diff --git a/app/src/main/java/com/freshkeeper/model/Activity.kt b/app/src/main/java/com/freshkeeper/model/Activity.kt
index 3a6d989..dc0d3d6 100644
--- a/app/src/main/java/com/freshkeeper/model/Activity.kt
+++ b/app/src/main/java/com/freshkeeper/model/Activity.kt
@@ -11,5 +11,9 @@ data class Activity(
     val productName: String? = null,
     val deleted: Boolean = false,
 ) {
+    companion object {
+        const val FIELD_ID = "id"
+    }
+    
     constructor() : this("", "", "", EventType.EDIT, "", 0, "", "", false)
 }
diff --git a/app/src/main/java/com/freshkeeper/model/FoodItem.kt b/app/src/main/java/com/freshkeeper/model/FoodItem.kt
index 8630f85..73df6c8 100644
--- a/app/src/main/java/com/freshkeeper/model/FoodItem.kt
+++ b/app/src/main/java/com/freshkeeper/model/FoodItem.kt
@@ -20,6 +20,23 @@ data class FoodItem(
     val nutriScore: String? = null,
     val picture: Picture? = null,
 ) {
+    companion object {
+        const val FIELD_ID = "id"
+        const val FIELD_BARCODE = "barcode"
+        const val FIELD_USER_ID = "userId"
+        const val FIELD_HOUSEHOLD_ID = "householdId"
+        const val FIELD_NAME = "name"
+        const val FIELD_EXPIRY_TIMESTAMP = "expiryTimestamp"
+        const val FIELD_DISCARD_TIMESTAMP = "discardTimestamp"
+        const val FIELD_QUANTITY = "quantity"
+        const val FIELD_UNIT = "unit"
+        const val FIELD_STORAGE_LOCATION = "storageLocation"
+        const val FIELD_CATEGORY = "category"
+        const val FIELD_STATUS = "status"
+        const val FIELD_NUTRIMENTS = "nutriments"
+        const val FIELD_NUTRI_SCORE = "nutriScore"
+        const val FIELD_PICTURE = "picture"
+    }
     constructor() : this(
         "",
         null,
diff --git a/app/src/main/java/com/freshkeeper/service/product/ProductServiceImpl.kt b/app/src/main/java/com/freshkeeper/service/product/ProductServiceImpl.kt
index 0e075db..be43173 100644
--- a/app/src/main/java/com/freshkeeper/service/product/ProductServiceImpl.kt
+++ b/app/src/main/java/com/freshkeeper/service/product/ProductServiceImpl.kt
@@ -100,18 +100,18 @@ class ProductServiceImpl
 
             val foodItemData =
                 mutableMapOf<String, Any>(
-                    "userId" to user.id,
-                    "name" to productName,
-                    "expiryTimestamp" to expiryTimestamp,
-                    "quantity" to quantity,
-                    "unit" to unit,
-                    "storageLocation" to storageLocation,
-                    "category" to category,
-                    "status" to FoodStatus.ACTIVE,
+                    FoodItem.FIELD_USER_ID to user.id,
+                    FoodItem.FIELD_NAME to productName,
+                    FoodItem.FIELD_EXPIRY_TIMESTAMP to expiryTimestamp,
+                    FoodItem.FIELD_QUANTITY to quantity,
+                    FoodItem.FIELD_UNIT to unit,
+                    FoodItem.FIELD_STORAGE_LOCATION to storageLocation,
+                    FoodItem.FIELD_CATEGORY to category,
+                    FoodItem.FIELD_STATUS to FoodStatus.ACTIVE,
                 ).apply {
-                    cleanedBarcode?.let { this["barcode"] = it }
-                    householdId?.let { this["householdId"] = it }
-                    picture?.let { this["picture"] = it }
+                    cleanedBarcode?.let { this[FoodItem.FIELD_BARCODE] = it }
+                    householdId?.let { this[FoodItem.FIELD_HOUSEHOLD_ID] = it }
+                    picture?.let { this[FoodItem.FIELD_PICTURE] = it }
                 }
 
             firestore
@@ -121,7 +121,7 @@ class ProductServiceImpl
                     firestore
                         .collection("foodItems")
                         .document(documentReference.id)
-                        .update("id", documentReference.id)
+                        .update(FoodItem.FIELD_ID, documentReference.id)
                         .addOnSuccessListener {
                             coroutineScope.launch {
                                 if (user.householdId != null) {
@@ -195,19 +195,19 @@ class ProductServiceImpl
         ) {
             firestore
                 .collection("foodItems")
-                .whereEqualTo("id", foodItem.id)
+                .whereEqualTo(FoodItem.FIELD_ID, foodItem.id)
                 .get()
                 .addOnSuccessListener { querySnapshot ->
                     val document = querySnapshot.documents.firstOrNull()
                     if (document != null) {
                         val updates: MutableMap<String, Any> =
                             mutableMapOf(
-                                "name" to productName,
-                                "quantity" to quantity,
-                                "unit" to unit,
-                                "storageLocation" to storageLocation,
-                                "category" to category,
-                                "expiryTimestamp" to expiryTimestamp,
+                                FoodItem.FIELD_NAME to productName,
+                                FoodItem.FIELD_QUANTITY to quantity,
+                                FoodItem.FIELD_UNIT to unit,
+                                FoodItem.FIELD_STORAGE_LOCATION to storageLocation,
+                                FoodItem.FIELD_CATEGORY to category,
+                                FoodItem.FIELD_EXPIRY_TIMESTAMP to expiryTimestamp,
                                 "consumed" to isConsumedChecked,
                                 "thrownAway" to isThrownAwayChecked,
                             )
@@ -362,7 +362,7 @@ class ProductServiceImpl
                 .collection("activities")
                 .add(activity)
                 .addOnSuccessListener { documentReference ->
-                    documentReference.update("id", documentReference.id)
+                    documentReference.update(Activity.FIELD_ID, documentReference.id)
                 }.addOnFailureListener { e ->
                     Log.e("Firestore", "Error when adding the activity", e)
                 }
diff --git a/gradlew b/gradlew
old mode 100644
new mode 100755