Studies on fruit jelly making (1)

Abstract

The study was undertaken to provide further information on test for various strength of horticultual products. A balance type of strength tester, composed of the balance arm (B), sample-platform (S), depressing disk (N), water reservor (T), and holding vessel (V), was deviced (Fig. 1). This experiment was made to investigate the application of the apparatus for measuring the jelly strength, and by so doing, the effect of pectic substance, sugar, and acid on jelly formation was also studied. The results are summarized as follows: (1) The method for measuring the jelly strength by using this apparatus is as follows. Placing the test jelly in the beaker on a sample-platform, let down a flat stainless-steel disk of 1cm2 until the base of disk barely touches the surface of the jelly, and then fix it. (Fig. 3 left). The pressure is developed, by flow of distilled water from reservor to the vessel at a constant rate of 200cc per minute. With increased pressure the disk sinks deeper and deeper into the jelly until the elastic limit is reached and the jelly breaks. When the depression reaches 20mm., quickly turn off the water corking (K), and thus the volume of water used is measured. The following table shows the breaking pressure in grams/cm2 against every degree of firmness in a series of jellies. Very weak jellies 10-30g/cm2 Weak jellies 31-60 Optimum firm jellies 61-90 Firm jellies 91-120 Very firm jellies 121-150 Rubbery jellies 151- (2) The effect of pectic substance, sugar, and acid on the jelly formation of their concentration was studied by using this apparatus, and it was known that the pectic substance 0.5-1.0% per every jelly product were the optimum amount of jelly formation. (3) Studied also in the same way the relation between the mechanical strength of jelly, and the analytical amout of pectic substance in jelly stock, extracted from Natsudaidai orange and Apple at different length of boiling time. The jelly strength. increases and reaches the maximum at 90 minutes boiling and gradually declines, but the extracted amount of pectic substance increases as the boiling time lengthens.