Food Structure Volume 5 Number 1 Article 2 1986 Features of Food Microscopy D. F. Lewis Follow this and additional works at: https://digitalcommons.usu.edu/foodmicrostructure Part of the Food Science Commons Recommended Citation Lewis, D. F. (1986) "Features of Food Microscopy," Food Structure: Vol. 5 : No. 1 , Article 2. Available at: https://digitalcommons.usu.edu/foodmicrostructure/vol5/iss1/2 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Food Structure by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. FOOD MICROSTRUCTURE, Vol. 5 (1986), pp. 1-18 0730-5419/ 86$1.00+.05 SEM, Inc., AMF O'Hare (Chicago), IL 60666- 0507 U.S.A. FEATURES OF FOOD l\UCROSCOPY D.F. Lewis Leatherhead Food Research Association, Randalls Road, Leatherhead, Surrey KT22 7RY, England Abnract Prologue The value of food microscopy is judged by its practical "Any fool can look down a microscope." The attitude to application to food handling. Hence microscopists must explain this statement has a profound influence on the operation of a the relevance of their findings to food technologists. The food microscopy department. Is the role of microscopists to microscopist has to deal with materials that are particularly maintain 'foolproof' techniques for others to apply, or should difficult to prepare for microscopy because they often contain microscopists involve themselves with all aspects of research high levels of fat, air, sugar, salt, starch or acid. Sometimes the programmes? methods used are unorthodox and could be regarded as questionable by microscopists in more traditional disciplines. Introduction This paper considers the relationship between food microscopists, food technologists and other microscopists. Food microscopy is the application of microscopy to tech­ An approach to interpretation of images is based on the nology. In this sense the microscopist has to act as the bridge following features. between food science and technology, and the classical branches of microscopy. This role requires a mastery of the skills of 1) All interpretations should consider preparation processes, microscopy and sufficient understanding of the rf'lf'vant however simple these may be. processes to be able to recognise and explain the significance of 2) Interpretations should be based, where possible, on microscopical observations to food technologists. These senti­ differences between treated and control samples pro­ ments may seem obvious but they establish the relationships cessed in the same way. between food microscopy, technology and other branches of 3) l\'licroscopical observations should be linked to technolo­ microscopy. ln this paper I should like to consider these gical, chemical or physical observations. relationships and demonstrate the contributions of microscopy 4) Key observations should be checked by more than one to food science. microscopical technique. Dealing with Food Technologists This paper uses past and recent work at the Leatherhead Food R.A. to demonstrate how these criteria have been applied In some establishments the microscopy staff is regarded as to fa ts, vegetables, meats, proteins, confectionery, surface 'just a service section', who provide pictures of relevant samples fouling and foreign bodies. on request. Indeed, in some cases the sample is accompanied by The future of food microscopy is an exciting prospect, a note of the observation required. In other places the applying recent microscopical techniques to novel manufac­ microscopists appear to operate in isolation, \vith little attempt turing problems. being made to integrate their observations into applied research. In my view, using a microscopy department in these ways is a quite inefficient use of a most valuable asset. The most impor­ tant feature that a microscopist can add to any project is that of Initial paper r eceived February 20 1986 considering the problem from a different perspective. The food Manuscript received May 4 1986 industry embraces a wide range of disciplines but most food Direct inquiries to D. F. Lewis scientists tend to view food from a background in chemistry, Telephone number: 44 372 376761 x237 physics, microbiology or engineering. The result of tl1is is that problems are tackled at two levels: either as a consideration of molecular interactions or in terms of bulk properties. At both levels the approach is normally numerical. Microscopists tend KEY WORDS: Foreign bodies, Heat exchanger fouling, to view foods in concepts rather than numbers and at a level of Microscopy of proteins, Microscopy of fats, Microscopy of fruit organisation which is intermediate between molecular interac­ and vegetables, Microscopy of meat products, Microscopy of tion and bulk behaviour. Hence the microscopist's ~cwpoint sugar confectionery, Artefacts, Microscopy of glass fragments, should add an extra dimension to the consideration of any Role of microscopy in food science. problem. However, it is often difficult for the non-microscopist 1 O.F.I.ewis to dcaJ with pictures rather than numbers and to :-tppreciatC' concep ts - respect for tht: micrvscope and respect for the intermediate le\·cls of structure. It is therefore esst:ntlitl for the sample . The first of these requires that the sa mple should be microscopist to be able to relate his findings tn bLLik behanour produced in a suitable fonn to aiiO\' reasonable interpretation or molecular interactions in order to communicate cffecti\cl)". and the second requires safeguards to be applied in considering This requires th at the microscopist is fully im·olved with the the validity of the techniques used. 1 he type of techniques planning and background o f any project and provides opinions sometimes needed will, quite naturally, present a fear of as well as photographs. This approach can lead to problems; in artefact production in most biologicotl microscopists and many particular, 'demarcation disputes' can occur and the practical food microscopists. In the s:une way as a positive approach to applications of microscopy often depend as much ()n the artefacts is useful in de a1in g with food technologists, so a personalities involved as on technical considerations. positive approach to artefacts should be adopted in dealing with Ont• of Ute problems that a microscopist faces is the other microscopists: 'having prl'pared your sample for question of artefacts. This fear of artefacts is often advanced as microscopy, remember what you have done to it'. In my view, a reason for not incorporating microscopy into a research if the sample h a.s been prepared for microscopy, the image programme. In my experience a technical defence expla ining obtained will invariably renect the preparation technique as well preparation techniques and precautio ns has only limited effect. as the intrinsic structure of the specimen. This view is probably A positive approach with more impact is to compart micr,>scopi· acceptable to most microscopists conct:rning electron cal procedures with other scientific approaches. In this way a microscopy but it also applies to light microscopy. At a simple microscopist's function is to interpret images which :lTC lc\cl t.he refractive indn .md dispcrsivity of a mounting produced by a controUed process in the same way as a medium affect the image produced in the light microscope. biochemist may interput a reading from an oxygen electrcde E\Cn as I '"Tite this paper I see that the Proceedings of the pl<tced in a slurry of tissue, or a chemist may intcrpn:l a burcnc Royal ~licroscopical SociC:t)' contains an article by Robinson reading as relating to a panicular level of a component. I n the (1986), making a similar point and U!oing the ap ) l~ar.mce of soft case of the microscopist, the thought process is more obvious margarine by different illumination techniques as an example. si nce a picture is, in ~:e nc ral , not immediatcl)' interpreted So ever)' image sh ould be mterpreted with the preparation numerically. With the advent o f many 'black box' instruments, procedures in mind, eH:n whcrl· those procedures arc regarded even in microscopy, all scientists need to be aware that their as the best available. 'rcsuhs' arc in fact interpretations, even if the interpretations arc A second safeguard in dealing with artef..tct.s is to base inter· carried out electroni cally. ~licrosc o pists should take a lear\ here. pre lations whereve r p ossible on differl·nccs between control and In dealing with food technologists, therefore, microscopists treated samples processed for microS('OPY in idcnticaJ ways. ln need to show that they can contribute to the develnpment of this manner differences in structure can be rehued hack to the ideas and should make every effort to integrate th eir findings treatment. into the overall research programme. Thirdly, all rnicroscopicaJ observations should be linked to parallel tcehnologica.l, chcmic:ll and/or physical nbscrvations on Dcalin with Other ~licrosc o )ists the samples. This is the 'inteKr.ltivc .tpprn:Kh' recommended by Davis and Gordon ( 1982). As I have prniously mentioned, food microscopy LS \t'l) Finally, key observations should bl' checked \\here possible much an applied branch of microscOp}. 8 etausc ur thi!o, ftod by altemati\·e preparation tec..hniqucs. Fur cx..tmple, \\here the microscopy is hea\;ly dependent on methodolng)' .tnd tech· method of choice is thin sectioning, some samples could be nology dC\·elopcd by microscopists in other disciplinc!o. lltiWl'\cr, prepared by freeze-etching: .lncl \·ice-,·ersa. \\here possible,light food miuoSCOjl) has special problems associated with ~pt•C"in• t•n and electron microscopy shnuld 1»<:" used w complement each preparation cnmpared with conventional biolugK,tl mtthods. uther. Almost irwari:tbly, processed foods arc 'dead' .md ~tn the f hope that by 110\\ 1 h..t\e rn.1de my \il'WS clear Oil the role comentional vie" of fixation as prcscT\;ng the living 'ltructurc and philosophy of microscop) in (nod science.