Effect of pre harvest Foliar sprays of Boron and Retain® for improvement of quality parameters of

255 Pages·2012·6.84 MB·English

Effect of Pre harvest Foliar Sprays of Boron and
®
Retain for Improvement of Quality Parameters of
Apricots (Prunus armeniaca L.) in Tasmania

A thesis submitted in fulfillment of the requirement for the degree of
Doctor of Philosophy

University of Tasmania
Australia

By

Bhavisha Mehta

University of Tasmania
November 2012

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Dedicated
To my beloved dad
In acknowledgement of his love, patience
and sacrifice…

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DECLARATION

Declaration of Originality
“This thesis contains no material which has been accepted for a degree or diploma by the
University or any other institution, except by way of background information and duly
acknowledged in the thesis, and to the best of the my knowledge and belief no material
previously published or written by another person except where due acknowledgement is
made in the text of the thesis, nor does the thesis contains any material that infringes
copyright”

Authority of Access
This thesis may be made available for loan. Copying of any part of this thesis is prohibited
for 1.6 years from the date this statement was signed; after that time limited copying and
communication is permitted in accordance with the Copyright Act 1968.

Statement of Ethical Conduct
“The research associated with this thesis abides by the international and Australian codes
on human and animal experimentation, the guidelines by the Australian Government’s
Office of the Gene Technology Regulator and the ruling of the Safety, Ethics and Institutional
Biosafety Committees of the University.”

Bhavisha Mehta
Signature:

Date:

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ABSTRACT

Techniques to improve fruit firmness and quality in apricot would enhance
marketability. Apricot is considered as one of the most delicious temperate fruits, and good
balance of sugars and acids and a strong apricot aroma are the major determinants of
exceptional fruit quality. Studies were conducted in three different varieties of apricot
(Prunus armeniaca L.) namely ‘Rival’, ‘Goldrich’ and ‘Orangered® Bhart’ to determine if pre-
harvest foliar applications of different concentrations of boron and ReTain® influences fruit
quality and fruit yield. Firmness and sugars were of specific concern as fresh apricot has a
very short shelf life of five to six days and transfer of fruit from farm to market within
limited time span is a major concern. Firm fruit with adequate sweetness will allow
Tasmanian orchardist to export more fruit.
The selection of the varieties for the main study was done by screening nine
different varieties based on their maturity periods and availability of maximum samples.
‘Orangered® Bhart’ is an early harvested variety and ‘Rival’ and ‘Goldrich’ are middle
harvested varieties. For this experiment, treatments consisted of four sprays of different
concentration of boron in the form of Solubor (20% boron) followed by two sprays of
Retain®. The pre-harvest foliar sprays were applied to trees exhibiting B deficiency as
follows: (i) applied before full bloom (at green and white bud stage, and when 1-5% of
flowers was at full bloom), (ii) at petal fall stage after flowering (iii) 7 days after petal fall and
(iv) 14 days after petal fall. Trees sprayed with water served as controls. Boron was applied
at 1.2 Kg ha-1, 1.8 kg ha-1, 2.4 kg ha-1 and 3.0 kg ha-1 for all varieties of apricots. ReTain®
application rates were 0.40 kg ha-1, 0.65 kg ha-1 and 1.0 kg ha-1 and was sprayed twice (v) 7
days before harvest (BCCH scale 87) and (vi) 14 days before harvest (BCCH scale 88).
Foliar boron application improved the number of flower clusters by 12-15% in Rival,
2-12% in Goldrich and 4-12% in Orangered® Bhart varieties and the fruit set from 2 - 5% in
Rival, 2- 8% in Goldrich and 2-8% in Orangered® Bhart variety. Thus, the sprayed trees had a
greater potential to be healthy and productive with decrease in fruit drop.
All three varieties are significantly different from each other in terms of quality
parameters. ReTain® eliminated the effects of Boron. ReTain® improved the firmness of
‘Rival’ and ‘Goldrich’ varieties from 10-20% and 6 – 29% respectively with decreases in
sugars from 7 - 20% and 4-12%. The titrable acidity increased with the combined effect of
boron and ReTain ® treatments.
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Boron levels at four different stages of spraying were measured with Induced Couple
Plasma-Optical Emission Spectroscopy (ICP-OES). This was done in order to examine the
absorption of boron in response to the foliar application. The results show increase in boron
absorption of 13-48% in fruits of Goldrich followed by 13-23% in fruits of Orangered® Bhart.
Boron sprays did not affect the Nitrogen (N) and magnesium (Mg) in plant tissues.
Aroma compounds are present in raw foods either as free compounds or
glycosidically bound (aroma precursors).To investigate the difference in volatile constituents
due to the treatment effects, the volatile compounds were investigated by means of SPME
(Solid Phase Micro Extraction) using Carboxen-Polydimethylsiloxane fibers. The free aroma
compounds were identified by Gas Chromatography and Mass Spectroscopy (GC-MS),
finding common compounds such linalool, α-terpineol, β-ionine, γ-decalactone and 26 other
compounds. Fenchone was used as internal standard. The Multivariate analysis showed a
significant effect on the volatiles released from different cultivars. The amount of esters,
lactones and terpenic acids released were more than carbonyl compounds. Though more
than 60 compounds were eluted with SPME, 30 identified volatiles were measured in the
process.
Successful development of new rural industries depends on understanding and
meeting consumer needs. A study was carried out to probe consumer understanding of
apricot fruit quality and their perceptions to sensory attributes. The results were correlated
to instrumental measurements. Three different varieties of apricot with two different
treatments of Boron and Boron + ReTain® making a total set of nine samples were used as
tastings for the consumers. Apricots were harvested at a similar maturity stage according to
commercial practices. Analysis and sensory assessments were carried out on equivalent
fruits from uniform samples.
Despite the variability of response of assessors, significant differences were found
between attributes of different treatments. Consumer preferences for some quality
attributes of flavor, firmness and sugar correlated with instrumental analysis. Even though
Rival is the firmest variety according to instrumental analysis, Orange red sprayed with
ReTain® scored highest for overall satisfaction according to consumer preferences. These
findings indicate that preharvest boron and ReTain® sprays can successfully increase apricot
fruit numbers, flower clusters and fruit quality respectively.
Keyword: Prunus armeniaca L., Boron, ReTain®, Volatiles, SPME, GC-MS, Fruit Quality,
consumer perceptions, fruit quality measurements.

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ACKNOWLEDGEMENTS
Throughout the study for this thesis, I was fortunate to have generous help and significant
support from many people, to whom I am deeply indebted and grateful.
Firstly, I would like to acknowledge the support of University of Tasmania and Tasmanian
Institute of Agriculture (TIA) in providing scholarship, which has enabled me to pursue
studies reported herein.
Secondly, I would like to gratefully acknowledge my principal supervisor, Professor David
McNeil for his invaluable support, expert guidance, sustained inspiration and patient
willingness to read countless drafts of manuscripts. With your magical ability the readability
of my drafts doubled. I would also like to thank my associate supervisor, Professor Robert
Menary for his insight and wealth of experience and knowledge of GC techniques that
helped the study to be rewarding. Specifically I appreciate the training and lessons on HS-
SPME you provided to me. I highly appreciate the scientific suggestions and insightful
feedback from both supervisors during proof reading the thesis chapters, which helped me
to produced quality scientific work.
My sincere thanks to Dr. Richard Doyle and Dr. Duglad Close to guide me during the absence
of my primary supervisor. Thanks to Professor Noel Davies for his expert guidance on
analysis of GC data.
I would like to express sincere gratitude to Dr. Sandra Garland and Dr. Mathew Gregory to
guide me GC techniques and helping me to design the structure of experiment for the study
of volatiles.
I would like to express my gratitude to Dr. Greg Lee and Dr. David Ratnowsky for their
statistical support and answers to my scores of statistical queries. Dr Greg lee gladly shared
his foundation of statistical wisdom, which sharpened my analytical skills.
I would even like to thank Mr Andrew Measham and Ms Angela Richardson for technical
assistance in laboratory experiments and inductions of different instruments throughout the
study and for solving machine oriented problems quickly.
I appreciate the administrative and friendly support of Ms. Jane Bailey and Ms Sally Jones
for their friendly support and guiding me through departmental procedures.
My heartiest thanks to Ms Heather Chong, owner of Qew Orchards who played an
important role as expert Advisor in the present project. Ms Heather generously supported
the project by allocating the experimental plots and willingness to guide me during field
trials. I am also thankful to Dr. Wayne Boucher to provide expert guidance on foliar spray
program for the present studies.
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I want to express my heartiest thanks to all my friends for providing continuous support and
encouragement to complete this thesis.
I am indeed very grateful to my husband Mr. Manish Popli and my family in India for their
patience, love and moral support. Finally, I would like to offer my deep appreciation and
dedicate my work to my beloved father Late Mr. Navinchandra Mehta who is no longer
present except in my heart for igniting the passion to bring my skills and knowledge to life.

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Abbreviation

Name Description
GC-MS Gas chromatorgraphy – mass spectrometry
HS-SPME Head space solid phase micro extraction
FAOSTAT Food and agricultural organization of United Nations
FAO Food and agricultural organization
ABS Australian bureau of statistics
VC Volatile compounds
ACS 1 – aminocyclopropane – 1 carboxylic acid
AVG aminoethoxyvinylglycine
SAM S-adenosyl-L-methionine
1-MCP 1-methylcyclopropane
EPP Effective pollination period
ATP Adenosine triphosphate
MDGC Multi-dimensional gas chromatography
AAPFCO Association of American plant food control officials
ICP-OES Inductively coupled plasma optical emission spectroscopy
BCCH Biologische Bundesanstalt, Bundessortenamt and Chemical
industry
TA Titrable acidity
FID Flame ionization detector
LIR Linear retention indexes
NIST Mass spectral data 2002
FAAS Flame atomic absorption spectrometry
GFAAS Graphite furnace atomic absorption spectrometry
ICP-AES Inductively couples plasma atomic emission spectroscopy
SSC Soluble solids content
TSS Total soluble solids

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INDEX

Declaration………………………………………………………………………………………………………………… III
Abstract……………………………………………………………………………………………………………………… IV
Acknowledgement……………………………………………………………………………………………………... VI
Abbreviation………………………………………………………………………………………………………………. VIII
Index………………………………………………………………………………………………………………………….. IX
List of tables…………………………………………………………………………………………………………….... XIV
List of figures…………………………………………………………………………………………………………….. XVII
List of appendices………………………………………………………………………………………………………. XXI

Chapter 1: General Introduction………………………………………………………………………………….. 1
1.1 Apricot (Prunus armeniaca L.)………………………………………………………………… 1
1.1.1 History of apricot……………………………………………………………………………… 1
1.1.2 Taxonomy and description……………………………………………………………….. 1
1.1.3 Cultivation………………………………………………………………………………………… 2
1.2 Nutritional benefits………………………………………………………………………………… 3
1.2.1 Edible uses………………………………………………………………………………………. 3
1.2.2 Medicinal uses…………………………………………………………………………………. 4
1.2.3 Other uses……………………………………………………………………………………….. 4
1.3 The apricot industry……………………………………………………………………………….. 4
1.3.1 The international apricot market………………………………………………………. 4
1.3.2 The Australian apricot markets…………………………………………………………. 5
1.3.3 Apricot production in Tasmania……………………………………………………….. 6
1.3.4 Market trends………………………………………………………………………………….. 7
1.3.5 Challenges for apricot industry…………………………………………………………. 7
1.3.6 Importance of study…………………………………………………………………………. 8
1.4 Thesis objective………………………………………………………………………………………. 9

Chapter 2: Literature review………………………………………………………………………………………… 12
2.1 Fruit development…………………………………………………………………………………… 12
2.1.1 Growth……………………………………………………………………………………………… 13
2.1.2 Maturation……………………………………………………………………………………….. 13
2.1.2.1 Maturity indices………………………………………………………………………….. 13
2.1.3 Ripening……………………………………………………………………………………………. 14
2.1.3.1 Respiration………………………………………………………………………………….. 15
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2.1.3.2 Ethylene………………………………………………………………………………………. 17
2.1.4 Senescence……………………………………………………………………………………….. 21
2.2 Development of stone fruit…………………………………………………………………….. 22
2.3 Fruit quality…………………………………………………………………………………………….. 25
2.3.1 Appearances…………………………………………………………………………………….. 26
2.3.2 Shape and size………………………………………………………………………………….. 27
2.3.3 Color………………………………………………………………………………………………… 28
2.3.3.1 Color measurements…………………………………………………………………… 29
2.3.4 Firmness…………………………………………………………………………………………… 30
2.3.4.1 Different techniques used to measure firmness………………………….. 31
2.3.5 Defects…………………………………………………………………………………………….. 33
2.3.6 Mouth feel………………………………………………………………………………………… 34
2.3.7 Flavor……………………………………………………………………………………………….. 34
2.3.7.1 Previous studies on apricot flavor……………………………………………….. 37
2.3.8 Nutritional value……………………………………………………………………………….. 41
2.4 Factors influencing fruit quality………………………………………………………………. 42
2.4.1 Pre-harvest factors…………………………………………………………………………… 42
2.4.1.1 Genetic……………………………………………………………………………………….. 42
2.4.1.2 Climatic………………………………………………………………………………………. 43
2.4.1.3 Cultural practices……………………………………………………………………….. 44
2.4.2 Harvesting factors……………………………………………………………………………. 44
2.4.3 Post-harvest factors…………………………………………………………………………. 45
2.4.3.1 Humidity…………………………………………………………………………………….. 45
2.4.3.2 Temperature………………………………………………………………………………. 46
2.4.3.3 Atmospheric gas composition……………………………………………………… 46
2.4.3.4 Light…………………………………………………………………………………………… 46
2.4.3.5 Mechanical injury……………………………………………………………………….. 47
2.5 Mineral nutrition……………………………………………………………………………………. 48
2.5.1 Macronutrients………………………………………………………………………………… 48
2.5.1.1 Nitrogen (N)……………………………………………………………………………….. 49
2.5.1.2 Phosphorous (P)…………………………………………………………………………. 49
2.5.1.3 Potassium (K)……………………………………………………………………………… 50
2.5.1.4 Calcium (Ca)……………………………………………………………………………….. 51
2.5.1.5 Sulphur (S)………………………………………………………………………………….. 52
2.5.1.6 Magnesium (Mg)………………………………………………………………………… 52
2.5.1.7 Silicon (Si)…………………………………………………………………………………… 53
2.5.2 Micronutrients…………………………………………………………………………………. 53
2.6 Selection of pre-foliar sprays of boron and ReTain®……………………………….. 55
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