the food product may be snack pellets , a snack product ( e . g . a third - generation snack ), or shredded cereal ( e . g . shredded wheat ) for use as a breakfast cereal . according to the invention , snack pellets may be produced by a process comprising the following sequential steps : b ) extruding and heating the mixture so as to gelatinize starch , the raw material mixture typically contains up to 32 % water ( e . g . 20 – 32 %), and may optionally be preconditioned by heating , e . g . up to 95 ° c . for 20 – 240 seconds . the extrusion cooking may be done in a single - screw or double - screw extruder with a residence time of 30 – 90 seconds . the extruder will typically comprise a cooking zone at 80 – 150 ° c . and a forming zone at 65 – 90 ° c . after the extrusion with heating , the mixture will be formed into long rods , typically having a temperature of 60 – 100 ° c . ( particularly 70 – 95 ° c .) and a moisture content of 25 – 30 % or 20 – 28 %. the holding ( also termed aging ) may take 8 – 24 hours ( particularly 10 – 16 hours ). before or during the holding , the rods will be cooled , typically to 15 – 30 ° c . the holding serves to affect at least partial retrogradation of the starch , either of the amylose component , the amylopectin component or both . advantageously , the xylanase added according to the invention accelerates the retrogradation , so the holding time may be shortened . the end - point is conventionally determined by testing the hardness and brittleness of the pellets . the drying of the pellets may be done at 70 – 95 ° c . for 1 – 3 hours to reach an exit moisture of 6 – 8 % in the snack pellets . the dried snack pellets may be stored or distributed to a snack processor . the snack pellets may then be expanded by heating , e . g . by frying in oil or puffing in hot air or in microwave or infrared oven . according to the invention , shredded cereals may be produced by a process comprising the following sequential steps : shredded cereals may be made by cooking whole grain , followed by cooling , tempering , shredding , forming into biscuits and baking . the whole grain may be wheat ( e . g . white wheat ), rice or corn . the cooking may be done for 30 – 35 minutes at atmospheric pressure or 2000 hpa to reach 45 – 50 % moisture after removal of excess water . the holding ( or tempering ) may take 8 – 28 hours with cooling to 15 – 30 ° c . after shredding , the shreds may be stacked to make a biscuit , and this may be baked at 200 – 315 ° c . to around 4 % end moisture . the invention uses a xylanase , i . e . an enzyme having the activity classified as ec 3 . 2 . 1 . 8 according to enzyme nomenclature . the enzyme may suitably have a ph optimum in the range 5 – 9 . the xylanase may have hydrolytic activity on arabinoxylan with a high specificity for soluble arabinoxylan compared to insoluble arabinoxylan . the specificity may be expressed as wsps defined as the ratio wsp / wip described in wo 9523514 ; the xylanase may have wsps above 0 . 1 , e . g . above 1 . 0 or above 2 . 5 . particular examples are xylanases i and ii from a . aculeatus described in wo 9523514 . the enzyme may suitably have a temperature optimum in the presence of starch in the range of 30 – 90 ° c ., preferably 50 – 80 ° c ., particularly 55 – 75 ° c ., e . g . 60 – 70 ° c . the temperature optimum may be measured in a 1 % solution of soluble starch at ph 5 . 5 . the enzyme is typically used at a dosage of 0 . 1 – 20 mg enzyme protein per kg of dry solids in the raw material , particularly 0 . 5 – 5 mg / kg . the xylanase may be of any origin including mammalian , plant or animal origin , e . g . of microbial origin . in particular the xylanase preparation may be derived from a filamentous fungus or a yeast . more particularly , the xylanase may be derived from a strain of the following genus or species : aspergillus , a . niger , a . awamori , a . aculeatus , a . oryzae , a . tubigensis , trichoderma , t . reesei , t . harzianum , penicillium , p . camenbertil , fusarium , f . oxysporum , thermomyces , t . lanuginosus , humicola , h . insolens , bacillus , b . pumilus . rod - type snack pellets were produced with addition of xylanase . the xylanase was shearzyme , a purified xylanase from aspergillus aculeatus produced by a genetically modified strain of aspergillus oryzae at a dosage of 150 fxu / kg of raw material ( the fxu xylanase activity unit is defined in | wo 9404035 |). a control was made without addition of xylanase . the following raw materials were mixed : potato starch , wheat flour , maize flour , potato granules , salt , paprika , vegetable oil , emulsifier and flavouring . the raw materials were treated by pre - conditioning at 20 – 95 ° c . for 1 – 2 minutes followed by extrusion at 80 – 150 ° c . for 30 – 90 seconds , and forming at 65 – 90 ° c . into long rods . after forming the rods were placed on racks and stored 16 – 24 hours before cutting . at the start of ageing the rods were rubber like and did not break when bended . a simple bending test was performed several times during storage , and the rods were judged to be ready for cutting when they readily broke at the bend point when bended . finally , the rods were cut and expanded by deep - frying in palm oil at 180 ° c . for 9 – 11 seconds . the results were that the rods made with the xylanase were ready after 18 – 19 hours whereas the control without endo - amylase was ready after 24 hours . the expanded pellets from the enzyme trials did not show any significant differences compared to the reference on physical parameters . snack pellets were produced according to a sheeted pellet procedure with addition of xylanase . a control was made without xylanase . the following raw materials were mixed : potato granules , glucose , salt , vegetable oil , mono - and diglycerides as emulsifiers , and dicalciumphosphate . the raw materials were treated by preconditioning at 20 – 80 ° c . for 1 – 2 minutes , followed by extrusion at 80 – 130 ° c . for 30 – 45 seconds , forming ( sheeting ) and drying of the single pellets . the pellets were allowed to rest for at least 24 hours to assure optimal water migration , before expansion . expansion was done in palm oil at approximately 180 ° c . for 9 – 11 seconds . the texture was judged by a panel of 4 persons . the xylanase , the dosage used and the observed effect were as follows : all enzyme - treated products looked nicer than the reference with fewer , smaller and better distributed air bubbles after expansion .
in the production of edible products which includes a holding period for starch retrogra - dation , the addition of a xylanase to cereal - based raw materials accelerates the retrogradation and thus allows a shortening of the holding period .