Effects of eggshell mixed with “Nukadoko” (NaCl rice bran paste for pickling) on the ripening of pickles were investigated.
As preliminary experiments, eggshell was soaked in vinegar or NaCl-vinegar solution and cucumber was dipped into the resulting solution. In vinegar, eggshell was easily dissolved and Ca content of the solution increased and pH value was elevated.
Cucumber soaked in this eggshell dissolved vinegar could maintain green color and keep its hardness longer. However, the hardness of pickles soaked in the eggshell-NaCl-vinegar solution was almost the same to this soaked in eggshell-vinegar only.
In the case of ripened “Nukadoko”, by the action of lactic acid in this, Ca in eggshell was dissolved and migrated into “Nukadoko”, then pH of this paste was increased. When cucumber pickles were prepared with this “Nukadoko”, characteristics of pickles resembled to those obtained by the preliminary vinegar experiments.
It was found that more than 80% of Ca dissolved to “Nukadoko” from eggshell and rice bran were in the ionic phase.
Sensory tests revealed that pickles prepared with eggshell containing vinegar or “Nukadoko” kept vivid green color than contrast pickles, and those were favored than constrast ones.
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