TIM PENGAMPU MK TEKNIK PENGOLAHAN DAN RANCANGAN PROSES

2015

EXTRACTION AND FERMENTATION

Definisi

Ekstraksi adalah operasi pemisahanMelibatkan 2 fasePelarut adalah bahan yg ditambahkan untuk

membentuk fase yang berbeda dari bahan yang mengandung ekstrak

Kemungkinan fase yang terlibat (padatan-cairan, immiscible liquid, padatan-gas).

Solid–liquid extraction is a basic operation to separate one or more components contained in a solid phase by a liquid phase or solvent.

The components transferred from the solid to the liquid phase are called solutes

the insoluble solid is called inert.

Applications of the solid–liquid extraction in the food industry extraction of animal and vegetable oils and lipids, obtaining extracts from animal or vegetable

materials, obtaining sugar, manufacturing tea and instant coffee

21.2 Solid–Liquid Equilibrium

extraction mechanism occurs in three successive stages until equilibrium is reached:

1. Phase change of the solute occurs when the solute changes from solid to liquid phase

2. the solute is diffused in the solvent contained inthe pores of the solid. Mass transfer rate in this stage is expressed as:

3. Once the solute reaches the particle’s surface, it transfers to the solution due to a concentration gradient. Mass transfer rate at this stage is expressed as:

the global transfer rate is affected by:1. including size of particle, 2. temperature, 3. stirring of the fluid, and4. Type of solvent

mass transfer takes place until equilibrium is reached concept of equilibrium

Equilibrium is reached when the solute is totally dissolved, thus obtaining a solution with uniform concentration.

If the system has reached equilibrium, two phases will separate when it is left to stand:

1. Extract or overflow, which is the separated solution, solute, and solvent, also called miscella

2. Exhausted solids or underflow, which is the residue formed by the inert solids and the solution retained within them. If equilibrium has been reached, this solution will have the same solute concentration as the extract; if the solution is saturated, the inert solids can also contain undissolved solute.

21.2.1 Retention of Solution and Solvent

Solution retention is defined as the amount of solution retained per unit mass of inert solid

Solvent retention is defined as the amount of solvent retained per unit mass of inert solid

Retention data are presented in graphic form by using triangular diagrams or diagrams in rectangular coordinates free of inert solids

solidinert kg

solvent kgr

21.2.2 Triangular and Rectangular Diagrams

Mass balances are employed. Calculations can be done by algebraic or

graphical methods.

21.2.2.1 Triangular Diagram

This type of diagram is a right triangle in which the vertex of the right angle represents the inert component (I), while the other two vertexes represent the solvent ( D) and the solute (S).

The mass fraction of the solvent is plotted against the mass fraction of the solute for the underflow phase.

The hypotenuse of the triangle represents the overflow or extract since it does not contain inert component.

For any point, the mass fraction of the solute is obtained on the horizontal axis, while that corresponding to the solvent is obtained on the vertical axis.

The mass fraction of inert component can be obtained from the difference of one minus the sum of the other two fractions.

The underflow data should be obtained experimentally, which allows representation of the retention curve (GK). Generally, the data experimentally obtained are:

The mass fractions of solute and solvent are obtained from these data:

The retention curve is obtained by plotting the values of XS against those of XD (Figure 21.1). If the amount of retained solution is constant, then the retention line is:

which is the equation of a straight line with an ordinate to the origin equal to r /(r+ 1) and a slope equal to –1, that is, a straight line parallel to the hypotenuse.

When equilibrium is reached during a solid–liquid extraction, the concentration of the overflow phase (YS, YD) is the same as the concentration of the liquid retained by the solids of the underflow.

21.3 Extraction Methods

The extraction of solutes contained in a solid phase can be performed in different forms.

1. single stage,2. multistage concurrent system, and3. continuous countercurrent multistage system.

21.3.1 Single Stage

The single-stage method is a batch operation.

A food (RA) is in contact with all the solvent (D) to obtain an underflow R1, which contains the inert solid and the solution retained in the solids, and the overflow E1 that contains the formed solution (Figure 21.5a)

This is considered an ideal stage, so the overflow and underflow streams are in equilibrium.

The data available are the feed stream or amount of food RA and its composition XSRA, and the amount of solvent D and its composition YDD.

On the other hand, the amount of overflow and underflow, as well as their composition, should be determined.

Mass balances should be set up to determine these variables

The mathematical model solved by algebraic or graphical methods.

The representative point M, called the pole, is fictitious and can be found in the triangular diagram from the intersection of the straight lines RA D R1 E1 that join the food with the solvent and the overflow with the underflow, respectively (Figure 21.5b).

To solve the stated problem, the M pole should be placed on the straight line RAD, having the following coordinates:

the solute fraction in the overflow is

21.3.2 Multistage Concurrent System

This method of operation consists of repeating the single-stage method in successive stages in such a way that the underflow obtained in each stage is fed to the following stage.

21.4 Solid–Liquid Extraction Equipment

21.4.1 Batch Percolators

This type of extractor consists mainly of an open deposit or container witha false bottom.

The solid particles are placed in the container on the falsebottom, which is usually a type of filter or grid.

The solvent is distributed on the surface of the solid in such a way that the solvent percolates.

The resulting solution crosses the false bottom so that it can be recovered as overflow or extract

21.4.2 Fixed-Bed Multistage Systems

There are cases in which the extraction rate is high and it is possible to perform the desired extraction in one stage. However, this does not happen frequently, so it is required to circulate the solvent under countercurrent through a series of tanks containing the solid.

Thus, the fresh solvent is introduced into the tank containing the most nearly exhausted material, flows through the different tanks, and leaves the system through the recently loaded tank.

21.4.3 Continuous Percolators

This type of percolator has a moving bed, and most of them operate under countercurrent.

Bollmann extractor. This extractor, also called Hansa–Mühle, consists of a

bucket elevator unit in a vertical chamber. As shown in Figure 1.11, buckets are loaded with solid at the top right side of the extractor and sprayed with a “half miscella” solution as they descend.

In this zone of the extractor, the solid and the solution descend concurrently.

The miscella recovered at the right bottom of the extractor is called full miscella.

The buckets with partially exhausted solids rise through the left side of the extractor and are sprayed with pure solvent at a determined place in the top zone of the extractor.

In this zone, the solid and the solvent circulate under countercurrent in such a way that a half miscella is obtained in the bottom while the bucket with exhausted solids is discharged through the top.

This type of extractor is usually employed in processes of extracting oil from seeds.

Hildebrandt extractor. This is an immersion extractor, since the solid is always

immersed in the solvent. It consists mainly of three elements placed in such a way

that they form a U, as shown in Figure 21.12. Solids are fed through one of the vertical branches and

conveyed to the bottom by a screw.

Bonotto extractor. This extractor consists of a vertical column divided into

compartments by horizontal plates (Figure 21.13). Each plate has an opening placed alternately on two

consecutive plates. A vertical axle contains rotating blades placed between plates that wipe the solids and cause them fall to the lower plate through the opening.

The solids are fed through the top of the column and go downwards, while the solvent enters at the bottom, so the miscella exits through the top of the column.

Liquid and solid flows are countercurrent. These extractors are used to extract oil from seeds and dry

fruits. Other extractors are based on this extraction principle by immersion in a column, although with some variants, such as Allis Chalmer, Oliver, etc.

Rotocel extractor. This equipment is based on percolation extraction. It consists of a closed cylindrical vertical chamber in which

a cylindrical tank divided into compartments rotates. The bottom of the tank is wedge shaped and perforated

(Figure 21.14). The solids are charged in these compartments at a determined point and successively sprayed with miscellas that are more diluted each time, until they are sprayed with pure solvent.

The liquid crosses the bed and is collected at the bottom, and the miscella obtained from one compartment is used as solvent for the preceding compartment.

There is a drain zone after solids are sprayed with pure solvent, and finally the exhausted solids are discharged.

This type of extractor is used for sugar and oil extraction.

21.4.4 Other Types of Extractors

Vertical immersion column extractor. This extractor consists of a vertical column, (Figure

21.15) in which the solid is fed into the top, and a conical screw axle that impels the solid material in an ascending and descending movement.

The solid that reaches the bottom of the column is driven to a second column by a conveyor screw.

In this second column, the solid is extracted by a perforated bucket elevator and then fed into the top of the second column, draining through the buckets and flooding the first column.

The highest part of the column has a truncated cone shape and is wider than the rest of the unit, making it easier to clarify and extract the solution.

The exhausted solids are eliminated at the top of the second column.

C.M.B percolation extractor. This is a moving-bed percolation extractor consisting of a metal

chamber that contains a perforated-bucket chain (Figure 21.16). The buckets contain the solid, which is sprayed with

intermediate solution coming from the bottom from the chamber. The solution drains through the solid while the buckets move. Fresh solvent is sprayed near the end of the chain. Once the solvent is drained through and the solids are

exhausted, the bucket is discharged. Then the empty bucket is filled with new solids, and the

extraction process begins again. The final miscella is collected at the bottom of the chamber at

the section corresponding to the back of the solids feed zone. It can be observed that, in this process, the solvent and solid

flow countercurrent due to a series of pumps that take the miscella to the different buckets.

This extractor is widely used because it is simple and easy to operate.

The De Smet extractor is similar to this one, but there the solid is transported on a conveyor belt.

Soxhlet Extractor. This apparatus is usually employed in laboratory

experiments, although it is used in low-capacity facilities; Figure 21.17 shows this type of extractor.

It can be observed that the solvent is boiled in a boiler and the condensed vapors are sent to the container where the solid is placed.

The overflow is sent back to the cauldron where solvent vapors are produced and used for new extractions.

In this way, the boiler accumulates the solute.

21.5 Applications to the Food Industry

Extraction of sugar from beets. Sugar can be obtained from sugar beet using water as the

extraction liquid. The extractors used are generally a diffusion battery or Hildebrandt

or Bonotto extractors. In order to facilitate the extraction operation, beets are cut in long

V-shaped slices to form the bed and are then immersed in water. The liquid may have difficulties crossing the bed, so it is convenient

to introduce water under pressure. The cellular structure should not be damaged since undesired

components, besides sugar, can be extracted. Also, the temperature should be controlled, because if it is too high,

undesired nonsugared compounds can be extracted. In general, the final extract obtained contains approximately 15% of

dissolved solids. The extract should be purified by a sedimentation and filtration

process and then concentrated in evaporators that work under pressure.

The crystals are separated by centrifugation, finally obtaining sugar.

Elaboration of instant coffee. The extraction process is one of the most important stages

in the production of instant coffee. The extraction is usually done on roasted and crushed beans,

using water as the extractive fluid, obtaining a final solution that contains around 25 to 30% of solids.

The solution is then taken to an atomizer, which yields instant coffee grains as a final product.

Coffee extraction is carried out in equipment especially designed for this process, consisting of extractors that work under countercurrent, multistage systems, and fixed beds.

The solid recently charged is extracted with water at 100°C and, as the process continues, the temperature of the water is increased.

High temperatures favor the hydrolysis of insoluble carbohydrates, which in this way become soluble, increasing the soluble solids content in the final solution.

However, very high temperatures can hydrolyze substances that may confer undesirable aromas and flavors to the extract.

Elaboration of instant tea. An initial stage to obtain instant tea is extraction with hot

water, an operation carried out in fixed-bed extractors, using water at 70°C in the first stages and reaching 90°C during the last.

Vacuum is applied to the extractor to facilitate the operation, filling it with dehydrated leaves and re-establishing the pressure with a carbon dioxide stream.

The final extract has a solids concentration between 2.5 and 5%, which is too low.

For this reason, a distillation that eliminates the volatile products is performed until the final product is obtained.

The residual solution, free from aromas, is concentrated by vacuum evaporation, obtaining a solution that contains 25 to 50% of soluble solids.

The aromatic fraction obtained during the distillation stage is added to the concentrated solution. Next, instant tea is obtained during a drying stage by freeze drying or atomization.

The initial extraction stage can also be performed in moving-bed extractors similar to the Rotocel type under countercurrent and continuously.

Extraction of vegetable oils. The process of extraction with solvent is very important

in order to obtain vegetable oils and can be used as an alternative to or in combination with a squeezing operation.

After the extraction process, the overflow should be filtered to eliminate suspended solids.

The filtrated solution that contains oil, solvent, and water is driven to an evaporation tower to eliminate the solvent, which can be recycled.

The oil, water, and residual solvent mixture is conveyed to a steam distillation tower, where oil free from solvent is obtained, while vapors are condensed and taken to a separator where water is eliminated and solvent recovered.

Extraction processes in fishes. Fish receives a series of treatments during the

obtaining of oil and flour, among which an extraction with solvent stage is included.

Initially, fish is cooked to coagulate proteins and sterilize raw material.

Next, there is a pressing stage that yields a cake and a solution that contains water and oil.

This solution is centrifuged to separate the water and oil; the cake obtained during the press stage is dried, and flour that still contains oil components is produced.

Oil components can be extracted with a solvent; in this way, flour with a high protein content and an oil-solvent stream, from which it is possible to separate the new oil fraction, are obtained.

Other applications. In addition to processes applied to obtain oils, many

others have the objective of obtaining specific final products.

One of these products is the pectin fraction of fruits, used to elaborate jams and marmalades.

A byproduct of the fruit juice industry is the exhausted pulp, which contains pectin that can be extracted with an acid solution and later precipitation with alcohol.

Problem

It is desired to extract oil contained in flour that has 10% oil and the rest inert material. Thus, 500 kg of flour and 3000 kg of an organic solvent are fed into a single-stage system. If the amount of solvent retained by the solids is 0.8 kg/kg of inert solids, calculate: (a) the composition of the overflow and the underflow; (b) the amount of overflow and underflow; and (c) the percentage of oil extracted.

FERMENTASI

FERMENTASI

: proses pengubahan BAHAN ORGANIK menjadi bentuk lain dengan bantuan mikroorganisme (bakteri, protozoa, jamur/kapang /fungi, ragi/yeast)

CONTOH FERMENTASI : PEMBUATAN TAPE, TEMPE, ONCOM, KECAP, ROTI, KEJU, BIR, YOGURT, SILASE, PENCERNAAN DALAM RUMEN.

Fermentasi bisa untuk :mengolah bhn pakan, mengatasi sampah & pencemaran, pembuatan Probiotik &Protein Sel Tunggal (PST).

CONTOH LIMBAH YG DAPAT DIFERMENTASI

JENIS ENSIM YANG DIHASILKAN M.O :1.      PROTEOLITIK2.      SELULOLITIK3.      HEMISELULOLITIK4.      AMILOLITIK5.      FERMENTOR GULA6.      LIPOLITIK7.      LIGNOLITIK8.      METANOGENIK9. PEMBENTUK ASAM DLL.

KEUNTUNGAN FERMENTASI 1.  MENGHILANGKAN ATAU MENGURANGI ZAT ANTINUTRISI2.  MENINGKATKAN KANDUNGAN NUTRIEN3.  MENINGKATKAN KECERNAAN4.  LEBIH MENYEHATKAN5. LEBIH AWET

JENIS MIKROBIA 1. BAKTERI LACTOBACILLACEAE AS. LAKTAT ACETOBACTER AS. ASETAT2. RAGI/YEAST SACCHAROMYCES T.U S. CEREVISIAE 3. JAMUR AEROB, PROD. ENSIM ↑ ASPERGILLUS PENICILLIUM

M.O JUGA MENGELUARKAN HASIL SAMPING :- ASAM ASETAT - RASA LEZAT & MENGAWETKAN PAKAN- ASAM LAKTAT- TEKSTUR : FERMENTASI SUSU PENGGUMPALAN PROTEIN

M.O ENSIM, INTRASEL & EKSTRASEL. ENSIM -- PROTEIN KOMPLEK -- SEBAGAI KATALISATOR REAKSI BIOKIMIA. ENSIM -- PROTEIN SENSITIF THD PERUB KONDISI :1.      KELEMBABAN2.      SUHU3.      PH4.      OKSIGEN5.      NUTRIEN6. INHIBITOR

Tipe bakteri

Minimum (0C)

Optimum (0C)

Maks (0C)

Sumber bakteri

Psychro philic

0 – 5 15 – 20 30 Air & mak beku

Meso philic

10 – 25 30 – 40 35 – 50 Bakteri patogen & non patogen

Thermo philic

25 – 45 50 – 55 70 – 90 Bakteri pembent spora dr

tanah, air

SUMBER MIKROBIA, DARI :- BAHAN PAKAN- TANAH- SALURAN CERNA HEWAN DSB. DARI ALAM -- CAMPURAN BBRP M.OSUMBER MIKROBIA -- PENTING U/ AKTIVITAS & KONDISI FERMENTASI- DARI SERASAH DAUN : SELULOLITIK, LIGNOLITIK & AEROB- DARI RUMEN : SELULOLITIK, PROTEOLITIK DAN AMILOLITIK SERTA ANAEROB

DAUN TANAMAN LIAR

SALURAN PENCERNAAN TERNAK

SALURAN PENCERNAAN SATWA LIAR

MIKROBA PROTEOLITIK

SERANGGA

CONTOH PROSES FERMENTASI

PILOT PLANT PRODUKSI PATI, TEPUNG DAN PENGOLAHAN LIMBAH

KULTUR BATCH Dalam kultur batch pertumbuhan mo terdiri atas

sejumlah fase. Pertumbuhan sel selama fase logaritmik (eksponensial) pada laju konstan ditunjukkan

Dimana:Co= Konsentrasi sel awalCb=Konsentrasi sel setelah waktu tμ = laju pertumbuhan spesifik (1/jam)t = waktu fermentasi (jam)

Laju pertumb. Maks. (μmaks) trjd pd fase logaritmik Laju pertumb sel menurun dikarenakan kehabisan

nutrisi dan terakumulasinya produk metabolit hasil fermentasi pd medium pertumbuhan

tCC ob lnln tCC ob lnln

tCC ob lnln

GAMBAR KURVA PERTUMBUHAN MO

Pertumbuhan sel proporsional dengan ketersediaan substrat

Dimana:Cb =konsentrasi selY =Yield FactorSo =Konsentrasi subtrat awalSr =Konsentrasi subtrat akhir

)( rob SSYC

Penurunan laju pertumbuhan terkait dengan konsentrasi substrat residu dengan persamaan:

Dimana:µmaks = laju pertumbuahan spesifik maksimum (1/jam)

Sr = konsentrasi substrat residu (l/mg)Ks = Konstanta penggunaan substrat (l/mg)

)( rs

rmaks

SK

S

Laju produksi produk metabolit (etanol, asam amino, asam sitrat) ditentukan oleh laju pertumbuhan sel, dirumuskan:

qp = laju spesifik pembentukan produks

Yp/s = yield produk terkait dengan jumlah substrat

yg dikonsumsi

spp Yq /

Produktifitas kultur

Dimana:Pb = Produktivitas kultur (g/l.jam)Cmax= konsentrasi sel maksimum selama

fermentasiCo = konsentrasi sel awalt1 =lama pertumb.pd saat laju pertumb spesifik

maksimumt2 = lama fermentasi ketika sel tidak tumbuh

pada laju pertumbuhan spesifik maksimum di tambah waktu persiapan dan pemanen kultur

21

max

tt

CCP ob

CONTOH:

Inokulum mengandung 3 x104 (mg/l) saccharomyces C ditumbuhkan pada glukosa dalam kultur batch selama 20 jam. Konsentrasi sel diukur dengan interval 4 jam dan hasilnya di plot pada gambar. Total waktu yang diperlukan untuk preparasi dan pemanenan 1.5 jam. Hitung laju pertumbuhan spesifik maksimum dan produktivitas kultur