KARAKTERISTIK BAKTERI ASAM LAKTAT AMILOLITIK LOKAL DAN PERANANNYA DALAM BAKING BEHAVIOUR PATI KASAVA ASAM
| Main Authors: | , WIDYA DWIRUKMI PUTRI, , Prof. Ir. Haryadi, M.App.Sc., Ph.D. |
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| Format: | Thesis NonPeerReviewed |
| Terbitan: |
[Yogyakarta] : Universitas Gadjah Mada
, 2011
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| Subjects: | |
| Online Access: |
https://repository.ugm.ac.id/89355/ http://etd.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=51480 |
Daftar Isi:
- Cassava (Manihot esculenta) is an important commodity in Indonesia, and potentially used as raw material for the manufacture of bakery product. Sour cassava starch, known as povildo azedo (Brazil) and amildon agrio (Colombia), is a natural fermented and sun-dried cassava starch that shows expansion properties during baking (baking behavior). Natural fermentation of cassava starch is characterized by the presence of a predominantly lactic acid microorganism. The main acid resulted from fermentation, lactic acid, was oxidized by sun drying and then causing structural changes of cassava starch. This modified structure is responsible to the baking properties of sour cassava starch. Natural fermentation of cassava starch taked a long time because of limited nutriens and the lactic acid bacteria involved in the fermentation must compete with other microorganism. The use of lactic acid bacteria as culture starter and enrich the medium by adding nutrien could shorten the fermentation time. The purposes of this study were to obtain indigeneous lactic acid bacteria from cassava fermentation, identify the isolates in strain level, use the strains for cassava starch fermentation and evaluate the role of fermentation on physicochemical and microstructure changes of cassava starch granules. The result of this reserach is expected to be useful for the development of cassava starch processing technology, especially for the production of sour cassava starch. This study was designed in several steps, including (1) isolation of lactic acid bacteria from cassava fermentation, (2) identification and characterization of LAB based on phenotypic and genotypic character, (3) formulation of a medium to enhance lactic acid bacteria growth and lactic acid production, (4) physicochemical and microstucture characterization of cassava starch granule which correlated with their baking expansion ability. Lactic acid bacteria isolation was done during five days of cassava fermentation. Two samples from the different batches of cassava roots during fermentation step of growol were purchased from local producer in Sangon Village, Kulonprogo, Yogyakarta. The samples were aseptically packaged in two pail usually used for fermentation and brought to the laboratory. They were stored at ambient temperatures of 29 + 1 o C and continued for fermentation during five day. During fermentation, samples for microbiological analysis were taken daily from soaking water and cassava root. Identification study was done according to to their phenotypic and genotypic characterization subjected to phenotypic and genotypic identification. The phenotypic characterization of these lactic acid bacteria was based on general morphology, physiological tests and API sistem. The genotypic characterization of LAB was based on 16S rRNA, pheS genes and random amplified polymorphic DNA (RAPD) analysis. Identified strains were used as starter culture in starch fermentation with an added nitrogen sources i.e peptones, ekstrak yeast or both. The selected media formulation with the type and amount of nutrien that could enhance cell growth and lactic acid production of LAB was used in the raw cassava starch fermentation. Cassava starches were fermented for 48 hours, then washed, precipitated and separated from the water. Furthermore, cassava starches were irradiated with UVA light at a wavelength 315-400 nm and an intensity 3500 flux. Baking expansion ability of fermented cassava starches were compared with native cassava starch and cassava starch which had been soaked in 1% lactic acid. The relationship between baking expansion characteristics, physicochemical properties and microstructure changes of cassava starches were evaluated to determenite the effect of fermentation. The analysis of cassava starches characteristics included pH, amylose content, swelling power, solubility, carbonyl and carboxyl content, crystallinity by X-ray diffraction (Shimadzu X-ray Diffaractometer XRD-6000), amylography by Amylographymeter ((Wingather V2.5, Brookfield Engineering Labs), thermal properties by Differential Scanning Calorymeter ((DSC-7, Universal V4.2E, TA Instruments), and starch grnules surfaces by Scanning Electron Microscope (SEM Hitachi Model S-800). The results showed that (1) lactic acid bacteria grew in cassava fermentation were domenitated by Lactobacillus sp and most of them did not have amylolytic ability, (2) The phylogenetic tree of 16S and pheS gene showed that all of selected lactic acid bacteria (twelve strains) were identified as Lactobacillus plantarum subps. plantarum But three of these strains had different pattern of template DNA as RAPD analysis and had different ability in sugar fermentation which determenited by API 50 CHL, (3) Supplementation of 1% ekstrak yeast as a protein source on cassava starch media could increase growth and lactic acid production of all LAB strains were used, i.e L. amylophylus NBRC 15881, L. plantarum subsp. plantarum NBRC 15891, L. plantarum subsp. plantarum AA2, L. plantarum subsp. plantarum AA11 and L. plantarum subsp. plantarum UA3, (4) cassava starch fermentation by using highly amylolytic lactic acid bacteria did not always produce the best baking expansion characteristic. Interrelated parameters affected the baking expansion ability of cassava starch were pH, carboxyl groups, crystallinity, amilography properties, thermal properties and magnitude of starch granules surface. Fermented cassava starch by L. plantarum subsp. plantarum AA2 had the highest specific volume compare to the other fermented starches, although still lower than lactic acid soaked (acidified) cassava starch.