Quality Characteristics of adhesion and Semolina Pasta
10 October 200214 min reading
Givoanni Mondelli \ Istituto di Igiene e Med. Preventiva, Univ. degli Studi di Catania, Italy
People working for the sector continuously repeat that raw material quality is the basis for both dry and fresh pasta quality and the best production technology enables protection and increase of raw material excellence within the finished product. It is not possible to refuse this general point of view. It is beneficial to state that although the “quality” seems to be an abstract term, it covers one or more specific features in relation with raw materials or finished products. When it is discussed about the pasta, “raw material” identifies durum wheat, even if many composition materials are included.
To illustrate, soft wheat flour is used for fresh pasta and other characteristic composite materials are added to the dough during production of dry pasta. Therefore, quality of durum wheat semolina is the basis of pasta quality. This quality corresponds with organoleptic and nutritiousness features in conceptual sense and the characteristics cared by the consumer in much more subjective sense. In the scope of Italian market (not only Italian market) pasta quality is measured on the basis of its color, appearance and cooking features.
In order to better understand these qualities, it shall be beneficial to think their contraries. For example, grey and/or dull color, unpleasant appearance (abnormal white or dark points, failures in shapes, lack of slack or consistency, etc.) and surface and general adhesiveness.
Entered to the universal vocabulary to identify main feature of precooked ready pasta, “al dente” term (biting vitality against well-cooked structure) is a more comprehensive and open phrase, when compared to any scientific article.
In the scope of this article, relation between the semolina and pasta quality shall be highlighted in terms of adhesiveness and main features of the adhesiveness shall be explained in terms of raw material and production technology applied. On the basis of general terms and explanations, failures or missing points in aforementioned notions shall be eliminated.
MILLING OF DURUM WHEAT
Durum wheat consists of caryopsis having glassy structure; in other words, it has core structure. Crushing caryopsis of durum wheat creates sharp edged parts in various dimensions.
Granulometric tables of durum wheat semolina includes indicators identified as µ and explaining particles having homogenous dimensions and detected within minimum and maximum size limits for percent composition of semolina.
Granulometric characteristics of semolina are explained in three levels: coarsely milled, medium level milled and finely milled semolina.
Medium level milled and medium/finely milled semolina is widely used in industrial pasta production, as finely milled semolina has higher hydration rate (<220 µ) due to which its kneading period is shorter and less white marks are available on pasta as a result of under-hydrated semolina particles.
Milling of durum wheat into extremely law semolina granulometric levels creates fractional particles (un) resembling to flour obtained as a result of soft wheat milling. Finely granulated semolina may include significant level of “un” (>4%). This is not optimum for the real-quality pasta protecting its characteristics and not being adhesive during cooking.
Against better hydration advantage of finely milled semolina, it presents production related risk, which is damage on wheat starch during milling; in other words, breaking of polysaccharide chains (amylose and amylopectin). This condition causes irreversible decomposition triggering series of complex chemical and biochemical reactions during storage of semolina and production of pasta as to initiate with preparation of dough and its molding process.
ITEMS FORMING THE SEMOLINA QUALITY
Four main items should be considered in terms of quality issue: homogenous granulometry, high protein content, low ash content and color. Other factors such as non-inclusion of foreign particles, low bacterial load and non-availability of pesticide and toxic (alfatoxines) may also be added to aforementioned four items.
In particular, an additional feature of raw material quality should also be considered in terms of pasta adhesion: reduced activity of enzyme splitting starch chains. This activity causes formation of components being directly or indirectly responsible from pasta adhesion. Activity of amylase enzymes is closely related with decomposition of starch physically during milling of durum wheat and microbial contamination level, as well as its storage and humidity conditions.
Amylase activity is naturally available within caryopses, but related enzymes exist largely on surface layers of caryopses (aleuronic layer) and within the seed disposed and being extremely rich in terms of fat as to decompose flour. Semolina obtained from central side of caryopses has medium/large granulometry (>400 µ) and accordingly, low level of physical starch damage. Amylase activity occurs at lower levels. Therefore, it is expected that such semolina type may be ideal raw material in terms of pasta adhesion, but its extraction level is as low as not to have economic benefit (approximately 50-55%). To increase crop, milling diagram should be obtained from more peripheral regions of semolina core. In addition, applicable compensation level is sought to limit ash content within the semolina due to intense wheat minerals in tegumental section.
This enables 70% extraction efficiency and increase in amylase activity. Therefore, if semolina is re-granulated to decrease its granulometric values, physical starch damage arisen accordingly shall cause to deprive of quality due to pasta adhesion problem.
PROTEIN CONTENT OF SEMOLINA
Proteins within the semolina play key role in terms of pasta cooking quality; the relevant reasons are explained below.
Two phenomena realize during pasta cooking process: denaturation of proteins and gelatinization of starch. Due to the heat emerging during cooking, starch granules absorb water and swell. In this way, granules expand volumetrically and fill the gaps between the granules by surrounded with protein structure of the pasta. In addition, as a result of same heat impact, proteins make protein structure stronger by means of coagulation and provide better resistance against increasing volume of starch volume (and weight). Such two phenomena are forces balancing each other (protein denaturation and starch gelatinization), but the final outcome is to obtain structural balance within the pasta. This structure shall decompose as protein structure is as weak as not to overcome swelling of starch particles or damage on starch occurs due to this swelling and accordingly, water absorption reaches to extraordinary levels or realizes abnormally in comparison with the rate of protein coagulation.
In this case, starch particles shall early precipitate even if the cooking period is short and accordingly, polysaccharides formed shall be left free, distributed as a result of which adhesion matter shall emerge. Quality of protein structure may balance this condition and hence, limits damages. This issue is identified with the quality of gluten, which is the most significant and general component of semolina. When any protein structure having flexible gluten coagulates during pasta cooking process, pasta adhesion due to semolina shall be limited and high starch damage levels are observed due to physical stress and/or high amylase activity.
Similar case is encountered during long-term cooking period of pasta (over-cooking), because this case causes suppression of the resistance enabled by the protein structure through extreme swelling of starch, collapse of gelatinized particles inward and distribution of starch components (regardless of strength of protein structure).
ADHESION ENCOUNTERED DURING KNEADING
Semolina having abnormally decomposed starch levels and high amylase activity may present problems during kneading process. The most significant of these troubles are as follows:
1) Decomposed starch siferülitleri absorb larger amount of water when compared to the full siferülitleri not hydrated properly (up to 200 times of their weight) due to partly protein component used for gluten formation, but mainly their extremely low water absorption coefficient (nearly zero level when dough is “cold” worked).
This case causes lack of homogeneity in gluten formation and in distribution, flexibility and adhesion of general dough mass.
2) Addition of water to the dough and re-mixing process of dough mass cause hydrolytic activity of amylase enzymes and starch is partly separated from the particles constituting itself. Sugars released by the starch decompose quality of dough and create damage on the product itself after formation. In this case, time period of kneading process is also important.
If kneading period is long (>15 minutes), damaged starch level shall be inevitably high; because, in addition to the physical damage on semolina (milling), chemical and biochemical damages are available (starch hydrolysis created by amylase enzymes).
3) Increase in concentration of sugars within the dough creates conditions causing other chemical reactions in following production processes. This condition realizes particularly when the pasta is dried and drying curve is not in line with the specific product condition.
Oxidizing of yellow pigments and loss of pasta brightness due to in appropriate hygrothermal process (pasteurization) of fresh product may also be encountered.
4) Components released by the starch hydrolysis (maltose, glucose, etc.) tend to move towards surface layers of the pasta and makes pasta adhesive irreparably. So much as their concentration (and accordingly, adhesiveness of the pasta), then above explained conditions shall become evident more. Although the product is conditioned and its surface is dried partly, surface adhesion of the pasta sustains its existence at least at potential level. Even if minimum amount of water is available on product surface (vapor condensation, hygrothermal process, cooking), sugar tends to re-create colloidal solutions every time.
Here, it is obvious that non-availability of amylase activity during kneading process establishes the optimum condition not preventing pasta adhesiveness in any manner. Although this possibility is hypothetical, the sole other alternative is to keep this activity at possible lower levels. To achieve this, level of amylase activity within the semolina should be identified and its increase during dough preparation process should be taken into consideration. Secondly, it is essential to consider semolina hydration, dough temperature and time period consumed during preparation process in order for accurate realization of dough preparation process.
PRODUCTION TECHNOLOGIES AND STRATEGIES FOR LIMITATION OF PASTA ADHESION
As it is identified that pasta adhesion is closely related with the characteristics of the raw material, it should be analyzed that which technological solutions may be practices to limit aforementioned impacts. This matter is more in relation with the technological solutions regarding drying of the pasta and its processing temperature. In case of dry pasta, the best solutions are achieved by means of high drying temperatures (>85°C), finely milled semolina usage and selections of the optimum temperature responding satisfactorily to the starch decomposition at higher levels. For such type of semolina, final outcome is related with directly general protein content, in other words, amount of protein content constituting the gluten (non-availability of adhesion or low adhesion levels).
In fact, high protein level is the primary feature for high-temperature drying technologies. However, quality of gluten is important for drying under low temperatures (<60°C). Therefore, finely milled semolina having high level of starch damage is not proposed.
Adhesion problem arisen during application of semolina type whose characteristics are explained above in pasta production (only in opened or filled form) is based on following specific product features:
1) High and constant pasta humidity level: Optimum condition for enzyme activity in general sense and amylase activity with high level of free water (Aw) in particular sense;
2) Microbial instability;
3) Potential chemical and biochemical interaction between the components released free during amylase activity and the components having various sources and structure emerging due to different product formations related with pasta opening and filling;
4) Impacts of microbial stabilization processes (pasteurization) in terms of protein structure and dough starch.
All pasta is a basic composition material and its inclusion is not only related with organoleptic and cerebral sides of the pasta during fresh pasta production. Besides, egg plays significant technological role, in particular, in terms of protein added to the semolina. This contribution improves resistance and flexibility of protein structure of the pasta and assists in balancing of surface adhesion of the product.
When the protein (and lipid) contribution of egg in terms of dough preparation is put aside, physical and biochemical starch damage becomes prioritized issue. If the objective is to obtain real pasta quality not complying with adhesiveness of opened pasta, the most logical solution is intelligent raw material selection.
Adhesiveness is not only related with cooling stage, but also production process has specific impacts during fresh pasta manufacturing. Main examples are as follows:
1) “Damage” on pasta during calibration or its adhesion onto grippers of cappelletti molding machineries, stamps of ravioli molding machineries and generally, molding equipment;
2) Adhesion of pasta to the vibrating and conveyor bands, creation of obstacles or barriers by accumulating on outlets and their upside-down return together with return movements of conveyors;
3) Surface adhesion of the product reinforces balanced distribution of the each particles of the product within pasteurization machinery or vibratory channels of weighing machines;
4) Accumulation of particles and their adhesion onto the internal sides of the packages.
If change of semolina is not desired and adhesion problem is not serious as explained above, what can be an effective solution?
Dough is the basis point in terms of practicing the most effective solutions. If it is possible, a pre-mixer may be used as to assist in hydration of dough or alternatively, humidity level of dough may be kept at lower levels and molding period may be shortened. Whether dough temperature is accurate or not should be controlled (optimum temperature is 25-28°C). This temperature requires short molding period, even if high quantity of egg is used (by taking into consideration the fact that whether dough is “warm” or not) and enables more regular starch hydration.
If dough temperature is low, temperature of water added to the semolina should be increased. Before adjusting dosage of composite materials within the dough, air humidity level in operation environment should be controlled and actual humidity level of semolina should be checked.
In case of pasta opened with decomposed starch, pasteurization and particularly, saturated vapor utilization turns into significant problem. Heat and high water content has extreme contributions to the swelling of starch as a result of which fast gelatinization occurs. This condition not only creates pasta having clear, semi-transparent appearance, but also it causes retrograde phenomenon occurring after cooling of the pasta and sets the water free, which decompose resistance and texture of the pasta after packing process, as a result of which pasta turns into yellowish loose pulp.
To eliminate gelatinization of the pasta, time period during which the product is left within treatment room should be less by considering that high amount of heat and humidity is released by the pasteurization machinery and accurate balance between the treatment process and its impact should be well-observed to remove microbial existence.
Air-conditioning applied to dry pasta surface coming from pasteurization machinery is an actual technological puzzle. If the air condition is equal to the ambient conditions, the pasta shall not only be dried, but also it shall get dirty again. In other words, the sole impact of pasteurization is the damage on organoleptic characteristics of the pasta. If the temperature is high or in other words, higher than 65°C (to prevent re-contamination of the product), gelatinization of the starch shall continue and semi-transparent appearance, as well as loss of color shall occur at highest level.
What is the solution? Current semolina should be changed, instead of which medium or more than medium level milled semolina having minimum or lower starch damage ratio should be used. Finally, surface adhesion shall be eliminated and improvement in appearance and general quality of the product shall be achieved.
(1) Amylase enzymes are hydrolytic enzymes breaking chains of starch components (amylose and amylopectin). Water molecule at glycosidic level emerges as a result of this decomposition. When compared to amylopectin enzymes, amylose is easily broken by amylase.
(2) Protein denaturation changes structural organization. This change especially affects physical and biological characteristics. Denaturation does not cover protein chemical reaction or hydrolytic phenomenon. In general sense, denaturation is the irremeable fact encountered together with breaking of hydrogen bonds.
(3) Sugars released as a result of amylase activity are generally reductive. In other words, it is responsible from chemical reaction identifying oxygen loss and significant level of hydrogen gains. Existence of reductive sugars within the dough results with maillard reaction, which identifies formation of abnormal components being responsible from loss of nutritive values, change of product color, emergence of extraordinary and abnormal odors.
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