CHAPTER 1.0. INTRODUCTION
Recently, the demand for fruit and fruit products in tropical countries is virtually increasing. Statistics show that more and more industrialized countries and developing countries are probing to fresh and processed tropical fruits (Gatchalian & de Leon, 1992). Hence, it is for this reason that the increasing agricultural productivity and rising consumer demands point to the urgency of fruit processing. Beside, being eaten fresh, fruits can be also preserved in various ways and one of them is by processing them into juices.
A fruit juice beverage, as defined by Gatchalian and de Leon (1992), is an apparent or nearly apparent unfermented liquid which is produced from the extraction of the sweet watery sap generally from the ripe fruit. It is classified as non-alcoholic beverages. According to Paul (1975), fruit juices have high acceptability in the market because of their relatively low cost and high nutritional value coupled with modern diet appeal. In the Philippines, consumption of fruit juices has increased considerably from P3 billion (at current prices) in 1993 to about P7.2 billion in 2000, a hefty increase of 137% (Monteclavo et. al., 2005).
As with every food processing operation, it is the primary object of technology to direct most research efforts toward process control and process and product optimization. According to Lazarides et. al. (1999), in addition to usual concerns of process, food processing design has to consider nutrition, sensorial characteristics, product stability,
and consumer safety. The preparation of fruit juices must be able to maintain their natural flavor and aroma characteristics under ordinary storage conditions over prolonged period of time. For fruit juices, the common undesirable problems that fruit processing manufacturers are encountering are fermentation spoilage for canned fruit juices, foodborne illnesses outbreaks, cloudy sedimentation, poor flavor, and browning. Among these problems, browning is regarded as one of the most important problems related to color deterioration in processed fruits.
Browning of fruit juices has two forms, namely, enzymatic browning and nonenzymatic browning. Enzymic browning is a chemical process involving polyphenol oxidase or other enzymes that create melanins, resulting in a brown color. While, nonenzymatic, or oxidative, browning is a chemical process that produces a brown color in foods without the activity of enzymes (www.wikipedia.com, 2008). Between the two, enzymatic browning of fruits and processed fruits creates heavy economic losses for growers.
Several methods can be applied to avoid enzymatic browning, based on inactivating the enzyme (heat) or by removing essential components (most often oxygen) from the product. These methods include blanching, refrigeration, freezing, change in pH, dehydration, irradiation, high pressure treatment, and addition of inhibitors. Among these methods, addition of inhibitors is the recently trend. Large amount of inhibitors are applied in food processing depending on the type of product and process (FAO, 2008).
Recent studies show that one of the most important inhibitors is the glutathione. Glutathione is the most abundant low molecular weight thiol which has a common name of GSH. As an inhibitor, GSH is categorized as reducing agents which main mode of action is the removal of oxygen. According to Naim et. al. (1997), orange juice fortification with glutathione reduced browning and inhibited ascorbic acid degradation during pasteurization. Moreover, glutathione also reduces off flavor generation during storage (Zheng et. al, 2006).
Due to the increase demand of fruit juices, researches continue to develop new formulations to improve the quality of the product. This research study focused on determination of the effect of glutathione in the quality of fruit juices.
1.1. Objectives The main objective of the study was to improve the quality of fruit juice by addition of glutathione. Specifically, it aims to 1. Address the problems associated with fruit juices regarding quality 2. Know the different methods used in the prevention of these problems in the processing of fruit juices 3. Gain information about the feasibility of using glutathione as an inhibitor of enzymatic browning among fruit juices 4. Recognize the biological and health benefits and risks of glutathione
1.2. Significance of the Study The significance of the study is to address problems in fruit juices and to promote processing of fruit juices with improved quality. This would also serve as baseline information on the use of glutathione in fruit juice.
1.3. Scope and Limitations of the Study