Changes Produce during Apple Refrigeration Storage in Textural and Structural Fruit Behavior

Received: August 19， 2011 / Published: June 20， 2012.

Abstract: The purpose of this study was to determine from the three different varieties of apple (Golden Delicious， Jonathan and Starkrimson)， which is best suited to storage at refrigeration temperature in constant conditions (5 °C and 85% relative humidity). In this order， the apples were stored in three variants of packages as bulk， packed in LDPE foil and alimentary paper for 23 days in a professional refrigerator. In this period， some textural and structural tests based on penetration and microstructure analyses were carried out with a 7-day frequency. As a conclusion of these tests the maximum values for mechanical determination are for Starkrimson variety 69.54 N at 4 mm depth for 15 days of storage while the minimum one is 24.34 N at 3 mm for Jonathan variety. The good part of the storage by refrigeration is the bulk variants there were no significant changes including quality damage， even the Starkrimson variety microstructure modification during refrigeration was the most affected.

Cultivated apple (Malus domestica) is among the most diverse and ubiquitously cultivated fruit species. Apple is a member of the Rosaceae family， which includes many commercial fruit (e.g.， pear (Pyrus communis)， strawberry (Frageria spp.)， cherry(Prunus avium)， peach/nectarine (Prunus persica)， apricot (Prunus armeniaca))， nut (almond (Prunus amygdalus))， forest (black cherry (Prunus serotina))， and ornamental (rose (Rosa hybrida))， crab apple(Malus coronaria)) species [1].

Like tomato， apple is a climacteric fruit， with a clear respiratory climacteric and ethylene peak associated with ripening. However， unlike tomato， which is a true berry fruit， the majority of apple fruit is derived from proliferated receptacle tissues， with the ovary-derived tissues restricted to the center of the mature fruit (core). The skin (epidermal and subepidermal cell layers) is strikingly different from the cortex， and， in almost all apple varieties studied thus far， biosynthesis of pigments and most volatile esters associated with aroma is concentrated in epidermal and subepidermal tissues. Pigmentation is dominated by anthocyanins (compared with carotenoids in tomato)， and tomato fruit is not known to synthesize volatile esters. Compared with most fruits， apple has an extremely long developmental sequence， often exceeding 150 d. Although ripening in apple is accompanied by changes in texture， it is one of the few commercially important fruits that undergo significant softening only after extended storage and deterioration.

An additional attraction of apple for studies of fruit biology is the enormous diversity in fruit-related traits among the large number of cultivars and related wild genotypes (3，000) available for analysis.

Deterioration of fruits and vegetables during storage depends largely on temperature. One way to slow

removing heat from and maintaining water in harvested vegetables [5].

Postharvest handling and storage systems influence the quality of harvested fruits by affecting the physiology of fruits harvested. Changes in the physiology of harvested vegetables are mediated through the influence of the environmental conditions created by the handling and storage system. The physiology of the harvested fruits， environmental conditions， and handling and storage systems all interact and therefore cannot be considered in isolation when successfully preserving and storing high quality fruits harvested.

Processing technologies being used to ensure food quality and safety are freezing; thermal processing， sterilization， drying， refrigeration， and the controlled distribution of fresh produce [6]. In addition to taste， texture is a quality attribute that is critical in determining the acceptability of apple fruits by consumers. Fruit wholesalers are therefore particularly interested in the measurement of fruit texture. However， direct measurement of texture through sensory analysis is very complex and time consuming. For this reason， many attempts have been made to replace sensory analysis with instrumental measurements [7].

The correlation coefficients obtained between sensory texture attributes and penetrometric force were very different from one study to another as a function of cultivars， ripening stages， global fruit evolution during storage， fruit origin， etc. [8].

The present paper has the aim to demonstrate the inherent modifications appeared during the refrigeration storage. As principal objectives of the changes produce during apple refrigeration storage regarded the textural and structural transformations and their comparison. For reaching these objectives there were used some instrumental methods to determine the textural and structural modifications.

immersed in the water mass， also another important aspect to observe is that the proportion between the principal components from the three apple variants are different.

After the storage， the Starkrimson variety alimentary paper packed were the most affected. The Starkrimson apple contains especially starch than pectin.

The sugars from the parenchyma tissues can be observed in the Fig. 1， in which the macromolecules are represented by the starch， micromolecules-phenols， respectively fibrous chains can be associated to pectin. 3.1. Bulk and Packed Starkrimson Variety Storage Textural Modifications

The puncture test is a simple and easy way to test puncture force that gives an idea about the hardness/stiffness of the solid samples. It is also a good and simple way to test food materials with heterogeneous structure (e.g.， cereal bars， chocolates with various layers， etc.) [9].

For Starkrimson variety the firmness of the bulk sample is presented in Fig. 2， where it can be see at a 4 mm depth the firmness value is 55.46 N， while after other 7-day of storage the necessary force for apple penetration is 60.79 N at 4 mm.

As much as the depth is growing (6-7 mm) the penetration force is decreasing (29.5 N， 22 N)， this action may be due to the composition of the first layer of the apple wax and pectin rich， which is a resistance force opponent to penetration plunger. Also it can be observed that after a specific depth as 6-7 mm the curves are almost constant that can be due to the pulp layer where the air globules and the chemical compounds are in perfect balance.

Opposite to the expectations， after the storage the firmness values were not decreasing， without any large variation the values being appropriate as for the alimentary paper packed after seven days of storage the penetration force is 57.31 N for 3 mm， while at 15 days of storage the force is 58.84 N at 3 mm and for the LDPE foil.

paper packed， the best behaviour is registered by the LDPE foil package.

The texture of the Golden Delicious variety is determined by the curves from the graphics showed in Fig. 4 generated by applying a force over the apple at different depths.

The first determination for the bulk sample had registered a 54.54 N for a 4 mm depth， the next determinations results being in decreasing at higher depth. At 15 days of storage the force value is 45.33 N at 4 mm. The firmness is just a little bit affected by storage. These results may be due to the higher quantity of air from the intercellular space or to the water higher quantity from the Golden Delicious variety.

As for the bulk variant for the alimentary paper and LDPE package the firmness results are similar， so for the first type of package at 4 mm the force value is 43.20 N， for 15 days of storage 49.99 N for the same depth， while for the other type of package at seven days of refrigeration the force value is 41.05 at 3 mm and at 15 days of storage 45.33 N at 4 mm depth.

apples， AgEng2002 Conference， Budapest Hungary 30 June-4 July: 02-PH-030.

[9] M.S. Hui， J. Barta， M. Pilar Cano， W. Todd， S. Jiwan Sidhu， K. Nirmal Sinha， Handbook of Fruits and Fruit Processing ， Blackwell Publishing， 2006.

[10] Y.H. Hui， F. Chen， P.F. Raquel， M. Guiné， I. Mínguez-Mosquera， L.P. Fernando Pessoa， et al.， Handbook of Fruit and Vegetable Flavors， John Willey Sons Inc. Publication， 2010.

[11] A.K. Thompson， Fruit and Vegetables: Harvesting， Handling and Storage， Blackwell Publishing， 2003.

[12] ?. Semih， N. Sozer， L. Kokini Jozef， Rheological instruments in food analysis， in: Handbook of Food Analysis Instruments， CRC Press， TaylorFrancis Group 2009.