Temperature effect apple juice

Most HPLC applications used for phenolic analysis simply allow the room temperature to determine the operating temperature of the column, but elevated temperatures of between 30°C and 40°C are often applied for phenolics and derivatives in apples (14), carrots (15), apple juice (6,13), bilberry juice (16), and for cis-trans isomers of caffeic and p-coumaric acids in wines (17). Generally, a change in temperature has only a minor effect on band spacing in reversed-phase HPLC and has essentially no effect in normal-phase separations. Thermostatic control of the column temperature is generally recommended to provide reproducible retention. 

When crushed apples are treated with pectolytic enzymes the temperature should not exceed 30°C, as otherwise there is likely to be a change in aroma quality (ester-type components of the apple juice aroma, in particular, may be destroyed). It is recommended that the juice be left for about an hour at this temperature. The minimum temperature of the juice for efficient enzyme use is 10°C, but at this temperature the time for which the juice needs to be left has to be trebled in order to achieve approximately the same effect as at 30°C. The enzyme should be added while in the mill. The yield can be increased by up to 10% by using special enzymes. 

The effect of temperature and concentration on the viscosity of concentrated apple juice can be combined to obtain a single approximate equation that can be used for estimating viscosity as a function of both temperature and concentration (°Brix) ... 

Kadakal and Nas (2002b) used apples, classified by the decay proportion on the fruit surface as sound, 30, 60, or 100% decayed, in the production of apple juice, to determine the effect of apple decay proportion on the patulin content of apple juice. Patulin increased in apple juice samples as the decay proportion increased. Patulin in juice samples produced with apples that were sound, 30, 60, and 100% decayed, were 0-15.9, 47.1-500.3, 156.4-2257.5, and 54.9-2508.6 pg/kg. Similar results have been reported by Jackson et al. (2003). Patulin was not detected in juice pressed from fresh tree-picked apples but was found at levels of 40.2-374 pg/L in juice pressed from fresh ground-harvested (dropped) apples. Another possible source of patulin contamination may be contamination of apple juice with P. expansum. McCallum et al. (2002) observed extensive fungal growth and high patulin levels after inoculation of apple cider with different isolates of P. expansum. Concentrations of 538-1822 pg/ml in apple ciders were associated with incubation at room temperature (25°C), and potentially toxic patulin levels of 75-396 pg/ml also were found in refrigerated ciders (4°C) inoculated with P. expansum. 

Table 2-6 Magnitudes of the Parameters of the Arrhenius Equation for the Effect of Temperature on Concentrated Apple and Grape Juices (Rao et al., 1986)...

Rao et al. (1984) studied the role of concentration and temperature on the viscosity of concentrated depectinized and filtered apple and grape juices. At a constant temperature, the effect of concentration could be well described by an exponential relationship. For example, at 20°C, the effect of concentration ( 41-68 °Brix) on the viscosity of apple concentrates was described by the equation (7 = 0.947) ... 

Pederson, C.S., Albury, M.N., and Christensen, M.D. 1961. The growth of yeasts in grape juice stored at low temperatures. IV. Fungistatic effects of organic acids. Appl. Microbiol. 9, 162-167. 

Heard, G.M. and G.H. Fleet. 1988. The effects of temperature and pH on the growth of yeast species during the fermentation of grape juice./. Appl. Bacteriol. 65 23-28. 

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