PHYSICOCHEMICAL, NUTRITIONAL, SENSORY AND MICROBIAL CHARACTERISTICS OF FRESH AND PASTEURIZED PINEAPPLE-CARROT-GINGER BEVERAGE

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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Item Type: Ghanaian Postgraduate Material  |  Attribute: 137 pages  |  Chapters: 1-5
Format: MS Word  |  Price: GH50  |  Delivery: Within 30Mins.
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