preference of south african consumers for the eating quality and appearance of apples

293 Pages·2016·15.62 MB·English

PREFERENCE OF SOUTH AFRICAN CONSUMERS FOR THE
EATING QUALITY AND APPEARANCE OF APPLES
By
Irene Akua Idun
Dissertation presented for the degree of Doctor of Philosophy (Horticultural Science) at the
University of Stellenbosch
Promoter: Prof W.J. Steyn Dept. of Horticultural Science
University of Stellenbosch
South Africa
Co-promoters: Ms M. Muller Dept. of Food Science
University of Stellenbosch
South Africa
Prof K.I. Theron Dept. of Horticultural Science
University of Stellenbosch
South Africa
Prof T. Næs Nofima Mat AS
Ås
Norway
December 2016
Stellenbosch University https://scholar.sun.ac.za
i

DECLARATION
By submitting this dissertation electronically, I declare that the entirety of the work contained
therein is my own, original work, and that I have not previously in its entirety or in part
submitted it for obtaining any qualification.

Signature: Date:

Copyright © 2016 Stellenbosch University
Stellenbosch University https://scholar.sun.ac.za
ii
SUMMARY
Considering that 27% of South Africa’s apple crop is sold locally, we aimed to determine the
attributes that drive South African consumers’ apple eating quality and appearance
preferences. Since a previous study focused on consumers from Stellenbosch in the Western
Cape Province, we focused on consumers from Pretoria in Gauteng Province as well as
consumers from Durban in Kwa-Zulu Natal Province of varying age (18-25, 26+), gender and
socio-economic backgrounds. Consumer preference analysis for apple eating quality and
appearance, and descriptive sensory analysis were performed on nine commercial apple
cultivars selected to obtain large variations in the various eating quality attributes and not
compared to each other per se.
On average, young (18-25) white and Indian consumers were found to prefer firm, sour
cultivars and green peel colour but disliked mealiness and sponginess. Black, older and male
consumers generally preferred sweetness, but disliked sourness. Appearance preferences
were generally consistent with eating quality preferences. Consumers’ actual liking scores
generally also associated with their conceptual preferences, except in the case of unfamiliar
cultivars. Ward’s statistical clustering indicated three consumer clusters with distinct
preferences for both eating quality and appearance. Eating quality clusters 1 and 2 (E1 and
E2) liked sweet taste, tolerated mealiness but disliked sour taste. E1 also associated with
sponginess, but E2 did not. E3 liked sensory attributes relating to firmness, tolerated sour
taste but disliked mealiness and sponginess. E1 and E2 were overrepresented with black and
older (26+) consumers while young white and young Indian consumers were overrepresented
in E3. Compared to international studies, the sweet-liking consumer group seemed to be
larger in South Africa due to the general sweet taste preference of black consumers.
However, since black consumers make up the majority of the total South African population,
firm and sour apples should also be marketed to these consumers. Appearance cluster 1 (A1)
preferred red and green/yellow apples, A2 preferred red and green apples while A3 preferred
green apples.
Ripening-related changes in eating quality attributes and appearance with increasing shelf-life
duration impact significantly on consumer preference. We studied the preferences of different
ethnic and age groups for ‘Golden Delicious’ and ‘Topred’ apples of varying ripeness levels.
Coloured consumers, but older coloured consumers in particular, showed little to no
difference in preference for the eating quality and appearance of riper, softer apples compared
to less ripe, firmer apples. White and black consumers showed a decrease in liking with
Stellenbosch University https://scholar.sun.ac.za
iii

increasing shelf life duration. The shelf-life of apples could possibly be extended in outlets
favoured by coloured consumers. Black consumers do not seem to have a high preference for
riper apples as suggested by the previous Western Cape study. Rather, their high preference
for sweetness results in some tolerance of riper apples. Peel colour did not provide a good
indication of eating quality characteristics. In ‘Topred’, the red overcolour masked yellowing
while in ‘Golden Delicious’, eating quality attributes changed much less than peel colour.
Stellenbosch University https://scholar.sun.ac.za
iv

OPSOMMING
Gegewe dat 27% van Suid-Afrikaanse appels plaaslik verkoop word, het ons die eienskappe
bepaal wat plaaslike verbruikers se eetkwaliteit- en appelvoorkomsvoorkeure dryf. ʼn Vorige
verbruikersvoorkeurstudie is op Stellenbosch in die Wes-Kaap Provinsie onderneem.
Gevolglik het ons gefokus op verbruikers van Pretoria in Gauteng Provinsie asook
verbruikers van Durban in Kwa-Zulu Natal Provinsie. Die verbruikers was van verskillende
ouderdomme (18-25, 26+), geslag en sosio-ekonomiese agtergronde. Analise van
verbruikersvoorkeure vir appel eetkwaliteit en – voorkoms asook beskrywende sensoriese
analise is uitgevoer op nege kommersiële kultivars wat geselekteer is om groot variasie in
eetkwaliteiteienskappe te verkry. Die kultivars is nie opsigself met mekaar vergelyk nie.
Jong (18-25) wit en Indiër verbruikers het oor die algemeen ferm, suur kultivars en
groenskilkleur verkies, maar het ʼn afkeur gehad in melerigheid en sponserigheid. Swart, ouer
en manlike verbruikers het oor die algemeen soetheid verkies en ʼn afkeur gehad in suurheid.
Voorkomsvoorkeure was oor die algemeen in ooreenstemming met eetkwaliteitvoorkeure.
Verbruikers se werklike voorkeure was oor die algemeen ook in ooreenstemming met hul
konseptuele voorkeure, buiten in die geval van onbekende kultivars. Met gebruik van Ward
se statistiese groepering kon ons op grond van voorkeure onderskei tussen drie
verbruikersgroepe vir beide eetkwaliteit en voorkoms. Eetkwaliteitsgroepe 1 en 2 (E1 en E2)
het soet smaak verkies, melerigheid getolereer, maar ʼn afkeer gehad in suur smaak. E1 het
ook met sponserigheid geassosieer. E3 het sensoriese eienskappe wat verband hou met
fermheid verkies, suur smaak getolereer, maar ʼn afkeer gehad in melerigheid en
sponserigheid. Swart en ouer (26+) verbruikers was oorverteenwoordig in E1 en E2 terwyl
jong wit en jong Indiër verbruikers oorverteenwoordig was in E3. Vergeleke met
internasionale studies, lyk dit of Suid-Afrika ʼn groter soet-voorkeur verbruikersgroep het,
waarskynlik vanweë die algemene soetsmaakvoorkeur van swart verbruikers. Tog moet ferm
en suur appels steeds aan swart verbruikers bemark word, gegewe dat hulle die oorgrote
meerderheid uitmaak van die totale Suid-Afrikaanse populasie. Voorkoms groep 1 (V1) het
rooi en groen/geel appels verkies, V2 het rooi en groen appels verkies en V3 het groen appels
verkies.
Rypheid-geassosieerde veranderinge in eetkwaliteiteienskappe en voorkoms het ʼn groot
impak op verbruikersvoorkeur. Ons het die voorkeure van verskillende etniese en
ouderdomsgroepe vir ‘Golden Delicious’ en ‘Topred’ appels van verskillende rypheidsvlakke
bestudeer. Bruin verbruikers, veral ouer bruin verbruikers, het eweveel gehou van die
Stellenbosch University https://scholar.sun.ac.za
v

eetkwaliteit en voorkoms van ryper, sagter appels en minder ryp, fermer appels. Wit en swart
verbruikers het ʼn afname in voorkeur getoon met ʼn toename in rakleeftyd. Die rakleeftyd
van appels sou moontlik verleng kon word in afsetpunte wat merendeel bruin verbruikers
bedien. Anders as wat deur ʼn vorige Wes-Kaap studie gesuggereer is, het swart verbruikers
nie ʼn hoë voorkeur vir ryper appels gehad nie. Dis eerder hul hoë voorkeur vir soetheid wat
lei tot ʼn mate van toleransie vir ryper appels. Skilkleur het nie ʼn goeie aanduiding van
eetkwaliteiteienskappe gegee nie. In ‘Topred’ het die oppervlakkige rooi kleur vergeling
gemaskeer terwyl in ‘Golden Delicious’ eetkwaliteitseienskappe aansienlik minder as
skilkleur verander het.
Stellenbosch University https://scholar.sun.ac.za
vi

ACKNOWLEDGEMENTS
I would like to express my profound gratitude to the following people and institutions for
making this research possible:
My promoter Prof W.J. Steyn for his mentorship, encouragement, guidance, patience and
priceless contribution throughout the course of my studies. Your academic skill and
commitment is exceptional.
My co-promoter Ms M. Muller for her patience and enthusiasm in training and assisting me
in the sensory and consumer science aspects of this research. Your invaluable contribution
towards this research, as well as your kind words of encouragement and motherly care is very
much appreciated.
My co-promoter Prof K.I. Theron for all her assistance in the course of my studies and her
keen interest in my total well-being. Your attention to the fine details of every sentence in the
entire dissertation is treasured.
My co-promoter Prof Tormod Næs for his assistance in solving the difficult statistical
questions in the course of my studies.
Mrs M. van der Rijst of the ARC Biometry Unit for all the hours of data analysis. Your door
was always open to me and you assisted me without reservation. Your kindness meant a lot to
me.
Mrs E.D. Moelich for your guidance and assistance with my trained panel sessions.
The sensory panel, for your dedication, kindness and interest in the success of this research.
Mr John Achilles, as well as colleagues and friends at the sensory research laboratory at the
Department of Food Science for assisting with all my laboratory and sample preparation.
Mr G. Lötze and the technical staff in the Department of Horticultural Science for assisting
me with my physical analyses.
The staff and students of the Department of Food Science, University of Pretoria and
Department Food and Nutrition: Consumer Sciences, Durban University of Technology for
assisting me in every possible way with consumer recruitments and tasting sessions.
Colors Fruit, Valley Parkers Co-op Ltd, Du Toit Agri (Pty) Ltd and Kromco (Pty) Ltd for
providing the apples needed for this research.
The Hope Project of Stellenbosch University for funding this research.
Stellenbosch University https://scholar.sun.ac.za
vii

The Vice-Chancellor and Registrar of Kwame Nkrumah University of Science and
Technology (KNUST) for granting me permission and assistance for my studies.
Colleagues, fellow students, extended family members and friends who encouraged and
supported me in diverse ways.
Thank you very much Kwesi, Maame Konadu and Kofi for your labour of love, firm support
and priceless sacrifice. I appreciate each one of you very much.
Above all, thank you dear Lord for granting me the needed grace to go through this journey.
Your faithfulness never failed and was renewed every morning.
Stellenbosch University https://scholar.sun.ac.za
viii

DEDICATION
This thesis is entirely dedicated to my dear husband and our wonderful children, for the
priceless sacrifice they made, to enable me embark on this journey.
Stellenbosch University https://scholar.sun.ac.za
ix

The language and style used in this dissertation are in accordance with the requirements of
the International Journal of Food Science and Technology. This dissertation presents a
compilation of manuscripts where each chapter is an individual entity and some repetition
between chapters, therefore, has been unavoidable.