ABSTRACT
A beverage was prepared from pineapple, carrot and ginger
juices using Response Surface Methodology to form a refreshing nutritional
drink. Three independent variables were used to prepare the beverage:
pineapple-to-carrot juice ratio (75/25-90/10), fibre size distribution (0.6-1.2
mm) and ginger concentration (2-5%). The effects of the variables were
investigated and represented using quadratic models on pH, total soluble
solids, beta-carotene and sensory attributes as responses. Responses for
independent variables and responses were optimized by setting goals to optimize
the beverage. The optimized beverage was obtained at pineapple-to-carrot juice
ratio, fibre size distribution and ginger concentration of 80/20, 0.6 mm and 3%
respectively. Optimized unpasteurized beverage was prepared and stored at -24,
-10 and 4 oC and quality changes studied every five (5) days for 40
days. Significant decrease in ascorbic acid, beta-carotene, total antioxidant
activity, total soluble solids was observed at the end of storage while total
phenolic content remained almost unchanged. Minimal quality changes occurred in
frozen samples. In another experiment, pasteurized (80 oC, 15 mins)
optimized beverage was treated with 0.1% sodium benzoate and 0.1% citric acid
and stored at 4, 28 and 38 oC and quality changes studied every
15-days for 90 days. Significant decrease in total phenolic, ascorbic acid,
beta-carotene and total antioxidant activity were observed at the end of
storage at rates depending on storage temperature. Frozen storage, therefore,
can help slow the degradation in the quality of fresh unpasteurized beverage,
while storage at low temperature can slow quality degradation in pasteurized
beverage.
CHAPTER ONE
INTRODUCTION
Background to the Study
Pineapple (Ananas comosus, L.
Merill) has long been referred to as one of the most popular non-citrus fruits
in tropical and subtropical regions of the world, largely because of its
attractive flavour and refreshing sugar-acid balance (Bartolomé, Rupérez, &
Fúster, 1996). The pineapple fruit is highly credited for adding important
minerals and bioactive compounds to diet, in addition to having a delicious
taste and refreshing aroma and flavour (Vasco, Ruales, & Kamal-Eldin,
2008).
Global production reached 24.79
million tonnes in 2013 with Costa Rica as the leading producer in the world
with 10.8% of global output followed by Brazil (10%), Philippines (9.9%),
Thailand (8.9%) and Indonesia with 7.4% (FAOSTAT, 2013). According to this
FAOSTAT, Africa’s total pineapple production stood at about 4.383 million
tonnes in 2013, and of these, Ghana contributed about 0.637 million tonnes
which was about 15% of Africa’s total production. Sugarloaf and smooth cayenne
are among the most prominent commercial cultivars (Thanaraj & Terry, 2011).
Sugarloaf cultivar being one of the most commonly cultivated pineapple
varieties is very sweet and is available almost all year round in Ghana, and
its consumption is mainly limited locally, due to constraints in its
shelf-life.
Many of the harvested pineapples
are consumed in fresh form in Ghana and many other developing nations, yet poor
postharvest management limits the shelf-life of the produce to just a few days
after harvest (especially sugarloaf variety), rendering it unsuitable for human
consumption. According to Kitinoja and AlHassan (2010),
pineapple ranks high among the crops that experience a high level of
postharvest losses for small-scale farmers in Sub-Saharan Africa (SSA), only
close to losses experienced by tomatoes, pepper, leafy greens, bananas and
mangoes among others. Figure 1 shows a heap of pineapple fruits on the ground
for sale under scorching sunshine, and this characterizes many situations in
developing nations. It is obvious that the fruits will start to undergo quick
quality deterioration under this condition.
Figure 1: Pineapple fruits for sale in an exposed environment
in the sun
The perishable nature of pineapple fruit makes it difficult
to store and preserve for a long time, especially given the low level of
postharvest management technologies available in many developing nations. This
always leads to a gradual loss of fruit flavour, nutritional quality and market
value, since postharvest loss does not only encompass the physical loss of the
commodity concerned (Kitinoja & AlHassan, 2010). Interventions must,
therefore, be sought to reduce the postharvest losses of the fruit as one of
the main tropical fruit crops.
Juicing has been one of the most commonly used technologies
to process and preserve perishable fruits in order to guarantee regular supply,
even during off-seasons. The manufacture of juices from fruits and vegetables is as old as or older than agriculture (Bates, Morris, &
Crandall, 2001). Juicing pineapple can be one of the ways to manage the
postharvest losses that the fruit undergo. Pineapple juice is consumed and
enjoyed by many people around the world, mainly in single-strength,
reconstituted or concentrated form; in blends for new flavour; and in beverages
as well as other products (De Carvalho, De Castro, & Da Silva, 2008). The
average pineapple contains 81.2 to 86.2% moisture and 13-19% total soluble
solids, of which sucrose, glucose and fructose are the main components (Dull,
1971), making the fruit very suitable for the juicing of a very tasty product.
Fruit juice is important in human nutrition far beyond its
use as a refreshing source of liquid. Many fruits contain a variety of minor
ingredients, particularly vitamins and minerals, as well as carbohydrates,
which are the predominant solid component (Ashurst, 2008), and these become
important component of juices. The health benefit of fruit juices is ascribed,
in part to vitamin C (ascorbic acid), a natural antioxidant which can inhibit
the development of major clinical conditions including cardiovascular diseases
and cancer (Diplock, 1994; Rekha et al., 2012). According to Ashurst, there is
supporting experimental evidence which indicates that ascorbic acid of natural
origin is superior to that of synthetic origin. Many fruit juices are also rich
in phenolic compounds and carotenoids which have antioxidant properties
(Gardner, White, McPhail, & Duthie, 2000).
Pineapple fruit juice is also very rich in natural dietary
fibres, and it is a well-known fact that dietary fibre plays an essential role
in human health, promoting several positive physiological and metabolic effects
(Raninen, Lappi, Mykkänen, & Poutanen, 2011). High consumption of dietary
fibre has been linked to reduced incidence of cardiovascular disease,
diabetes, hypertension, obesity, and gastro-intestinal disorders (Anderson et
al., 2009). Due to these, a tendency in the development of products enriched
with fibre or with specific fibre claims has already been observed for quite some
time now (Selani et al., 2014).
To improve the colour and nutritional composition, pineapple
juice can be blended with carrot juice. Among common fruits and vegetables,
carrots are rich in fibres, carotenoids, vitamins C and E, and phenolics
(Alasalvar, Grigor, Zhang, Quantick, & Shahidi, 2001). Alpha and
beta-carotene are the predominant carotenoids in orange carrots (Arscott &
Tanumihardjo, 2010). Carrot juice is frequently blended in fruit type
concoctions where only the colour and natural sweetness carry over.
Pineapple and carrot juice can form a unique fruit and
vegetable juice drink with characteristic nutritional value and high appeal to
the consumers’ eyes. Many epidemiological studies have shown that a correlation
exists between the consumption of fruits and vegetables and their products and
reduced incidence of chronic diseases (Bazzano et al., 2002; Carter, Gray,
Troughton, Khunti, & Davies, 2010; He et al., 2004; Hung et al., 2004;
Joshipura et al., 1999; Lampe, 1999; Liu et al., 2000; Maynard, Gunnell,
Emmett, Frankel, & Smith, 2003; Rissanen et al., 2003). Also, healthy
dietary behaviours that avoid consumption of artificially-sweetened drinks has
been associated with lower body weight and reduced incidence of obesity in
children (Ludwig, Peterson, & Gortmaker, 2001). Several components with
antioxidant activity are found in pineapple-carrot beverages. These include,
among others, ascorbic acid, tocopherols (vitamin E), phenolic compounds, beta-carotene and flavonoids which can quench the free
radicals responsible for many body disorders.
For improving the taste, aroma, acceptability, palatability,
nutritive value and to reduce bitterness, pineapple–carrot juice can be blended
with spice extracts such as ginger. Ginger is a herbaceous perennial rhizome,
traditionally used in culinary for its flavour and pungency. It is also used as
a carminative, stimulant and for its anti-emetic properties due to gingerols
and shogaols which it contains. According to Wadikar, Nanjappa, Premavalli, and
Bawa (2010), ginger is also useful as an appetizer. Ginger juice extracts can
be used as an additional ingredient to the pineapple-carrot beverage to add to
it improved sensory and nutritional values.
The fruit and vegetables discussed above are highly valued
for their characteristic nutritional, medicinal and refreshing properties, and
ginger juice is also believed to have antibacterial and anti-fungal properties,
implying extended shelf-life for beverages containing its content (Bhardwaj
& Mukherjee, 2011). The blending of the fruit and vegetable juices for the
preparation of a beverage can be a convenient approach and can provide an
economic alternative for the utilization of under-utilized abundant tropical
fruits and vegetables.
Despite juicing being a vital tool to check the postharvest
management of pineapples to provide a refreshing and nutritional drink, the
process alone cannot help retain the original quality of the raw product from
which they came from for longer duration. The development and marketing of
fresh fruit/vegetable juices are limited due to short shelf-life resulting from
the growth of microorganisms (Chia, Shamsudin, Mohd Adzahan, & Wan Daud, 2012; Song et al., 2007). Interventions which can help
maintain the quality of the juice product for a longer duration so that it is
similar in quality to the raw fruit and/or vegetable must be sought.
Refrigeration and frozen storage have been used for centuries
to slow down the quality degradation of stored food products and extend their
shelf-life. Production of fresh and unpasteurized fruit juice products have
also become common due to consumers’ preference for fresh natural product with
intact quality. These products are always marketed in small-scale operation,
and they always have a challenge with their short shelf-life. Even under
refrigeration, fruit juices still have short shelf-life, but it is longer
compared to room temperature storage. Freezing of unpasteurized fruit and
vegetable juices is one of the most common ways of retaining the quality of
these products (Cortés, Esteve, & Frígola, 2008). Several studies have
shown the effects of storing fruit and their extracts at low temperatures, but
few have actually examined these effects at very low temperatures, such as the
temperature of liquid nitrogen (Polinati, Faller, & Fialho, 2010). Frozen
storage of unpasteurized juice products gives a longer and extended shelf-life
than refrigerated storage, providing the producer or marketer an opportunity of
a flexible time schedule for distribution. It has been specified that the most
important nutritional changes in frozen foods are due to storage time (Sahari,
Boostani, & Hamidi, 2004).
To store the juice products for long at room temperature,
juice products are always pasteurized and treated with chemical preservatives.
Pasteurization deactivates microorganism and enzyme activity that are
responsible for degradation reactions. However, the process also destroys
essential nutrients in the product being pasteurized. Degradation in the quality
of pasteurized products will also continue to take place during storage, albeit
at rates dependent on the storage conditions.
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