Bhat, S. Keshav

Hebbar, K. B.

Manikantan, M. R.

Mathew, A. C.

Padmanabhan, Sugatha

Pandiselvam, R.

Ramesh, S. V.

Shameena Beegum, P. P.

English

Update Publishing (E-Journals)

136Arecanut (Areca catechu L.), also called betelnut, is an economically important palm species(Jaiswal et al., 2011). The palm is cultivated in mostSouth Asian countries, including its majorproducers, India and China and other countries likeBangladesh, Japan, Malaysia, The Philippines, andSri Lanka (Ramesh and Mohanraju, 2017). India isthe largest producer of arecanut, accounting for49.74 per cent of the world’s output, and the crop isgrown in an area of 4.95 lakh ha with a productionof 8.09 lakh tonnes of the dry kernel (http://www.fao.org/faostat/en/#data/QC). The economicallyimportant component of the palm, the fruit, goesfor chewing as “supari” owing to its stimulanteffects and a minor fraction of the production forother commercial purposes. Thus, the edibleendosperm is widely used as a masticatory in Indiaand South East Asia, either alone or as a constituentof the quid along with betel leaves, lime and tobacco.Depending upon the nature of end products, the fruitis harvested at different stages of maturity forprocessing. The most popular traded form ofarecanut is the whole dried nut known as chali orkottapak. The fruit of the palm is dried under directsunlight for around three weeks or even more toreduce the moisture content to around 12-15 per cent(d.b.) (Kulanthaisami et al., 2007; Kalamullah andGunasekar, 2002). Subsequently, they are stored ingunny bags or wooden boxes as whole nuts ordehusked nuts until they are sold (Mathew et al.,Moisture content and water activity of arecanut samples:A need to revisit storage guidelinesK.B. Hebbar*, Sugatha Padmanabhan, S.V. Ramesh, S. Keshav Bhat1,  P.P. ShameenaBeegum, R. Pandiselvam, M.R. Manikantan and A.C. MathewICAR-Central Plantation Crops Research Institute, Kasaragod-671 124, Kerala, India1Arecanut Research and Development Foundation, Mangaluru-575 001, Karnataka, India(Manuscript Received: 21-01-2021, Revised: 30-06-2021, Accepted: 02-07-2021)Keywords: Arecanut, food standards, moisture content, storage, water activitydoi:10.25081/jpc.2021.v49.i2.7260 Journal of Plantation Crops, 2021, 49(2):136-141Short Scientific Report*Corresponding Author: hebbar.kb@icar.gov.in1963). They are available in different grades likenew rashi, old rashi, supari, patora, ulligadde etc.Another important form of traded arecanut isprocessed semi-mature varieties (such as bette,choor, rashi, and saraku), also known as red type,wherein tender nuts of 6-7 months maturity aredehusked, cut into pieces, boiled with water ordiluted extract from a previous boiling, followedby tannin coating and drying. The number of cutsand dimensions of the cut pieces is categorized intoapi, bette, hasa, gorabulu etc. Dried nuts of bothchali and red type are stored for marketing. Improperstorage leads to spoilage of nuts and reduction inthe market value rendering it unsuitable as amasticatory (Koti and Nambiar, 1979). One-year-old nuts during storage showed a significant declinein protein, fat, phenols, sugars and arecoline content(Chempakam and Saraswathy, 1985).Moisture content (MC) of agricultural produceis an important physiological factor as it has aninverse relationship with the storage period. Thehigh MC (>14% w.b.) during the storage increasesthe respiration rate of agricultural products, resultingin mould/fungus infection (Aspergillus spp., whichproduces aflatoxins) and insect infestation. Furtherdiscolouration (due to heat buildup) and a severeloss in the fresh odour and sensory characteristicsof products were observed. Further, the rate ofphysiological and biochemical changes in products137aggravates with an increase in MC. Water activity(aw), a measure of the energy status of water, isdefined as a ratio of the vapour pressure of water ina sample to the vapour pressure of pure water atidentical temperature and environmental conditions.A decrease in aw level below 0.7 prevents thespoilage caused by microorganisms (Labuza et al.,1972). To extend the storage life of food andagricultural products, the water activity has to be ina lower range where the deterioration rate isminimised (Ayub et al., 2003).In arecanut, studies on the moisture content ofprocessed nuts are scarce, and there are hardly anyreports on the water activity of arecanuts. Thepermissible and critical limits of MC fixed for driedmature nut chali (13.1 and 15.2%, respectively) andprocessed tender nut (11.0 and 12.32 per cent,respectively) seemed to be very high to prevent itfrom deterioration (Shivashankar and Govindarajan,1963; Viraktamath 1963; Nambiar andRadhakrishnan Nair, 1970). On the other hand, themaximum standard moisture level of 7 per cent fixedby the Food Safety and Standards Authority of India(FSSAI) is too low to attain by the farmers (https://www.thehindu.com/news/cities/Mangalore/re-fix-standard-moisture-level-in-arecanut-to-14-stakeholders/article31035233.ece). Therefore, thereis a need to optimise the moisture content ofprocessed arecanut for its safe storage and ideal formastication. In this context, the goal of the presentstudy was to analyse the MC and aw of arecanutsamples (red and chali) collected from differentparts of arecanut growing regions of Karnataka,India and to identify suitable moisture content andwater activity parameters so that it could berecommended for compliance by farmer growersand merchants during storage.Arecanut samples were sourced from differentplaces of Karnataka during dry and rainy seasons,including tender processed (red) and mature driedchali and their subtypes. Subtypes under redincluded api (4), bette (17), rashi (4), hasa (10),gorabalu (4). On the other hand, white 1 (4), newrashi (3), old rashi (3) patora (3) and ulligadde (1)are included under chali. A total of 53 samples werecollected for the analysis. The samples (~250 g nuts)were drawn from collection centres of ‘The MalnadAreca Marketing Co-operative Society(MAMCOS)’ of Koppa, Shringeri, Bhadravathi,Hosnagara, Shivamogga, and Thirthahalli locatedin Karnataka, India, and private vendors and farmersfrom Sirsi, Sagar, and Shivamogga. These sampleswere placed in sealed polythene bags for furtheranalysis.Prior to the analysis, the arecanut samples werebroken into pieces using a supari cutter and groundFig. 1. Relationship between moisture content (MC) of arecanut  samples (n=16)measured by gravimetric method and using infrared moisture metreMC based on gravimetric methodMC based on infra redmoisture analyser151413121110988                         10                          12                        14                        16R3 - 0.838(p<0.001)Arecanut moisture content and water activity138into a fine powder using a laboratory blender. MCof the samples was estimated using moistureanalyser A&D MX-50 (Oxfordshire, UK). In fewsamples (n=16), the MC of the arecanut sampleswere further estimated using a gravimetric methodto calibrate the infrared moisture analyser forarecanut samples. The aw of the samples weremeasured using Novasina-Lab Master-aw: benchtop metre (Novasina AG Neuheimstrasse 12 CH-8853 Lachen). Each experiment was conducted inthree replications. The data were analysed using oneway ANOVA, and the treatment means werecompared by Duncan multiple range test. The singlefactor ANOVA and MC and aw frequencydistribution pattern were analysed using SASsoftware.Table 1. Water activity (aw) and moisture content (MC) of arecanut samples collected from different places of Karnataka,IndiaSample Types and sub types Water activity (aw) Moisture content (%)Across all samples (n=159) 0.689 10.21Type Red (n=117) 0.689 10.16 chali (n=42) 0.676 9.54 SEm  0.013  0.62Sub types: Red Api 0.696 10.43 Bette 0.682 9.96 Rashi 0.705 11.22 Hasa 0.689 10.21 Gorabalu 0.695 9.69 SEm NS NSChali White 1 0.658 b 9.07 b New Rashi 0.679 b 9.43 b Old Rashi 0.690 ab 10.08 ab Patora 0.666 b 9.22 b Ulligadde 0.727 a 11.11 a SEm 0.039 1.32Collection season Summer 0.670 9.09 c Monsoon 0.684 10.17 b SEm NS 0.92Collection from different locations Shivamogga 0.709 10.91 Sagar 0.701 10.48 Koppa 0.686 9.74 Shringeri 0.661 8.96 Thirthahalli 0.681 9.73 Sirsi 0.673 9.75 Kumta 0.707 10.26 Thrissur 0.686 9.6 Puttur 0.684 10.63 Others 0.691 10.32 SEm NS NS[There were totally 53 samples of which 39 are red [Api(4); Bette (17);Rashi (4); Hasa (10); Gorabalu (4)] and 14 are chali[White (4); New Rashi (3); Old Rashi (3); Patora (3); Ulligadde (1)] types. Data are mean value of three replicates. Analysis ofvariance was calculated across types (red and chali), sub types, summer and monsoon collections and collection from differentlocations. Mean with same superscript letter represents non significance while different letter represents significance. Significancelevel of each factor is indicated by p-values and standard error of mean (SEm)]Hebbar et al.139MC, determined by infra-red moisture analyser,had a strong positive correlation with the moisturecontent estimated by the gravimetric method(R2(16)=0.84, p<0.001) (Fig.1). It suggests thatpowdered arecanut samples could be directlymeasured for MC using an instant infra-red-basedmoisture analyser rather than following a relativelycumbersome and time-consuming gravimetricmethod. Hence, the arecanut growers and processingindustries may use an infra-red-based moistureanalyser to estimate the moisture content of differenttypes of arecanut.Table 2 depicts the MC and aw values acrossall the arecanut samples. The MC and aw valuesranged from 8.33 to 14.46 per cent (w.b.) and 0.63to 0.75, with a mean of 10.21 per cent and 0.689,respectively (Table 1). The red type arecanutsamples had significantly high mean MC and aw(10.16% and 0.689) compared to chali samples(9.54% and 0.676). However, the MC values of boththe types were lower than the earlier suggestedpermissible limits for chali (13.1%) and processedtender nut (https://www.thehindu.com/news/cities/Mangalore/re-fix-standard-moisture-level-in-arecanut-to-14-stakeholders/article31035233.ece).Analysis of MC and aw of various subtypes of redand chali arecanut samples revealed that there wereno significant differences among the subtypes ofred samples. Nevertheless, the subtypes of chalisamples showed significant differences for MC andaw (p-value 0.05). Significantly high MC and awwere documented in ulligadde sub-samplesfollowed by old rashi, whereas the least MC and awwas observed in white-I subsamples (Table 1).Expectedly, the samples collected during the rainyseason (monsoon) had significantly (p≤0.01) moremoisture (10.17%) than the samples obtained duringthe summer season (9.09%). However, there wasno significant difference in their aw. The MC (%)and aw of the samples collected from differentlocations were analysed, and it was found that theplace of the collection did not cause any significantchange in both the parameters suggesting therobustness of this method for various agro-ecological zones of the country.The frequency distribution charts of MC andaw of arecanut samples are depicted in Figure 3. Itis apparent that 44.2 per cent (23 out of 52) of theFig. 2. Correlation between moisture content (%) and water activity (aw)of arecanut samples (n=53). Samples included dried red and chaliand their sub types collected from different locations during summerand monsoon seasonsMoisture content (MC) %Water activity (aw)0.80.760.720.680.640.68 10 12 14 16Arecanut moisture content and water activity140samples recorded a MC of 9.1 to 10.19 per cent(w.b.). Whereas 40.4 per cent of samples exhibitedaw of 0.685-0.709 and 36.5 per cent samplesrecorded aw of 0.66-0.684. Overall, more than 90per cent of the samples recorded the MC and aw of<11.3 per cent and <0.71, respectively. Theminimum aw required for the growth of bacteria andfungi is around 0.8 and 0.75, respectively.Viraktamath (1963) reported the loss of flavour,crispness, development of stale odour and mouldformation on nuts stored at a moisture content of13-14 per cent while Nambiar and RadhakrishnanNair (1970) observed an increase in fungal infectionof nuts stored in jute bags from 16 to 32.3 per centwith an increase in moisture content from 9.5 to15.6 per cent. Aspergillus flavus is the main fungiproducing aflatoxin in arecanut. The fresh nutshaving high MC are therefore easily contaminatedwith Aspergillus flavus. These studies indicated thatAspergillus flavus requires minimum water activityof 0.78 at 33 °C, 0.81 at 30 °C and 0.80 at 37°C(Pitt and Hocking, 2009). Astoreca et al. (2012)reported that the storage of corn at <0.77 wateractivity would be safe regardless of the storagetemperature. As gunny bags are used to store thedehusked nuts, the fresh chali nuts are moreFig. 3. Frequency distribution of (a) moisture content (MC) and (b) water activity (aw) of arecanut  samples.X-axis represents the frequency distribution class and the values above the bar indicate count against eachclass from n=538-9.09 9.1-10.19 10.2-11.29 11.3-12-39 12.4-13.49 13.5-14.590.61-0.63 0.635-0.659 0.66-0.685 0.685-0.709 0.71-0.735 0.735-0.759(a)(b)11231320222451921Hebbar et al.141susceptible to insect infestation and moulds orfungal infections with high moisture content (Thubeet al., 2017).In this study, arecanut samples sourced fromdifferent places during dry and rainy seasons,processed (red) and chali and their sub-types had amean aw of <0.71 (corresponding moisture contentof <11.3%), which is safe and unlikely to cause nutdeterioration during storage. This study had notevaluated the plausibility of fungal or bacterialcontamination and deterioration in other physicalattributes depending on aw. Nevertheless, priorinvestigations in various food products (Barbosa-Cánovas et al., 2003; Erkmen and Bozoglu, 2016,Asagbara et al., 2019) suggest that aw values <0.71is safe. Therefore, mycotoxin accumulation anddeterioration of quality of nuts seem improbable at awvalues <0.71. Hence, the arecanut growers, processingindustries and quality standard organization’s likeFSSAI must ensure aw of <0.71 for dried arecanutsamples for its safe storage and mastication.ReferencesAsagbara, A.E., Onawola, O.O. and Okeagu, M.O., 2019.Identification of critical control points in some Nigerianfermented foods and seasonings. World Journal ofInnovative Research 6(4): 55-60.Astoreca, A., Vaamonde, G., Dalcero, A., Ramos, A. J. andMarín, S. 2012. Modelling the effect of temperatureand water activity of Aspergillus flavus isolates fromcorn. International Journal of Food Microbiology 156(1):60-67.Ayub, M., Wahab, S. and Durrani, Y. 2003. 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The stability of intermediate moisturefood. Journal of Food Science 37: 154.Mathew, A.G., Venkataraman, S.D., Jaleel, S.A., Govindarajan,V.S., and Subramaniyan, V. 1963.  Storage of arecanutfruit: 1- Preservative Steeping Storage. Arecanut Journal14: 51-52.Nambiar, K.K.N., and Radhakrishnan Nair, R. 1970. Spoilageof the processed arecanuts. Arecanut and Spices Bulletin11: 8-10.Pitt, J. I., and Hocking, A. D. 2009. Aspergillus and relatedteleomorphs. In: Fungi and Food Spoilage. Springer,Boston, MA. https://doi.org/10.1007/978-0-387-92207-2_8.pp. 275-337.Ramesh, C. H. and Mohanraju, R. 2017. Evaluation ofantiluminous bacterial efficacy of Areca catechu nutmethanol crude extraction in controlling luminousbacteria Vibrio campbellii in shrimp culture systems.Indian Journal of Geo-Marine Sciences 46: 2075-2080.Shivashankar, S. and Govindarajan, V.S. 1963. Equilibriumrelative humidity (ERH) relationships of processedarecanut  and whole dried ripe nuts. Food Science 12(11):317-321.Thube, S. H., Pandian, R. T. P., Bhavishya, E. K., Mohan, C.and Nagaraja, N. R. 2017. Major storage insect pests ofarecanut  Areca catechu L.- A Survey. Journal ofEntomology and Zoology Studies 5(4): 1471-1475.Viraktamath, C, S. (1963). Packing and storage studies onscented supari (Processed arecanut s). Food Science. 12:322-325.Arecanut moisture content and water activity

Moisture content and water activity of arecanut samples:  A need to revisit storage guidelines

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Moisture content and water activity of arecanut samples: A need to revisit storage guidelines

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