Load a single field of an entity.

drupal_load_single_field_from_entity.php

<?php  
  // Save the original field collection data.
  $query = new EntityFieldQuery();
  $query->entityCondition('entity_type', 'commerce_product')
    ->entityCondition('bundle', $entity->type)
    ->propertyCondition('product_id', $entity->product_id);
  $result = $query->execute();

  if (isset($result['commerce_product'])) {
    $original_product = $result['commerce_product'];

    $field_fc_product_description_info = $field_info = field_info_field('field_fc_product_description');
    $field_fc_technical_specification_info = $field_info = field_info_field('field_fc_technical_specification');

    field_attach_load('commerce_product', $original_product, FIELD_LOAD_CURRENT, array('field_id' => $field_fc_product_description_info['id']));
    field_attach_load('commerce_product', $original_product, FIELD_LOAD_CURRENT, array('field_id' => $field_fc_technical_specification_info['id']));

    $entity->field_fc_product_description = $original_product[$entity->product_id]->field_fc_product_description;
    $entity->field_fc_technical_specification = $original_product[$entity->product_id]->field_fc_technical_specification;
  }