This patch forces bibclean tu use curly braces instead of quotes so you get
   publisher =   {Heyne},
instead of
   publisher =   "Heyne",

 -- Max Dornseif <hackers@c0re.23.nu>

diff -ru bibclean-2.11.4-orig/bibclean.c bibclean-2.11.4/bibclean.c
--- bibclean-2.11.4-orig/bibclean.c	Thu May 20 15:32:53 1999
+++ bibclean-2.11.4/bibclean.c	Mon Jul 14 18:16:40 2003
@@ -1634,6 +1634,11 @@
 const char *token;
 #endif
 {
+    if((*token == '"') && token[strlen(token)-1] == '"')
+    {
+        *token = '{';
+        token[strlen(token)-1] = '}';
+    }
     if (KEEP_PREAMBLE_SPACES())
 	out_verbatim(token);
     else if (KEEP_STRING_SPACES())
@@ -1669,7 +1674,7 @@
     out_c('\t');
     out_s(type_name[(int)type]);
     out_c('\t');
-    out_c('"');
+    out_c('{');
     for (; *token; ++token)
     {
 	switch (*token)
@@ -1721,7 +1726,7 @@
 	    break;
 	}
     }
-    out_c('"');
+    out_c('}');
     out_c('\n');
 }