Available via license: CC BY 4.0
Content may be subject to copyright.
Food and Nutrition Sciences, 2015, 6, 1371-1380
Published Online November 2015 in SciRes. http://www.scirp.org/journal/fns
http://dx.doi.org/10.4236/fns.2015.615143
How to cite this paper: Treftz, C., Zhang, F. and Omaye, S.T. (2015) Comparison between Hydroponic and Soil-Grown
Strawberries: Sensory Attributes and Correlations with Nutrient Content. Food and Nutrition Sciences, 6, 1371-1380.
http://dx.doi.org/10.4236/fns.2015.615143
Comparison between Hydroponic and
Soil-Grown Strawberries: Sensory Attributes
and Correlations with Nutrient Content
Chenin Treftz, Fannie Zhang, Stanley T. Omaye
Environmental Sciences and Health Graduate Program, Agriculture, Nutrition and Veterinary Sciences
Department, University of Nevada, Reno, USA
Received 25 September 2015; accepted 16 November 2015; published 19 November 2015
Copyright © 2015 by authors and Scientific Research Publishing Inc.
This work is licensed under the Creative Commons Attribution International License (CC BY).
http://creativecommons.org/licenses/by/4.0/
Abstract
Hydroponic growing methods are growing in popularity and seem to have numerous benefits (i.e.,
environmental, increased product yields, year round growing) compared to soil grown crops. Al-
though these advantages are attractive, they do not guarantee a high quality product. Taste is a
driver of consumer acceptance; therefore, sensory analysis of the hydroponic product will be an
important indicator in its success. In this study, we evaluated the sensory differences and prefe-
rences in hydroponically grown and soil-grown strawberries (Fragaria x ananassa) using unspeci-
fied discriminatory and preference analyses, and descriptive testing correlated with nutrition
content data. Most (87%) of participants could identify differences between hydroponically and
soil grown strawberries and 70% preferred the hydroponically grown strawberry (p = 0.06). The
nutrient composition of the strawberries significantly influenced several sensory analysis catego-
ries (sweetness, overall flavor and overall taste (p < 0.05)). The use of sensory studies in relation
to consumer acceptance and nutrient quality will be an important factor to consider for exploring
growing methods and techniques in hydroponic technology.
Keywords
Hydroponic, Sensory Evaluation, Sustainable Foods, Strawberry, Greenhouse
1. Introduction
Consumers are becoming more aware of nutritious and sustainable food options. Soilless grown fruits and vege-
tables have been gaining momentum and have caught the attention of many producers, consumers and scientists
C. Treftz et al.
1372
because of the plethora of benefits offered by soilless growing methods [1]. Hydroponics is one type of soilless
growing method, among others, are aquaponics, aeroponics and fogponics. For soilless products to be successful,
the environmental, nutritional quality and sensory attributes must be equal to or better than soil grown produce.
From an environmental perspective, soilless food production offers increased yields, higher plant survival rates,
decreased water use and decreased pesticide use. From a producer standpoint, these environmental benefits offer
greater profits resulting from increased yields and decreased use of resources (i.e., water, pesticides, labor). Nu-
tritionally, some studies have indicated that soilless growing methods have superior nutritional quality, while
others indicate no significant differences [2]-[4].
Few studies have investigated the sensory comparison between hydroponically grown produce and soil grown
produce. Sensory evaluation can be affected by several factors such as genetic composition, pre-harvest factors
(light, temperature, moisture and wind) and post-harvest factors [5]-[7]. Other influences include price, branding
and the mood of the consumer has been shown to affect the sensory evaluation of a product [8]-[10]. All of these
are important factors to consider when evaluating a hydroponically grown product for sensory attributes. Pre-
vious sensory analyses of hydroponically grown produce have predominately focused on lettuce or tomatoes.
Some of these studies indicate higher ratings for hydroponically grown produce, while others indicate no signif-
icant differences. Little research has focused on sensory evaluation of hydroponically grown strawberries. Straw-
berries are rich in health promoting bioactive compounds and the consumption of them is associated with de-
creased risk for obesity, cardiovascular disease and certain types of cancer [11] [12].
The goal of this study was to evaluate the sensory differences in hydroponically grown and soil grown straw-
berries (Fragaria x ananassa). First, unspecified discriminatory and preference tests were conducted. Then, de-
scriptive evaluation of 13 sensory attributes between the hydroponic and soil grown strawberries were con-
ducted, and determined if an association existed between nutritional composition of the strawberries.
2. Methods
2.1. Growing Conditions
The growing conditions have been described previously [3]. Briefly, soil and hydroponically grown strawberries
were grown at the University of Nevada, Reno (UNR) Experimental Station. During the growing season, the
greenhouse temperature was kept at 70˚F during the day and 60˚F at night. The humidity averaged at 30%. Hy-
droponic and soil strawberries were randomized within the available space in the greenhouse. Soil grown straw-
berries were planted in a 1:1 ratio of Miracle-Gro
®
potting soil (Maryville, OH) and Nevada top soil. The
strawberries were watered by a drip irrigation system three times weekly. General Hydroponics Flora Series
(Sebastopol, CA) was the nutrient solution used for the hydroponic strawberries and nutrient ratios were ad-
justed according to the manufacturer instructions during different stages of plant development. The pH and parts
per million concentration (ppm) of the nutrient for the strawberries was maintained between 6.0 - 6.4 and 400
ppm, respectively. These strawberries were adjusted three times weekly, as needed.
2.2. Harvesting and Sample Preparation
Strawberries were harvested between 7 AM and 8 AM by hand when they reached 100% visual red surface col-
or. The strawberries were placed in a plastic laboratory bag and immediately transported to the UNR sensory
laboratory. UNR sensory evaluation booths were designed according to the American Society of Testing Mate-
rials standards. The sensory evaluation laboratory booths were 34” × 60” × 72” and were designed to ensure
participation privacy during testing. These booths were built with an 11” sliding door serving hatch to serve par-
ticipants.
The strawberries used for sensory evaluation were harvested on the same day they were evaluated by partici-
pants. These strawberries were rinsed with tap water before serving and allowed to dry on a paper towel. Berries
were served at room temperature in two ounce, clear plastic cups coded with a three digit random number. The
average sample size for each portion was bite size, approximately 10 grams.
2.3. Participant Selection
The study was approved by the UNR Institutional Review Board (project number: 583149-1). Participants were
untrained in sensory evaluation and were undergraduate or graduate students at UNR. Participants were re-
C. Treftz et al.
1373
cruited through word of mouth as well as undergraduate nutrition classes and asked to come to the UNR sensory
analysis laboratory to give their preferences on locally grown strawberries.
2.4. Surveys for Sensory Evaluation
Unspecified discriminatory tests, unspecified preference tests, and descriptive tests using 13 descriptive attributes
were used to evaluate the strawberries. The discriminatory test used to determine a difference in the strawberries
was the tetrad test. The students were presented with four samples (two hydroponically grown strawberries and
two soil grown strawberries) and were asked to group the samples into two groups of two based on similarity.
The tetrad test offers advantages compared to other discriminatory tests because it allows for increased statistical
power explained by the Thurstonian theory [13]. The tetrad also has advantages because it decreases effect size
and reduces unexplained variations within the samples, therefore using less panelists and samples [13].
Preference tests were conducted after the discriminatory test was completed. Volunteers participating in the
preference tests were given two coded samples (one hydroponically grown berry and one soil grown berry). The
participants were asked to circle the sample they preferred, or to circle “no preference” if they did not have a
preference between the two samples.
Descriptive analysis was conducted using a 5-point hedonic scale using a “smiley face” which depicted car-
toon faces with smiles to frowns [14]. The cartoon faces were labeled from “very satisfied” to “vey unsatisfied”.
The following attributes were evaluated: overall color, color uniformity, overall appearance, overall aroma,
aroma intensity, amount of sweetness, amount of sourness, fruit juiciness, overall taste, fruit firmness, overall
texture, overall mouthfeel and overall flavor.
3. Statistical Analysis
Data for the tetrad and preference tests were analyzed using IBM SPSS Statistics
®
, version 23.0 (IBM, Armonk,
New York, USA). Data for the correlation analysis was analyzed using SAS
®
, version 9.4 (Cry, N.C., USA).
The tetrad test was analyzed by calculating the test statistic (d’) and used to determine the effect size [15]. A d’
of 1 can be considered as a threshold value for psychophysics [16]. Sample sizes for the tetrad test was calcu-
lated at α-level = 0.05 and power = 0.8 [17]. Preference tests were first evaluated by chi-square analysis and then
by binominal statistics. Descriptive tests were first compared using the independent t-test (p < 0.05) and corre-
lated to existing nutritional data ordered linear regression. Results were adjusted for sex, age, ethnicity, and
fresh strawberry consumption.
4. Results
4.1. Discrimination Test
Sensory evaluation for the discrimination determined if volunteers could detect an overall difference between
hydroponically and soil grown strawberries. Descriptive characteristics for all tests are outlined in Table 1. The
panel included 15 participants, aged 17 - 64 with the majority of volunteers between the ages 17 - 29. Results
indicated, out of 15 participants, 87% completed the questionnaire correctly. By using the Thurstonian theory, a
d’ was calculated at 2.0, and with a threshold of d’ = 1.0, the majority of participants were generally able to dis-
criminate between hydroponically and soil grown strawberries.
4.2. Preference Test
Preference test data results are outlined in Table 2. The chi-square was first used to determine significance in
distributions between prefer hydroponic, prefer soil and no preference (p < 0.05). Zero participants chose the
“no preference” option and binomial statistics were used to determine significance between preference for hy-
droponically grown strawberries and soil grown strawberries. For the strawberries, 70% of participants indicated
that they preferred hydroponically grown strawberries compared to the soil grown strawberries; however, the
preference was not significantly different (p = 0.06).
4.3. Descriptive Test
The results for the descriptive tests between hydroponically and soil grown strawberries are outlined in Table 3.
C. Treftz et al.
1374
Table 1. Demographics of participants participating in the discrimination test,
preference test and descriptive test.
Tetrad Test (N = 15)
Number Percent
Sex
Male 7 47
Female 8 53
Age
17 - 29 7 47
30 - 49 7 46
50 - 64 1 7
65+ 0 0
Fresh Berry Consumption
More than once per day 0
Once a day 0
Two to four times per week 3 20
At least once per week 5 33
Once per month 7 47
Rarely 0
Ethnicity
American Indian 0 0
Asian 4 27
African American 0 0
Hispanic 3 20
White 8 53
Other 0 0
Preference Test (N = 20)
Number Percent
Sex
Male 8 40
Female 12 60
Age
17 - 29 11 55
30 - 49 6 30
50 - 64 2 10
65+ 1 5
Fresh Berry
Consumption
More than once per day 1 5
C. Treftz et al.
1375
Continued
Once a day 0 0
Two to four times per week 3 15
At least once per week 7 35
Once per month 5 25
Rarely 4 20
Ethnicity
American Indian 1 5
Asian 4 20
African American 0 0
Hispanic 2 10
White 13 65
Other 0 0
Descriptive Survey (N = 20)
Number Percent
Sex
Male 9 45
Female 11 55
Age
17 - 29 15 75
30 - 49 3 15
50 - 64 1 5
65+ 1 5
Fresh Berry Consumption
More than once per day 1 5
Once a day 2 10
Two to four times per week 3 15
At least once per week 10 50
Once per month 3 15
Rarely 1 5
Ethnicity
American Indian 0 0
Asian 4 20
African American 1 5
Hispanic 6 30
White 9 45
Other 0 0
C. Treftz et al.
1376
Table 2. Preference test results between hydroponically grown berries and soil grown berries.
Number
Preferred Hydroponically
Grown
Preferred Soil
Grown
Proportion preferred
hydroponic
p
Strawberries 20 14 6 70% 0.06
Table 3. Sensory analysis results of hydroponically compared to soil grown strawberries.
Hydroponically Grown Soil Grown t p
Overall Color 3.7 ± 0.2 3.3 ± 0.2 1.4 0.163
Color Uniformity 3.8 ± 0.2 3.6 ± 0.2 1.2 0.235
Overall Appearance 3.5 ± 0.2 3.4 ± 0.3 0.3 0.758
Overall Aroma 4.6 ± 0.1 3.3 ± 0.2 4.8 <0.001
Aroma Intensity 4.3 ± 0.1 3.1 ± 0.2 4.4 <0.001
Amount of Sweetness 3.7 ± 0.2 3.8 ± 0.2 0.3 0.725
Amount of Sourness 3.7 ± 0.1 3.6 ± 0.2 0.6 0.547
Fruit Juiciness 4.4 ± 0.2 4.0 ± 0.2 1.6 0.100
Overall Taste 3.8 ± 0.2 3.7 ± 0.2 0.2 0.734
Fruit Firmness 3.9 ± 0.2 4.1 ± 0.2 0.6 0.517
Overall Texture 4.2 ± 0.2 4.0 ± 0.2 0.6 0.541
Overall Mouth Feel 3.9 ± 0.2 3.8 ± 0.2 0.6 0.580
Overall Flavor 4.0 ± 0.2 3.6 ± 0.2 1.1 0.194
Means ± standard deviations are based 20 judges’ scores on 5-point hedonic scale (5 = very satisfied, 4 = satisfied, 3 = neutral, 2 = unsatisfied, 1 =
very unsatisfied).
Of the 13 attributes studied, overall aroma and aroma intensity were the only attributes that reached statistical
significance (p < 0.05). Hydroponically grown strawberries showed higher mean ratings for these two categories.
Among the other 11 attributes assessed, nine of the attributes showed higher mean scores for hydroponically
grown strawberries compared to soil grown strawberries. Overall appearance and fruit firmness showed higher
ratings for soil grown strawberries compared to hydroponically grown strawberries; however, results were not
significant.
4.4. Correlation between Sensory Analysis Data and Nutrient
Methods and quantification of nutrient composition of the soil and hydroponically grown strawberries have been
previously reported [3]. Additional nutrient data was collected for matching the correlational analysis. The up-
dated results are reported in Table 4. It was assumed the nutrient data matched the sample for sensory analysis.
For the soil grown strawberries, the correlational analysis indicated no significant association between sourness,
appearance, aroma, color uniformity, fruit firmness, overall mouthfeel, fruit juiciness, or overall texture (Table
5). Significant associations were observed with amount of sweetness and ascorbic acid, α-tocopherol, % mois-
ture and Brix. Aroma intensity and overall color were significantly correlated with ascorbic acid. Overall flavor
was significantly associated with ascorbic acid, α-tocopherol and percent moisture. Overall taste was signifi-
cantly associated with ascorbic acid and α-tocopherol. For the hydroponically grown strawberries, the correla-
tional analysis indicated no significant association between sourness, appearance, aroma, aroma intensity, color,
color uniformity, fruit firmness, fruit juiciness, or overall texture (Table 6). Significant observations were ob-
served with amount of sweetness and moisture content, overall mouthfeel and glucose. Overall taste and α-to-
copherol, percent moisture and fructose were also significantly associated.
C. Treftz et al.
1377
Table 4. Selected nutrients, Brix and % moisture content of soil and hydroponic strawberries (mean ± SD).
Hydroponic Strawberries Soil Strawberries t p
Brix (%) 7.6 ± 0.29 8.5 ± 0.23 1.39 0.17
% moisture 86.9 ± 1.36 88.6 ± 0.61 1.36 0.18
Hydroponic Strawberries Soil Strawberries t p
Ascorbic Acid (mg/100g) 32.32 ± 1.27 18.62 ± 0.92 8.82 <0.0001
α-tocopherol (mg/100g) 1.80 ± 0.12 0.99 ± 0.10 5.11 <0.0001
Total phenolics (mg/100g) 344 ± 6.72 268 ± 2.90 18.76 <0.0001
Hydroponic Strawberries Soil Strawberries t p
Ructose (g/100g) 2.89 ± 0.06 5.10 ± 0.15 14.27 <0.0001
Glucose (g/100g) 1.67 ± 0.03 4.43 ± 0.06 36.92 <0.0001
N = 20 with 3 replicates.
Table 5. Soil grown strawberries sensory ratings vs. nutritional attributes (odds ratio point estimates).
Nutrient Sourness
Pr >
Chi Sq
Overall
appearance
Pr >
Chi Sq
Sweetness
Pr >
Chi Sq
Aroma
Pr >
Chi Sq
Aroma
intensity
Pr >
Chi Sq
Color
Pr >
Chi Sq
Ascorbic
Acid
0.857 0.2744 1.234 0.1356 0.595 0.022 0.801 0.1338 0.677 0.0254 1.996 0.0064
Tocopherol
0.035
**
0.473 0.4978 0.003 0.0101 0.325 0.3268 0.129 0.0999 10.062 0.0704
Total
Phenolics
1.029 0.5545 1.113 0.0568 1.141 0.0612 1.049 0.3443 1.072 0.1719 1.007 0.8806
Moisture 0.871 0.5433 1.138 0.5502 2.293 0.015 0.886 0.5876 1.183 0.4586 1.006 0.9782
Glucose 0.08 0.2906 1.225 0.9253 0.158 0.4468 12.544 0.2807 4.355 0.5131 1.891 0.7723
Fructose 2.547 0.365 3.344 0.2211 0.253 0.1991 1.004 0.9966 0.431 0.3927 0.654 0.6488
Brix 0.942 0.805 1.37 0.203 0.535 0.0408 0.694 0.1572 0.779 0.3024 2.166
**
Nutrient
Color
Uniformity
Pr >
Chi Sq
Overall
flavor
Pr >
Chi Sq
Fruit
firmness
Pr >
Chi Sq
Overall
Mouthfeel
Pr >
Chi Sq
Fruit
Juiciness
Pr >
Chi Sq
Overall
Taste
Pr >
Chi Sq
Texture
Pr >
Chi Sq
Ascorbic
Acid
44.35 0.3999 0.654 0.0476 0.95 0.7197 0.836 0.2193 1.037 0.8092 0.563 0.039 0.915 0.5411
Tocopherol
93.955 0.0681 0.005 0.0107 0.427 0.4599 0.016
**
1.245 0.8608 0.004 0.0138 0.035
**
Total
Phenolics
0.923 0.2922 1.035 0.5305 0.954 0.3499 1.075 0.1867 0.995 0.9279 1.052 0.4484 1.061 0.2758
Moisture 0.831 0.5106 3.006 0.0219 1.434 0.2269 1.286 0.294 0.506 0.0726 1.259 0.3928 1.238 0.3812
Glucose 8.811 0.4019 5.898 0.4825 0.052 0.2169 0.314 0.6197 199.339 0.0894 2.031 0.7813 0.058 0.2606
Fructose <0.001 0.1682 3.945 0.2599 3.951 0.2217 36.503
**
0.406 0.3814 4.477 0.2685 16.444 0.0546
Brix 2.962 0.1754 1.315 0.2964 1.427 0.1746 1.093 0.7161 0.749 0.2918 1.128 1.853 1.107 0.6797
**
Indicates p > 0.05, globe model is not significant.
C. Treftz et al.
1378
Table 6. Soil grown strawberries sensory ratings vs. nutritional attributes (odds ratio point estimates).
Nutrient Sourness
Pr >
Chi Sq
Overall
appearance
Pr >
Chi Sq
Sweetness
Pr >
Chi Sq
Aroma
Pr >
Chi Sq
Aroma
intensity
Pr >
Chi Sq
Color
Pr >
Chi Sq
Ascorbic
Acid
1.06 0.616 0.87 0.1981 0.89 0.3242 1.08 0.6587 0.94 0.5455 0.90 0.293
Tocopherol
8.80 0.1822 0.18 0.2521 0.09 0.125 0.90 0.9566 0.44 0.5824 0.14 0.2146
Total
Phenolics
0.97 0.1794 1.01 0.6031 0.98 0.4775 1.00 0.9027 0.98 0.4405 1.02 0.4413
Moisture 0.62 0.1756 1.82 0.1278 1.93 0.0219 3.68 0.6137 75.84 0.4572 1.21 0.4208
Glucose 43.74 0.5573
*
0.3273 0.19 0.7595
*
0.6764 12.82 0.6889
*
0.2318
Fructose 0.45 0.8136
*
0.069 116.29 0.2195
*
0.539 4.81 0.6459
*
0.3293
Brix 1.12 0.8486 0.48 0.2759 0.14 0.0567 1.58 0.6747
*
0.3557 2.166
**
Nutrient
Color
Uniformity
Pr >
Chi Sq
Overall
flavor
Pr >
Chi Sq
Fruit
firmness
Pr >
Chi Sq
Overall
Mouthfeel
Pr >
Chi Sq
Fruit
Juiciness
Pr >
Chi Sq
Overall
Taste
Pr >
Chi Sq
Texture
Pr >
Chisq
Ascorbic
Acid
0.23 0.1088 0.69
**
1.04 0.6835 0.91 0.3975 0.53 0.0678 0.82 0.0852 0.84 0.1933
Tocopherol
*
0.244
*
0.105 0.50 0.5736 0.08 0.1178
*
0.065 0.01 0.0263 0.12 0.2086
Total
Phenolics
1.00 0.9202 1.30 0.2075 1.01 0.6938 1.03 0.2886 1.04 0.1425 1.03 0.2587 1.03 0.2863
Moisture 17.96 0.097 1.43
**
1.23 0.1577 1.32 0.0925 1.38 0.0562 1.86 0.008 1.20 0.258
Glucose
*
0.1314
*
0.1731
*
0.0554
*
0.0431
*
0.1862 0.01 0.417
*
0.1582
Fructose
*
0.1404
* **
0.02 0.2032 0.85 0.9578
* ** *
0.0254 2.92 0.7727
Brix
*
0.3928 1.54 0.522 2.30 0.2204 1.46 0.5919 0.37 0.163 0.92 0.9065 0.97 0.9605
*
Extreme value, model not well fit;
**
Indicates p > 0.05, globe model is not significant.
5. Discussion
Hydroponic growing methods are growing in popularity and seem to have a positive overtone because of the
numerous environmental benefits of soilless methods compared to soil grown crops [1]. Although there are nu-
merous benefits to the hydroponic system, it does not automatically guarantee a high quality product. As this
technology is advancing, it is important to consider the sensory attributes of the hydroponic product since taste
is one of the main drivers of consumption [18]. Our study indicated 87% of the participants could correctly
identify unspecified differences between hydroponically and soil grown strawberries. Since our participants
were untrained, it can be assumed that consumers, in general, may also be able to identify unspecified differ-
ences. Unspecified preference tests indicated that 70% preferred the hydroponically grown berry compared to
the soil grown berry; however, the results were not significant (p = 0.06). Additionally, the majority of the sen-
sory analysis categories indicated higher ratings for hydroponically grown strawberries, but significance was
reached only with aroma and aroma intensity. Our study sample was limited to students enrolled in classes at
UNR and the majority of study participants were between the ages of 18 - 29 years old. Larger studies from the
general population should be conducted with a random sample to diversify the demographics and make the re-
sults more generalizable.
The correlational analysis showed several significant associations with the amount of sweetness in soil and
hydroponic strawberries. Additionally, significant associations were observed with overall flavor and overall
taste with soil grown strawberries and overall taste with hydroponic strawberries. Although there is a high level
C. Treftz et al.
1379
of variability in consumer acceptance and preference with fruit, it is essential to identify key sensory properties
that drive preference. In the correlational analysis, it appears sweetness, flavor and taste correlated with several
nutrients and sensory ratings. The results indicate the nutritional composition of the berry may influence sensory
scores. With hydroponic food production, it is possible to change parameters in the solution to encourage the
plant development of sugars or bioactive compounds. Identification of nutrition factors driving sensory ratings
may aid in the development in hydroponic produce production. Additionally, researching these factors in future
studies will be important in determining the success of the hydroponic product.
Although this study shows significant findings for nutrient and descriptive sensory data, it is limited with the
use of untrained panelists. Untrained panelists are generally considered to be less accurate than trained panelists
when using descriptive testing, since they are not oriented to the sensory attributes of interest and there will
likely be high variability in the data [19]. However, recent research has suggested this variation might not be as
large as previously thought and indicated untrained panelists may be appropriate for descriptive testing [20].
Additional research should be conducted with trained panelists to confirm the findings of this study.
6. Conclusion
Findings from this study suggest that consumers do not have significant preference between hydroponic and soil
grown strawberries. However, due to the small sample size, further research should be conducted with larger
panels of different demographics to verify findings. With the environmental benefits of hydroponic produce
production combined with the favorable descriptive sensory analysis ratings, it may be desirable to the consumer
and beneficial to the environment to grow strawberry cultivars in non-arable regions to provide fresh fruit.
However, much more research should be done to determine the optimum feasibility as well as methods to im-
prove sensory evaluation scores.
Acknowledgements
We greatly appreciate the Nevada Agricultural Experiment Station, University of Nevada, Reno for the support
of this study. HATCH #0745. The research was done and reported to partially fulfill dissertation requirement of
C. Treftz.
References
[1] Resh, H.M. and Howard, M. (2012) Hydroponic Food Production: A Definitive Guidebook for the Advanced Home
Gardener and the Commercial Hydroponic Grower. St. Bárbara, EUA. http://dx.doi.org/10.1201/b12500
[2] Gruda, N. (2009) Do Soilless Culture Systems Have an Influence on Product Quality of Vegetables ? 147, 141-147.
[3] Treftz, C. and Omaye, S.T. (2015) Nutrient Analysis of Soil and Soilless Strawberries and Raspberries Grown in a
Greenhouse. Food and Nutrition Sciences, 6, 805-815. http://dx.doi.org/10.4236/fns.2015.69084
[4] Buchanan, D.N. and Omaye, S.T. (2013) Comparative Study of Ascorbic Acid and Tocopherol Concentrations in Hy-
droponic- and Soil-Grown Lettuces. Food and Nutrition Sciences, 4, 1047-1053.
http://dx.doi.org/10.4236/fns.2013.410136
[5] Mattheis, J.P. and Fellman, J.K. (1999) Preharvest Factors Influencing Flavor of Fresh Fruit and Vegetables. Post-
harvest Biology and Technology, 15, 227-232. http://dx.doi.org/10.1016/S0925-5214(98)00087-8
[6] Ng, M., Chaya, C. and Hort, J. (2013) The Influence of Sensory and Packaging Cues on Both Liking and Emotional,
Abstract and Functional Conceptualisations. Food Quality and Preference, 29, 146-156.
http://dx.doi.org/10.1016/j.foodqual.2013.03.006
[7] Garruti, S. and Virginia, H. (2010) Sensory Evaluation in Fruit Product Development.
[8] Rao, A.R. (2005) The Quality of Price as a Quality Cue. Journal of Marketing Research, 42, 401-405.
http://dx.doi.org/10.1509/jmkr.2005.42.4.401
[9] Bronnenberg, B.J., Dhar, S.K. and Dubé, J.-P. (2007) Consumer Packaged Goods in the United States: National Brands,
Local Branding. Journal of Marketing Research, 44, 4-13. http://dx.doi.org/10.1509/jmkr.44.1.4
[10] Macht, M. (2008) How Emotions Affect Eating: A Five-Way Model. Appetite, 50, 1-11.
http://dx.doi.org/10.1016/j.appet.2007.07.002
[11] Steinmetz, K.A. and Potter, J.D. (1996) Vegetables, Fruit, and Cancer Prevention: A Review. Journal of the American
Dietetic Association, 96, 1027-1039. http://dx.doi.org/10.1016/S0002-8223(96)00273-8
C. Treftz et al.
1380
[12] Giampieri, F., Tulipani, S., Alvarez-Suarez, J.M., Quiles, J.L., Mezzetti, B. and Battino, M. (2012) The Strawberry:
Composition, Nutritional Quality, and Impact on Human Health. Nutrition, 28, 9-19.
http://dx.doi.org/10.1016/j.nut.2011.08.009
[13] O’Mahony, M. (2013) The Tetrad Test: Looking Back, Looking Forward. Journal of Sensory Studies, 28, 259-263.
http://dx.doi.org/10.1111/joss.12045
[14] Beckley, J.H., Moskowitz, H.R. and Resurreccion, A.V.A. (2006) Sensory and Consumer Research in Food Product
Design and Development. Wiley-Blackwell, Oxford. http://dx.doi.org/10.1002/9780470277706
[15] Meilgaard, M.C., Carr, B.T. and Civille, C.G. (2006) Sensory Evaluation Techniques. 4th Edition, CRC Press, Boca
Raton.
[16] O’Mahony, M. and Rousseau, B. (2003) Discrimination Testing: A Few Ideas, Old and New. Food Quality and Prefe-
rence, 14, 157-164. http://dx.doi.org/10.1016/S0950-3293(02)00109-X
[17] Ennis, J.M. and Jesionka, V. (2011) The Power of Sensory Discrimination Methods Revisited. Journal of Sensory Stu-
dies, 26, 371-382. http://dx.doi.org/10.1111/j.1745-459X.2011.00353.x
[18] Ho, L.C. (2004) The Contribution of Plant Physiology in Glasshouse Tomato Soilless Culture. Acta Horticulturae,
19-25. http://dx.doi.org/10.17660/ActaHortic.2004.648.2
[19] Stone, H. and Sidel, J.L. (2004) Sensory Evaluation Practices. Academic Press, London.
[20] Worch, T., Lê, S. and Punter, P. (2010) How Reliable Are the Consumers? Comparison of Sensory Profiles from Con-
sumers and Experts. Food Quality and Preference, 21, 309-318. http://dx.doi.org/10.1016/j.foodqual.2009.06.001
