Termalna obrada stočne hrane utiče i pozitivno i negativno na dostupnost glavnih nutrijenata hrane, a od posebnog je značaja u slučaju skroba i proteina. Prilikom obrade stočne hrane skrob i proteini su izloženi jedinstvenim i nepovratnim hemijskim modifikacijama. Ove modifikacije uključuju promene u molekularnoj strukturi kroz procese želatinizacije skroba, odnosno denaturacije proteina i mogu da rezultuju u povoljnim funkcionalnim osobinama odnosno nutritivnim vrednostima pomenutih komponenti. Međutim, pregrevanje stočne hrane prilkom termalne obrade vodi do degradacije skroba i proteina praćeno formiranjem novih kompleksa među komponentama hrane, što na kraju rezultuje negativnim nutritivnim vrednostima. Namera iznetog rada je ustanovljenje generalnih međusobnih odnosa između proizvodnih faktora koji karakteristišu termalnu obradu stočne hrane i hemijskih modifikacija skroba i proteina, kao i njihovog pratećeg uticaja na fizički kvalitet peleta

Zimonja, Ozren

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IV MEĐUNARODNA KONFERENCIJA ”RIBARSTVO” - ZBORNIK PREDAVANJA   111EFFECTS OF CHEMICAL CHANGES OF STARCH AND PROTEINS ON PHYSICAL PELLET QUALITY IN RES-PECT TO EXTRUSION TECHNOLOGYOZREN ZIMONJANorwegian University of Life Sciences, Centre for Feed Technology, Fôrtek, Ås, NorwayEFEKTI HEMIJSKIH PROMENA SKROBA I PROTEINA NA FI-ZICKE OSOBINE PELETA U ODNOSU NA TEHNOLOGIJU EKST-RUDIRANJAAbstraktTermalna obrada stočne hrane utiče i pozitivno i negativno na dostupnost glavnih nutrijenata hrane, a od posebnog je značaja u slučaju skroba i proteina. Prilikom obrade stočne hrane skrob i proteini su izloženi jedinstvenim i nepovratnim hemijskim modi-fikacijama. Ove modifikacije uključuju promene u molekularnoj strukturi kroz procese želatinizacije skroba, odnosno denaturacije proteina i mogu da rezultuju u povoljnim funkcionalnim osobinama odnosno nutritivnim vrednostima pomenutih komponenti. Međutim, pregrevanje stočne hrane prilkom termalne obrade vodi do degradacije skro-ba i proteina praćeno formiranjem novih kompleksa među komponentama hrane, što na kraju rezultuje negativnim nutritivnim vrednostima. Namera iznetog rada je ustanov-ljenje generalnih međusobnih odnosa između proizvodnih faktora koji karakteristišu termalnu obradu stočne hrane i hemijskih modifikacija skroba i proteina, kao i njihovog pratećeg uticaja na fizički kvalitet peleta.Kljucne reči: želatinizacija skroba, denaturacija proteina, fizički kvalitet peletaINTRODUCTIONA majority of the 600 million tons of compound feed produced annually are pelleted (G i l l, 2003). By the agglomeration of the various feed particles into pellets, chal-lenges of the mash feeding such as selective eating and/or segregation of the ingredients could be solved. Supplementary benefits of pelleting includes: reduced dust problems, decreased feed wastage, destruction of pathogenic organisms, less energy spent for 112 CONFERENCE PROCEEDINGS - IV INTERNATIONAL CONFERENCE „FISHERY“prehension, and eventually improved animal performance. The physical quality of the pellets is instrumental in achieving these goals. If the durability and hardness is insuf-ficient, pellets may break during storage and transport resulting in dust problems and feed loss. Although a lot still remains to be elucidated on the causes for varying physical pellet quality, composition of the diet and processing conditions have been shown to be major factors.Extruders are assembled as either single- or twin-screw machines. Screws are de-signed as changeable segments that enable mixing, conveying of the feed mash (forward and backward), kneading and developing of shear forces, with an ultimate generation of temperature and pressure. Although a huge variety of screw elements and consequent configurations exists, generally three different regions/zones along the extruder barrel can be identified; feeding zone (moistening and preheating of feed mash), kneading zone (transition of the feed mash to a plasticized dough-like mass) and final a cook-ing zone. Shaping of the extruded material is achieved at the outlet die by the action of rotating knifes (mounted at the die outlet) and by the shape of the die. Interrelations among screw configurations associated with application of the either thermal (steam) or electrical energy, facilitate great flexibility in control of production conditions such as temperature (90 to over 140ºC), total moisture content (about 30 %), residence time (up to 60 seconds), and subsequent pressure generation (up to 40 bars). The advantage of extrusion process compared to conventional pelleting is a greater flexibility in product applications, better sterilization of the feed and an improved pellet quality. Generally, processing of the feeds comprises physical, chemical and thermal treat-ments of feed previous to animal utilization (M a i e r and B a k k e r – A r k e m a, 1992). Processing treatments of the feed can vary from the simple process such as blending in the form of mash, over conventional pelleting to more complex processes when ex-pander or extruder is used (P i p a and F r a n k, 1989). Often, they are applied in order to achieve certain specific goals such as gelatinisation of starch, denaturation of proteins, inactivation of anti-nutritional factors (endogenous enzymes, trypsin inhibitors, etc.), drying/cooling and product shaping (V o r a g e n et al. (1995). These changes have influence and/or overall beneficial effect on physical characteristics, digestibility and nutritional value of the feeds.STARCH: GELATINISATION AND PHYSICAL PELLET QUALITYWhen subjected to thermo-mechanical treatments of the feed, starch can be modi-fied by mechanisms such as swelling, gelatinisation and retrogradation. Swelling com-mences along more accessible and amorphous regions, while crystalline regions mainly remain intact. As the temperature rises above the characteristic temperature known as the gelatinisation temperature, disruption of intermolecular hydrogen bonds between amylose in amorphous regions and amylopectin in crystalline regions increases. At a certain point, when a sufficient amount of heat is present, the crystalline regions are rapidly and irreversibly broken down, indicating gelatinisation. At excess water, gelati-nisation temperature for most cereal starches ranges between 50 and 70°C. Aside from swelling and disruption of the molecular and granular structures of the starch during gelatinisation, the viscosity of the media also increases. Under processing conditions where water and/or other solvents are present in limited amounts (<30 %), differences in gelatinisation behaviour can be expected (E l i a s s o n and G u d m u n d s s o n, 1996). IV MEĐUNARODNA KONFERENCIJA ”RIBARSTVO” - ZBORNIK PREDAVANJA   113C o l o n n a et al. (1992) reported a dramatic increase of gelatinisation temperature from 50-60ºC at excess water to above 100ºC at limited (<35%) moisture systems. L u n d (1984) and J a c o b s and D e l c o u r (1998) reported a minimum ratio of 0.3:1 (water: starch) as a prerequisite to initiate starch gelatinisation during heating process. Compared to a conventional pelleting, extrusion processing causes more complete gelatinisation and disintegration of the starch granules (Z i m o n j a and S v i h u s, 2008). However, the extent of gelatinisation is a function of the variable produc-tion parameters during extrusion. H o n g t r a k u l et al. (1998) showed that ex-trusion of maize with a barrel temperature of 103ºC resulted in a rate of starch ge-latinisation of 38.7 % at moisture content of approximately 30 %. When temperature increased up to 137ºC the rate of the gelatinisation was 89.3 %. C h i a n g and J o h n s o n (1977) showed that lowering screw speed lead to increase of the gelatinisation due to prolonged residence time in the extruder. A similar observation was reported by T h o m a s et al. (1999) when expander-pelleting process was used. In a study by Z i m o n j a and S v i h u s (2008), a doubled input of specific mechanical en-ergy was required to gelatinise wheat starch to the same extent as oat starch. Similar observations were also found by C a s e et al. (1992), where different cereal sourc-es required different extrusion conditions to achieve the same level of gelatinisation. C a s e et al. (1992) also showed that increase in gelatinisation resulted in increased volume and breaking strength of extrudate, while bulk density decreased. B h a t t a c h a r y a and H a n n a (1987) and C a s e et al. (1992) showed positive correlation between increase in gelatinisation and expansion ratio of the extruded pellets. This clearly indi-cates beneficial effect of gelatinised starch to a physical pellet quality. However, mecha-nism that follows starch contribution to binding of feed particles is still to be revealed.PROTEINS: DENATURATION AND PHYSICAL PELLET QUALITYWhen subjected to thermo-mechanical treatments proteins undergo disorganisation of the overall molecular structure, usually as unfolding or uncoiling of a coiled or pleat-ed structures, or as a separation of the protein into subunits, followed by aggregation. If thermo-mechanical treatment ceases before aggregation is initiated, unfolding is a re-versible process and protein can retain its native structure. However, if sufficient heat is present, non-covalent interactions (hydrophobic and electrostatic) which maintain pro-tein structure may lead to irreversible alteration of the quaternary, tertiary or secondary orders of the proteins. Under severe and/or prolonged heating, however, protein dena-turation may be followed by association and disassociation reactions, which ultimately may result in destruction of primary structure, often referred to as a degradation of the protein (F i n e l y, 1989). Transition from the native state of the protein to denatured and/or more destructed forms is interrelated with the production parameters, source of the protein and subsequent interactions among proteins and other components in solu-tion. The denaturation temperature (Td) for most protein sources is usually below 100ºC, but is highly dependent on the water content in the solution. A study by K i t a b a t a k e and D o i (1992) showed that at excess water Td of the main storage proteins in soybean meal, conglycinin (7S) and glycinin (11S), is 76.5 and 93.3ºC, respectively. When mois-ture content decreased to 29 %, however, Td of glycinin could not be detected, while Tdof conglycinin shifted to over 180°C. This indicates that proteins such as soy globulins and/or sunflower globulins are relatively heat stabile in low moisture systems. Work by 114 CONFERENCE PROCEEDINGS - IV INTERNATIONAL CONFERENCE „FISHERY“H o s e n e y (1994), on the other hand, showed that gluten proteins such as those in wheat will unfold at moisture content of 16 % even at room temperature. Beneficial effect of the proteins on physical pellet quality has been shown by W i n o w i s k i (1988) where a dramatic increase in pellet durability was observed by increasing overall protein content through addition of wheat rations from 0 to 600 g kg-1 diet. Similar results were also shown by B r i g g s et al. (1999), where a positive correlation between pellet durability and increased protein content in the diets was found. Although a number of investiga-tions suggest that proteins derived from plant sources such as wheat (W i n o w i s k i, 1988; B r i g g s et al., 1999), barley (M o r a n, 1989) and soybean meal (C a v a l c a n t i, 2004) will improve physical pellet quality, a mechanism for binding of the feed parti-cles and role of the proteins is not clear. Results by W o o d (1987), for example, showed a considerably higher physical quality of the diets containing raw soy protein compared to those containing denaturated protein. H a s h i m o t o et al. (2002) examined measures of beneficial functional properties of wheat gluten during extrusion, such as expansion ratio and specific volume, and found that wheat gluten was not as efficient as cassava starch. C a v a l c a n t i (2004) reported that protein derived from maize (e.g. maize glu-ten) had a negative effect on pellet durability. Considering the conflicting results in re-gard to denaturation of proteins and physical pellet quality, research is needed to investi-gate effects of chemical modifications of proteins and/or protein sources on pelletability.REFERENCESBhattacharya, M., Hanna, M. A., 1987. Kinetics of starch gelatinisation during ex-trusion cooking. Journal of Food Science 52: 764-766. Briggs, J. L., Maier, D. E., Watkins, B. A., Behnke, K. C. 1999. Effect of ingredients and processing parameters on pellet quality. Poultry Science 78: 1464-1471.Case, S. E., Hamann, D. D., Schwartz, S. J. 1992. Effect of starch gelatinisation on physical properties of extruded wheat and corn-based products. Cereal Chemistry 69: 401-404. Cavalcanti, W. B. 2004. The effect of ingredient composition on the physical qual-ity of pelleted feeds: a mixture experimental approach. Ph.D. Dissertation, Manhattan, Kansas State University, USA.Chiang, B. Y., Johnson, J. A. 1977. Gelatinisation of starch in extruded products. Cereal Chemistry 54: 436-443. Colonna, P., Leloup, V., Buleon, A. 1992. Limiting factors of starch hydrolysis. Eur. J. Clin. Nutr. 46: 517-532. Eliasson, A. C. and Gudmundsson, M., 1996. Strach: Physicochemical and Function-al Aspects. Pages 451-503 in: A. C. Eliasson, Carbohydrates in Food. Marcel Dekker, New York, USA.Finley, J. W. 1989. Effects of processing on proteins: An overview. Pages: 1-8 in: R. D. Phillips, J. W. Finley, Protein quality and the effects of processing. Marcel Dekker, New York, USA.Gill, C. 2003. Back to basics of growth. Feed international 24: 6-9.Hongtrakul, K., Godband, R. D., Behnke, K. C., Nelsson, J. L., Tokach, M. D., Berg-ström, J. R., Nessmith, W. B., Kim, I. H. 1998. The effects of extrusion processing of carbo-hydrate sources on weanling pig performance. Journal of Animal Science 76: 3034-3042. Hoseney, R. C. 1994. Principles of Cereal Science and Technology, 2nd edition. American Association of Cereal Chemists, Inc., St. Paul, USA.IV MEĐUNARODNA KONFERENCIJA ”RIBARSTVO” - ZBORNIK PREDAVANJA   115Jacobs, H., Delcour, J. A. 1998. Review: hydrothermal modifications of granular starch, with retention of the granular structure. J. Agric. Food Chem. 46: 2895-2905.Kitabatake, N., Doi, E. 1992. Denaturation and texturization of food protein by ex-trusion cooking. Pages: 361-371 in: Food Extrusion Science and Technology, Marcel Dekker Inc., New York, USA.Lund, D. 1984. Influence of time, temperature, moisture, ingredients and processing conditions on starch gelatinisation. CRC Crit. Rev. Food Sci. Nutr. 20: 249-273.Maier, D. E., Bakker-Arkema, F. W. 1992. The counterflow cooling of feed pellets. Agric. Eng. Res. 53: 305-319.Moran, E. T. Jr. 1989. Effect of pellet quality on the performance of meat birds. Pages: 88-107 in: W. Haresign and D. J. A. Cole, Recent Advances in Animal Nutrition. Butterworths, London, UK.Pipa, F., Frank, G. 1989. High-pressure conditioning with annular gap expander. A new way of feed processing. Advanced Feed Technology 2: 22-30.Thomas, M., Huijnen, P. T. H. J., Van Vliet, T., Van Zuilichem D. J., Van der Poel, A. F. B. 1999. Effects of process conditions during expander processing and pelleting on starch modification and pellet quality of tapioca. J. Sci. Food Agric. 79: 1481-1494.Voragen, A. G. J., Gruppen, H., Marsman, G. J. P., Mul, A. J. 1995. Effect of some manufacturing technologies on chemical, physical and nutritional properties of feed. Pages: 93-126 in P. C. Garnsworthy, D. J. A. Cole, Recent Advances in Animal Nutri-tion, Nottingham University Press, NWinowiski, T. 1988. Wheat and pellet quality. Feed Management 39: 58-64. Wood, J. F. 1987. The functional properties of feed raw materials and their effect on the   production and quality of feed pellets. Anim. Feed Sci. Technol. 18: 1-17.Zimonja, O., Svihus, B. 2008. Effects of processing of wheat or oat starch on techni-cal pellet quality and nutritional value for broilers. Animal Feed Science and Technol-ogy, 149: 287-297. 

Efekti hemijskih promena skroba i proteina na fizicke osobine peleta u odnosu na tehnologiju ekstrudiranja

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Efekti hemijskih promena skroba i proteina na fizicke osobine peleta u odnosu na tehnologiju ekstrudiranja

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