Advances in design and performance evaluation of fresh fruit ventilated distribution packaging : a review

CITATION: Mukama, M. et al. 2020. Advances in design and performance evaluation of fresh fruit ventilated distribution packaging : a review. Food Packaging and Shelf Life, 24. doi:10.1016/j.fpsl.2020.100472The original publication is available at https://www.sciencedirect.com/journal/food-packaging-and-shelf-lifeThis review was initiated to realise the state-of-the art in optimising the ventilation and structural requirements of corrugated packaging carton design. Researchers have been using computational methods: computational fluid dynamics, particularly, the finite volume method, to analyse the airflow and heat transfer performances, and computational structural dynamics, particularly, the finite element method, to analyse the loss of compression strength due to vent-holes. Models are validated using actual testing: wind tunnel based forced air cooling system to study the produce cooling kinetics and box compression test machine for the package industry to study the structural dynamics. Studies on the rate and uniformity of produce cooling and the loss of structural strength in corrugated cartons as a function of size, shape, and location of vent-holes are reviewed. Based on experimental data, results show that the loss in strength can range between 10–40 % on addition of vent and hand holes on cartons, and reasonable increase in cooling rates is only achieved with increase in carton face ventilation area only up to 7–8 %. With regards to internal packaging components, increasing awareness of consumers to the environmental degradation of especially disposable plastic packaging means packers and suppliers must devise means to cut back and eventually eliminate plastic packaging from fruit and vegetables.https://www.sciencedirect.com/science/article/pii/S2214289419306519?via%3DihubPublishers versio

Optimising ventilated package design for postharvest handling of pomegranate fruit in the cold chain

Thesis (PhDFoodSc)--Stellenbosch University, 2019.ENGLISH ABSTRACT: Packaging is an indispensable unit operation in handling and distribution of fresh fruit. Studies on postharvest handling of a number of horticultural products highlighted the importance of package design and knowledge of fruit and package thermophysical properties to effectively accomplish the precooling, cold storage, and refrigerated transport processes. However, the thermal properties of pomegranate fruit and its parts are unknown, and packages for postharvest handling of pomegranates have not been properly investigated. The aim of this study was to address the multi-parameter design requirements of ventilated packages for handling pomegranate fruit to ensure efficient cooling, high precooling throughput, reduction in packaging material used, and improved space utilization during cold storage and refrigerated transport. Firstly, the thermal properties of whole fruit and the parts (epicarp, mesocarp, and arils) of early (‘Acco’) and late (‘Wonderful’) commercial pomegranate cultivars were determined experimentally using a transient heating probe. The values of thermal conductivity and diffusivity of both cultivars increased significantly with an increase in tissue temperature. The aril part was observed to have the highest thermal conductivity and specific heat capacity, respectively. For example, at 7 °C, the thermal conductivity (W m-1 K-1) of ‘Acco’ was 0.419 ± 0.047, 0.352 ± 0.040, and 0.389 ± 0.030 for arils, mesocarp, and epicarp, respectively. Next, a survey of the packaging used for pomegranate fruit in South Africa was conducted. Over 10 different corrugated fibreboard carton designs, with largely open tops, were found with different ventilations, ranging from 0.74–4.66% on bottom, to 0.71–5.33% on short (width), and 4.60–13.82%on the long (length) faces. The cartons were largely poorly ventilated on the short faces that leads to vent-hole misalignment and vent-hole blockage on pallet stacking which increases fruit cooling time and energy requirements. Then, a virtual prototype approach based on computational fluid dynamics (CFD) was used to redesign the ventilation of one of the most commonly used pomegranate fruit cartons with intent to improved cooling performance. Fruit cooled in the new design had more uniform temperature distribution and significantly cooled faster (1.6 hours faster in fruit in polyliner) compared to fruit in the commercial design. This result highlights the need of proper carton vent design and vent-hole alignment in stacks. Furthermore, a virtual prototype approach, based on CFD and computational solid dynamics (CSD) was used to design new ventilated corrugated paperboard cartons that hold pomegranate fruit in multilayers. Running virtual airflow and strength measurements enabled selecting the best alternatives, the ‘Edgevent’, and ‘Midvent’, which were then manufactured and evaluated for cold chain performance. The new designs improved fruit throughput by over 1.8 tonnes more fruit in a reefer compared to commercial single layer designs. For similar volume of fruit contained, the new designs saved over 31% cardboard material and an estimated equivalent of 11 trees per fully loaded 40-ft refrigerated container. Overall, the ‘Midvent’ performed best under cold chain conditions in terms of cooling efficiency and mechanical strength requirements. This warrants its commercialisation. Lastly, the quality of fruit stored in ‘Midvent’ for 12 weeks under cold chain condition (7 ± 1 °C, 90% RH) and an additional 2 weeks at ambient (shelf life) condition (20 ± 1 °C, 65% RH) was compared with fruit in commercial carton under similar conditions. Fruit respiration followed a similar pattern in both carton designs marked by a 64% reduction after precooling. At the end of the shelf life period, fruit weight loss was 5.7% and 8.9% in the ‘Midvent’ and commercial design, respectively. Sensory attributes, decay incidence and colour changes were similar in new and commercial carton designs over the storage period. Overall, research reported in this thesis has provided new data on thermophysical pomegranate fruit and has applied the virtual prototyping tool for horticultural packaging design. The new ‘Midvent’ carton design provides additional benefits in savings in packaging material, energy for fruit cooling, and bioresources efficiency. Future research should focus on performance test of this carton design in the commercial chain. New data on the thermal properties of pomegranate fruit provide needed input towards the modelling and prediction of fruit internal temperature profile during cooling processes.AFRIKAANSE OPSOMMING: Verpakking is 'n noodsaaklike eenheid in die hantering en verspreiding van vars vrugte. Studies oor na-oes hantering van 'n aantal tuinbouprodukte het die belangrikheid van pakketontwerp asook kennis rakende die termosfiese eienskappe van vrugte en verpakking beklemtoon. Dit is 'n manier om die voorverkoelings-, koelberging- en verkoelde vervoerproses effektief te bewerkstellig. Die termiese eienskappe van granate en die dele daarvan is onbekend, en pakkette vir die hantering van granate ná die oes is nog nie behoorlik ondersoek nie. Die doel van hierdie studie was om aandag te gee aan die ontwerp-vereistes van veelvuldige parameters van geventileerde verpakkings. Dit sluit in die doeltreffende verkoeling van granate om hoë voorverkoelings-deurset, vermindering van gebruikte verakkingsmateriaal, en verbeterde gebruik van die ruimte tydens verkoelde berging en vervoer te verseker. Eerstens is die termiese eienskappe van heelvrugte en die vrugdele (epikarp, mesokarp en arillus) van vroeë ('Acco') en laat ('Wonderful') kommersiële granaat kultivars eksperimenteel bepaal met behulp van 'n oorgangs verhittingsensor. Die waardes van termiese- geleiding en diffusie van beide kultivars het aansienlik gestyg met 'n toename in weefsel temperatuur. Daar is waargeneem dat die arillus gedeelte onderskeidelik die hoogste termiese geleidingsvermoë en spesifieke hittekapasiteit gehad het. By 7 °C was die termiese geleidingsvermoë (W m-1 K-1) van 'Acco' 0.419 ± 0.047, 0.352 ± 0.040 en 0.389 ± 0.030 onderskeidelik vir arillus, mesokarp en epikarp. Vervolgens is 'n oorsig gedoen oor die verpakking wat vir granate in Suid-Afrika gebruik is. Meer as tien verskillende geriffelde veselbord kartonontwerpe, met grootliks oop bokante, is ondersoek, met verskillende ventilasies, wat wissel van 0.74–4.66% onderaan, tot 0.71–5.33% op kort (breedte) aansig en 4.60–13.82% op die lang (lengte) aansig, onderskeidelik. Die kartonne was grotendeels swak geventileer op die kort-aansigte, wat gelei het tot wanopstelling van die ventilasieopening asook die verstopping daarvan op die stapel van die palet. Dit verhoog dus die afkoeltyd en energiebehoeftes van die vrugte. Daarna is 'n virtuele prototipe-benadering, gebaseer op berekeningsvloeidinamika (BVD) gebruik om die ventilasie van een van die mees gebruikte granaat kartonne te herontwerp, met die oog op verbeterde verkoeling. Vrugte wat in die nuwe ontwerp afgekoel is, het 'n meer eweredige temperatuurverspreiding gehad en vinniger afgekoel (1.6 uur vinniger in vrugte in 'polyliner') in vergelyking met vrugte in die kommersiële ontwerp. Hierdie resultaat beklemtoon die behoefte aan behoorlike karton-opening ontwerp asook ventilasiegopening opstelling in stapels. Verder is 'n virtuele prototipe benadering, gebaseer op BVD en berekeningssolieddinamika (BSD), gebruik om nuwe geventileerde geriffelde papierbord kartonne te maak, wat granate in meer lae kan verpak. Met die uitvoering van virtuele lugvloei- en sterktemetings is die beste alternatiewe, die 'Edgevent' en 'Midvent', gekies wat vervolgens vervaardig en geëvalueer is vir koue-ketting prestasies. Die nuwe ontwerpe het vrug-produksie oor 1.8 ton meer vrugte verbeter in 'n koeltrok, in vergelyking met kommersiële enkellaagontwerpe. Vir 'n soortgelyke hoeveelheid vrugte, het die nuwe ontwerpe meer as 31% kartonmateriaal bespaar met 'n geraamde ekwivalent van 11 bome per volgelaaide koelhouer van 40 voet. In die algemeen het die 'Midvent' die beste presteer onder koue-ketting toestande ten opsigte van verkoeling en meganiese sterktevereistes. Dit bevestig dus die kommersialisering daarvan. Laastens is die kwaliteit van vrugte wat gedurende 'Midvent' in koue-ketting toestand gestoor is (7 ± 1 °C, 90% RH) asook 'n ekstra twee weke by die omgewingstoestand (rakleeftyd) (20 ± 1 °C, 65% RH) is onder soortgelyke toestande met vrugte in kommersiële kartonne vergelyk. Die respirasie van vrugte het 'n soortgelyke patroon in albei kartonontwerpe gevolg, met 'n afname van 64% na voorverkoeling. Aan die einde van die rakleeftydperk was die gewigsverlies van vrugte onderskeidelik 5.7% en 8.9% in die 'Midvent' en kommersiële ontwerp. Sensoriese eienskappe, verval voorkoms en kleurveranderings was dieselfde in nuwe en kommersiële kartonontwerpe gedurende die bergingstydperk. Oor die algemeen het navorsing wat in hierdie proefskrif gerapporteer is, nuwe data oor die termofisiese eienskappe van granate verskaf, en is die virtuele prototiperings-instrument vir die ontwerp van tuinbouverpakkings toegepas. Die nuwe 'Midvent'-kartonontwerp hou ekstra besparings voordele in vir verpakkingsmateriaal, energie vir vrugteverkoeling en doeltreffendheid van biobronne. Toekomstige navorsing moet fokus op die prestasietoets van hierdie kartonontwerp in die kommersiële ketting. Nuwe data oor die termiese eienskappe van granate lewer die nodige insette vir die modellering en voorspelling van die interne temperatuurprofiel van vrugte tydens verkoeling.Doctora

Resistance to airflow, cooling characteristics and quality of pomegranate fruit inside ventilated packaging

Thesis (MScFoodSc)--Stellenbosch University, 2017.ENGLISH ABSTRACT: Ventilated packaging has found wide scale industry applications in fresh fruit handling and cooling operations. Given variations in fruit physical and thermal properties, optimal package design for a particular product and supply chain requires a multi-parameter approach incorporating cooling, mechanical and economic performance, as well as resource utilisation efficiency. A wide range of ventilated package designs are used in postharvest handling and marketing of fresh fruit, and several studies have investigated the cooling performance of fruit such as apples, citrus and table grapes; however, very little is known about the performance of pomegranate ventilated packaging. Therefore, the overall aim of this study was to evaluate the cold chain performance of some of frequently used ventilated cartons and internal packages (liners) during forced-air cooling (FAC) and cold storage in the South African pomegranate industry, in terms of resistance to airflow (RTA), cooling characteristics, energy efficiency and fruit quality. The two studied carton designs, CT1 and CT2 had 5.4% difference in total ventilation. CT2 had relatively higher ventilation in both length and width directions (8.82% and 6.67%, respectively) compared to CT1 (6.52% and 2.86%). In a stack of cartons packed with fresh pomegranate fruit (cv. Wonderful), this resulted into a generally faster fruit cooling rate (29.19%) in CT2. However, the obstruction of vent-holes in the lengthwise orientation of the stack of CT2 resulted in over 50% higher RTA compared to CT1. The results also showed that packaging fruit inside a liner offered up to 50% greater RTA than fruit packaging with no liner. Consequently, the use of liners also delayed fruit cooling and increased energy consumption, with seven-eighths cooling times close to 3 times those of fruit inside packaging with no liner. Packaging fruit with liner required about 3.9 and 8.7 times more energy to cool fruit in CT1 and CT2, respectively, compared with no-liner. Fruit in carton stacks also exhibited a heterogeneous cooling pattern, with fruit in the upstream position to incoming air cooling about 36% faster compared to fruit at back stack position. During FAC of fruit over a period of 11.6 and 4.5 hours in liner and no liner, respectively, the use of humidification to maintain 95±1% relative humidity (RH) minimised weight loss by about 13.63% compared to precooling fruit inside cold room at 90±1% RH. Fruit packaged without liners also lost about 17.39% more weight during precooling compared to fruit packaged with liners. Fruit in liners and without liners which took longer to cool to set temperature (7oC) lost more weight than fruit that got to set storage temperature faster. A further study into the effects of RH on pomegranate fruit quality during ambient (20oC) storage showed that storing fruit under high RH (95%) minimised weight loss, maintained fruit colour, firmness and physicochemical quality attributes. Storing fruit under low RH (65%) led to excessive weight loss up to 29.13±1.49% after 30 days (compared to 5.78±0.44% at 95% RH), thereby resulting into an estimated financial loss of ZAR7.78 kg-1 and ZAR1.54 kg-1 at low and high RH storage conditions, respectively. The onset of visible signs of shrivels occurred when fruit weight loss reached about 5.16%. Linear regression equations developed to estimate weight loss in pomegranates during ambient storage gave a high goodness-of-fit (R2) of 0.9931 and 0.9368 for low and high RH environments, respectively. This research has provided an insight into the effects of packaging design used in the pomegranate industry on cooling performance and impacts on fruit quality. Although the use of internal packaging (liners) minimised fruit weight loss, it increased RTA, precooling time, energy consumption and cooling costs. Cold room humidification offered potential remedy to the problem of high moisture loss of pomegranates. Further studies are warranted to optimise the vent design of pomegranate packaging, including the use of perforated liners, to improve cooling performance cost-effectively without compromising structural/mechanical performance in the cold chain.AFRIKAANSE OPSOMMING: Geventileerde verpakking het 'n wye skaal bedryfstoepassing in vars vrugte behandeling en verkoelings bedrywighede gevind. Sekere variasies in fisiese en termiese vrug eienskappe, optimale verpakkings ontwerpe vir 'n spesifieke produk en voorsieningsketting vereis 'n multi-parameter benadering wat insluit verkoeling, meganiese en ekonomiese prestasie, sowel as hulpbronbenutting doeltreffendheid.‘n Groot verskeidenheid van geventileerde verpakkings ontwerpe word gebruik in na-oes behandeling en bemarking van vars vrugte. Verskillende studies het die verkoelings uitwerking op vrugte soos appels, sitrus en tafeldruiwe ondersoek; Daar is egter baie min bekend oor die prestasie van granate in geventileerde verpakking. Die oorkoepelende doel van hierdie studie was om die verkoelings prestasie van sommige van die dikwels gebruikte geventileerde kartonne en interne pakkette tydens geforseerde lugverkoeling (GL) en koue storing in die Suid-Afrikaanse granaat bedryf te evalueer in terme van lugvloei weerstand (LW), verkoelings eienskappe, energie-doeltreffendheid en die kwaliteit van vrugte. Die twee bestudeerde verpakkings ontwerpe, CT1 en CT2 het met 5.4% verskil in die totale ventilasie. CT2 het relatief hoër ventilasie in beide die lengte en breedte rigtings (8.82% en 6.67 % onderskeidelik) getoon in vergelyking met CT1 (6.52% en 2.86%). In 'n stapel van kartonne met vars granate (cv.Wonderful), was die verkoeling vinniger (29.19 %) met die CT2 verpakking. Die obstruksie van ventilasie openinge in die lengte van die stapel van die CT2 verpakking het gelei tot meer as 50% hoër LW in vergelyking met CT1 verpakking. Resultate het ook getoon dat die vrugte verpak in 'n sak, meer as 50% groter as LW vrugte verpakking is sonder ‘n sak. Die gevolg was dat die gebruik van sakke ook verkoeling van die vrugte vertraag en energieverbruik verhoog met sewe-agstes verkoelingtyd; omtrent 3 keer die van vrugte binnekant verpakking met geen sak. Verpakte vrugte in ‘n sak vereis omtrent 3.9 en 8.7 keer meer energie om vrugte af te koel in CT1 en CT2, onderskeidelik, in vergelyking met die sonder sakke. Vrugte in karton stapels toon ook 'n heterogene verkoelings patroon, met vrugte in die stroomop posisie van inkomende verkoeling sowat 36% vinniger in vergelyking met vrugte aan die agterste stapel posisie. Gedurende GL van vrugte oor 'n tydperk van 11.6 en 4.5 ure met of sonder sakke, onderskeidelik, het die gebruik van bevogtiging om 95±1% relatiewe humiditeit (RH) te behou, gewigsverlies met sowat 13.63% geminimaliseer in vergelyking met vooraf verkoelde vrugte binnekant ‘n koelkamer by 90±1% RH. Vrugte sonder sakke verloor ook oor die 17.39% meer gewig tydens vooraf verkoeling in vergelyking met vrugte verpak in sakke. Vrugte in en of sonder sakke neem langer om af te koel na voorgeskrewe temperature (7°C) verloor meer gewig as vrugte wat vinniger in opgestelde koel stoorgeriewe blootgestel word. 'n Verdere ondersoek na die uitwerking van RH op die vrugte kwaliteit van granate onder omringende (20°C) berging toestande, het getoon dat die vrugte onder hoë RH (95%) lei tot minimale gewigsverlies, behou vrugte kleur, fermheid en fisio-chemiese kwaliteite. Vrugte gestoor onder lae RH (65 %) het gelei tot oormatige gewigsverlies tot 29.13±1.49% na 30 dae (in vergelyking met 5.78±0.44% op 95% RH) en sodoende tot 'n geskatte finansiële verlies van ZAR7.78 kg-1 en ZAR1.54 kg-1 teen 'n lae en hoë RH bergingstoestande, onderskeidelik. Die aanvang van sigbare tekens van “shrivels” het plaasgevind toe vrugte gewigsverlies van omtrent 5.16% bereik het. Lineêre regressievergelykings was ontwikkel om te skat wat gewigsverlies in granate tydens berging was; gevolglik was hoë passingstoets (R2) van 0.9931 en 0.9368 vir lae en hoë RH omgewings. Hierdie navorsing het 'n insig verskaf in die uitwerking van verpakkings ontwerpe wat gebruik word in die granaatbedryf op verkoelings prestasie en die impak op vrugkwaliteit. Hoewel die gebruik van interne verpakking (sakke) die vrugte gewigsverlies geminimaliseer het, het dit LW verhoog, voorafverkoelings tyd verleng en energie verbruik en verkoeling koste opgestoot. Koelkamer bevogtiging het moontlike oplossings vir die probleem van hoë vog verlies van granate gebied. Verdere studies is gewaarborg om die ventileringsontwerp van granaat verpakking te optimaliseer, asook die gebruik van geperforeerde sakke, om verkoelings prestasie kostedoeltreffend sonder om strukturele/meganiese prestasie prys te gee in die verkoelingsproses