1.1 Background to the study

Fruits have been a part of human diet over the years. They are also considered as food supplements and are recommended internationally as essential to healthy nutrition, because they contain high quantity and quality of water, sugars, vitamins and minerals (Wardlaw, 2004; Potter and Hotchkiss, 2006). Fruit consumption has been reported to contribute to the prevention of degenerative processes, particularly lowering the incidence and mortality rate of cancer and cardio-cerebro-vascular diseases (Wenkam, 1990; Wardlaw, 2004; Mannay and Shadaksharaswany, 2005). They also contain phytochemicals which act against oxidative reactions in the human body (Vanamala et al., 2006; Okwu and Emenike, 2006). Orange fruits have been reported as a rich source of these phytochemicals such as flavonoids, especially flavanones, which have been shown to posses several physiological properties which can help inhibit cell proliferation and promote cell differentiation (Vanamala et al., 2006; Ndife and Abbo, 2009).

However, due to the perishable nature of fruits and vegetables, high post harvest losses occur immediately after harvest, during distribution and marketing (Mannay and Shadaksharaswany, 2005; Potter and Hotchkiss, 2006), resulting from lack of cold storage facilities on the farms, improper handling and inadequate processing facilities (Alaka et al., 2003; Landon, 2007; Adubofuor et al., 2010). Reports show that the post harvest losses for oranges range between 31-50% (Alaka et al., 2003; Landon, 2007). One of the ways of preserving these fruits and vegetables from deterioration and subsequent loss is to process them into fruit juices (Wenkam, 1990; Vanamala et al., 2006).

During the processing, a large part of the quality characteristics of the fresh fruits under-go remarkable changes which could reduce the nutritional value of the products (Wenkam, 1990; Landon, 2007). Moreover, the fruit juices may be stored for several months in unfavourable conditions beforeconsump-tion, thus leading to undesirable quality changes due to the influence of temperature, time, oxygen content, light exposure and packaging material (Mannay and Shadaksharaswany, 2005; Landon, 2007; Averbeck and Schieberle, 2010). The consumption of fruit juices is popular in Nigeria because of their health and invigorating benefits (Alaka et al., 2003; Okorie et al., 2009). Though some fruit juices are produced locally, most of the fruit juices and drinks found in the market are imported (Dosumu et al., 2009; Okorie et al., 2009). The consumption of fruit juices is popular in Nigeria because of their health and invigorating benefits (Alaka et al., 2003; Okorie et al., 2009). Though some fruit juices are produced locally, most of the fruit juices and drinks found in the market are imported (Dosumu et al., 2009; Okorie et al., 2009).

Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops like oranges, lemons, grapefruit, pomelo and limes.

The most recent research indicates an origin in the Himalayas.(Ibanez,2005). Previous research indicated an origin in the part of Southeast Asia bordered by Northeast India, Burma (Myanmar) and the Yunnan province of China,(UN,2015) and it is in this region that some commercial species such as oranges, mandarins, and lemons originated. Citrus fruit has been cultivated in an ever-widening area since ancient times. It has also been cultivated for the production and consumption of citrus juice.

Fruit juices contain a microflora which is normally present on the surface of fruits during harvest and postharvest processing which include transport, storage, and processin. Many microorganisms such as acid tolerant bacteria and fungi (moulds, yeasts) use them as a substrate for their growth. Yeasts form the main flora of fruits before processing because of acidic pH. The major genera include Candida, Dekkera, Hanseniaspora, Pichia, Saccharomyces, and Zygosaccharomyces. Penicillium, Byssochlamys, Aspergillus, Paecilomyces, Mucor, Cladosporium, Fusarium, Botrytis, Talaromyces, and Neosartorya are filamentous fungi most frequently isolated from fresh fruits and juices. Among bacteria, lactic acid bacteria and acetic acid bacteria have been isolated from fruit juices (ICMSF,2005)

The critical factors affecting the spoilage of juices include juice pH, oxidation reduction potential, water activity, availability of nutrients, presence of antimicrobial compounds, and competing microflora. Among these factors, pH and water activity are the most influential factors affecting the spoilage of juices. The spoilage caused by microorganisms in juices includes cloud loss, development of off-flavours, CO2 production, and changes in colour, texture, and appearance resulting in degradation of product Lawlor,2009; Rubert,2015). The most commonly reported bacterial genera include Acetobacter, Alicyclobacillus, Bacillus, Gluconobacter, Lactobacillus, Leuconostoc, Zymomonas, and Zymobacter. Among yeasts Pichia, Candida, Saccharomyces, and Rhodotorula are commonly encountered genera responsible for spoilage of juices(Bevilacuqua,2011). Certain common moulds such as Penicillium sp., Aspergillus sp., Eurotium, Alternaria, Cladosporium, Paecilomyces, and Botrytis have also been reported in spoilage of fruit juices [ICMSE,2005; Lawlor,2015).

1.2 Statement of Problem

Microorganisms are associated, in a variety of ways with all the food we eat. They may influence the quality availability, and quantity of our food. Naturally occurring foods such as fruits and vegetables normally contain some microorganisms and may be contaminated with additional organisms during handling (Lund, 1971). Food can serve as a medium for the growth of microorganisms and as a result, transmit diseases. Other microorganisms, if allowed to grow in certain food products, produce toxic substances that result in food poisoning when ingested (Pelczar et al., 1993). Different disease problems arise when crops are harvested, because seed, fruit or other storage organs are essentially dormant structures and their cells are physiologically unlike those of growing plant (Daveport, 2013).

Citrus species probably originated in northeastern India in Burma and in the adjoining areas. Early in the spread of citrus, some species crossed into China where the sweet orange, the mandarins and kumquat developed (Hill, 1952; Abayomi, 2004). The lemons, the limes and the grapefruit appear to have developed and spread from India to the Mediterranean region. The ripened fruits are infected easily while the green ones show instance to infection due to the following reasons: green fruits don’t meet the nutritional requirements of the fungus; the enzyme potential necessary for invading green fruits is greater than for ripe ones and is temporarily beyond the capability of the fungus; and some toxins present in the green fruits disappear or become inactive in the ripe ones (Mehrota, 2010).

The principle of spread of fungal infection in Citrus fruits supports that a single infected orange can be the source of infection to other oranges during storage and on transit (Jay, 2003). Soil-infesting fungi and bacteria that cause loss of fleshy tissue typically infect plants at the time of or just before harvesting. Infection may occur, however, during post harvest handling or storage. Common air molds such as Penicillium species may gain entry into the susceptible tissue and cause loss during packaging (Ronald, 1988).

During the period 1970–2004, US per capita consumption of fruits and vegetables increased by 19.9%, to 694.3 pounds per capita per year (ERS, 2007). Fresh fruit and vegetable consumption increased by 25.8 and 32.6%, respectively, and far exceeded the increases observed for processed fruit and vegetable products. If US consumption patterns continue in this direction, total per capita consumption of fresh fruits and vegetables would surpass consumption of processed fruits and vegetables within the next decade(Sperber,2009).

1.3 Objectives of the study

The objectives of the study were to determine;

  1. The effect of storage method on nutritional contents of mixed selected citrus juice
  2. The effect of storage method on sensory attributes of mixed selected citrus juice

Significance of the Study

The study will be of great importance to agriculture scientist, farmers, it will also serve as a veritable source of information to agriculture research students and other stakeholders in the sphere of agriculture.

It will help create awareness to farmers specialized in fruits production on the effect of storage method on fruits quality and it consumption rate.

Scope of Study

The study will aim at finding the effect of different storage facilities on the nutritional contents and sensory attributes of mixed selected citrus juices. Six selected citrus fruits collected from different sources will be used to analyzed the study, namely; Orange, grape, tangerine and lemon, pineapple and lime.