Effects of Shorttime Temperature Perturbations on Hydroponically Grown Tomatoes II' Quality of Tomat

1
Effects of Short-time Temperature Perturbations
on Hydroponically Grown TomatoesII. Quality of
Tomato Fruits

• Catalin Moraru1 Arend-Jan Both1
• Tung-Ching Lee1 Thomas Gianfagna1
• David Fleisher2 James Cavazzoni1
• Logan Logendra1 Harry Janes1
• 1 Rutgers, the State University of New Jersey
• 2 USDA-ARS

2
Background

• Food - important ALS component, providing energy,
  nutrients, general wellness as well as improving
  crew morale (Hanford and Ewert,
  2002)
• Tomato second most popular vegetable crop in US
  (Lucier, 1999)
• Selected as candidate crop for NASAs ALS
  Program (Hanford and Ewert, 2002)
• Within ALS, crops are to be grown hydroponically
• Growth conditions within ALS typically tailored
  to optimize edible biomass production
• Not many studies investigated the effects of
  chosen conditions on the crop quality for fresh
  eating or further processing in foods

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Background

• Short-term temperature perturbations were
  described previously as means of controlling
  plant development, influencing growth, yield and
  quality indexes of crops (Sauser, 1998)
• Disturbances can also occur due to malfunctions
  of the equipment or various other reasons
• The effect of such disturbances on the quality of
  crops as food sources is less well documented
• Is it possible to use such disturbances in order
  to improve food quality for ALS-type applications?

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Objective

• Identify the effect of a 14-day temperature
  perturbation applied 10 days after fruit set, on
  the tomato fruit quality.

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Experimental Setup

• Tomato plants of Laura cultivar, grown
  hydroponically
• Plants subjected to above perturbations 10 days
  after fruit set, for 14 days
• 5C day/night temperature perturbation
• HT level 28C day/23C night
• LT level 18C day/13C night
• Control (C) 23C day/18C night

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Experimental Setup

• Fruits harvested at 3 stages
• 2nd replicate of the experiment
• Tomato fruit quality evaluated using physical and
  chemical indexes
• min. 2 replicates/fruit were analyzed
• Statistical analysis to quantify significance of
  results
• performed using Minitab

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Quality Analyses

• Physical
• moisture content (total solids)
• soluble solids
• pH
• Bostwick consistency
• color indexes (CIELAB color space)
• firmness (measured in compression using TA.XT2
  Texture Analyzer)
• Chemical
• titratable acidity,
• lycopene content
• ascorbic acid content (ongoing)

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Difference between growth chambers ?

• Two growth chambers used in parallel for each
  treatment
• Significance of the difference between growth
  chambers quantified using the t test
• Example of analysis

Two-sample T for MC, (B6,LT) chamber_B6 (LT)
N Mean StDev SE Mean 1 6
5.817 0.194 0.079 2 6 5.792
0.244 0.10 Difference mu (1) - mu
(2) Estimate for difference 0.025000 95 CI for
difference (-0.262753, 0.312753) T-Test of
difference 0 (vs not ) T-Value 0.20
P-Value 0.849 DF 9
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Effect of Perturbation Temperature

• Significance of differences between samples grown
  at HT, C or LT quantified using ANOVA and
  Fishers test
• Example of analysis

One-way ANOVA for Soluble Solids Source DF
SS MS F P Temp (B6) 2
1.3854 0.6927 7.31 0.002 Error 32
3.0303 0.0947 Total 34 4.4157 S 0.3077
R-Sq 31.37 R-Sq(adj) 27.09 Fisher 95
Individual Confidence Intervals All Pairwise
Comparisons among Levels of Temp
(B6) Simultaneous confidence level 88.03 Temp
(B6) C subtracted from Temp (B6) Lower
Center Upper -------------------------------
----- HT 0.2035 0.4652 0.7268
(-------------) LT -0.1684
0.0875 0.3434 (-------------)
--------------------
----------------
-0.35 0.00 0.35 0.70 Temp
(B6) HT subtracted from Temp (B6) Lower
Center Upper ------------------------------
------ LT -0.6393 -0.3777 -0.1160
(-------------)
------------------------------------
-0.35 0.00
0.35 0.70
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Results
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Effects on Tomato Quality

• Moisture content
• No significant differences for B and B3 stages
• Significant differences for B6 stage HT samples
  had lower moisture content
• Difference very small
• Soluble solids
• Significant differences at all stages HT samples
  had higher soluble solids content than C or LT
  samples
• Possible reason higher temperature boosts
  physiological changes during fruit set stage
• Of practical importance especially for processing
  tomatoes important quality criterion
• Also important for Earth application pricing
  index

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Effects on Tomato Quality (cont.)

• pH
• Small but significant differences only for B
  stage HT samples had higher pH than C or LT ones
• Difference very small
• Acidity
• Significant differences at B3 and B6 stages HT
  samples more acidic than C or LT samples
• Probably physiological changes boosted by HT
  during fruit set stage
• Of practical importance for ALS
• fresh-eating tomatoes (flavor, taste)
• processing tomatoes (effect on processing methods)

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Effects on Tomato Quality (cont.)

• L color index
• Significant differences at B stage, but not in
  later growth stages
• HT perturbation during fruit set
  probablyaccelerates lightness changes, but while
  ripening lightness differences disappear
• a color index
• Significant at B3 and B6 stages
• Not significant at B stage expectable
  (harvesting decision)
• Confirms that HT perturbation has accelerating
  effects on the physiological transformations
  leading to fruit color
• Important practical significance color is
  important accep-tance criterion for both
  fresh-eating and processing tomatoes

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Effects on Tomato Quality (cont.)

• Lycopene content
• Effect unclear only significant at B3 stage
  HT samples had more lycopene than C or LT ones
• More studies required Arias et al (2000) found
  a correlation between a color index and lycopene
  content
• Lycopene content of large interest for ALS
  antioxidant, other health benefits

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Effects on Tomato Quality (cont.)

• Bostwick consistency
• Informs on the consistency of homogenate flowing
  on an angled plane, due to its own weight
• Clear effect the HT perturbation causes less
  consistent homogenate
• Of interest especially for processing tomatoes
  within ALS lower need to remove moisture for
  achieving products like paste or ketchup
• Firmness
• Quantified as the force required by a spherical
  probe to compress for 5 mm in the tomato
  equatorial area
• Clear effect the HT perturbation causes softer
  fruits
• Of interest especially for processing tomatoes
  better handling
• Results consistent with Bostwick consistency

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General Conclusions

• In general, no significant differences between
  chambers
• data from both chambers pooled together
• HT perturbation yielded
• softer, more reddish tomatoes, with higher
  soluble solids and acidity
• no effects found on the moisture content and pH
• the effect on lycopene content is still unclear

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General Conclusions (cont)

• In most cases, the significant differences were
  between HT and LT and/or HT and C samples
• raising temperature effective, lowering
  temperature not significant
• previous study temperature exerts primary
  control on tomato pH, which is linear with
  thermal time from anthesis of flowers
  (Renquist et al, 2001)
• possible explanation at higher temperatures
  during growth, more assimilates move to fruiting
  clusters at the expense of roots (Yoshioka
  and Takahashi, 1981)
• Practical relevance
• can trigger quality changes by raising
  temperature
• some tolerance to equipment failure

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Acknowledgements