The pectase activity of apples

Abstract

knowledge the control of ventilation is largely empirical, and although this may be satisfactory for certain shapes and sizes of stock of which experience exists, the more general application of this method of control depends upon a detailed study of the subject. Fig. 6 resembles Fig. 5 in lay-out but refers instead to a 2-m. column of bag material impregnated with palm-kernel fat. A general comparison of the two Figures shows that the shorter column of bag material has a heating tendency of the same order as that of the longer column of kernels. This reflects the greater reactivity toward oxygen of the bag material.A study has been made of the pectin-demethylating enzyme system in apple tissue and the level of activity compared with that in some other fruits. The apple varieties tested show considerable differences in their pectase content, The enzyme shows a maximum activity a t pH 0.6 : over the pH range of the fruit the activity is much lower, but the enzyme can still produce appreciable effects. Methods for the extraction and concentration of the enzyme are described. The concentrated enzyme preparations are readily inactivated by normal pasteurizing temperatures (68-70" c.), but in juices the enzyme shows a much greater stability. The significance of these findings is discussed in relation to the production of apple juice and pectin.

Partial characterization of the in situ activity of pectinesterase in Bramley apple

“…These authors also found PE activity extended over a broader pH range, especially to more acidic pH, i.e. pH 4.5 (Pollard & Kieser, 1951;Lee & Wiley, 1970). However, these workers used an extracted PE preparation, i.e.…”

“…3), above which there was a rapid drop in activity to inactivation at 70°C for sample A, 80°C for sample C and 90°C for sample B. Pollard & Kieser (1951) found a much more rapid drop in activity, to below 10% after 1 min, in a purified enzyme preparation heated at 68°C and over a pH range 3.5-6.0. However, when apple juice was heated under the same conditions the heat stability of PE was greatly enhanced, with juice from Laxton's Superb retaining over 80% and Blenheim Orange nearly 60% of the initial PE activity after 20min.…”

“…The optimum pH is considerably higher than those reported in the literature of 6.6 for var. Worcester Permain (Pollard & Kieser, 1951), 6.5-7.5 for var. Golden Delicious (Lee & Wiley, 1970) and 7.3 for var.…”

“…The level of PE activity is reported to be very low in Bramley apples. Pollard & Kieser (1951) found a ratio of 1:200:5800:24000 for PE activity in Bramley apples, Cox's orange pippin, oranges and tomatoes, respectively. Although the activity of PE appears very low its properties are important because of the commercial use of Bramley seedlings and this paper describes some of the properties of PE in waste material (peel, cores and offcuts) obtained from apples stored in a cool, dry shed for 2 , 4 and 12 weeks.…”

“…Pectinesterase in apples has not been studied to the same extent as that from citrus and tomato although some work has been reported for several dessert varieties including McIntosh (Pollard, 1975), Golden Delicious (Lee & Wiley, 1970), Ralls (Miyain et al, 1975), Sharabi (Al-Delaimy & Ah, 1969), Cox's Orange Pippin, Ellisons Orange, Worcester Permain (Pollard & Kieser, 1951) and five Iraqui varieties, Ajmy, Sharabi, Basri, Koofi and Sukkari (Al-Jasmin & Ali, 1974). Very little work has been reported on cooking-type apples, although these are important for processing.…”