WORK PACKAGE 6

1
WORK PACKAGE 6
2
COATING FORMULATION

• 10 Kaffirin
• Ethanol as solvent
• Plasticiser mixture (111)
• Polyethylene Glycol
• Lactic Acid
• Glycerol
• Relaxation Time 16 hrs

3
OBJECTIVES OF THE STUDY

• To determine the effect of 10 Kaffirin coating

On the sensory acceptability of litchi
On the post-harvest response shelf-life of
litchi over the distribution chain
4
COATING PROCEDURE
Cleaned, freshly harvested litchi
Dipped with stalk in coating for 10 secs
Allowed to air dry for 1 hour
Stalk clipped off and litchi placed on trays or
plastic bag
5
EXPERIMENTAL CONDITIONS

• AMBIENT (25-30 OC, RH 70-77 )
• 13 OC, RH 85
• 4 OC, RH 45
• Packaging was included as trials as UEM, CSIR
  showed that packaging can reduce whitening.

6
PACKING

• Primary objective of Packing was to reduce the
  white deposit on coated litchi
• However Packing
• did not prevent whitening- may decrease it to
  some extent )
• Favoured mould growth and reduced the shelf life
• Gave the impression that the litchis were mouldy
• Thus data for packing was not further processed

7
Day 6, Ambient Temp
Packing favoured mould growth
Day 9, Ambient Temp
8
Day 6, Ambient Temp
9
Day 6, 13oC
10

• In practical terms, coating does not have a major
  effect on pH, TSS, TA

11
Weight loss IV

• Coating does not seem to act as a barrier to
  water loss
• Possible explanations
• No proper film formation on the litchi as
  depicted by white deposit
• Kaffirin coating (as other protein coatings) is
  permeable to water (SIK )

12
RESPIRATION IV

• Litchi, being a non-climacteric fruit, will
  exhibit a decreasing respiration rate
• The coating does not seem to affect the
  respiratory pattern significantly
• Possible explanations
• Kaffirin has very good gas barrier properties
  (SIK study but experience from Pears)
• In litchi, it would seem that a perfect film was
  not formed on the litchi

13
COLOUR I
Litchi Lightness L Redness a Yellowness b Hue angle h
Fresh, uncoated 40 31 21 34
Freshly coated 36 27 19 34
Uncoated, brown, 3 days 38 20 16 40
Coated, brown, 3 days 48 10 11 48
14
COLOUR IV

• Main observations
• Coating significantly changed the colour
  characteristics of the peel
• Darkening of the peel white deposit
• Mechanisms underlying the darkening different
  from browning of uncoated peel

15
MICROBIOLOGY

• Main observations
• Coliforms, TVC, yeasts moulds
• Coating tends to decrease the load for these
  flora
• Lower values recorded for 4C
• Moulds identified Torula, Scopulariosis,
  Cladosporium, Aspergillus, Geotrichum, Rhizopus

16
Properties of ideal coating for litchi

• To reduce water loss
• To maintain red colour and hence slow down
  browning

17
UNDERSTANDING THE MECHANISM I

• Darkening of pericarp (distinct from natural
  browning process)
• Last meeting, one hypothesis was ethanol may have
  killed the pericarp
• Import of litchi from Reunion, Trial with
• water only,
• ethanol only,
• ethanolplasticiser
• Observation
• Combination of ethanol plasticiser brought this
  darkening very early as from day 2

18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
UNDERSTANDING THE MECHANISM II

• WhiteningIn the absence of the protein,
  darkening occurs but no white deposit appears
• One probable explanation for white deposit may be
  some form of precipitation of the protein on the
  peel
• It can have some relationship with RH as in
  packed containers, it is less (as drying occurs,
  water coming out of the peel may cause it)
• Probably, no proper film is formed on the surface
  of the peel, thus it does not act as a barrier
  to gas and water
• Can the rough spikes on the pericarp account for
  failure of film formation?
• Or is it some properties of the litchi pericarp
  that makes the coating incompatible?

25

• Bozdemir and Tutas (2003) studied the barrier
  properties of edible films prepared from
  polysaccharide polymer (locust bean gum) and
  various plasticisers (glycerol, propylene glycol,
  sorbitol, and polyethylene glycol 200) together
  with hydrophobic modifiers (stearopten and
  beeswax). They too observed the presence of a
  white residue and reported that the appearance of
  a white residue on edible films containing
  plasticisers has been referred to as blooming"
  or blushing" -this occurs when the plasticiser
  concentration exceeds its compatibility limit in
  the polymer causing phase separation and physical
  exclusion of the plasticiser. A similar
  phenomenon of blooming can have occurred in this
  study

26

• Consumers preferred uncoated litchi to coated
  litchi

27
APPLICATIONS OF COATINGS TO FRUITS AND
NUTS INTRODUCTION The main aim of the
ENVIROPAK project was to improve the quality of
southern African export fruits and nuts by
extending their shelf-life through application of
edible coatings made from sorghum protein,
kafirin. These coatings can potentially provide
a semi-permeable barrier to gases and water
vapour, thereby reducing respiration rate and
water loss. Studies have therefore been carried
out to determine the effect of selected kafirin
coatings on the post-harvest response and
shelf-life of litchis, pears and cashew
nuts. EXTENDING THE SHELF-LIFE OF EXPORT
QUALITY LITCHIS Daya GoburdhunUniversity of
MauritiusFaculty of AgricultureReduitMauritius
E mail number daya_at_uom.ac.mu From a baseline
study conducted, the major post harvest problems
associated with litchis were identified as rapid
peel (pericarp) browning resulting in a loss of
the favourable red colour as well as water loss.
The effect of a kafirin coating on the
post-harvest response and shelf-life of litchis
stored under conditions simulating domestic,
retail and export conditions were investigated.
28
Immediately after coating, the litchis appeared
red in colour and were glossier than the uncoated
litchis (Figure 1). However, after only one day
of storage, an unacceptable darkening of the
whole peel (pericarp) surface occurred as well as
the formation of a white powdery deposit on the
peel (Figure 2). It was therefore not surprising
that the external colour of the uncoated litchis
were preferred to that of the coated litchis by
the majority of panelists in a consumer sensory
evaluation test.
29
Although the kafirin coating did not affect the
pH, titratable acidity or total solids content of
the litchis during storage, it decreased the
respiration rate of the litchis stored at 4 C.
. Compared with the uncoated litchis, slight
decreases were observed in microbial counts for
the coated litchis in terms of aerobic bacteria,
coliforms and moulds. However, the kafirin
coating did not provide a suitable water vapour
barrier, since the use of the coating did not
reduce water losses