Apple juice, acid concentrations

Mycotoxins are toxic secondary metabolites produced by fungi growing within or on foods. They can be a serious threat to human and animal health (Nagler el al., 2001). Table 11.4 details mycotoxins associated with soft drinks and fruit juice manufacture and raw materials. Patulin is the most common mycotoxin associated with fruit juice, particular ly apple juice (Pitt Hocking, 1997). It commonly occurs if juice is produced from stored apples. Mould growth in infected apples increases with time, raising levels of patulin. The use of windfall apples for juice is also a factor. Avoidance of windfall apples, filtration of juice and pressing quickly after harvest are all methods to reduce the incidence of patulin in juice. Patulin can be destroyed by fermentation to cider or by the addition of ascorbic acid (Marth, 1992). Within Europe, the European Union has set a limit of 50 ig/kg for patulin in both apple juice and cider. A recent survey of apple products in Chile found that 28% of samples of juice and concentrate exceeded this limit (Canas Aranda, 1996). 

The presence of fumaric acid in fruit juices can be the result of added synthetic malic acid and it is then considered as an index of adulteration. This is confirmed by analysis of D-malic acid, which is not normally present in malic acid from natural sources. Guidelines of the Association of the Industry of Juices and Nectars from Fruits and Vegetables of the European Economic Community (AIJN) considers 5 mg/kg as the limiting concentration for fumaric acid content in apple juices (Trifiro, Saccani, and Gherardi, 1997). 

The sample that yielded chromatogram A is the sample of apple juice under scrutiny. The peak at retention time 4.9 min is malic acid and the one at 7.2 min is fumaric acid. The malic acid peak should always be present in a given quantity. The concentration in fumaric acid should not be more than 2 ppm, if otherwise, it is indicative of a juice sample that was submitted to some kind of non-approved treatment or that was adulterated. 

Chromatogram E is the sample of apple juice under scrutiny, spiked with 100 ppm of malic acid. The increased concentration of both malic and fumaric acids is due to the presence of these organic acids in the original sample, plus the addition of malic acid contaminated with fumaric acid. The verification of the purity of the standard is very important as contamination will give an erroneous result. Spiking is essential in that it 1) contributes to identify the peak of interest through comparison of retention times, 2) enables the analyst to perform a recovery experiment since the original concentration of the standard is known. From these data, it can be concluded that the sample under scrutiny meet the standards of the authentic apple juice sample. 

The storage of apple juice and juice concentrates results in phenolic degradation. After storage for 9 months at 25°C, apple juice concentrates showed an approximate 36% degradation of hydroxycinnamic acids, 60% degradation of quercetin and phloretin glycosides and total loss of procyanidins. Flavan polymerisation was also detected [181]. 

Apple flavor The sometimes marked differences between aromas of individual varieties of apples are mainly due to quantitative variations in the composition of apple flavor substances. Key components are ethyl (+)-2-methylbutanoate and other esters of 2-methylbutanoic acid, in addition to ethyl and hexyl bu-tanoates, hexyl acetate, (E)-2- and (2)-3-hexenyl acetates (see fruit esters) and j3-damascenone. ( )-2- Hexenal, ( )-2- hexen-l-ol, and hexanal (see alka-nals) play a special role in A. f. These are trace aroma substances in intact apples. When the fruit cells are destroyed, the concentration of the Cg units increase strongly due to enzymatic processes. They are the main aroma components of apple juice. Accordingly, the aromas of fresh apples and apple juice differ markedly. Apricot flavor The typical aroma is due to the combined effects of numerous components with flowery and fruity characters these include linalool, 1-ter-pinen-4-ol, a-terpineol (see p-menthenols), 2-phen-ylethanol, a- and )8- ionones, /5- damascenone, and (Z)-jasmone for the flowery part together with fruit esters and lactones, e. g., 4-octanolide, 4- and 5-deca-nolide, 4-dodecanolide (see alkanolides), hexyl acetate and hexyl butanoate for the fruity part, rounded off by benzaldehyde. 

With this huge amount of concentrations it is possible to detect frauds like the addition of sugar, exhaustive enzymatic treatment (galacturonic acid), addition of citric acid or lemon juice (e.g. in apple juice), extraction of orange peel (phlorin) or the usage unripe Suits (quinic acid in apple juice). 

In the pineapple industry, the fruit hulls are pressed for their juice content and the residue dried for use as a feed supplement. The clarified pineapple mill juice, obtained from pineapple hulls and other waste portions of the fruit, is decolorized after liming and filtration to recover calcium citrate. The demineralized syrup produces a sugar solution which when concentrated may be used as a syrup for sweetening sliced pineapple or as sugar syrup for use in fruit canning operations. Apple juice expressed from peels, cores, and hulls has been deionized to produce bland apple syrup. Ion exchange produced a stable apple syrup from which was removed not only a major portion of the fruit ash but also some of the introduced insecticides. Apple juice, on demineralization and subsequent concentration by evaporation, yields heavy syrup which has fine humectant properties. In apple juice demineralization, the malic acid in the juice was concentrated on an anion-exchange resin [160]. 

Apple polyphenols are present in different parts of the fruit. A major source is the skin, which contains all the flavonols and anthocyanins in addition to an important amount of dihydrochalcones. ° Phenolic acids are present in the flesh whereas most of the dihydrochalcones are in the core and the seeds. This distribution in different parts of the fruit also affects polyphenol concentration of apple juice where only small amounts of quercetin glycosides and dihydrochalcones are present. However, polyphenol content is also affected by the technological procedure. The oxidative conditions and the clarification process during the production of clear apple juice reduces the phenolic content. In contrast, the anaerobic conditions and the lack of a clarification step during cloudy apple juice production prevents an important loss of polyphenols. ... 

The chiral malic acid figures strongly in the original discovery of inversion of configuration in the Sn2 reaction. Malic acid is sometimes called apple acid because of its high concentration in apples, nectarines, and some other fruits. In fact, it was first isolated from apple juice as early as 1785. It functions as a molecular carrier of the carbon dioxide absorbed by plants. The CO2 appears in the CHjCOOH group of malic acid. The principal actor in the early mechanistic work on the S>j2 reaction was Paul Walden, a chemist born in 1863 in what is... 

The media outlined for the cultivation of lactic acid bacteria are the apple juice Rogosa medium (King and Beelman, 1986) and the tomato juice-glucose-fructose-malate medium (Izuagbe et al., 1985). These media use either apple juice or tomato juice serum to provide the so-called tomato juice factor (Section 2.3). Liver extract or concentrate has a number of vitamins that improves bacterial growth and is available from Sigma Chemical Company. Both media can be made selective against Sac-charomyces by the addition of cycloheximide. 

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