Кондиціювання бульб картоплі як елемент технології стабілізації їх якості

Анотація

CONDITIONING potato tubers as an element of technology quality stabilization

A. Davydenko

Potato crops are exposed to mechanical damage during process of harvesting, transportation, loading, unloading and sorting. As a result, vacuolar membranes get torn apart and polyphenols located inside them become oxidized by oxygen air. Substances, which are the aftermath of such reaction, are the reason of denaturation of proteins and darkening of potato tubers. Consequently, commercial consignment may consist of products, 40% of which has darkening. Potato tubers are more likely to be exposed to damage if they were stored at low temperature (less than 6 °С). One of the technological methods that reduce level of damage is conditioning (warming) of potato at higher temperatures. It was established that tubers’ temperature build-up from 2 ºС to 14 ºС facilitates reduction of the damage from 18 to 4 %.

Purpose: development of efficient temperature regimes of potato tubers conditioning for stabilization of their quality.

Objects of study were potato tubers from companies HZPC (Netherlands) and Solana (Germany) of two ripeness groups: medium-early and medium-ripe.

Potato tubers were warmed from 4 ºС (storage temperature) to 6-24 ºС (interval of temperature change – 2 ºС). Then the density, level of pulp darkening and quantity of darkening tubers were determined. 

Efficient temperature is defined as conditioning temperature at which pulp density of tubers remained unaltered. Results show that potato tubers were of a different pulp density because of the cultivar specifics as well as the impact of temperature factor. The least values of this exponent at the storage temperature (no conditioning) belongs to potato tubers of the cultivar Sifra (9.31 kg/cm²) and the greatest ones (10.6 kg/cm²) – the cultivar Mozart.

Densities of tubers of all varieties were decreasing with the temperature growth. However, stable values of density were received at different temperatures. Red Lady (pulp density 9.55 kg/cm²) from the medium-early ripeness group required least warming temperature (8 ºС). Same conditioning temperature (14 ºС) was required by varieties Satina and Mozart, though their pulp density was different – 8.23 kg/cm² and 9.32 kg/cm², respectively. Efficient temperature for medium-ripe group was for Arosa – 14 ºС (pulp density 9.12 kg/cm²) and for Sifra – 18 ºС (density 7.92 kg/cm²).

         Analysis of the results on the influence of conditioning temperature on resistance to darkening of potato tuber pulp points out that there is strong correlation between these two factors. After sorting procedure at temperature 4 ºС (no conditioning) potato tubers received low points for resistance to darkening: raw tubers – from 3 to 5 points, boiled tubers – 2-3 points.

Tuber conditioning at 8 ºС facilitated greater resistance to darkening in raw tubers (Satina up to 5 points, Mozart, Arosa up to 6 points, Sifra up to 7 points and Red Lady up to 9  points) and in boiled tubers up to 5 points (Red Lady) and 4 points (Satina, Arosa). Further conditioning temperature growth to 12 and 16 ºС influenced the resistance to darkening in raw and boiled tubers only in several varieties. At 12 °С fresh tubers of all varieties had resistance at 7-8 points. Therefore, temperature growth facilitated the value increase of this exponent in all varieties except Red Lady (its resistance dropped one point). Same resistance tendency was observed for the boiled tubers. Important to mention that at these conditions Satina and Arosa recieved maximum resistance points – 5.

         At 16 °С maximum resistance results were found in raw tubers of Satina, Mozart and Arosa, and in boiled tubers of Satina, Arosa and Sifra. Red Lady tubers had decreased level of resistance at this temperature in both raw and boiled tubers – 6 and 4 point, respectively.

         Conditioning temperature at 20 °С had positive influence on resistance to darkening only in Sifra, the values of this exponent in raw and boiled tubers – 9 and 4 points respectively. Other varieties had decreased level of resistance to darkening at this temperature in raw tubers - to 6-7 points and to 3-4 points in boiled tubers. Therefore, temperature growth above the level determined as efficient based on studies of pulp density causes decrease in resistance to darkening.

Application of 24 °С facilitated loss of resistance in raw tubers of all varieties (4-5 points) and only Sifra had quite high results: 8 points in raw tubers and 4 points in boiled tubers. 

Therefore, resistance to darkening in raw and boiled potato tubers depends on warming temperature. The best resistance results correlate with temperature values that were determined to be efficient ones based on studies of pulp  density: for Satina, Mozart and Arosa – 12 and 16 °С, for Red Lady – 8 and 12 °С and for Sifra  – 16 and 20 °С.

         Studies of the influence of conditioning on the lost due to pulp darkening show that the increase of temperature reduces lost.  Its minimum quantity accords with efficient conditioning temperatures, which were determined empirically depending on pulp density.

         Therefore, conducted studies allow to conclude that efficient temperatures of conditioning of potato tubers for the medium-early group: 8 ºС (Red Lady, density 9.55 kg/cm²) and 14 ºС (Satina, density 8.23 kg/cm² and Mozart, density 9.32 kg/cm²), and for the medium-ripe group: 14 ºС (Arosa, density 9.12 kg/cm²) and 18 ºС (Sifra, density 7.92 kg/cm²).

         Best result of resistance to darkening in raw and boiled potato tubers were provided  by following conditioning temperatures: for Satina, Mozart and Arosa – 12 and 16 °С, for Red Lady – 8 and 12 °С, for Sifra  – 16 and 20 °С.

         Minimum rate lost for medium-early potato tubers were: for Satina – 5 % at temperature – 16 ºС, for Red Lady – 4 % at 8 and 12 ºС, for Mozart – 2 % – at 16 ºС. For medium-ripe potato tubers results were the following: Arosa – 6 % at 16 ºС and Sifra 3 % – at 20 ºС.