Use of skin in the elaboration of concentrated products of cactus pear (Opuntia ficus-indica (L.) Miller)

The use of processed fruit by-products for human consumption has increased significantly in recent years. The objective of the present paper was the sensorial evaluation of two products that used the skins of cactus pears that normally are not eaten. These new products were concentrated and preserved by combinations of methods. The first product combined cactus-pear skins, which normally are not eaten; pulp of the fruits that are normally eaten; and sucrose to develop a concentrated sweet product. The second product, termed marmalade, used ground skins and sucrose, but without additional pectin. Preservatives and acids in low concentrations also were added. For the first product a factorial design 3 X 2 X 2 was used whose factors were: (BS) sodium bisulphite (0, 50 and 100 ppm), (Aw) water activity (0.94 and 0.96), and acids [(AF) (phosphoric acid (50% v/v) and in mixture with citric acid (AF + AC) (50% v/v)]. In this product the (SK) potassium sorbate (1000 ppm) and (AC) ascorbic acid (500 ppm) were kept constant. In the second experiment, a single formulation with 63 degrees Brix was developed with pH = 4.0; and SK = 250 ppm. Various dilutions of the first product containing both the pulp and the ground skins were diluted to obtain a final Brix of 15 (referred to as a nectar in this paper) before organoleptic evaluation by trained panel. The marmalade was not diluted prior to organoleptic evaluation. The optimum formulation for the pulp plus skin product had an Aw = 0.94; addition of AF, BS = 100 ppm and a '' Good '' rating. The second product, marmalade, had a slightly lower acceptance with an overall '' acceptable '' rating.