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Peer-reviewed | Manuscript received: March 24, 2016 | Revision accepted: June 08, 2016 A comparative study of various screw caps

Is there any correlation between the results of a target group study and instrumental measurement?

Simone Sohnle, Myriam Braun-Münker, Felix Ecker, Fulda

TS 15945 [2]. The team also de- Summary veloped a measuring device and a way of measuring the force required Many consumers, including elderly persons, have difficulty opening pack- to open different screw caps. This aging. Screw caps are often identified as a type of packaging which is difficult device simulated the hand move- to open. A target group study and an instrumental analysis were carried out ment required to open screw caps. to evaluate different screw caps; the results were then compared. The target The study examined whether the group study revealed significant differences in the operability of individual force that participants subjectively bottles. Operability is obviously influenced by a number of different factors: felt they expended correlated with surface feel of the bottle, dimensional stability, size of the bottle and diameter the results of instrumental measure- of the cap. The study showed a correlation between the target group study ment. and the instrumental analysis. Keywords: screw caps, bottles, easy opening, ONR CEN/TS 15945:2011, The process of opening a bottle in- target group study, instrumental measurement, easy operability volves three important levels: cog- nitive, motor and strength (• Figure 1) [3]. The principle of screw caps on drink bottles is widely known. We can therefore assume that cognitive and motor levels play a minor role Introduction and that force expended is crucial to In December 2003, the Bundesar- the process of opening screw caps. beitsgemeinschaft der Senioren-Or- We postulated that there would be a ganisationen e. V. (BAGSO) (Federal correlation between the results from Association of Senior Citizens’ Or- the target group study and the re- ganizations), which represents the sults from instrumental measure- interests of elderly persons, pub- ment. lished the results of a survey on A key concern in food packaging is packaging: 26% of elderly persons the conflicting interests of conveni- stated that they often had difficulty ence and food safety. A global trend opening drink bottles [1]. for convenience packaging has been People want to live independently observed. This type of packaging is for as long as possible. When food supposed to be easy to open and to Citation: and drink packaging is difficult to guarantee maximum consumer sa- Sohnle S, Braun-Münker M, Ecker F open, this causes dissatisfaction tisfaction and brand loyalty. This (2016) A comparative study of and a willingness to switch to other has already been clearly demonstrat- various screw caps. Is there any products. The target group above 60 ed by the authors in a study on the correlation between the results years of age should not be subjected operability of packaging for milk of a target group study and to age-related restrictions as a result and sausage products [4, 5]. instrumental measurement? of packaging and consequently dis- However, in terms of food safety, Ernahrungs Umschau 63(9): tance themselves from the product. product protection and safety are 186–191 of primary importance. The risks This study is based on a target which may arise from incorrectly This article is available online: group study carried out to evaluate opened packaging have already been DOI: 10.4455/eu.2016.039 packaging in accordance with CEN/ studied elsewhere [6].

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Materials and methods Materials cognitive level This study looked at six commercial drink bottles (• Figure 2). Three ref- erence pairs were formed from the six examples of packaging tested: motor level Bottles A and B were glass bot- tles (Brunneneinheitsfl asche, a stand- ardized type of glass bottle made strength in Germany) of the same volume level (0.7 L). These bottles had different caps. Bottle A had a “rolled-on” alu- minum screw cap; a tamper-evi- dent seal was provided by means of Fig. 1: The levels of action for the process of opening packaging [3] a paper strip. Bottle B had a plastic cap. Specimens C and D were PET water mance and motor skills as well as the opening mechanism and the bottles of different sizes; both bottles hand strength. opening instructions and fi nally had an identical cap (Ø = 28 mm). As part of the study, six groups of open the packaging. The stage Bottle C had a volume of 1.5 L, 20 participants (male and female) was regarded as successful if Bottle D 0.5 L. aged between 65 and 80 opened this occurred within fi ve min- Bottles E and F differed in bottle size the above-mentioned bottles. Each utes. (volumes: Bottle E = 1 L; Bottle F = participant opened only one drink 2. The study then tested the effi - 0.33 L) but had the same cap size bottle, to exclude any potential lear- ciency of the opening process. The (Ø = 38 mm). The screw caps on ning effects. The age distribution of participants received a new iden- Bottles B to F had integrated tam- participants is shown in • Table 1. tical packaging. The “effi ciency” per-evident caps. In these cases, the The participants were approached criterion was regarded as fulfi l- tamper-evident seal has to be broken randomly in cafés and at public led if this packaging was opened when fi rst opened; the band is then events. A belief that they led an “in- within one minute. detached. dependent lifestyle” was a require- 3. After sampling a portion of the ment for participation. product, e.g. pouring the drink The testing situation was particu- into a glass, the participants age group male [%] female overall larly important in the target group stated their satisfaction with the [years] [%] [%] study; we aimed to reproduce the opening process according to a 65–69 10 25 35 calm atmosphere of the domestic kit- fi ve-tier scale (from +2 “very 70–74 10 25 35 chen table. Requirements of space [7] good” to -2 “very bad”). This 75–80 10 20 30 and suffi cient lighting (at least 300 stage was regarded as successful overall 30 70 100 Lux) were taken into account [8]. if the satisfaction rating was level Participants who needed reading 0 or higher. Tab. 1: Composition of test group glasses were invited to wear them. according to CEN/TS 15945 The hand movements adopted by the participants in the test were vi- deo-recorded, to improve our inter- Methods pretation of results and analysis of Target group study opening behavior. The target group The target group study was based study was divided into three stages on the technical specifi cation CEN/ in accordance with the requirements A B C TS 15945:2011 [2]. This specifi ca- of the technical specifi cation CEN/TS tion describes a standard procedure 15945:2011: to determine the ease of opening 1. The study fi rstly determined consumer packaging as well as the effectiveness of the opening consumer satisfaction. It makes al- process. Here the participants lowance for the fact that increasing were expected to familiarize age leads to decreasing visual perfor- themselves with the packaging, D E F

Fig. 2: Packaging studied

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Instrumental measurement pletely loosened from the thread of drink bottle distance [mm] The opening of the screw caps was the drinks bottle and rests loosely Bottle A 200 characterized by the Texture Ana- on top. Bottle B 350 lyser® (Texture Analyser®.HD Plus) The speed of the pull movement Bottle C 240 based on the positive surface [in of the Texture Analyser® was the Bottle D 230 newton meters, NM]. Taking into same for all bottle types. The so- account the test speed, the data was called pre-speed was determined Bottle E 160 supplied as force conducted [in Nm]. at 5 mm/s up to the tightly Bottle F 160 The device to open the screw caps stretched steel wire. The subsequent Tab. 2: Method for instrumental (• Figure 3) was developed by the test speed, the pull movement of the measurement of screw caps authors to replicate real conditions. Texture Analyser®, was 20 mm/s. using Texture Analyser® (pre- The jaws which surround the lid of The distance required for the bottle speed = 5 mm/s, test and re- turn speed = 20 mm/s, release the bottle assume the function of cap to rest loosely on the thread of value = 0.049 N) fingers in opening the screw caps. the bottle differed for each drinks The three pairs of jaws are covered bottle and was a crucial factor in the A uniformly moderate learning ef- with rubber to imitate the struc- measurement (• Table 2). fect was apparent in the repeat- ture and characteristics of human The study aimed to ensure that the ed opening of individual bottles skin. The jaws’ prism shape pro- six different bottles were measured (• Table 4); only for Bottle C did some duces four main points of contact. in comparable conditions. The bra- participants require significantly cket used to clamp the bottle was longer for repeated opening. The re- height adjustable, ensuring that the sults of the sub-test on efficiency are pulley and spool were on the same not represented graphically. level. This produced comparable measuring conditions. Instrumental Satisfaction with the opening process measurement was performed for 20 Participants’ satisfaction with opening opening processes per bottle type. the drink bottles is shown in • Fig- ure 5. The participants gave different evaluations for the bottle caps. Discon- Results tinued opening processes were rated -2 (“very bad”) in accordance with CEN/ Results of the target TS 15945. group study Bottle A which was opened successfully Effectiveness and efficiency by all participants, was graded from Fig. 3: Device for instrumental of the opening process “very good” to “neutral” and thus was measurement of opening force (jaws for clamping the The results for individual bottles the only bottle to meet the require- cap are marked green in the in the sub-test on effectiveness are ments of CEN/TS 15945. The partici- foreground; steel wire pulled shown in • Figure 4. Opening time pants rated Bottle B as “good” to “very upwards by the Texture Anal- percentages are listed in • Table 3 in bad”; one opening attempt was dis- yser® is marked red) the time categories of 0–11 seconds continued and was therefore rated -2. and 11–31 seconds. Bottle C was graded from “very good” The jaws are fixed in a frame made All 20 participants were able to open to “very bad”. Like the glass bottle with from aluminum U-profile, on which the glass bottle with the rolled-on the rolled-on aluminum cap, Bottle D lies a spool. This spool is wrapped aluminum cap within 11 seconds. proved popular with participants. Aside twice round with steel wire (Ø = 0.5 The glass bottle with the plastic from the discontinued opening process, mm). The jaws are pressed onto the cap was opened more slowly. One exclusively positive evaluations were screw cap by a threaded rod and two opening process was discontinued given. Bottles E and F with wide plas- compression springs, so that the cap for Bottles B, D and E; two opening tic caps received ratings from “very is loosened as soon as the Texture processes were discontinued for good” to “very bad”. Analyser® starts to pull the steel Bottles C and F. The 1.5 L PET water cable upwards. The spool is held in bottle (C) was opened more slowly Results of instrumental position with an arm. The frame than Bottles D to F, yet faster than measurement with green jaws and the spool then Bottle B. The small PET water bottle turn anticlockwise and the Texture (D) and both orange juice bottles The distributions of the opening Analyser® executes a vertical pull (E and F) were opened at a similar force required for individual drink movement until the cap is com- speed. bottle caps are shown in • Figure 6.

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There is no standard distribution in drink eff ectiveness [%] effi ciency [%] the measurements. bottles time time time time disconti- disconti- 20 caps per drink bottle were stu- category category category category nuation nuation died using the Texture Analyser®. 0–11 s 11–31 s 0–11 s 11–31 s As the packaging of Bottle C had Bottle A 100 0 0 95 5 0 meanwhile changed, the study in- Bottle B 55 40 5 74 26 0 stead measured instrumentally Bottle C 70 20 10 61 39 0 identical bottles of sparkling water. Bottle D 90 5 5 100 0 0 Bottle A was the easiest to open; the Bottle E 90 5 5 100 0 0 arithmetic mean of the force expen- Bottle F 80 10 10 100 0 0 ded was 2.4 Nm. The rolled-on alu- minum cap was only secured with Tab. 3: Results of sub-tests on eff ectiveness and effi ciency a paper strip. The force required to All fi gures are in percentages, in relation to the number of participants open the screw cap was lower in in the respective categories comparison to the caps with integ- rated tamper-evident bands (Bottles drink bottle eff ectiveness [s] effi ciency [s] satisfaction [degree of satisfaction] B to F). Bottle A 5.06 4.68 1 The second glass bottle, Bottle B, Bottle B 11.31 7.23 0 required much more force to open. Bottle C 8.66 9.53 0.5 The mean from 20 measurements Bottle D 7.56 5.52 1 was 8.8 Nm. The spread of mea- Bottle E 7.40 6.19 2 surements for individual caps was Bottle F 5.88 4.38 1 relatively wide; the force required was between 6.0 and 11.0 Nm. Tab. 4: Median opening times and satisfaction Bottles C and D had the same cap; the mean opening forces were cor- Discussion 100%. Familiarity with juice bottles respondingly similar (mean: Bottle was lower: 85% for Bottle E and 90% C: 4.4 Nm; Bottle D 4.6 Nm). The The bottles differed in terms of ma- for Bottle F. instrumentally measured force terial, volume and cap diameter. Al- The glass bottle with the aluminum required to open the juice bottles most all participants were familiar cap was rated positively. was also similar (mean: Bottle E with the concept; familiarity with Bottle B was more diffi cult to 3.4 Nm; Bottle F 3.2 Nm). water bottles (Bottles A to D) was open in comparison to Bottle A;

16 Bottle A 14 Bottle B 12 Bottle C 10 Bottle D 8 Bottle E 6 Bottle F 4 2 number of participants 0

0–3 4–7 8–11 12–15 16–19 20–23 24–27 28–31

discontinuation opening time [s]

Fig. 4: Time taken to open the bottles (eff ectiveness test)

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12 Bottle A

10 Bottle B Bottle C 8 Bottle D Bottle E 6 Bottle F 4

number of participants 2

0 -2 -1 0 1 2

degree of satisfaction

Fig. 5: Satisfaction of participants with the opening process (according to CEN/TS 15945)

the satisfaction of study partici- diffi cult to pour out a portion of the 0.33 L only “good”. In compa- pants was correspondingly lower. water. The dimensional stability rison to the 1.5 L water bottle, the This was due to the integrated of the bottle was low; the bottle 1 L juice bottle caused no diffi cul- tamper-evident cap and the sa- often buckled when pouring and ties when pouring and the partici- fety band which was diffi cult to the participants spilt water. Bottle pants found no fault with its shape loosen. These difficulties were D was rated better in the target or size. confi rmed by instrumental mea- group study; it was smaller and The median opening times for in- surement. The force required to fi tted better in the hand and it was dividual bottles differed (• Table open this cap was particularly easier to pour. 4). Bottle B was opened more high, between 6.0 and 11.0 Nm, The screw caps on the juice bot- slowly overall in comparison with fi ve times greater than the force tles were larger, the participants the other bottles. required for the aluminum cap. were able to grasp them well and The participants’ age and gender had Bottles C and D were rated posi- the transmission of force was no infl uence on the effectiveness or tively. Instrumental measurement therefore better. The measured effi ciency of the opening process, required a force between 4.0 and force required to open the juice or the satisfaction. However, all the 6.0 Nm to open both PET water bottles (Bottles E and F) was be- study participants who discontinued bottles and to loosen the tam- tween 2.0 and 5.0 Nm. In the the opening process were female and per-evident band. The size and target group study, the 1 L juice aged between 75 and 80 (however, unwieldiness of Bottle C made it bottle was rated “very good”, and one female participant from the

20 Bottle A Bottle B Bottle C

15 Bottle D Bottle E Bottle F

10

5

0

Number per category 80–119 120–159 160–199 200–239 240–279 280–319 320–359 360–399 400–439 440–479 480–519 positive surface[Nm] [Nm]

Fig. 6: Results of the force used by the Texture Analyser® to open the bottles Nm = Newtonmeter

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65–69 age group also discontinued to apply less force. Furthermore, References opening Bottle C). They stated that the two predetermined breaking they could not apply enough force points on the tamper-evident cap 1. Beschwerdepool für ältere Verbraucher. and they usually received support did not work. The tamper-evi- Ergebnisse der Befragung zum Thema Ver- from various aids or their husbands dent band was not detached and packung. URL: www.bagso.de/fileadmin/ in everyday situations. the cap stuck when lifted up the Aktuell/Verbraucherforum/Verpackungen_ Only Bottle A fulfilled the require- bottle thread. This bottle was Ergebnisse_Langfassung_01.pdf Zugriff ments of CEN/TS 15945 for easy- rated worst in the target group. 13.03.16 to-open packaging in the target Instrumental measurement also 2. DIN Deutsches Institut für Normung e. V. group study. Bottles B to F are not showed that this bottle required Verpackung – Leichtes Öffnen – Kriterien easy-to-open packaging accor- the greatest force to open. und Prüfverfahren für die Bewertung von ding to this standard, as the par- The posited hypothesis was there- Verbraucherverpackungen. Deutsche Fas- ticipants discontinued the opening by confirmed: the smaller the sung CEN/TS 15945: 2011 process or gave a negative evalua- force required to open, the greater 3. Ecker F et al. (2015) Ease of opening – a tion (-1 corresponding to “bad”). the satisfaction of participants in target group study based on CEN/TS 15945 opening screw caps. for blister packed stacked sliced sausage. As water and sufficient fluid intake Conference Innovations in Food Packaging, Conclusion are particularly important in old Shelf Life and Food Safety. Fraunhofer In- age, elderly persons should be able stitut and Elsevier Verlag, Erding 15.09.15– The 1.5 L water bottle was found to open bottles easily in everyday 17.09.15 to be unwieldy; its poor dimen- situations. The above research on 4. Braun-Münker M, Turwitt T, Ecker F (2015) sional stability made it difficult to drink bottles has demonstrated, in Verbrauchergerechte Milchverpackungen pour out a portion of water. The both the target group study and im Test. dmz – Deutsche Molkerei Zeitung aluminum screw cap proved to be the instrumental analysis, that 23(11): 8–10 an advantage in the target group further action is required. 5. Braun-Münker M, Günther A, Ecker F study. This was also confirmed by (2015) Leichtes Öffnen von Wurstverpack- instrumental measurement. ungen – Zielgruppenprüfung nach CEN/TS The satisfaction results showed 15945 zur Handhabbarkeit unterschiedli- that consumers prefer a larger cher Verpackungen von gestapelter Wurst. diameter of bottle cap. The par- Fleischwirtschaft Frankfurt 95(12): 103– ticipants were better able to grip 105 large bottle caps (motor level, see 6. Braun-Münker M, Ecker F, Günther • Figure 1). The thread lengths of A (2016) Von wegen einfach! – Wie the juice bottles were also shor- erklärungsbedürftige Verpackungen Pa- ter in comparison to the PET tienten herausfordern. Deutsche Apotheker water bottles. Positive influences Zeitung 17: 30–33 on opening behavior should be 7. DIN EN ISO 8589:2010-06: Sensorische further discussed. Analyse - Allgemeiner Leitfaden für die Pouring out a portion of liquid Gestaltung von Prüfräumen. Beuth Verlag, was also easier with the juice Berlin (2010) bottles. The dimensional stability 8. DIN EN 12464-1:2011-08: Licht- und of these bottles was better than Beleuchtung - Beleuchtung von Arbeitsstät- the 1.5 L water bottle. The size ten – Teil 1: Arbeitsstätten in Innenräumen. and shape of the 1 L juice bottle Beuth Verlag, Berlin (2008) also performed well. The small Conflict of Interest DOI: 10.4455/eu.2016.039 bottles (Bottle D and F) were on The authors declare no conflict of interest. average rated positively; instru- mental measurement confirmed the satisfaction of participants. Simone Sohnle The screw cap on Bottle B dem- Myriam Braun-Münker Prof. Dr. Felix Ecker onstrated clear room for im- Hochschule Fulda provement in comparison to the Fachbereich Lebensmitteltechnologie other drink bottles. This cap is Leipziger Straße 123, 36037 Fulda obviously not suited to elderly E-Mail: [email protected] persons, who are perhaps able

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