Fruit assessment

Each month from October a sample of each store/orchard combination should be taken out and assessed.

• It should be remembered that the store atmosphere is lethal, and under no circumstances should anybody enter the store.
• The safety of the operator must be stressed.
• At no time should the operator place any part of his or her body in the store.
• People should always work in pairs, and use a ‘boat hook’ or similar extended hook to remove the netted samples.
• Store owners and growers should have appropriate Risk Assessments and Standard Operating Procedures in place for sampling fruit from store hatches – these need to be specific for the type of store design present.

Blemishes and disorders

Each apple in the sample should be carefully examined externally for any signs of blemish or storage disorders of the skin.  Such disorders include lenticel blotch pit, carbon dioxide injury, superficial scald or damage due to calcium sprays or the use of a post-harvest drenching solution.

Colour

Colour is very difficult to quantify without the aid of sophisticated instruments.  The skin of an apple is variable with patches of different shades of green and bleached areas where leaves have shaded fruit.  With dessert apples the stripes of red colour within the background colour makes it very difficult to assess.

A subjective method has been adopted in which the 20 fruits are laid out and, using a colour card as a reference (see section on Fruit Quality Standards) ,  the overall background colour described as dark green, green, light green, light yellow or yellow.

The percentage of the surface area of the fruit coloured red is estimated for each fruit and expressed as a range.  To ensure consistency the light condition used should be good and the same for each assessment.

Firmness

Ten fruits from the sample should be selected at random for firmness measurements. Average values taken from month to month provide a general indication of the softening rate of stored apples.

The most widely used instrument for measuring firmness is the hand-held ‘Effigi’ penetrometer.  For more consistent results this should be mounted in a drill stand and supported on a firm base. An 11 mm diameter probe should be used for apples and an 8 mm probe for pears.

The instrument should be calibrated against an accurate balance at least once a year. Fruit juice is very corrosive and thus the instrument should be washed, dried and coated in a thin mineral oil after use.

The following procedure should be adopted when carrying out the test:

1. Remove a thin slice of peel from opposite sides of each of 10 apples.
2. Lower probe into the flesh at a steady rate.
3. Take 2 seconds to travel 8 mm into the fruit.
4. Record value and reset.
5. Repeat on the opposite side of the fruit.

Where this procedure has been adopted little difference has been found in the readings obtained by different operators.  However, to guard against any possible ‘operator error’ the same person should carry out the tests whenever possible.  It is recommended that individuals using penetrometers should compare their results occasionally to safeguard against any operating errors. Where access to a motorised penetrometer is available (e.g. Fruit Texture Analyser – FTA), this avoids discrepancies in results between operators.

Disorders

The ten apples used for measurement of firmness are then examined internally for the presence of disorders of the flesh.

• A transverse cut is made close to the calyx end of the apple and the presence or absence of bitter pit or browning recorded.
• A second cut is made across the equator of the fruit through the core area and the cut surface assessed for core flush, low temperature breakdown and senescent breakdown.
• In Gala, Braeburn and Envy, it is advisable to undertake an additional cut at the stalk end of the fruit to examine for ‘shoulder breakdown’ in fruit.
• The severity of the breakdown is quantified by assessing the area of the cut surface affected.  Slight is up to one third, moderate is between one and two thirds and severe above two thirds.
• During the examination fruits are tasted and scored for eating quality and the presence of any taints or ‘off-flavours’ should be noted.
• The remaining ten apples are placed in a room at 18oC and the external and internal condition assessed after seven days.

The mean fruit firmness, together with the percentage of fruit with various disorders, should be calculated and recorded on a purpose designed form. By using one form for each store/orchard combination the change in fruit quality or the development of storage disorders with time can be followed clearly.