Drain pasta well and add to large bowl. Let cool for a few minutes. Add 1 tbsp lemon juice, 1/2 tsp salt and 1/2 tsp ground black pepper. Mix well. Add tuna, celery, scallions, green peas, parsley, mustard and mayonnaise. Mix well. Taste and add more salt or pepper if necessary. If you like heat, add a little hot sauce. Cover and refrigerate for at least 4 hours before serving.