Particle size reduction and its impact in the food industry
PARTICLE SIZEREDUCTION AND ITSIMPACT IN THE FOODINDUSTRY
BACKGROUNDFood particle size has become increasingly more important to the foodindustry. Many food ingredients exist in some particulate form whether itbe powders, emulsions, suspensions, and/or pellets. Moreover, theshape and size of these particles as well as their distribution affect flavor,texture, and appearance of foods that we eat. Size and shape ofingredients also affect the stability of a given product as well asprocessability and functionality of the desired end product.Advancements in research in terms of general food technologies,biotechnologies, and nanotechnologies are bringing about an awarenessof the importance of food particle size/shape and its significance onpalatibility, digestion, bioavailability, and metabolism along with handling,packaging, storage and transport of food stocks. The physical andchemical properties of food ingredients such as particle size are ofincreasing importance to insure consistent quality and safety of products.These properties are also important to keep processing equipmentworking properly and keep maintenance to a minimum.
For those of you who are chocolate lovers, chocolate particle size is criticalfor sensory perception. The particle size will determine how the productfeels in your mouth, taste, and how it melts. Continued production anddevelopment of new products is dependent on sensory and texturalproperties for continued success to prevent product failures that have beenseen in the past. Proper texture and sensory experiences tends to ensurerepeat consumer purchases. As the public is demanding the production ofhealthy foods that contain less fat and sugar, there is a need to find bioactiveor nutraceutical ingredients. These types of ingredients provide health andmedical benefits that have have been tested through research and clinicaltrials and are known to prevent and treat diseases. As the food ingredientsare changing, this requires different forms of processing not only for tasteand texture but proper machine handling as well as new types of processingequipment.BACKGROUND(CON’T)
The medical community has made it clear that diets that are low in fatand cholesterol and high in fiber reduce the risk of cardiovasculardisease, diabetes, and certain cancers. If you recall, the first foods thatcame out that were high in fiber tasted like the cardboard box theycame in. That certainly didnt settle well with the consumer so theseproducts did not sell well. However, we have come a long way sincethen but this has taken millions of dollars of research to get here.A fair amount of research has been done on particle size distributionwhere pasting and rheological properties are concerned in terms ofstarch and flour powders. This impacts how creamy a product is aswell as how crispy and crunchy it is. Pasting refers to foods that havebeen pounded until they are reduced to a smooth creamy mass.Whereas, rheology refers to the flow of liquids and/or soft solids.Creamy texture and liquid flow are commonly found with substancesthat have complicated micro-structures as is often found in foods andfood additives.BACKGROUND(CON’T)
BACKGROUND(CON’T)All in all, many industries depend on some form of particlesize reduction. This allows for separation of components tocreate a desired product while controlling taste, texture,quality, and safety. This is particularly important for the foodand pharmaceutical industry. Particle size determinesbioavailability for both nutrients in food as well asmedications.
PARTICLE SIZECONTRIBUTIONParticle size controls a number of chemical and physicalproperties which include; reaction and dissolution rate,packing density, sedimentation, appearance, and texture.This list is by no means exhaustive but covers the majorcontributions of particle size effects.
RATE OFREACTIONChemical reactions are dependent on the surface area of aparticle. Smaller particles are more likely to participate in themaking and breaking of bonds than larger ones. Biologicalsystems have developed enzymes to increase the rate atwhich chemical reactions take place. Non-biologically,particle size is another way to increase reaction rates.
DISSOLUTION RATEParticle size also effects how well it will go into solution.This is particularly important for the food and pharmaceuticalindustries. This is directly related to bioavailability. Thesmaller the particle whether drug or food, the greater thechance of it being absorbed by the gut. Whether the particleof interest is water or fat soluble determines dissolution rateas well. Molecules that are both water and lipid soluble oftenhave the best of both worlds.
PACKING DENSITYPacking density refers to how well particles fit together. Usually, largerparticles dont pack as well in that they have more space between thembecause they have a larger surface area. Smaller particles tend to pack moredensely because they have a smaller surface area. This is probably moreimportant when you are concerned about unoccupied volumes if you aretrying to maximize content and minimize cost of packaging and shipping.Flour sacks often pack down during shipping and handling. Manufacturersoften suggest that you sift the flour before you use it. Food products suchas chewy health bars require larger particles to maintain their integrity.Smaller food particles tend to be to hard to chew and crumble. Packingdensity is particularly important to the metal industry where unoccupiedspace creates a flawed product.
SEDIMENTATIONSedimentation has to do with a particles ability to precipitateout of solution or soft solid. This is of particular interest tothe food and drug industries. Many products require thatthey remain evenly distributed in solution (suspended). Thismay be important to maintain drug dosages when the drugscome in the form of a liquid. On the other hand, it could besalad dressings (oil and vinegar suspension) which hasmore to do with product perception.
PRODUCTAPPEARANCEParticle size and distribution is an important characteristiccontributing to product appearance. Particle size affects theoverall bulk properties of the food item such as visual textureand density as well as color. Larger particle size mayindicate a chewy food, whereas smaller particle size mayindicate crunchy and less moist.
PRODUCTTEXTUREProduct texture can be easily affected by particle size.Particle size also affects how you perceive a given product.Large particle size and hence a more coarse texture altersflavor. Large particle size tends to have less distinct flavor,whereas fine particles have more flavor. One way to think ofthis on a larger scale is with lunch meats. Consider the slicethickness of prosciutto. A thick slice of this is difficult tochew and has an unpleasant flavor. Thinly sliced, it melts inyour mouth and has a very delicate flavor.
CHOCOLATESTUDYResearchers at the University of Nottingham, School of Biosciences, in the UKhave demonstrated the impact on particle size on rheological and texturalproperties of chocolate with reduced fat content. As the public is concerned withconsuming chocolate with a lower fat content due to health concerns, this groupof researchers were interested in how this would change the molten chocolateviscosity. It was known that reducing fat content would increase viscosity. Thisleads to a loss in mouth melting properties which makes the chocolate hard anddifficult to swallow. Current literature demonstrated that optimizing particle sizedistribution (increased packing fraction) actually decreases the viscosity ofsuspensions that are highly concentrated.
CHOCOLATE STUDY(CON’T)Their focus was on the impact of particle size distribution and fat content on flowproperties (rheology) and melting characteristics in this dispersion of sugar infat. They were able to demonstrate that optimizing the particle size distributionwhile reducing the fat content to a critical amount (22 percent by weight) candecrease the viscosity of the heated material and at the same time reduce thehardness of crystallized chocolate. This decreases the inter-particle contactwhich in turn reduces particle aggregate strength and structure buildup duringmelting. In its crystallized state, the molecular network is less connectedproviding for lower resistance to breakage and meltdown. This allows thechocolate to have a lower fat content and still be creamy. In this case, particlesize and distribution allows for a healthier chocolate product (lower in fat) thatretains a positive sensory input important for palatability.
GRAIN STUDYResearchers at the University Department of Medicine in Bristol UK looked atthe effects of plasma glucose and insulin responses to changes in particlesize of wheat, maize, and oat meal as well as the rate of starch digestion invitro. Data was collected from normal volunteers who ate isocaloric wheat-based meals and their plasma glucose and insulin levels were monitored.Isocaloric refers to a diet that has moderate carbohydrate and fat intakewhere the dieter can take in the same amount of carbs, proteins, and fatseach day. This diet is often used by bodybuilders for quick weight loss withminimal muscle (protein) loss.
GRAIN STUDY(CON’T)In this study, wheat-based plasma insulin levels increased in a stepwise fashion with whole grains less than cracked grains less thancoarse flour less than fine flour. They also found that insulin levelswere also greater with fine maize meal than with whole or crackedmaize grains but were similar with whole groats, rolled oats, and fineoatmeal.The high-to-low ratio of blood glucose was greater with wheat flour thancracked or whole grains. They also demonstrated that in vitro starchhydrolysis by the pancreatic enzyme amylase was faster withdecreasing particle size with all 3 cereals. They were able to determinethat particle size influences the digestion rate and changes inmetabolism of wheat and maize but not oats. They suggest that theincreased insulin response to finely ground flour may be relevant to thecause of diseases linked to hyperinsulinemia (excess blood insulinlevels) and to the management of diabetes.
SUMMARYFood technology has come a long way. Research is pavingthe way to finding approaches that create a balance betweenparticle size reduction and improving the functional aspectsof foods. Particle size reduction increases sensoryperception such as taste and texture while increasingbioavailability of bioactive molecules while improving on thenutritional properties. This is great news for the consumeras well as the medical community.
RESOURCE LIST:General information on food processing and new equipmenthttp://www.chemicalprocessing.com/http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/FoodIngredientsandPackaging/ucm300661.htmParticle size of wheat, maize, and oat test meals: effects on plasma glucose and insulin responses and on the rate ofstarch digestion in vitro.http://ajcn.nutrition.org/content/47/4/675.shorthttp://www.leatherheadfood.com/droplet-and-particle-sizehttp://www.leatherheadfood.com/food-innovation-researchhttp://www.izon.com/applications/industrial-research-applications/http://certifiedfoodscientist.org/Knowledge-Center/Read-IFT-Publications/Science-Reports/Scientific-Status-Summaries/~/media/Knowledge%20Center/Science%20Reports/Scientific%20Status%20Summaries/FuncationlMaterialsinFood_1106.pdfPasting Characteristics of Wheat and Sweet Potato Flour Blendshttp://www.pjbs.org/pjnonline/fin1702.pdfImpact of particle size distribution on rheological and textural properties of chocolate models with reduced fat content.http://www.ncbi.nlm.nih.gov/pubmed/18034724Fat reduced chocolate: can it ever taste good?http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4SKPT_enUS412US412&q=improving+chocolate+flavor+with+decreased+particle+size