PhD

Studies were conducted at the College of Horticulture, Vellanikkara
to analyse the fruit development pattern in cashew. The changes associated
with growth and development of cashew apple and nut were evaluated.
Storage behaviour of cashew apple was assessed under different conditions
of storage. Cashew apple from different varieties/types were evaluated based
on apple quality characteristics.
Fruit development in cashew was completed in 52 to 60 days after
fruit set. In early varieties like Anakkayam-I and Madakkathra-I fruit
development and ripening of apple was completed in 52 days after set while
in mid and late season varieties the period varied between 55 to 60 days after
fruit set (DAFS). Difference between varieties in terms of apple length,
circumference, fresh weight and dry weight at all stages of growth was
significant. Absolute growth rate in terms of apple length, circumference,
fresh weight and dry weight was also significantly different between stages
of growth. The increase in fresh weight of cashew apple ranged from O.666g
per day in variety Anakkayarn-I to 1. 129g per day in variety Madakkathara-
2 among the varieties studied. Absolute growth rate in terms of apple fresh
weight was maximum during the period between 40 and 60 DAFS stage. The
relative growth rate was maximum between 'Pea' stage and 20 DAFS stage.
Volume of cashew apple showed a marked increase from 35 - 40
DAFS stage onwards. The specific gravity of cashew apple decreased from
1.072-1.14 at the early stages of growth to less than one in the ripe apple.
Apple colour also changed along with ripening. Typical colour of the variety/
type was observed at the fully ripe stage of apple. Flesh firmness also
showed a sharp decrease during ripening phase.


Critical dependence of apple on presence of nut for its growth was observed
till 45 DAFS stage. Removal of nut up to 25 DAFS stage resulted in termination of
apple growth. Increased rate of growth for a short period was observed when nut
was detached after 35 DAFS stage.
Highest rate of growth for cashew nut was observed during the early stages
of growth. Nuts attained maximum size and fresh weight at 30 to 40 DAFS stage.
The Relative Growth Rate (RGR) was maximum during the first fifteen days after
'pea' stage. A second peak in RGR was observed between 41 and 50 DAFS stage.
Kernel formation commenced from 20 DAFS stage and the dry weight increase of
kernel continued throughout the growth period.
Composition of cashew apple changed with maturity. There was an increase
in moisture, total soluble solids (TSS), carbohydrate content and ascorbic acid
content in cashew apple as the maturity advanced Acidity of cashew apple pulp and
pectin content decreased during development. The crude fibre content increased up
to the ripening stage and declined during ripening. The content of phenolic
constituents decreased as the apple ripened.
Peak activity of Polyphenol oxidase (PPO) enzyme was observed at 30
DAFS stage and 50 DAFS stage. The activity of PPO was stable at ambient
temperature.
Rate of respiration of cashew apple at all sta~es of growth was observed to
be very high. The rate of respiration declined as the maturity advanced indicating
non-climacteric behaviour. The rate of release of ethylene also declined during
ripening.
The cashew apple had typical dicot stem anatomy. Presence of lysogenously
formed resin ducts was a characteristic feature. Accumulation of phenolic substances
and starch grains was observed. Formation and expansion of resin ducts had a major
role in the growth of cashew apple.

Ripe cashew apples suffered severe damage by insect and non-insect pests as
well as pathogens. More than 63 per cent of cashew apple collected at ripe stage had
moderate to heavy damage. Cashew apples collected from fallen fruits suffered
heavily due to mechanical damage.
Storage of cashew apple under ambient conditions resulted in of 35 to 100
per cent spoilage by the second day. Storage up to 12-13 days was possible under
refrigerated conditions with 15 to 1 ri: temperature and 85 per cent relative
humidity. Apple collected from fallen fruits could be stored for 6-11 days under
similar conditions. Packing cashew apple in polythene bags with or without
ventilation decreased the storage life. Fungal decay and shrinkage were the main
causes of spoilage of cashew apple.
Pre storage treatments with warm water influenced storage life of cashew
apple under refrigerated conditions. Calcium chloride dip treatment as well as
vacuum impregnation could not improve the storability of cashew apple. Pre storage
treatment with chemicals such as potassium meta-bisulphite, sodium benzoate or
hydrogen peroxide was also not effective. Storage at temperature lesser than 8°C
resulted in chilling injury. Appearance of sunken spots, pitting, water soaked lesions
and discolouration was observed when apples were stored under freezing
temperature.
Twenty-five varieties/types of cashew were evaluated with reference to their
apple quality characters. Significant variation in apple size, weight, juice yield, TSS,
acidity, phenolic substances, ascorbic acid and TSS/acid ratio was observed.
Varieties were grouped into six clusters based on Euclidean distance coefficients.
Varieties H-1593, H-1600, V-4, K-19-1, Madakkathara-2, Dhana, Kanaka and M
2612 had desirable attributes with reference to quality parameters.