Berlanga-Del Pozo Marta, Gallardo-Guerrero Lourdes, Gandul-Rojas Beatriz
Chemistry and Biochemistry of Pigments, Food Phytochemistry, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, Edificio 46, Ctra. Utrera km 1, 41013 Sevilla, Spain.
Foods. 2020 Jun 1;9(6):701. doi: 10.3390/foods9060701.
Alkaline treatment is a key stage in the production of green table olives and its main aim is rapid debittering of the fruit. Its action is complex, with structural changes in both the skin and the pulp, and loss of bioactive components in addition to the bitter glycoside oleuropein. One of the components seriously affected are chlorophylls, which are located mainly in the skin of the fresh fruit. Chlorophyll pigments are responsible for the highly-valued green color typical of table olive specialties not preserved by fermentation. Subsequently, the effect on chlorophylls of nine processes, differentiated by NaOH concentration and/or treatment time, after one year of fruit preservation under refrigeration conditions, was investigated. A direct relationship was found between the intensity of the alkali treatment and the degree of chlorophyll degradation, with losses of more than 60% being recorded when NaOH concentration of 4% or greater were used. Oxidation with opening of the isocyclic ring was the main structural change, followed by pheophytinization and degradation to colorless products. To a lesser extent, decarbomethoxylation and dephytylation reactions were detected. An increase in NaOH from 2% to 5% reduced the treatment time from 7 to 4 h, but fostered greater formation of allomerized derivatives, and caused a significant decrease in the chlorophyll content of the olives. However, NaOH concentrations between 6% and 10% did not lead to further time reductions, which remained at 3 h, nor to a significant increase in oxidized compounds, though the proportion of isochlorin -type derivatives was modified. Chlorophyll compounds of series were more prone to oxidation and degradation reactions to colorless products than those of series . However, the latter showed a higher degree of pheophytinization, and, exclusively, decarbomethoxylation and dephytylation reactions.
碱处理是绿橄榄生产中的关键阶段，其主要目的是使果实迅速脱苦。其作用较为复杂，会导致果皮和果肉的结构发生变化，除了苦味糖苷橄榄苦苷外，还会造成生物活性成分的损失。受影响严重的成分之一是叶绿素，其主要存在于新鲜果实的表皮。叶绿素色素赋予了未经发酵保存的特级初榨橄榄油特有的高价值绿色。随后，研究了在冷藏条件下保存一年后，9种因氢氧化钠浓度和/或处理时间不同而区分的处理方法对叶绿素的影响。结果发现碱处理强度与叶绿素降解程度之间存在直接关系，当使用4%或更高浓度的氢氧化钠时，叶绿素损失超过60%。异环开裂的氧化是主要的结构变化，其次是脱镁叶绿素化和降解为无色产物。在较小程度上，还检测到了脱甲氧基化和脱植基反应。氢氧化钠浓度从2%增加到5%可将处理时间从7小时缩短至4小时，但会促进更多异构化衍生物的形成，并导致橄榄中叶绿素含量显著降低。然而，6%至10%的氢氧化钠浓度并未进一步缩短处理时间，处理时间仍为3小时，也未导致氧化化合物显著增加，不过异叶绿酸型衍生物的比例发生了变化。系列的叶绿素化合物比系列的更容易发生氧化和降解为无色产物的反应。然而，后者显示出更高程度的脱镁叶绿素化，并且仅发生脱甲氧基化和脱植基反应。
