Juice content

In most markets fmit juice must be 100% juice and contain no additives. Fmit nectars consist of pulp, juice, sugar, and water, and contain from 25 to 50% juice, depending on the fmit used. In the EEC the minimum juice content is 50% for orange and apple, 40% for apricot, and 25% for passion fmit and guava (26). Other fmit juice drinks include cocktails, which usually contain at least 25% juice and a variety of juice drinks which can contain from 1.5—70% juice (Table 2). 

Commonly, a juice drink contains 10% fruit juice, which usually is a blend of several fruits. The 1990 Federal Nutrition and Labeling Act requites declaration of juice content so that the consumer can make a more informed choice (3). With cocktails and juice drinks, added sugars, acids, flavorings, colorings, and nutrients can be used to provide a wide variety of stable products of uniform quaUty. Because drinks requite less juice than 100% juice products, the drinks can be sold at a lower price. 

Although sugars are found in juices, the high-intensity sweeteners are not. However, they are often used in juice-based drinks or nectars, and here it is important to ensure that there is resolution of the sweeteners of interest from the compounds naturally present in fruit juices. This can be a particular problem in drinks with a high juice content as naturally occurring polyphenolic materials in the juice can disturb the analysis. 

Flowever, if only a simple approach to establish the juice content of a drink is used, such as assessing the levels of nitrogen, phosphorus and potassium, it is easy for an unscrupulous supplier to circumvent this method of assessment by the addition of potassium and ammonium phosphate salts, which enhances the nominal juice content of the product. 

Estimation of orange juice content in soft drinks... 

While our work on the RIA and EIA for limonin was in progress, a research group in Israel (35) reported on an immunoassay for estimating the orange juice content of commercial soft drinks and reconstituted juice. This is of great importance to the citrus industry since adulterated or improperly reconstituted products greatly affect the quality of the product and thus ultimately reflect upon citrus quality control credibility. 

Morgan (81) proposed serine concentration as a possible index of orange juice content. He found serine to be uniformly distributed between the peel, pulp and juice. For orange juices... 

Minerals. Determinations of inorganic constituents (e.g. total ash, alkalinity of the ash) are classical methods for estimating juice content of citrus juices and beverages. Refinements were made to correct for inorganic sulfites, benzoates and phosphates used as adulterants or preservatives (34). 

Automation of a modified version of this assay was recently reported by Vandercook et aK (163). In the automated system, each sample is inoculated with a massive number of cells. The rate of pH change is followed automatically for a standard and the samples. The rate of pH change is proportional to the concentration of orange juice in each sample. Ten samples can be assayed in triplicate in 80 min. Data from 72 retail FCOJ samples compared with a composite sample of authentic orange juice showed an average estimated orange juice content of 97% and standard deviation of 11.5%. 

Experimental data obtained by any of the assay methods must be evaluated by someone. Judgements are commonly based on the experience of the analyst and accumulated laboratory data or published results. The evaluations range from comparison with a simultaneous standard to highly sophisticated statistical equations requiring many calculations. Evaluation of juice content should be considered as an estimate in the context of placing the sample somewhere in the natural population distribution, and the probability of that estimate should be reported. Unfortunately, many literature reports fail to mention or minimize the uncertainty of the estimate. In samples where the presence of foreign substances is proven, one can state with absolute certainty that the juice has been adulterated. 

Most researchers agree that measurements of several constituents give better estimates of juice content than a single parameter. The question of how many and which constituents is open to debate. Furthermore, an optimum statistical treatment of the data has not been agreed upon. 

An elaborate and novel system was devised by Richard and Coursin (168,169,170,171) whereby 19 constituents (minerals, sugars, acids, amino acids) were determined and evaluated by a heirarchial classification approach. By means of a series of inequalities, based on deviations from the mean, a region of authentic juice is defined in a multidimensional space. A series of regression equations between parameters (with R > 0.9) are considered next to verify that the relationships between constituents are normal. Finally, the above information may be combined in a matrix approach to give an estimate of juice content. 

A subgroup of the German Chemical Society (173,174) recently published a system which proposed a means of evaluating the juice content of low-juice beverages. It is based on the concentrations of potassium, phosphorus, proline, formol number, isocitric acid and malic acid. Equations for the juice content of lemonades and orange juices (with possible mixture of tangerine or mandarin juice) based drinks are ... 

The equations were performed on the data obtained from the 416 FC0J samples previously discussed. Qualitatively the absorption and fluorescence spectra did not indicate the presence of orange pulpwash. Therefore, the juices were examples of Case 3, and orange juice content reported as % TCM (equation 7). Statistical analysis of the results showed a mean of 99.6% TCM and standard deviation of 8.5. 

To further verify the equations, 29 unknown samples (4 sets) composed of various combinations of orange juices, and/or pulp-washes and/or product dilutions were prepared by others for analysis. Calculated values were correlated with actual values and gave the following coefficients of determination orange juice content r2 = 0.942 pulpwash content r2 = 0.981 and dilution r2 = 0.937. Even with significant coefficients of determination, it must be stressed that the equations provide only approximations of sample formulations. The constants used in the equations were based on results obtained from commercial Florida... 

Ester production is susceptible to variations in nutrient and fermentation conditions however, acetates and ethyl esters do not always vary in the same way, reflecting their different metabolic pathways. Variations in juice contents of sugar, oxygen, lipids, and assimilable nitrogen, juice turbidity and fermentation temperature are important factors, as observed under brewing conditions (Verstrepen et al. 2003a). 

The taste of these products is usually clean but flat and less aromatic than normal juice. A result of the higher pectin content, pulp wash products usually have an extremely good turbidity and cloud stability which makes them well suited for the production of drinks with low juice content. 

Soft Drinks Based on High Juice Content... 

High juice content is defined by a content of more than 20% by weight in the final drink. In this category, the turbidity derives from a stable colloidal dispersion of fruit cells. Stability and quality of the final drink are mainly based on the quality of fruit juice concentrates formulated into the product. Additional stabilisers, mainly hydrocolloids, might be added. 

Low juice content is defined by a content of 1 to 20% by weight of juice in the final drink. These products are mainly based on citrus juices. As mentioned before, citms juices provide good turbidity and stability even with low juice content. In combination with special raw materials made from citrus, like cloudy concentrates or peel oils, very stable low-juice drinks can be obtained. Turbidity comes from a complex mixture of dispersions of fruit cells and oil-in-water emulsions, stabilised by fruit pulp particles and hydrocolloid stabilisers, such as locust bean gum [9]. 

Example Formula for Premium Cherry Juice Liqueur (25% v/v)- Juice Content 40%... 

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