Subcellular structures in fermenting cocoa beans: effect of aeration and temperature during seed and fragment incubation
Chemical reactions in cocoa seeds during fermentation and roasting may depend on post-mortem structural changes in the mesophyll cells. Aeration, temperature and acetic acid concentration vary considerably during commercial fermentation. Light and electron microscopic studies of seeds after artificial fermentations give evidence that the kind and the degree of subcellular structural changes depend on these variations. At 50 grade centigrade in the presence of acetic acid (35 mM/litre, pH 4.0) water-containing compartments are destroyed shortly before the lipid vacuoles fuse. The hydrophilic particles of the plasm become dispersed within the lipid phase. These changes occur within 6-20 h independent of the presence of air. At 40 grade centigrade in the absence of acetic acid (citric acid, pH 5.5) the seeds germinate and protein vacuoles in many cells of the mesophyll inflate considerably within 6h, which is before post-mortem structural changes, different from those following treatment in acetic acid at 50 grade centigrade, become obvious. Incubation of cotyledon fragments instead of whole seeds submerged in buffer induced these structural changes as well and were even more pronounced. The significance of temperature differences in the range of 40-50 grade centigrade and induction of germination during fermentation is discussed.
| Main Authors: | , , |
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| Format: | biblioteca |
| Published: |
1977
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| Subjects: | CACAO, FERMENTACION, TOSTADO, AIREACION, TEMPERATURA, ACIDO ACETICO, MICROSCOPIA, |
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| Summary: | Chemical reactions in cocoa seeds during fermentation and roasting may depend on post-mortem structural changes in the mesophyll cells. Aeration, temperature and acetic acid concentration vary considerably during commercial fermentation. Light and electron microscopic studies of seeds after artificial fermentations give evidence that the kind and the degree of subcellular structural changes depend on these variations. At 50 grade centigrade in the presence of acetic acid (35 mM/litre, pH 4.0) water-containing compartments are destroyed shortly before the lipid vacuoles fuse. The hydrophilic particles of the plasm become dispersed within the lipid phase. These changes occur within 6-20 h independent of the presence of air. At 40 grade centigrade in the absence of acetic acid (citric acid, pH 5.5) the seeds germinate and protein vacuoles in many cells of the mesophyll inflate considerably within 6h, which is before post-mortem structural changes, different from those following treatment in acetic acid at 50 grade centigrade, become obvious. Incubation of cotyledon fragments instead of whole seeds submerged in buffer induced these structural changes as well and were even more pronounced. The significance of temperature differences in the range of 40-50 grade centigrade and induction of germination during fermentation is discussed. |
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