Wood Fruit Production situation

7/27/2019 Wood Fruit Production situation

1/12

Fresh fruit microstructure, texture and quality

Delilah F. Wood, Syed H. Imam, William J. Orts and Gregory M. Glenn

U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center,800 Buchanan St. Albany, CA 94710

ABSTRACT

Fresh-cut produce has a huge following in todays supermarkets. The trend follows the need to decrease preparation timeas well as the desire to follow the current health guidelines for consumption of more whole heart-healthy foods.

Additionally, consumers are able to enjoy a variety of fresh produce regardless of the local season because produce is

now shipped world-wide. However, most fruits decompose rapidly once their natural packaging has been disrupted by

cutting. In addition, some intact fruits have limited shelf-life which, in turn, limits shipping and storage. Therefore, abasic understanding of how produce microstructure relates to texture and how microstructure changes as quality

deteriorates is needed to ensure the best quality in the both the fresh-cut and the fresh produce markets. Similarities

between different types of produce include desiccation intolerance which produces wrinkling of the outer layers,

cracking of the cuticle and increased susceptibility to pathogen invasion. Specific examples of fresh produce and their

corresponding ripening and storage issues, and degradation are shown in scanning electron micrographs.

Keywords: Fresh-cut roduce, fruits and vegetables, microstructure, parsley, carrot, broccoli, kiwifruit, mushroom

1. INTRODUCTIONThe origin of plant tissue components during development and maturation determines the nomenclature used for the

resulting component1. Thus, the edible portion of a plant encompasses a wide array of tissue types

2and constitutes

vegetative and reproductive tissues. Leafy greens (lettuce, spinach, parsley) stems (celery, rhubarb), roots (carrot,

radish), tubers (potatoes), and bulbs (onion, garlic) are all vegetative tissues. Flower buds (broccoli florets, artichokes),fruits (bananas, squash, green beans), seeds (mature beans, almonds), and grains (wheat, corn) are examples of

reproductive tissues.

Intact fruits and vegetables have inherent preservation in their designs. As a first line of defense, a fruit or vegetable is

protected from degradation by a resilient outer layer which forms a skin. The skin which consists of several cell layers, is

covered by a thin, continuous, waxy layer, the cuticle3

The cuticle slows dehydration and serves as an effective barrier topathogens and insects

4and thus, serves as a natural package. Beneath the cuticle lies the epidermis consisting of cells

which may possess thick outer cell walls. The skin may also contain additional cell layers with thickened cell walls. Cell

walls aid in dehydration prevention and provide structure to edible plant tissues and to mushrooms. Unlike plants,

mushrooms are fungi which are non-photosynthetic organisms. Edible mushrooms are comprised of a mass of hyphae

joined together to form a basidiocarp, or fruiting body, the edible portion. The cell walls of both plants and fungi arerigid and rely on appropriate water potential to provide turgor pressure to the cells allowing them to retain their shapes

and their fresh characteristics.

Fruits which are consumed ripe are usually harvested green to allow time for transport to the consumer. Generally,

ripening is due to a loss of firmness in texture due to cell wall depolymerization and the dissolving of the middle

lamella5. The middle lamella, the substance between adjoining, adjacent cell walls, functions as the glue that holds

cells together. Thus, as the middle lamella dissolves, the adhesion between cells decreases and continues to decrease overtime resulting first in ripening and then in aging

6. Fruit firmness is also related to cellular characteristics such as cell wall

strength, cell turgor, the number and sizes of intercellular spaces as well as intercellular adhesion7. Intercellular adhesion

plays a significant role in the texture of produce. The physiological and chemical processes ultimately responsible for

ripening and aging have been well-documented8. Many papers on ripening have been published and these provide insight

into some of the physiological changes that continue to occur as the fruit decays.

Dehydration accelerates fruit decay and is largely due to vapor diffusion through stomata, the gas exchange system of the

plant, and the cuticle9. Therefore, storage in a dry atmosphere can be detrimental and accelerate dehydration, however, a

Scanning Microscopy 2009, edited by Michael T. Postek, Dale E. Newbury, S. Frank Platek, David C. Joy,Proc. of SPIE Vol. 7378, 73781J 2009 SPIE CCC code: 0277-786X/09/$18 doi: 10.1117/12.821351

Proc. of SPIE Vol. 7378 73781J-1


2/12

moist atmosphere may make it easier for the entry of pathogens into stomata or other openings in the plant surface.

Produce shows an increase in susceptibility to postharvest diseases and infestation during prolonged storage partly due to

ongoing physiological changes that enable pathogen development on or in the fruits10

. Thus, protective mechanisms fail

over time and when any one of the protective systems are compromised, degradation and a loss of quality will occur.

Therefore, an understanding of each produce system is essential in developing methods of handling fresh produce.

A few selected plant materials are included by discussing a brief survey of the literature and by showing scanning

electron micrographs of specific commodities which were purchased at the local supermarket. We hope to acquaint thereader with a general idea of structure as it relates to the changing of microstructure of produce over time. This paper is

excerpted, in part, from a book chapter11

.

2. MATERIALS AND METHODSFresh material was prepared for microscopy as soon as it was purchased. Aged material was purchased fresh and then

allowed to age at ambient conditions for a week or more prior to preparation for microscopy. Plant material was fixed informalin-acetic acid-ethanol

12or in a solution containing 3% glutaraldehyde, 2% formaldehyde in sodium cacodylate

buffer, pH 6.9. The aldehyde-fixed tissue was then post-fixed in aqueous 1% osmium tetroxide13

and dehydrated in a

graded series of ethanol12, 13

. The samples were then either cryofractured in liquid nitrogen14

or sliced under 100%ethanol, critical point dried in a Tousimis Autosamdri 815 (Tousimis, Rockville, MD), sputter coated with gold-

palladium in a Denton Desk II sputter coating unit (Denton Vacuum, Moorestown, NJ), and observed and photographed

in a Hitachi S-4700 field emission scanning electron microscope (Japan).

3. RESULTS AND DISCUSSION3.1 Leafy greens Italian parsleyThe turgor of plant cells and cell walls is essential in providing the characteristic textural crispness attributes to leafygreens such as parsley. Fresh, Italian parsley has a characteristic, triangular stem (Fig. 1a) which carries water up to the

leaves and can be placed in water post-harvest to increase the shelf life. The lower (abaxial) leaf surface of fresh parsley

(Fig. 1b) reveals plump, epidermal cells indicating that they have adequate turgor and are fully hydrated. The vascular

bundles are distinct and stomata are evident. In contrast, the abaxial surface of the aged leaf (Fig. 1c) has an irregular,

wrinkled surface and the vascular bundle is not distinct as it blends with the extensive folds in the epidermis. The fresh

parsley leaf has a relatively flat epidermis, the vascular bundle has plump, rounded cells (Fig. 1d) and the stomata are in

evidence (Fig. 1e). However, early signs of degradation are also apparent in the fresh leaf in areas where the epicuticular

wax has started to peel and crack (Fig. 1f). The epidermis of the aged leaf (Fig 1g) has shriveled and wrinkled due todehydration also has surface lesions (Fig 1g, h) and other disruptions which allow the proliferation of bacteria (Fig 1i, j).

The bacterial colony was in association with a fibrous substance, probably a biofilm. Biofilms, exudates of some types of

bacteria, provide adherence properties to bacteria allowing them to colonize tissues. Biofilms are typically composed of

highly hydrated polysaccharides15, 16

. The polysaccharides are difficult to preserve using aqueous fixation techniquesused in preparation for scanning electron microscopy because portions of the polysaccharide dissolve in the aqueous

fixative. The insoluble remains of the polysaccharides lose definition and tend to clump together forming fiber-like

structures. The larger fibrous components are part of the parsley leaf which disintegrated from the microbial activity.

Roots Carrot

Carrots have a long shelf life but the shelf life can be shortened by root-rotting pathogens, such as Chalara elegans, a

pathogen common in the Fraser Valley of British Columbia, Canada17

. Carrots may be harvested at any size,however, carrots harvested too late tend to be woody and are unacceptable to consumers. Small, ready-to-eat carrots

were chosen for this study because of their convenience to consumers. Ready-to-eat carrots are peeled, scrubbed,packaged and shipped in bags. The surfaces of prepackaged carrots, whether fresh or aged, consist of crushed cells



3/12

-

Figure 1. Italian parsley. A cross section of fresh, triangular-shaped stem (a). Lower leaf surfaces show the outer epidermis of fresh

(b, d, e, f) and aged (c, g, h, i, j) leaves. A fresh leaf has distinct vascular bundles (b), epidermal cells and stomata. An aged leaf hasextensive wrinkling or folding, epidermal cells have lost turgor pressure, and the vascular bundle is indistinct (c). A fresh leaf showingplump vascular bundle cells (d) and open stomata (e). Vascular bundle cells that have adequate turgor (f); the "flaky" appearance isdue to epicuticular wax which has cracked. Aged leaf showing folds and an irregular surface blemish ( g, h). The surface of an agedleaf showing a vascular bundle and wrinkled epidermal cells and stomata ( i). The dark, fibrous area is a bacterial colony enlargementshown inj associated with possible biofilm (arrows) (j). Large fibers (*) are decomposing plant material. VB, vascular bundle; S,stomata. Scale bars: a-c, 500 m; d, 300; e, 100 m; f, 50 m; g, 1 mm; h, 200 m; i 50 m; j, 10 m.



4/12

I h

from the outer cortex (Fig. 2a, b). Peeled and stored carrots often have a white translucent appearance. The whiteappearance is due the dehydration of the shredded cells on the carrot surface

18. Treatment of carrots by slicing or peeling

can cause physical damage, stress and the increased risk of microbial growth. The risk and severity of damage was lesswith gentle handling and cutting with sharp knives

19and was further reduced following vacuum

packaging20

. Fresh (Fig. 2c) and aged (Fig. 2d) carrots have similar microstructure even though the aged carrot hadwilted. Carrots are resilient and the aged carrot was almost completely rehydrated during aqueous fixation for scanningelectron microscopy, therefore, most of the cell walls in the aged carrot appear turgid. However, some aged carrot cellshad broken cell walls. Thus, large gaps in the tissue (Fig. 2e) and collapse were apparent (Fig. 2f). Broken cell walls andcollapsed cells were not apparent in the fresh sample (Fig. 2g).

Figure 2. Prepackaged peeled and washed baby carrot. Outer surface of fresh carrot (a). Cross section of the outer layers of freshcarrot showing crushing of the cells due to initial processing steps of peeling and washing (b). Cross section of fresh carrot (c). Crosssection of aged carrot showing cell wall breakage and cell collapse (d, arrows). Aged carrot, close view showing the effects of cellwall breakage (e). Aged carrot, close view showing cell wall breakage and cell collapse (f). Fresh carrot cross section showing no cellwall breakage or collapse (g). Scale bars: a, 200 m; b, 50 m; c, d 1 m; e-g, 200 m.

3.3 Flower buds Broccoli

Broccoli is harvested when the immature flowering heads are growing rapidly21

. Broccoli should be consumed within amonth if stored at 0 C or 3 days if stored under ambient conditions

22. The floret buds (Fig. 3a, b) are more susceptible to



5/12

decay than the stalk and quickly show dehydration and superficial mold growth (Fig. 3a-c) upon aging. Undesirable

changes in color is accelerated by microbial growth as the pH decreases resulting in the conversion of chlorophyll to

pheophytin23

. Fresh broccoli epidermis is smooth because the cells are turgid (Fig. 3c). The aged epidermis is dehydrated

and moldy (Fig. 3d). Cross sections of fresh (Fig. 3e) and aged (Fig. 3f) stems are similar at low magnification and show

minor differences at higher magnifications (Fig. 4a, b). Intercellular spaces appear smaller and cell walls appear thickerin the fresh (Fig. 4a) and than those in the aged (Fig. 4b) sample. Cell walls in the aged carrot were wavy, indicative ofdehydration and less turgidity.

Figure 3. Scanning electron micrographs of broccoli florets. Aged broccoli flower buds showing dehydration and fungal growth onthe epidermis (a, b).Epidermis of a fresh stalk (c) showing smooth, hydrated cells and an aged stalk (d) showing dehydration andfungal growth. Cross section of a fresh stalk showing tissue organization (e). Cross section of an aged stalk (f). C, cortex; CW, cellwall; IS, intercellular space; P, pith; VB, vascular bundles. Scale bars: a, e, f, 1 mm; b, 500 m; c, d, 200 m.

3.4 Fruit Kiwifruit

Kiwifruit is harvested mature and unripe when the fruit is firm and softening occurs during the ripening process.

Microscopy has been used to document changes occurring during ripening at the microstructure level and correlated with

penetrometer tests to measure the hardness of the whole fruit28

. During ripening, the angular cells become more rounded

and starch granules degrade. Kiwifruit consists of distinct regions including the outer and inner pericarp and



6/12

a

Figure 4. Scanning electron micrographs of broccoli florets. Cortex of the fresh stalk showing thickened parenchyma cell walls (a),turgid cells, and small intercellular spaces. Aged cortex cells of the stalk (b) showing somewhat wavy cell walls, less apparent turgor,thin cell walls and large intercellular spaces. CW, cell wall; IS, intercellular space. Scale bars: a, b, 10 m.

the core. The rate of change and composition of cell wall components differs in each tissue region. Cell walls in all

tissues change considerably in structure and become thicker during ripening24, 25

. The thickening of the cell walls

coincides with the solubilization of pectin26

. Pectin hydrolysis and the modification of hemicelluloses are also involved

in ripening and fruit softening in papaya27

.

Intercellular air space volumes were shown to increase with ripening using morphometric studies. The volume increase

correlated with the disintegration of the middle lamella, thus, the middle lamella was replaced by air. However, as fruit

became very ripe, intercellular spaces decreased probably due to the loss of tissue integrity and collapse. Cellularstructure changes are, however, tissue dependent. Intercellular air spaces did not increase in the locular region in the

inner pericarp with ripening. Cell walls exhibit less change, i.e., cell wall thickening was less, in the locular region than

those of other tissues. Intercellular space did increase, however in the locular wall28

.

The desirable soft texture of kiwifruit is due to swelling of the cell walls and weakening of the middle lamella24

. The

changes that occur in kiwifruit during ripening are similar to those in other fruit. The ripening changes in kiwifruit,

however, occur before the start of ethylene production as is common in climacteric fruits. Tensile strength measurementswhich show structure changes indicated that cell walls in unripe kiwifruit ruptured. Whereas, as the tissue got softer, the

stress breaks occurred around cells, indicating that the adhesive substance between cells, the middle lamella, was weaker

than the cell walls in ripe fruit29

.

Kiwifruit skin has a multitude of trichomes, which is responsible for the fuzzy appearance and feel to the fruit. Thetrichomes are of two size classifications. The large trichomes are about 2.5 mm long; the twisted short trichomes are

about 200 m long (Fig. 5a-c). Platelets also occur on the surface of the skin and might be flattened trichomes or

outgrowths of the epidermis rather than wax1. In fresh kiwifruit, the platelets appear to be closely appressed to the

surface of the fruit (Fig. 5a) whereas those in the aged fruit are more at an angle from surface of the fruit (Fig. 5b,c).

The outer pericarp of fresh kiwifruit (Fig. 5d) contains a mixture of large and small cells. The outer cells, just beneath the

skin are radially compressed in the fresh (Fig. 5d) and in the aged (Fig. 5e) fruits. Cells further into the outer pericarp ofthe aged fruit show increased compression (Fig. 5e). Starch granules in the fresh (Fig. 5d) kiwifruit have virtually

disappeared in the aged (Fig. 5e) fruit in agreement with Hallett et al in their observations of starch degradation30

.



7/12

(

) Figure 5. Scanning electron micrographs of kiwifruit. Fresh fruit showing the various types of trichomes covering the skin surface (a)without evidence of fungal growth. Aged fruit showing the short, twisted trichomes and platelets (b) covering the skin surface; theplatelets might be flat trichomes since they do not appear to be wax and appear to be outgrowths of the epidermis. An extensivegrowth of fungal hyphae and the lifting of the surface platelets is also evident. Aged fruit showing the base of a long trichome andthe growth of fungi (c). Fresh cross section of the outer pericarp showing a mixture of large and small cells in the flesh and the radiallycompressed cells near the surface (d). Aged cross section showing areas of further compression resulting from aging; note the ovals(e). S, starch granules. Scale bars: a, 1 mm; b, c, 200 m; d, e, 1 mm.

3.5 Fungi mushroomA fresh, white button mushroom of high quality has a tightly closed cap (pileus), the gills are covered by a membrane

(velum), the stalk is short and the mushroom is white. Browning, which might occur during storage, of the mushroom is

unacceptable. Mechanisms associated with browning range from rough handling to microbial activity. Low-dose

irradiation was shown to be effective in the prevention of browning and microbial growth31

. As the mushroom ages, it

continues to grow and creates undesirable quality changes. The stipe grows, the velum stretches and breaks, and thepileus opens to expose and release the spores on the surfaces of developing gill tissue. The broken velum leaves a ring of

tissue on the stipe, the annulus32

. Part of the pileus structure is shown in Figure 6a. Spores form on the inner portions of

the gills shown by the arrows (Fig. 6a); the remaining pileus and stipe are composed of hyphal masses (Fig. 6b-d). Freshmushroom hyphae are tightly compacted, have smooth, plump, hydrated cell walls and evident cytoplasm (Fig. 6b, d).

More space is apparent between hyphal strands in the aged mushroom (Fig. 6c) and cell walls are somewhat collapsedand wrinkled (Fig. 6c, e), due to dehydration stress. Cytoplasm is no longer evident in the aged mushroom (Fig 6e)

agreeing with findings of Braaksma et al.32

where growth of the pileus was reported to occur by



8/12

Figure 6. Scanning electron micrographs of white button mushroom. Cross section of the cap showing the cap body and the gills ( a),on the surfaces of which spores are formed (arrow). Fresh mushroom hyphae (b) showing the close appression of the hyphae withlittle air space. Aged mushroom hyphae (c) showing the separation of hyphae and resulting air spaces. Fresh mushroom hyphaeshowing evident cytoplasm and plump cell walls (d). Aged hyphae showing collapsed, wrinkled hyphae (e) indicative of dehydration.

Scale bars: a, 500 m; b, c, 100 m; d, e, 10 m; f, g, 20 m.

expansion of the vacuoles which would push the cytoplasm to the limits of the cell walls. Fresh mushroom spores are

smooth, rounded and immature (Fig. 7a, d) and the majority are covered by a smooth substance (Fig 7d). Spores in the

aged mushroom are ovoid and areas of mesh-like material are apparent (Fig 7c). Close examination of individual spores

shows that they are covered with irregular deposits or precipitates on their surfaces (Fig 7d), probably the remnants ofthe digested and dehydrated smooth, membranous substance apparent in Figure 7c.

4. CONCLUSION4.1 Textural Characteristics

Produce texture is determined by tissue structure and physiology. Microscopy has been used to relate tissue

microstructure and texture by measuring tissue failure under tension followed by observation of the areas of failure using

various microscopy methods. Texture is largely dependent on cell structure and the relationships between cells.

Microstructure studies can show many of the characteristics giving rise to texture in any given produce commodity.

All fruits and vegetables are composed of cells. Cell characteristics include cell structure, composition, size, shape, type,

water content; air spaces between cells; cell wall structure, composition and thickness; and adhesion between cells.Adhesion is determined mainly by the state of the middle lamella. Fruits and vegetables are dynamic, living systems,

thus, structural and textural changes occur continuously. Textural diversity at the cellular level has been studied invarious tissues using tensile strength measurements and correlating the measurements with observation by microscopy.

Examination of the fracture surfaces allowed the detection of differences in tissue strength and juiciness and provided

insight into the cellular basis of plant texture. It also helped to identify specific cell characteristics which influence the

sensory texture attributes of hardness and juiciness33

.



9/12

Figure 7. Scanning electron micrographs of white button mushroom. Immature spores at low magnification (a) from a fresh

mushroom. Mature spores from an aged mushroom at low magnification (b). Immature spores at high magnification from a freshmushroom (c) showing the smoothly covered spores. Mature spores from an aged mushroom ( d) showing the precipitate which isprobably the digested and dehydrated formerly smooth covering seen in h. Scale bars: a, b, 20 m; c, d, 5 m. Soft texture is a desirable characteristic in kiwifruit. In contrast to apple fruit, kiwifruit cells remain in close apposition

whereas apple cells have more intercellular spaces and have very little cell-to-cell contact, thus the intercellular spaces

account for part of the reason the two fruits have such differing textures28

.

4.2 Shelf life extension

Considerable time might elapse between harvest and the consumers table because fresh produce is shipped world-wide.

Thus, cold storage and commodity-specific packaging is essential for the protection and preservation of fruits and

vegetables. Minimally processed, i.e., those that are cut into bite-sized pieces or ready-to-eat salads, require modified

atmosphere packaging and controlled atmosphere storage34

.

At the consumer level, dehydration can be controlled by applying water sprays and using open refrigeration in the

supermarket. Refrigeration alone is insufficient to meet the demands of todays marketing techniques. Therefore, otherpost-harvest treatments are needed to provide an increase of storage life. Edible coatings, such as waxes, and those which

also include anti-browning agents form a semi-permeable barrier to air to control respiration and prolong shelf-life 35, 36.

Due to increasing concern of unacceptable residues on fruit surfaces following chemical treatments, a number of

chemical-free post-harvest techniques have been investigated to increase shelf life.

Post-harvest heat treatment has been in commercial use for many years37

, however, the technology is still being perfected

for different commodities. Short hot water rinses were investigated as a method of reducing post-harvest losses of

cantaloupe (Galia melon, Cucumis melo cv. reticulatus)38

and sweet peppers39

. Scanning electron microscopy showed



10/12

that the fruit surfaces were free of debris and fungal spores and that superficial cracks in the epidermis were sealed. Hot

water immersion proved to be effective in disinfestations and maintenance of fruit quality of Valencia orange40

. Light

and electron microscopy showed that there was little effect on surface waxes of the orange fruit as a result of heating.

Mandarin oranges were heat-treated for 3 min prior to storage at temperatures ranging from 50 C to 58 C in the

assessment of temperature effectiveness in storage performance. Treated and control fruit surfaces were compared bySEM observation of mandarins. Heat treatment at 50-54 C smoothed the granular waxy surfaces of mandarins, at 56 Cpartly removed the wax and treatment at 58 C completely removed the wax

41. Hot water brushing of organic citrus fruits

reduced postharvest decay and scanning electron microscopy showed that the epicuticular waxes had been smoothed by

the treatment and the cracks and stomata were sealed by the wax, thus, reducing pathogen entry sites42

.

Heat treatment of heat-sensitive mango cultivars was ineffective due to the resulting tissue damage. Such heat-related

injuries were investigated using scanning and transmission electron microscopy where cuticle and exocarp ruptured and

exposed internal cells. Cell walls of the mesocarp were convoluted and thickened and starch granules still remained in

the tissue suggesting that the carbohydrate metabolic enzymes had been disrupted43

.

Other non-toxic shelf life extension methods include treatment with carbon dioxide followed by refrigerated storage.

Firmness was increased and decay susceptibility decreased (compared to those at harvest) in strawberries followingstorage at 0 C. The positive effects were enhanced by treatment with CO2 followed by storage at 0C. Examination ofthe fracture surfaces of strawberry following tensile testing indicated that the primary mode of tissue failure was cell-to-cell debonding, not cell breakage, in both air and CO2-treated fruit

44. An increase in firmness over harvest is common in

fruit that is stored at 0 C. The mechanism is not well understood but is theorized to be due to an increase in viscosity ofpectin because no change in structure or chemistry is observed

45, 46.

4.3 Quality and Specific Disorders

Electron microscopy demonstrated the withered juice sac or dry pulp disorder, where the soluble solids content is

higher in the rind than in the pulp, in Ponkan mandarin orange at the cellular level. Prior to the onset of symptoms of the

disorder, nuclear divisions occurred in the cells of the flavedo (the colored part of the rind). The appearance of symptoms

corresponded to further changes in the flavedo cells, the enlargement of the cells and their vacuoles and a decrease in thecytoplasm content. The tonoplast disappeared in latter stages of the disorder with only a nucleus and small amounts of

cytoplasm remaining. Thus, the disorder was caused by changes occurring in the rind: cell division, growth andsenescence, which caused water to be translocated to the rind due to a water potential gradient. Treatment with

gibberellic acid, a plant hormone which slows senescence, prior to storage delayed the onset of the disorder47

.

Water loss, determined by weight loss, was found to be a non-destructive predictor of chilling injury in grapefruit and

lemon. Chilling injury appears as distinct, swollen areas with pitting and cuticular damage. Prior to the appearance of the

gross symptoms of chilling injury, scanning electron microscopy revealed calcium oxalate crystals growing inside cracks

which had developed around the stomata48

.

Ultrastructure and electrophoresis were useful in determining the reason for degreening inhibition of bananas. In

bananas, degreening is inhibited above 24 C, ripening at higher temperatures results in retaining thylakoid membranesand a delayed breakdown in chlorophyll b as well as a reduced break-down of pigment-protein complexes. Retention ofthylakoid membranes is an important factor in the failure of Cavendish bananas to degreen when ripened at tropicaltemperatures

49. Fruit softening in banana is the result of the coordinated degradation of pectin, hemicelluloses and starch

in the banana pulp50

and was shown using stress-relaxation probe measurements to describe the changes in physical

properties during softening of the banana fruit pulp.

4.4

Microscopy as a tool

Microscopy can be used as an effective tool to understand and explain the physiological, chemical and structural

processes involved in determining parameters that indicate fresh produce quality. Correlating physical measurements

with findings from microscopy may be used to illustrate where improvements are needed in a specific commodity.



11/12

REFERENCES

[1] Esau, K., Development of the seed plant, [Anatomy of Seed Plants], 2nd

edition, John Wiley & Sons, Inc., NewYork, 7-16 (1977).

[2] Jewell, G.G., Fruits and vegetables, [Food Microscopy], Vaughn, J.G., ed., Academic Press, New York, 1-34

(1979).

[3] Glenn, G.M., Chiou, B-S., Imam, S.H., Wood, D.F. and Orts, W.J., Role of cuticles in produce quality andpreservation, [Produce Degradation: Pathways and Their Prevention], Lamikanra, O. and Imam, S., eds., CRC Press,

Boca Raton, FL, 19-53 (2004).

[4] Bukovac, M.J., Rasmussen, H.P., and Shull, V.E., The cuticle: surface structure and function, Scanning Elect.

Micros. 3, 213-223 (1981).[5] Roy, S., Watada, A.E., and Wergin, W.P., Characterization of the cell wall microdomain surrounding

plasmodesmata in apple fruit, Plant Physiol. 114(2),539-547 (1997).

[6] de Barsy, T., Deltour, R., and Bronchart, R., Ultrastructrual and microstereological study of aging in Golden

Delicious apples during coldstorage, Acta Hort. 258, 379-388 (1989).[7] Harker, F.R., Redgwell, R.J., and Hallett, I.C., Texture of fresh fruit, Hort. Rev. 20, 121-224 (1997).

[8] White, P.J., Recent advances in fruit development and ripening: an overview, J. Exper. Bot. 53(377), 1995-2000

(2002).

[9] Possingham, J.V., Chambers, T.C., Radler, F., and Grncarevic, M., Cuticular transpiration and wax structure and

composition of leaves and fruit ofVitis vinifera, Aust. J. Biol. Sci. 20, 1149-1153 (1967).

[10] Eckert, J.W. and Ogawa, J.M., The chemical control of postharvest diseases: deciduous fruits, berries, vegetables

and root/tuber crops, Ann. Rev. Phytopath. 26, 433-469 (1988).[11] Wood, D.F., Imam, S.H., Sabellano, G.P., Eyerly, P.R., Orts, W.J., and Glenn, G.M., Microstructure of produce

degradation, [Produce Degradation: Pathways and Their Prevention], Lamikanra, O. and Imam, S., eds., CRC Press,

Boca Raton, FL, 529-561 (2004).

[12] Jensen, W.A., Histological procedures, [Botanical Histochemistry], W.H. Freeman, San Francisco, 55-99 (1962).

[13] Wood, D.F. and Cornish, K., Microstructure of purified rubber particles, Int. J. Plant Sci. 161(3), 435-445 (2000).[14] Humphreys, W.J., Spurlock, B.O., and Johnson, J., Critical point drying of ethanol-infiltrated, cryofractured

biological specimens, Scanning Elect. Micros.1, 275-281 (1974).

[15] Costerton, J.W., Cheng, K.J., Geesey, G.G., Ladd, T.I., Nickel, J.C., Dasgupta, M., and Marrie, T.J., Bacterial

biofilms in nature and disease, Annu. Rev. Microbiol. 41, 435-464 (1987).

[16] Costerton, J.W., Lewandowski, Z., Caldwell, D.E., Korber, D.R., and Lappin-Scott, H.M., Microbial biofilms,

Annu. Rev. Microbiol. 49, 711-745 (1995).

[17] Punja, Z.K., Chittaranjan, S., and Gaye, M.M., Development of black root rot caused by Chalara elegans on freshmarket carrots, Can. J. Plant Path. 14(4),299-309 (1992).

[18] Tatsumi, Y., Watada, A.E., and Wergin, W.P., Scanning electron microscopy of carrot stick surface to determine

cause of white translucent appearance J. Food Sci. 56, 1357-1359 (1991).

[19] Barry-Ryan, C. and OBeirne, D. Quality and shelf-life of fresh cut carrot slices as affected by slicing method, J.Food Sci. 63, 851-856 (1998).

[20] Buick, R.K. and Damoglou, A.P., The effect of vacuum packaging on the microbial spoilage and self-life of

ready-to-use sliced carrots, J. Sci Food. Agric. 38, 167-175 (1987).

[21] Tian, M.S., Downs, C.G., Lill, R.E. and King, G.A., A role for ethylene in the yellowing of broccoli after harvest,

J. Amer. Soc. Hort Sci. 119, 276-281 (1994).

[22] King, G.A. and Morris, S.C., Early compositional changes during postharvest senescence of broccoli, J. Amer.

Soc Hort. Sci. 119, 1000-1005 (1994).[23] Gunawan, M.I. and Barringer, S.A., Green color degradation of blanched broccoli (Brassica oleracea) due to acid

and microbial growth J. Food Processing Preserv. 24, 253-263 (2000).[24] Sutherland, P., Hallett, I., Redgwell, R., Benhamou, N., and MacRae, E., Localization of cell wall polysaccharides

during kiwifruit (Actinidia deliciosa) ripening Int. J. Plant Sci., 160(6), 1099-1109 (1999).

[25] Bauchot, A.D., Hallett, I.C., Redgwell, R.J., and Lallu, N., Cell wall properties of kiwifruit affected by lowtemperature breakdown, Postharvest Biol. Technol. 16(3), 245-255 (1999).

[26] Redgwell, R.J., MacRae, E., Hallett, I., Fischer, M., Perry, J., and Harker, R., In vivo and in vitro swelling of cell

walls during fruit ripening Planta, 203(2), 162-173 (1997).



12/12

[27] Paull, R.E., Gross, K., and Qiu, Y., Changes in papaya cell walls during fruit ripening, Postharvest Biol. Technol.

16, 79-89 (1999).

[28] Hallett, I.C., Macrae, E.A. and Wegrzyn, T.F., Changes in kiwifruit cell wall ultrastructure and cell packing during

postharvest ripening, Int. J. Plant Sci. 153(1),49-60 (1992).[29] Harker, F.R. and Hallett, I.C., Physiological and mechanical properties of kiwifruit tissue associated with texture

change during cool storage, J. Amer. Soc. Hort. Sci. 119(5), 987-993 (1994). [30] Hallett, I.C., Wegrzyn, T.F. and MacRae, E.A., Starch degradation in kiwifruit: in vivo and in vitro ultrastructural

studies, Int. J. Plant Sci. 156(4), 471-480 (1995).

[31] Beaulieu, M., B liveau, M., D'Aprano, G., and Lacroix, M., Dose rate effect of irradiation on phenolic

compounds, polyphenol oxidase, and browning of mushrooms (Agaricus bisporus), J. Agric. Food Chem. 47(7), 2537-

2543 (1999).

[32] Braaksma, A., Van Doorn, A.A., Kieft, H., and Van Aelst, A.C., Morphometric analysis of ageing mushrooms(Agaricus bisporus) during postharvest development, Postharvest Biol. Technol. 13(1),71-79 (1998).

[33] Harker, F.R., Stec, M.G.H., Hallett, I.C., and Bennett, C.L., Texture of parenchymatous plant tissue: a comparison

between tensile and other instrumental and sensory measurements of tissue strength and juiciness, Postharvest Biol.Technol. 11(2),63-72 (1997).

[34] Mattheis, J. and Fellman, J.K., Impacts of modified atmosphere packaging and controlled atmospheres on aroma,

flavor, and quality of horticultural commodities, HortTechnol. 10(3),507-510 (2000).

[35] King, A.D. and Bolin, H.R., Physiological and microbiological storage stability of minimally processed fruits and

vegetables, Food Technology 43(2),132-135 (1989).

[36] Lee, J.Y. Park, H.K., Lee, C.Y. and Choi, W.Y., Extending shelf-life of minimally processed apples with edible

coatings and antibrowning agents, Lebensm.-Wiss. U.-Technol. 36, 323-329 (2003).

[37] Barkai-Golan, R. and Phillips, D.J., Postharvest heat treatment of fresh fruits and vegetables for decay control,Plant Dis. 75, 1085-1089 (1991).

[38] Fallik, E., Aharoni, Y., Copel, A., Rodov, V., Tuvia-Alkalai, S., Horev, B., Yekutieli, O., Wiseblum, A., and Regev,

R., Reduction of postharvest losses of Galia melon by a short hot-water rinse, Plant Pathol. 49(3),333-338 (2000).

[39] Fallik, E., Grinberg, S., Alkalai, S., Yekutieli, O., Wiseblum, A., Regev, R., Beres, H., and Bar-Lev, E., A uniquerapid hot water treatment to improve storage quality of sweet pepper, Postharvest Biol. Technol. 15(1),25-32 (1999).

[40] Williams, M.H., Brown, M.A., Vesk, M., and Brady, C., Effect of postharvest heat treatments on fruit quality,

surface structure, and fungal disease in Valencia oranges, Aust. J. Exper. Agric. 34(8),1183-1190 (1994).

[41] Schirra, M. and D'hallewin, G., Storage performance of Fortune mandarins following hot water dips, Postharvest

Biol. Technol. 10(3), 229-238 (1997).

[42] Porat, R., Daus, A., Weiss, B., Cohen, L., Fallik, E., and Droby, S., Reduction of postharvest decay in organiccitrus fruit by a short hot water brushing treatment, Postharvest Biol. Technol. 18(2),151-157 (2000).

[43] Jacobi, K.K. and Gowanlock, D., Ultrastructural studies of 'Kensington' mango (Mangifera indica Linn.) heatinjuries, HortSci. 30, 102-103 (1995).

[44] Harker, F.R., Elgar, H.J., Watkins, C.B., Jackson, P.J., and Hallett, I.C., Physical and mechanical changes in

strawberry fruit after high carbon dioxide treatments, Postharvest Biol. Technol. 19(2),139-146 (2000).

[45] Werner, R.A. and Frenkel, C., Rapid changes in the firmness of peaches an influenced by temperature, HortSci.,13, 470-471 (1978).

[46] Werner, R.A., Hough, L.F., and Frenkel, C. Rehardening of peach in cold storage, J. Amer. Soc. Hort. Sci. 103,

90-91 (1978).

[47] Wang, S., Physiology and electron microscopy of the withered juice sac of ponkan ( Citrus reticulata) during

storage, Acta Hort. 343, 45-50 (1993).

[48] Cohen, E., Shapiro, B., Shalom, Y., and Klein, J.D., Water loss: A nondestructive indicator of enhanced cell

membrane permeability of chilling-injured Citrus fruit, J. Amer. Soc. Hort. Sci. 119(5),983-986 (1994).[49] Blackbourn, H.D., Jeger, M.J., and John, P., Inhibition of degreening in the peel of bananas ripened at tropical

temperatures. III. Changes in plastid ultrastructure and chlorophyll-protein complexes accompanying ripening in bananas

and plantains, Ann. Appl. Biol. 117, 147-161 (1990).

[50] Kojima, K., Sakurai, N., and Kuraishi, S., Fruit softening in banana: correlation among stress-relaxationparameters, cell wall components and starch during ripening, Physiol. Plant. 90(4), 772-778 (1994).

P f SPIE V l 7378 73781J 12

Wood Fruit Production situation

Documents

Transcript of Wood Fruit Production situation