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Crystallisation Behaviour of Sunflower and Longan Honey with Glucose Addition by Absorbance Measurement

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Crystallisation Behaviour of Sunflower and Longan Honey with Glucose Addition by Absorbance Measurement International Food Research Journal 27(4): 727 - 734 (August 2020) Journal homepage: http://www.ifrj.upm.edu.my Crystallisation behaviour of sunflower and longan honey with glucose addition by absorbance measurement Suriwong, V., *Jaturonglumlert, S., Varith, J., Narkprasom, K. and Nitatwichit, C. Graduate Program in Food Engineering, Faculty of Engineering and Agro-Industry, Maejo University, Chiang Mai 50290, Thailand Article history Abstract Received: 11 February 2020 The present work aimed to study the crystallisation behaviour of honey with glucose addition Received in revised form: by using the absorbance measurement at 660 nm. The Avrami model was used to explain the 7 May 2020 crystallisation kinetic. The effect of glucose addition on the colour and microstructure of Accepted: 4 June 2020 crystallised honey was also determined. Sunflower and longan honey were used in the present work. The biochemical compositions of honey samples were analysed before the addition of glucose powder at four concentrations (1.0, 1.5, 2.0, and 2.5%; w/w) and stored at 10 - 15°C. Keywords The absorbance at 660 nm, colour, and microstructure were measured until full crystallisation. crystallisation model, The results showed that different honey compositions exhibited different crystallisation glucose, behaviours, which could be monitored by the absorbance measurement at 660 nm as well. The longan honey, addition of glucose powder could stimulate the crystallisation time, thus affecting the crystal- sunflower honey lisation rate. The Avrami equation was found to be a good model for describing the crystallisa- tion behaviour from the intensity of absorbance values. The highest crystallisation rate was found at 2.0% (w/w) glucose addition at the rate constant (k) of 0.177 ± 0.038 and 0.083 ± 0.039 in sunflower and longan honey, respectively. The Avrami index (n) was relevant to the crystallisation rate, but not clearly related to crystal shape or size. The crystals of all glucose-added honey contained small crystals in bouquets. The yellow colour became lighter during storage period. Suitable glucose content and absorbance monitoring at 660 nm could be used to control the crystallisation of honey for obtaining creamed honey product with good texture. © All Rights Reserved Introduction honey with the crystallisation process controlled, and it is normally produced from honey that is ready to Honey is a naturally sweet and viscous food crystallise during storage. However, a coarse and gritty produced by bees and some related insects. It consists texture is often found due to the crystallised honey of approximately 181 substances including fructose, being subjected to an uncontrolled crystallisation glucose, water, maltose, and other constituents (Hagr process. By controlling the crystallisation process and et al., 2017; Singh and Singh, 2018). Its physicochemi- proper raw material preparations, this can result in a cal properties and flavour depend on the flower sources, value-added honey product. In Thailand, sunflower geographical regions, and honeybee types. These honey tends to crystallise during storage and might factors affect the crystallisation behaviours as well. easily be produced into a creamed honey product. The most popular and abundant kind of honey in North- Therefore, we selected two honey types to be assessed ern Thailand is longan honey (Chaikham et al., 2016), in the present work, which is sunflower and longan which has a strong fruity scent and unique taste with honey, which consisted of different properties. dark brown colour. Due to the honey’s brown colour Dyce method is a method of producing and strong aroma, it is almost impossible to further creamed honey, and the process is as follows: 5 - 10% develop it into another food product; hence, almost all (w/w) of granulated honey is added and stored at 14°C longan honey found in Thailand markets is pure liquid until full crystallisation (Elhamid and Abou-Shaara, longan honey. To further increase its market value, 2016). However, many researchers have found differ- longan honey should and could be developed into new ent textures when using different honey types. There- food product. One such product which would likely be fore, the crystallisation behaviour and glucose effect popular and interesting in Thailand is creamed honey. are important parameters for the design of suitable Creamed honey product is produced from creamed honey processing. Some reports (Conforti *Corresponding author. Email: [email protected] 728 Suriwong, V., et al./IFRJ 27(4) : 727- 734 et al., 2006; Costa et al., 2015; Jaturonglumlert et al., were manually stirred with a spatula at room tempera- 2015; Elhamid and Abou-Shaara, 2016) have studied ture for about 10 min to thoroughly mix between the the influence of storage temperature and glucose glucose powder and liquid honey (Dettori et al., 2018). content on crystallisation behaviour and colour of Samples were then stored at a chilling temperature (10 honey (Kędzierska-Matysek et al., 2016a; 2016b). - 15°C) to allow for crystallisation process. The However, no studies have correlated these with temperature in the refrigerator was daily checked creamed honey texture. Moreover, there are few during the experiment. Creamed honey samples were reports that have endeavoured to develop a quick spec- periodically measured for absorbance at different trophotometric method to monitor the crystallisation sampling periods and visual observation was conduct- process of creamed honey production from sunflower ed to check the overall appearance. If there were and longan honey. Several studies (Lupano, 1997; crystals occurring throughout the honey sample, it was Venir et al., 2010; Laos et al., 2011; Dettori et al., deemed as full crystallisation. 2018) have been published about the crystallisation kinetics of honey and sugar mixtures using differential Biochemical compositions of honey scanning calorimetry (DSC), and tried to explain the The moisture content was determined follow- kinetics of honey crystallisation with the mathematical ing a refractive index method (Bogdanov, 2009) by model. measuring the refractive index of honey with a digital The Avrami equation was found to suitably Abbe refractometer (KRUSS, Germany). Three describe the honey crystallisation kinetics from DSC samples from each trial were analysed for determina- measurement during induced crystallisation (Dettori tion of moisture, and the average moisture content et al., 2018), but has not applied the absorbance value was reported. Sugar content (fructose, glucose, at 660 nm. Conforti et al. (2006) and Lupano (1997) sucrose, and maltose) was determined by HPLC, reported that turbidity measurement at 660 nm can be following the method 977.20 (AOAC, 2000). Water taken as an indicator of honey granulation. The activity was measured by using a water activity meter increase in turbidity indicates the presence of more (AQUA Lab 3TE, USA). The measurements of each honey crystals. But there is a lack of study concerning sample were duplicated, and the average water activity honey crystallisation modelling, both for monitoring was calculated. the crystallisation kinetic, and further application in The colour was measured by using a spectro- the design of creamed honey process. photometer (HunterLab Miniscan XE plus, Germany) Therefore, the objective of the present work and reported in values of L*, a*, and b*. Calibration was to describe the crystallisation behaviour of honey of instrument was done with a black and white standard with glucose addition by measuring the absorbance at tile before each set of measurements. The L* colour 660 nm and Avrami model. The information obtained value presented the degree of brightness or whiteness was applied to design a creamed honey process with of the sample, while a* and b* colour values indicated the best texture. The effects of glucose addition on the the degree of redness and yellowness, respectively. colour and microstructure of crystallised honey were Three measurements were done in each sample. All also determined. parameters were used to calculate the hue angle (h°) and Whiteness Index (WI) (Briones and Aguilera, Materials and methods 2005; Costa et al., 2015) as in Eqs. 1, 2, and 3: * Raw materials and sample preparation h° = arctan gent b ( a* ) Sunflower and longan honey (fresh and non-crystallised honey) were purchased from Supha when a* > 0 and b* > 0 (Eq. 1) Bee Farm in Chiang Mai, Thailand. Samples were * heated at 50°C to eliminate natural crystals and osmo- h° = arctan gent b +180 ( a* ) tolerant/osmophilic yeasts by using a water bath (Tosi et al., 2004). Heated honey samples were kept at room when a* < 0 (Eq. 2) temperature before seeding addition. Glucose mono- 0.5 hydrous powder (C H O , Merck, Germany) was * 2 *2 *2 6 12 6 WI =100 − (100 − L ) + a + b employed as seed (Elhamid and Abou-Shaara, 2016; Dettori et al., 2018). Four levels of glucose were added (Eq. 3) at 1.0, 1.5, 2.0, and 2.5% (w/w) of ~40 g of liquid honey. Glucose powder was added in both honey types, Microstructure analysis but none was added to the control sample. Samples Honey samples were microstructurally Suriwong, V., et al./IFRJ 27(4) : 727- 734 729 observed at room temperature using a light microscopy time, as shown in Eq. 5 (Dettori et al., 2018). (Olympus, model BX51TF, Japan) at a magnification n of 40× (Lupano, 1997). X (t) =1− EXP −k (t ) ∈[0, 1] (Eq. 4) Turbidity of honey where, k = rate constant of crystallisation process, and Honey samples were poured into a cuvette of n = Avrami index, a parameter characteristic of nuclea- about 1 cm path-length. Some trials with many types tion and growth mechanisms of the crystals. of liquid honey were taken to scan for wavelength in a range between 200 - 700 nm which presented a Statistical analysis smooth curve in a range between 600 - 700 nm. There- As an independent experiment, the results fore, the absorbance was measured at 660 nm at room were expressed as mean ± standard deviation (mean temperature by a spectrophotometer (Model SPEC- ± S.D.) of triplicate testing (n = 3).
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