Effects of pectolytic enzymes and antioxidants on the quality of dry wines made from pineapple (Ananas comosus L. Merr) peel

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Food, Agriculture & Environment V
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Science and Technology
Effects of pectolytic enzymes and antioxidants on the quality of dry wines made from
pineapple (Ananas comosus L. Merr) peel
Owen S. Graham, Majeed Mohammed*, Lawrence A. Wilson and Lynda D. Wickham
Department of Food Production, Faculty of Science and Agriculture, The University of the West Indies, St. Augustine,
Trinidad & Tobago, West Indies. *e-mail: mohd2332@hotmail.com or owengraham@yahoo.com
Received 28 December 2003, accepted 15 April 2004.
Abstract
A study was conducted to investigate the effects of pectolytic enzymes and antioxidants on the quality of wines made from the pineapple peel. The
wines produced had alcohol contents ranging from 13.42 to 13.56% which was above the minimum requirement of 9 to 12% for wines. For all four
wines pH maintained the optimum value of 3.50 and all were microbiologically safe as total plate counts were less than 10 cfu ml-1 of wine. The
addition of sodium metabisulphite and ascorbic acid (antioxidants) prevented oxidative browning resulting in the production of lighter coloured wines
but not the clearest. Addition of antioxidants generally slowed the clarification process. The addition of pectolytic enzymes resulted in the production
of the clearest wine of 3.5 NTU with a distinct fruity flavour. Wines treated with pectolase or treated with antioxidants were acceptable while wines
treated with both pectolase and antioxidants and the control were unacceptable. The most preferred wine was that treated with pectolase which
accounted for the highest ratings among taste panelists for colour, clarity, flavour and aroma, while the wine treated with both pectolase and
antioxidants was least preferred. During the second month of ageing all wines were found to be stable as only very negligible changes were detected
in the physicochemical quality attributes which was supported positively by results from protein heat stability tests.
Key words: Pectolase, antioxidants, alcohol, wine, pineapple, Ananas comosus.
Introduction
Pineapple (Ananas comosus L. Merr) is eaten as a fresh fruit and
of wines.
is most acceptable when sweet and moderately acid. It is also
The clarity of wines is a major quality requirement and as such
processed into juice, products in dried forms as candied fruits
potassium or sodium metabisulphite and ascorbic acid are also
and as canned pulp. Beverages, wines, fruits drinks, jams, jellies
added to protect the wine against microbial development and
and sauces are additional uses. While the pulp of the pineapple is
minimize oxidation which can result in the production of hazy
widely utilized commercially, the skin or the peel is generally viewed
wines13, 14, 27. The addition of sulphite just before the bottling of
as waste and as such is usually discarded. Since the peel is rich in
wines thus aids in the clarification process to result in stable
flavour compounds and aroma volatiles and contains a small
colour and clarity throughout storage and shelf-life.
quantity of pulp, a method of utilization was sought hence it was
The objectives of this study were to determine if the peel of the
decided to develop a wine from the peel.
pineapple could be used to develop an acceptable dry wine and
Although grape wine is one of the most popular low-alcohol
to determine the effects of pectolytic enzymes and antioxidants
drink, similar beverages from other fruits have not been as popular.
(specifically sodium metabisulphite and ascorbic acid) on the
However rarely, research investigations have focused both on
quality of wine produced.
the development of wines from other fruits like apples, bananas
and carambolas among others and on improving wine quality23.
Enzymes play a pivotal role in the winemaking process12.
Materials and Methods
Consequently it is of utmost importance to develop an
Ripe pineapple fruits purchased from a local grower were placed
understanding of the nature and behaviour of these enzymes and
in single-ply cardboard boxes and transported to the laboratory
to create the optimal conditions for exploiting beneficial enzymes
in the Department of Food Production at the University of the
while inhibiting those that are detrimental to wine quality 12.
West Indies, St. Augustine. Fruits were sorted and washed with
A major group of beneficial enzymes to the winemaking process
tap water for the removal of extraneous material and dipped for 3
is the pectolytic enzymes or pectolases. Pectolytic enzyme
minutes in 300 µg ml-1, sodium hypochlorite solution to control
preparations have been used for many years in wines and fruit
surface pathogens.
juices mainly to increase juice yield33. Recent research has shown
Preparation of musts: Fruits were peeled manually and peels diced.
that these enzymes have a profound effect on the flavour of
The extract derived from blending 2 kg of peel in 1 litre of water
wines12. The use of pectolytic enzyme preparations can affect
was added to each of twelve 10 litre buckets. Blending was done
sensory quality, since they often contain other enzymes for
using a Waring Commercial laboratory blender (Model 34 BL97,
example, cinnamylesterase, and glucosidase, oxidase thereby
Waring Products Corp, Hartford, CT., U.S.A.). The extract was
causing a negative effect on wine quality18. Nevertheless, several
then pasteurized at 85oC for 10 minutes to reduce the microbial
researchers including Fundira et al.12 have reported that commercial
load31. Pectolytic enzyme at 2.0 g kg-1 was added to the must in 6
enzymes are also marketed for their ability to improve the clarity
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buckets while sodium metabisulphite (100 µg ml-1) was added to
and was expressed as % citric acid procedure # 962.12 as outlined
three of those buckets using the concentration recommended by
in A.O.A.C.1. TSS content was determined on the musts using a
the supplier. Three of the six remaining untreated buckets were
hand-held Leica refractometer with a measuring range of 0-50 oBrix
used as the controls while the other three were each treated with
(Model #10431, Leica Inc. Buffalo, N.Y.). As described by Bradely7
100 µg ml-1 of sodium metabisulphite. There were a total of four
one drop of each must was used. Following these analyses 1.5 kg
treatments each of which was replicated three times. All twelve
of granulated sugar was added to each of the musts to increase
buckets were then covered and left to stand at 26-28oC for 24
the TSS from between 1.5–2.5oBrix to 24oBrix after which citric acid
hours to allow for depectinizing of the musts treated with pectolase
was added to increase the TTA from between 2.7-4.2 g kg-1 to 6.0
(Fig.1).
g kg-1 4. The pH of each of the musts was again measured and then
After 24 hours, samples of the musts were removed from the
the specific gravity determined using a Wine and Beer Hydrometer
buckets, filtered and analysed for clarity, pH, total titratable acidity
(Peter Stevenson Ltd, U.K.). Yeast nutrient at 2.0 g kg-1 was added
(TTA) and total soluble solids (TSS). Clarity was measured using
to each of the buckets as recommended by the supplier. Each of
a HF Scientific Turbidimeter (HF Scientific. Fort Myers, FL., U.S.A.)
the musts was then inoculated with 4 grams of Super Wine Yeasts
and was reported as Nephelometric Turbidity Units (NTU) while
Saccharomyces cerevisiae var. elliipsoideus as recommended by
the pH was determined with an Orion Research digital pH meter
the supplier13, 27.
(EA 920, Orion Research Inc. Boston, MA., U.S.A.) standardized
with two buffer solutions of pH 7.01 and 4.01. TTA was determined
Fermentation: The musts were left in the buckets and placed at
by titration using 0.1 M NaOH and phenolphthalein as an indicator
26-28oC for primary fermentation for 7 days3. At the end of primary
fermentation, the liquid was separated from the solid materials
Ripe Pineapples

Sort & Wash

Peel fruits & dice the peel

Blend

Pasteurise must at 80oC for 10 mins

Addition of sodium metabisulphite (100 g/ml) and pectolase (2 g kg-1) to the must and
incubate must for 24 hours at 26-28oC

Addition of sugar to increase Brix to 24o and adjust acidity to 6 g kg-1 using citric acid

Addition of yeast nutrient (2 g kg-1) and yeast (4 grams)

Primary fermentation for 1 week at 26-28oC

Rack

Secondary fermentation for 3 weeks at 26-28oC

Rack

Addition of 50 g kg-1bentonite suspension and incubation for 1 week

Rack

Addition of sodium metabisulphite (100 g/ml) and ascorbic acid (25 mg/L)

Bottling in 750 ml dark glass bottles and storage/ageing for 2 months
Figure 1. Flow chart of pineapple peel wine production.
136
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using a strainer. The liquid was collected and transferred to
the session and were presented in a random order. The degree of
sterilized demijohns. The demijohns were then immediately fitted
acceptability of the 4 descriptors were rated using a hedonic scale
with air-locks. Samples of the liquid were removed and analysed
of 1 to 9; a score of 1 indicated that a descriptor was disliked
for pH, TTA, TSS, clarity, specific gravity, colour (L*a*b* values)
extremely and a score of 9 indicated that a descriptor was liked
and alcohol content. Colour was determined with a portable
extremely. All descriptors were rated on the same scale. A reference
tristimulus Minolta Chromameter (Model CR-200, Minolta Corp,
standard of a commercial dry wine was also present in the booths
Ramsey, N.J.), the meter was calibrated with a white standard tile
for the judges to use at any time during the sessions. The wine
(Minolta calibration plate CR-A43). The fruits chromaticity was
samples were chilled to 8oC for about 1 hour prior to serving. The
expressed as L,* a*, b* coordinates (CIE, 1976). The “L” colour
temperature of serving is important as tannins are less obvious at
component represented the lightness of colour and it was greater
low temperatures19. The 25-ml samples were presented in random
for lighter colours. The “a” values were negative for green and
order at 22oC+1oC in 30-ml, clear glasses randomly coded with
positive for red while the “b” values were negative for blue and
3-digit numbers. Filtered water was provided for rinsing between
positive for yellow. A 25 ml sample of wine was placed in a glass
wines. All evaluations were conducted under white fluorescent
beaker and readings were taken at the bottom of the beaker with
light in separate booths.
the white standard tile on top of the beaker32. Alcohol content
was determined by the refractive index of the distillate using an
Microbiological analysis: Microbiological analyses were
immersion refractometer (ABBE-60, Bellingham and Stanley, Kent,
conducted on the wines at bottling and at the end of each month
U.K.) as outlined in procedure # 920.581. All the wines were left to
of ageing. Total numbers of aerobic mesophilic viable micro-
ferment for an additional 3 weeks where secondary fermentation
organisms were enumerated as colony forming units per millitre
occurred (Fig. 1), during which physicochemical quality attributes
(cfu ml-1) on plate count agar (Oxoid Limited, Hampshire, UK) as
namely pH, TTA, TSS, clarity, specific gravity, colour and alcohol
was described by Fugelsang11. Plates were prepared in triplicate
content as well as weighing of fermentation bottles were assessed
and incubated at 35oC for 48 hours.
at weekly intervals.
Statistical analysis: The experiment consisted of a completely
Racking and clarification: By the end of the third week after
randomized design with a factorial arrangement of variables. There
secondary fermentation had commenced, the fermentation process
were four treatments with each treatment replicated three times.
was considered to be complete as the weights of the fermentation
Data were subjected to analysis of variance, using Minitab
bottles or demijohns remained constant during the third week12.
statistical software Minitab Release 13.1 (Minitab Inc., PA., U.S.A.)
Additionally the hydrometer readings had fallen to fairly low levels
and the levels of significance determined by the F-test. Comparison
(below 1.000 because of the low density of alcohol) and remained
of the means using the least significant difference (LSD) method
unchanged during the third week4. The racked wines were
was done at the 5% level.
separated from the sediments or lees by siphoning with a length
of clear, sterilized plastic tubing, from the original demijohns into
Results and Discussion
freshly sterilized 4.5 litre demijohns and to each a sieved 50 g
Wines were successfully developed using the peel of pineapple
kg-1 bentonite suspension without lumps was added to stabilize
fruits some of which were found to be highly acceptable by the
the wines against protein haze 3, 4, 6, 10, 18. The wines were then left
taste panelists who rated samples for the quality attributes of
to incubate with the added bentonite for one week, after which
colour, clarity, flavour and aroma (Table 1). These ratings were
they were racked again and physicochemical analyses conducted
supported by several objective measurements which were
(Fig. 1). The four wines treated previously with sodium
conducted with time (Tables 2-6 and Figs 2A-D).
metabisulphite were again treated with 100 µg ml-1 of sodium
metabisulphite in addition to 25 mg l-1 of ascorbic acid4.
Sensory evaluation, clarity and colour: Sensory evaluation of
all four wines showed that the wine treated with pectolase and
Maturation and ageing: The wines were then bottled in 750 ml
that treated with antioxidants were considered to be acceptable
dark brown bottles and aged (stored) for two months at 26-28oC
by the taste panelists in contrast to the wine treated with both
(Fig. 1). Protein heat stability tests were conducted at 2 week
pectolase and antioxidants and the control which were found to
intervals during the period of ageing. This was done by filtering
be unacceptable (Table 1). Quality is a composite response to the
50 ml of each sample and heating for 2 hours in a water bath at
sensory properties of a wine based on the assessor’s expectations
80oC followed by incubation for 2 hours at 4oC. If the difference
and therefore an individual response on the basis of preference
between the NTU values before heating of the wines and after did
and experiences22. Greatest appreciation (P<0.001) was for the wine
not exceed 2 NTU then the wine was considered to be stable21.
treated with pectolase as this wine received the highest ratings
Additionally, physicochemical analyses were conducted at 2 week
for colour (8.00), clarity (8.00), flavour (8.00) and aroma (7.17)
intervals, and sensory evaluation was conducted on the wines at
(Table 1). It was also noted that with this wine, panelists were able
the end of the second month of ageing.
to detect a slight pineapple flavour which was absent from the
Sensory evaluation: Sensory evaluations were conducted on the
other wines. Neubeck21 reported that commercial pectic enzymes
wines using a semi-trained panel of 16 judges, (graduate students
produced wines with a fruitier flavour and bouquet. This was a
and faculty) comprising of 8 males and 8 females between the
major contributing factor to the taste panelists giving this wine
ages of 20 to 45 years of age. Panelists had expressed interest in
the highest rating for flavour. The wine treated with antioxidants
participating and were available. Evaluations took place between
received the second highest ratings for clarity (6.83) and flavour
9.30 am and 10.30 am. The 4 wine samples were assessed during
(6.83) (Table 1). According to Ribereau-Gayon et al. 28 clarity is
one of the leading consumer requirements. It is the consumer’s
Food, Agriculture & Environment, Vol.2 (2), April 2004
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(after 9 weeks) for the wine treated with pectolase and the wine
Table 1. Sensory evaluation of pineapple peel wines treated with
pectolase with or without antioxidants after 13 weeks.
treated with both pectolase and antioxidants, respectively

(Fig. 2A). NTU values also declined from 272 and 322 at the
Treatment Colour Clarity Flavour Aroma
beginning of fermentation to 26.2 and 27.5 at the end of the first
Pectolase 8.00c 8.00c 8.00c 7.17c
month of ageing for the control wine and the wine treated with
Pectolase + Antioxidants 4.50a 4.17a 3.33a 4.00a
antioxidants respectively (Fig. 2A). After the completion of
Antioxidants 6.17b 6.83b 6.83b 6.33bc
Control 6.00b 5.17a 3.67a 5.67b
fermentation and the addition of bentonite to the wines for
LSD(0.05) 1.42 1.15 1.10 1.42
increased clarification, there were major declines in NTU values
zMeans followed by the same letter(s) are not significantly different (P<0.05). Level of significance (P<0.01)
for all the wines except the control, one week later after bottling
Scale used: 1= disliked extremely, 2= disliked very much, 3=disliked moderately, 4= disliked slightly,
5= neither liked or disliked, 6= liked slightly, 7= liked moderately, 8= liked very much, 9= liked extremely.
(Fig. 2A). It is well established that at present bentonite is one of

several additives that are used to stabilize wines against protein
first contact with a wine and is the key element in visual
haze23, 6, 10, 18, 3. The use of bentonite as a clarification agent in
satisfaction. The wine treated with both pectolase and antioxidants
wines is due to its protein adsorption capacity24. During the first
had the lowest ratings across all four quality attributes assessed.
month of ageing the settling of suspended particles in the wines
This wine along with the control did not receive favourable ratings
particularly the wines treated with pectolase and antioxidants aided
for clarity 4.17 and 5.17 respectively and received unacceptable
in clarification and this was supported by objective measurements
flavour ratings of 3.33 and 3.67 respectively (Table 1).
of decreased NTU values. Values for the wine treated with pectolase
The appearance of a wine as judged by clarity and colour is a
and antioxidants decreased from 111 to 28.6 during that period.
major consumer requirement of wine quality28. These authors also
However, beyond the first month of ageing NTU values remained
stated that the presentation of a wine can be adversely affected
unchanged for all wines.
by the presence of particles in suspension which either form a
Reductions in NTU values were indicative of an increase in
haze or remain dispersed throughout the liquid.
clarity as a higher percentage of light was transmitted through the
During fermentation, generally NTU decreased with time
wine samples12. Thus the wine treated with pectolase which was
(P<0.001) for all the wines irrespective of treatments (Fig. 2A).
given the highest rating of 8.00 for clarity by the taste panelists
NTU values declined from 258 and 470 at the beginning of
also had the lowest NTU value of 3.5 (Table 1 and Fig. 2A).
fermentation to 3.5 and 28.6 at the end of the first month of ageing
Throughout the ageing period this wine remained clearer than the
Pectolase
Pectolase+Antioxidants
Antioxidants
Control
500
32
TU)
A
B
450
N
LSD
(
30
(0.05)= 1.2
s
400
LSD(0.05)= 21.6
s
350
28
Unit
y
l
ue
300
a
v 26
bidit
250
L*
Tur
24
200
our
t
r
ic
150
Col 22
lome
100
20
phe
50
Ne
0
18
0
1
3
5
7
9
11
13
0
1
3
5
7
9
11
13
Weeks
Weeks
1.2
3
C
D
1
2.5
LSD(0.05)= 0.3
0.8
0.6
s
es
2
l
ue
0.4
a
v
0.2
1.5
b*
r a* valu
u
0
lo
our
o
1
C -0.2 0
1
3
5
7
9
11
13
Col
-0.4
0.5
-0.6
LSD(0.05)= 0.2
-0.8
0
0
1
3
5
7
9
11
13
Weeks
Weeks
Figure 2. Changes in clarity and colour in pineapple peel wines treated with pectolase with or without
antioxidants measured as nephelometric turbidity units (NTU) and L*a*b* values. Levels of significance
for the treatment x weeks interaction for NTU, L* values and a* values was P<0.001 and P<0.05 for b*
values. Baseline values were not used in the calculation of LSD values.
138
Food, Agriculture & Environment, Vol.2 (2), April 2004

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other 3 wines which were not significantly different from each
on ‘Carlos’ grape juice also found that darker coloured juice had
other in terms of clarity (Fig. 2A). Many researchers including
lower L* values and higher b* values. During the next two weeks
Chatonnet et al. 8; Colagrande et al. 9; Haight and Gump15 and more
(the latter two weeks of the first month of ageing) although there
recently Fundira et al. 12 have reported that commercial enzymes
were increases in b*values for all four wines the wine treated with
have been marketed for their improvement of clarification or the
both pectolase and antioxidants and also that treated with
extraction of colour and aroma. The majority of these being
antioxidants, maintained much lower b* values than the control
pectolytic enzymes that act on the skin by degrading it hence
wine and the wine treated with pectolase (Fig. 2D).
facilitating sedimentation of colloidal particles resulting from the
The addition of antioxidants to the wines thus resulted in the
degradation of pectins. Pectolytic enzymes accelerate the
production of lighter coloured wines (Fig. 2B). At bottling the
breakdown of cell wall tissue thereby improving clarity.
addition of more antioxidants (sodium metabisulphite along with
Sreekantiah33 recommended that the application of enzymes in
ascorbic acid) to the wine previously treated with pectolase and
the clarification of fruit juices and fruit wines aided in the partial or
antioxidants and also the wine treated with antioxidants resulted
complete hydrolysis of suspended starches, proteins and pectins.
in further lightening of their colours during ageing. The production
Also tannins as a source of phenolics which could combine with
of lighter coloured wines suggested that the addition of the
proteins by hydrogen bonds and hydrophobic interactions to
antioxidants prevented oxidation or enzymatic browning of those
induce haze in wines29, 30, 28. It was also noted that during
wines as opposed to the untreated wines which were darker in
fermentation, wines without added antioxidants were cleared of
colour. According to Berry5 to completely stabilize wines, sodium
suspended particles more rapidly than those with added
metabisulphite solution of a concentration of 100 µg ml-1 can be
antioxidants. The addition of antioxidants to the wines therefore
added. The addition of ascorbic acid to wines can aid in the
delayed the clarification process (Fig. 2A).
clarification process by minimizing persistent browning due to
During the first week of fermentation L* and b* values decreased
oxidation25. Koffi et al.16 found that the addition of potassium
significantly (P<0.001) across all four wines in contrast to a* values
metabisulphite (100 mg l-1) was very effective in producing a light
which increased significantly (P<0.001) across all four wines as all
coloured banana juice with stable colour. Palmer24 also reported
the wines became darker in colour (Figs 1B-D). Subsequent to
that enzymatic browning contributed to colour changes in banana
this, during fermentation, only the two wines with added
wines. This was attributed to the presence of dopamine in bananas
antioxidants showed increases in their L* values as they became
which is the primary substrate responsible for enzymatic browning
lighter in colour (Fig. 2B). In contrast L* values decreased for the
by polyphenoloxidase. There were no changes in the b* values
wine treated with pectolase as it continued to darken (Fig. 2B).
for all the wines during the second month of ageing (Fig. 2D).
During this period b* values increased for the wine treated with
During the first two weeks of ageing a* values increased from
pectolase, the wine treated with antioxidants and the control wine
0.7 to 1.0 for the wines with pectolase but declined from 1.1 to 0.7
but decreased for the wine treated with both pectolase and
for the control wine after which a* values remained unchanged
antioxidants (Fig. 2D). However, a* values increased during
for both wines (Fig. 2C). The wine treated with both pectolase and
fermentation for the wine treated with pectolase, and the wine
antioxidants and the wine treated with antioxidants had much
treated with both pectolase and antioxidants, decreased for the
lower a* values than the other two wines as both had major declines
wine treated with antioxidant and remained relatively unchanged
from 0.7 to 0.3 and 0.5 to 0.3 respectively during the first two
for the control wine (Fig. 2C). After the addition of bentonite to
weeks of ageing. Subsequent to this a* values remained
the wines L* values increased (P<0.001) for the wine treated with
unchanged for the wine treated with both pectolase and
pectolase and that treated with both pectolase and antioxidants
antioxidants but declined to 0.0 two weeks later for the wines
(Fig. 2B). However, a* values decreased and increased for the
treated with antioxidants which then remained unchanged
wine treated with antioxidants and the control wine respectively
(Fig. 2C). Although both the control wine and the wine treated
(Fig. 2C). During this period there was an increase in the b* values
with pectolase were much darker in colour than the two wines
for the wine treated with both pectolase and antioxidants and the
with added antioxidants whereas the taste panelists disliked the
wine treated with antioxidants (Fig. 2D). Increases in L* values
colour of the control they found the colour of the wine treated
for two of the wines due to lighter colour was probably due to the
with pectolase very acceptable. This was attributed to the clarity
presence of the bentonite which resulted in the precipitation and
of the latter which was superior to that of the control
settling of previously suspended particles present in the wines.
(Fig. 2A and 2B).
During the two months ageing period, the wine treated with
pectolase had decreases in L* values as it darkened during the
Alcohol content, specific gravity and total soluble solids:
first two weeks of storage after which it remained unchanged but
Generally, there were no differences in the alcohol content of the
L* values remained unchanged for the wine treated with both
wines treated with pectolase when compared to the wines that
pectolase and antioxidants (Fig. 2B). In contrast L* values for the
were not treated with pectolase nor there were differences in the
wine treated with antioxidants and for the control wine increased
alcohol content of the wines treated with antioxidants when
during the first 2 weeks of ageing then remained unchanged
compared to the wines that were not treated with antioxidants
thereafter. There were major increases in b* values across all four
(Table 2). Therefore the presence of pectolase and/or antioxidants
wines during the first 2 weeks of ageing. It became apparent that
had no influence on the alcohol content of the wines. The final
the wine treated with pectolase and the control (wines without
alcohol content of the wines ranged from 13.42 to 13.56%
added antioxidants) were much darker in colour and therefore had
(Table 2) and were classified as table wines, which normally
higher b* values than the other two wines which had added
contains a minimum of 9 to 12% alcohol by volume4, 26. A general
antioxidants (Fig. 2D). Sistrunk and Morris31 in studies conducted
decline in specific gravity and increase in the alcohol content of
all the wines during the fermentation period corresponded with a
Food, Agriculture & Environment, Vol.2 (2), April 2004
139

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major (P<0.001) decrease in the TSS 26. The specific gravity of all
content also had the highest pH of all the wines, a value of 3.10
four wines declined (P<0.01) from an initial value of 1.100 at the
(Fig. 3C). The pH for the other three wines ranged from 2.89 to 2.97
beginning of the fermentation process to a terminal hydrometer
and were considerably lower (P<0.05) than those of the wines
reading of 0.990 three weeks later when fermentation had ceased
treated with pectolase and antioxidants (Fig. 3C). Amerine et al.2
while TSS declined (P<0.01) from an initial value of 240Brix at the
reported that high acidity (pH below 3.00) did not promote yeast
beginning of the fermentation process to between 7.0–7.50Brix
growth but inhibited the growth of undesirable spoilage organisms
four weeks later (Tables 3 and 4). The decline in specific gravity
in wines. This was a likely contributant to the very low total plate
with time was due to the production of alcohol which had a lower
count values obtained during ageing (< 10 cfu ml-1), as three of
density than water, originally present in the must 4 whereas the
the wines had pH values below 3.00. Additionally, the appropriate
major decline in TSS was as a result of alcoholic fermentation of
quantity of acid helps to give a pleasing tang to the flavour of a
sugars by the yeasts26. Major increases in alcohol content during
wine4. Hence, acids play an important role in both the chemical
fermentation was due to increased yeast activity which resulted
and sensory quality of wines. The pH for all of the wines were well
from yeast growth2.
within the optimum pH value for wines of 3.502. Generally the pH
values for the wines were variable throughout this study
Total titratable acidity and pH: The TTA content was similar for
(Fig. 3D). Changes in TSS, alcohol content, colour and specific
all of the wines ranging from 11.0 g kg-1 to 11.3 g kg-1 except for the
gravity were all negligible during the two months of ageing,
wine treated with both pectolase and antioxidants which had a
although TTA and pH values declined during the first month
considerably lower value (P<0.05) of 8.5 g kg-1 (Fig. 3A). The
(Tables 2-4 and Figs 2-3A-D). These results generally indicated
average TTA value for all the wines combined, initially declined
that in terms of quality the wines were stable. This was strongly
from 10.2 g kg-1 at the end of primary fermentation to 9.8 g kg-1 by
supported by the values obtained for differences in turbidity
the end of the second week of secondary fermentation then
which did not exceed 2 NTU during protein heat stability testing
increased to a peak of 11.5 g kg-1 just before ageing. Values then
of the wines during the second month of ageing20.
decreased to 10.6 g kg-1 by the end of the first month of ageing
(Fig. 3B). Declines in TTA content during the first two weeks of
Microbiological analysis: The level of micro-organisms detected
secondary fermentation were likely to be as a result of the
in the wines (total plate count) was consistently less than 10
fermentation of organic acids by the yeast2.
colony forming units per ml (<10 cfu ml-1) across all four wines at
Generally, pH differed across all four wines and the wine treated
bottling and after 1 and 2 months later.
with both pectolase and antioxidants which had the lowest TTA
12
12
A
LSD
LSD
(0.05) = 0.50
(0.05) = 0.50
B
10
11.5
11
8
)
)
-1
-1 g
g 10.5
g k 6
g k
10
TTA (
TTA (
4
9.5
2
9
0
8.5
e
s
s
l
1
3
5
7
9
11
13
ro
ctolas
Cont
Pe
ioxidant
oxidant
+ ant
Anti
olase
Weeks
Pect
Treatments
3.15
3.05
D
C
3.1
3
LSD
3.05
(0.05) = 0.01
LSD(0.05) = 0.01
2.95
3
2.95
pH
pH 2.9
2.9
2.85
2.85
2.8
2.8
2.75
2.75
ts
s
trol
1
3
5
7
9
11
13
tolase
idant
Con
Pec
tioxidan
iox
+ an
Ant
ctolase
Pe
Treatments
Weeks
Figure 3. Changes in total titratable acids content (TTA) and pH of pineapple peel wines treated with pectolase
with or without antioxidants. Levels of significance for the main effects of treatments and weeks were P<0.05 and
P<0.01 for TTA and pH respectively. Baseline values were not used in the calculation of LSD values.
140
Food, Agriculture & Environment, Vol.2 (2), April 2004

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0.990a
0.990a
7.5b
ithout antioxidants.
.42cd 13.42cd 13.42cd
13.42cd 13.56d 13.42cd
0.990a 0.990a 0.990a

13.56d 13.42cd 13.56d
13.22bc 13.42cd 13.42cd
without antioxidants.
0.990a 0.990a
0.990a 0.990a 0.990a
ase with or without antioxidants.
0a 0.990a 0.990a
7.0a 7.0a 7.0a
pectolase with or w
7.5b 7.5b 7.5b
7.0a 7.0a 7.0a 7.0a
7.5b 7.5b 7.5b 7.5b
7 9 11 13
7 9 11 13
7.0a
7 9 11 13
ed with pectolase with or
0.990a 0.990a



ificance (P<0.01)
n
nificance (P<0.01)
7.3ab 7.0a
nificance (P<0.01)
neapple peel wines treated with pectol
e
vel of sig
L
e
vel of sig
e
vel of sig
Brix) of pineapple peel wines treated with
. L
0
different (P<0.05).

different (P<0.05). L
different (P<0.05)
nificantly
nificantly
nificantly
not sig
tal soluble solids (
are not sig
the same letter(s) are
the same letter(s) are not sig
the same letter(s)
Changes in the alcohol content (%) of pi
0.19
Changes in the specific gravity of pineapple peel wines treat
0.002
Changes in the to
0.29
1 2 3 4 5
ent
e 7.0a 7.0a 7.3ab 7.0a 7.0a
ent
1 2 3 4 5
ent
1 2 3 4 5
(0.05)

(0.05)
eeks
(0.05)
eeks
eeks
ectolas

Table 2.


W
Treatm
Pectolase 13.04ab 13.56d 14.39f 13.42cd 13.42cd 13.42cd
Pectolase + Antioxidants 12.88a 13.42c 14.04e 13.42cd 13.42cd 13.22bc 13
Antioxidants 12.88a 14.39f 13.42cd 13.42cd 13.42cd 13.42cd
Control 12.88a 13.42cd 14.22ef 13.42cd 13.22bc 13.42cd
LSD
Means followed by
a
seline value = 0
a
seline value = 24.0
z
B
Means followed by

W
Treatm
P
Pectolase + Antioxidants 7.5b 7.0a 7.5b
Antioxidants 7.5b 7.5b 7.5b 7.5b 7.3ab
Control 7.0a 7.5b 7.3ab 7.5b 7.5b
LSD
Table 3.
W
Treatm
Pectolase 0.998d 0.991ab 0.990a 0.990a 0.990a 0.990a
Pectolase + Antioxidants 0.998d 0.992bc 0.990a 0.990a 0.990a 0.990a
Antioxidants 1.000e 0.992bc 0.990a 0.990a
Control 0.993c 0.990a 0.990a 0.990a 0.990a 0.99
LSD
Means followed by
a
seline value = 1.100

Table 4.
z
B
z
B
Food, Agriculture & Environment, Vol.2 (2), April 2004
141

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Conclusions
11Fugelsang, K.C. 1997. Wine microbiology. New York: Chapman &
Acceptable dry wines of superior quality were produced using
Hall, International Thomson Publishing.
12
the pineapple peel. Therefore wine production can be used for the
Fundira, M., Blom, M., Pretorius, I.S. and Van Rensburg, P. 2002.
utilization of the pineapple peel which is currently viewed as a
Comparison of commercial enzymes for the processing of marula pulp,
wine and spirits. Journal of Food Science 67(6): 2347-2351.
waste and is normally discarded. The wines produced in this
13Garcia, A., Carel, C., Dulah, L., Samson, A., Aguera, E., Agosin, E. and
investigation met the requirements of a table wine in their alcohol
Gunata, Z. 2002. Influence of a mixed culture with Debaromyes vanriji
content of 13.40 to 13.57% which was above the minimum
and Saccharomyces cerevisiae on the volatiles of a muscat wine.
requirement of 9 to 12% alcohol. Two of the four wines produced
Journal of Food Science 67(3): 1139-1143.
were found to be acceptable that is the wine treated with pectolase
14Gutierrez, A. 2002. Sensory descriptive analysis between white wines
and the wine treated with antioxidants while the wine treated with
fermented with oak chips and in barrels. Journal of Food Science
both pectolase and antioxidants and the control were both found
67(6): 2415-2419.
15
to be unacceptable. The most preferred wine was that treated with
Haight, K.G. and Gump, B.H. 1994. The use of macerating enzymes in
pectolase, as it received the highest ratings from the taste panelists
grape juice processing. Am. J. Enol. Vitic 45: 113-116.
16Koffi , K.E., Sims, A.C. and Bates, P.R. 1991. Viscosity reduction and
for colour, clarity, flavour and aroma while the wine treated with
prevention of browning in the preparation of clarified banana juice.
both pectolase and antioxidants was least preferred. The addition
Journal of Food Quality 14: 209-218.
of sodium metabisulphite and ascorbic acid (antioxidants) resulted
17Lao, C., Lopez,-Tamames E., Lamuela-Raventos, R.M., Buxaderas, S.
in the production of lighter coloured wines due to the prevention
and De La Torre-Boronat, M.C. 1997. Pectic enzyme treatment
of oxidative browning, but not the clearest wine. Addition of
effects on quality of white grape musts and wines from A.O.C. Penedés.
antioxidants also delayed the clarification process of the wines.
Journal of Food Science 62: 1142-1149.
The addition of pectolytic enzymes resulted in the production of
18Lubbers, S., Guerreau, J. and Feuillat, M. 1995. Etude de l’ efficacite
the clearest wine, which also had a fruity flavour. The pH of all
deproteinisante de bentonites commerciales sur un mout et des vins
four wines remained well within the optimum pH value for wines
cepages Chardonnay et Souvignon. Bulletin de l’O.I.V. (769-770):
225-244.
of 3.50 and all of the wines were microbiologically safe as total
19Meilgaard, M., Vance, G. and Carr, B.T. 1991. Sensory evaluation
plate count were always less than 10 colony forming units per ml
techniques. Florida: CRC Press. pp. 34-39.
of wine. During the second month of ageing all wines were found
20Moine-Ledoux, V. and Dubourdieu, D. 1999. An invertase fragment
to be stable as only very negligible changes were detected in the
responsible for improving the protein stability of dry white wines.
physicochemical quality attributes assessed and this was further
Journal of the Science of Food and Agriculture 79 (5): 537-543.
supported by results obtained from protein heat stability tests
21Neubeck, C. 1975. Fruits, fruit products and wines. In: Reed, G. (ed.)
conducted.
Enzymes in food processing. New York: Academic Press. pp.
397-438.
Acknowledgements
22Noble, A.C., Williams, A.A. and Langron, S.P. 1988. Descriptive analysis
Appreciation is expressed to Mr. Keshwar John and Ms. Vidya
and quality ratings 1976 wines from four Bordeaux communes. J. Sci.
Bridgebassie, Laboratory Technicians at the Department of Food
Food Agric. 35: 88-98.
23
Production, for their invaluable assistance.
Pachova, V., Ferrando, C., Guell, C. and Lopez, F. 2002. Protein
adsorption onto metal oxide materials in white wine model systems.
Journal of Food Science 67(6): 2119-2121.
24
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