. indicating that none of the varieties were
oy e rm attire .

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DOMINANT WAVELENGTH
Fig. 1. —Correlation between dominant wavelength and taste panel color scores
for 14 varieties of sweet corn.
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