QUALITY EVOLUTION OF ASPARAGUS (ASPARAGUS OFFICINALIS L.) AS AFFECTED BY STORAGE

Asparagus contains 93–94 % water. To be really palatable it must be tender and pleasant in taste (bitter-free). In order to preserve its water content in store it should be harvested at the proper developmental stage. In cool conditions (1–4 °C) and at high, 80–90 %, relative humidity spears can be stored reliably for several days. Yet, even under favourable conditions 6–8 °C weight loss can be expected on the way to consumers.

As asparagus has a relatively short harvest time (60–65 days) but demand continues the whole year, processing methods have to be found to satisfy the market. Deep freezing is one of the best methods of preserving the biological, nutritional and dietary values of food (Almási et al., 1977).

In recent years the deep freeze industry has progressed dynamically in Hungary, too. Quality has improved and variety has increased. In this process asparagus deserves special attention.

Two types of asparagus are known: the white and the green. The cultivation of white asparagus is more expensive (Dávid and Koródi, 1979; Fehérné, 1986) and in the case of green asparagus plant protection during harvest time causes problems.

Both white and green types are adapted to deep freezing. Special requirements involve a smooth surface, fine structure, fibre free texture and firm head. Heads and spears should not be separated easily. The raw material must be bitter free, characteristic of the variety and of uniform colour (Almási et al., 1971; Erdélyi et al., 1987).

In our trials the processing usability of the variety Braunschweig was evaluated with a view to enlarging the deep freeze selection by introducing some new products. Solo I. class spears were used. The texture of head and spear, the cleaning loss, the effect of blanching and freezing and changes in plant tissues were studied.

Cleaning loss was expressed as a percentage. For instrumental measurements 1 cm long pieces of 55 g of the head and spear were used. The force needed to crush it was read on a sping force (F°). For the determination of total solids, samples were dried at 105 °C till weight stability was reached. Water soluble solids were evaluated in a Zeiss-Abbé refractometer.

Trials indicated cleaning losses up to 27 %, out of which the skin came up to 78 %. According to penetrometer readings the head part was always softer than the spear part.

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