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1 LWT - Food Science and Technology 47 (2012) 117e125 Contents lists available at SciVerse ScienceDirect LWT - Food Science and Technology journal homepage: Effect of packaging techniques on shelf life of brown peda, a milk-based confection Gajendra Londhe a,1, Dharam Pal b, P. Narender Raju b, * a College of Agriculture, Marathwada Agricultural University, Parbhani , Maharashtra, India b Dairy Technology Division, National Dairy Research Institute, Karnal , Haryana, India article info abstract Article history: Received 4 July 2011 Received in revised form 7 December 2011 Accepted 27 December 2011 Keywords: Brown peda MAP Vacuum packaging Shelf life Texture profile analysis Brown peda, a traditional Indian heat desiccated milk (khoa)-based confection characterized by caramelized colour and highly cooked flavour, is expected to have good shelf life in comparison with other khoa-based sweets due to low moisture content, higher amount of sugar and severe heat treatment applied during its preparation. However, brown peda is also very much susceptible to microbial spoilage due to unhygienic conditions adopted during its manufacture and handling and its poor packaging. Hence, with a view to improve the shelf life of brown peda by packaging interventions, the effect of conventional cardboard boxes, modified atmosphere and vacuum packaging techniques on the sensory, physico-chemical, textural, biochemical and microbiological quality of brown peda during storage for 40 days at 30 C was studied. The rate of loss of most quality attributes was rapid in control and modified atmosphere packaged samples compared to vacuum packaged samples. Based on the results obtained in the study it was concluded that brown peda could be best preserved up to 40 days at room temperature (301 C) without appreciable quality loss. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Historically, in India, surplus milk in the rural areas where it is produced has been converted into a variety of traditional products primarily as a means of preservation. Traditional dairy products and sweets are an integral part of Indian heritage and have great social, religious, cultural, medicinal and economic importance. They have been developed over a long period with the culinary skills of homemakers and halwais (sweetmeat makers). In addition to preservation of milk solids for longer time at room temperature, manufacture of traditional dairy products add value to milk and also provide considerable employment opportunity (Pal & Raju, 2007; Patil, 2011). Khoa, an important traditional milk product conventionally prepared by continuous boiling of milk in an open kettle until desired desiccation (about 70% total solids) and texture is achieved, is used as a base material for the preparation of a wide range of sweetmeats such as burfi, peda, gulabjamun, milk-cake, kalakand and kunda in India and neighbouring countries (Acharya & Sapkota, 2008; Aneja, Mathur, Chandan, & Banerjee, 2002). Peda, highly popular in Indian subcontinent, is essentially made from khoa by adding sugar in different proportions according to the * Corresponding author. Tel.: þ ; fax: þ addresses: londheg@rediffmail.com (G. Londhe), narender_raju@ yahoo.com, pnr.ndri@gmail.com (P. Narender Raju). 1 Tel.: þ demand of consumers. Consequently, the quality of peda varies extremely. Peda is normally made into round balls of about 20e25 g size by rolling between the palms (Pal, 2000). Two types of peda are available in market, viz. plain (creamy or white colour) and brown (lal) peda. Among the available varieties of peda, brown peda is more popular and prepared throughout the country on a small scale. Brown peda is characterized by caramelized colour, highly cooked flavour and longer shelf life. Depending on the area of consumption, it differs in the intensity of characteristic colour and flavour (Londhe & Pal, 2008). It is popular in Uttar Pradesh as Mathura peda, in Karnataka as Dharwad peda, and in Maharashtra as Mishra peda (Raju, Londhe, & Pal, 2008). In almost all the types of brown peda, khoa is first cooked to brown colour in ghee (clarified butter) and then peda is prepared from it by blending sugar and other additives such as cardamom. It is usually sold after wrapping in glossy-paper/paper-board which does not render perfect protection to the sample. Milk sweets during storage undergo several physical, biochemical and microbiological changes making them unfit for human consumption. The short shelf life of khoa-based sweets is one of the major constraints limiting their marketing in both domestic and export markets. Peda is expected to have good shelf life due to low moisture content and high percentage of sugar. The sugar-in-water concentration (sugar ratio) of finished product should be at least 60 giving an osmotic pressure of MPa which is sufficient to inhibit bacterial growth. However, due to poor /$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi: /j.lwt Downloaded from

2 118 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e125 handling and packaging, peda is most susceptible to microbial spoilage. Because of its intermediate moisture range and non-acidic nature (Thakur, Semwal, & Arya, 1992), spoilage in peda is mostly caused by growth of surface yeasts and moulds and manifests as fermentative and acidic odour. This is a recurrent problem in humid and warm atmospheric conditions that are prevalent in tropics. With innovations in packaging materials and systems like vacuum packaging, modified atmosphere packaging (MAP), smart packaging, etc., globally, it was possible to extend the shelf life of many perishable and non-perishable foods. However, commercial application of modern packaging techniques for Indian milk products is still at a nascent stage. Several studies have been reported to extend the shelf life of plain peda (Biradar, Dev, & Ingle, 1985; Kumar & Srinivasan, 1982; Kumar, Bandyopadhyay, & Punjrath, 1997; Thakur et al., 1992) and malai peda (Sharma, Singhal, & Kulkarni, 2001) using different preservation techniques. However, no information is available on the use of MAP and vacuum packaging for shelf life extension of brown peda. In the present work, attempts were made to extend the shelf life of brown peda by employing MAP and vacuum packaging. 2. Materials and methods 2.1. Raw materials Good quality pooled buffalo milk was obtained from the Experimental Dairy of the National Dairy Research Institute, Karnal (India). Milk was standardized to 5.9 g/100 g fat and 9.0 g/100 g milk solids-not-fat (MSNF). Milk was clarified before use to remove dirt and other extraneous matter. Cardamom powder and boora (dried sugar syrup with about 5e6 g moisture/100 g) which is analogous to castor sugar were procured from local market Preparation of khoa and brown peda Khoa, the base material for brown peda was prepared from buffalo milk in a stainless steel double jacketed kettle as per the method suggested by De (1980) with slight modification. The lab scale method standardized in our laboratory was followed for the production of brown peda. For preparing brown peda, previously prepared khoa was transferred to an iron pan (karahi) (60 cm diameter and 25 cm depth) and started heating till the temperature of khoa reached to about 80 C. Sugar and cardamom powder were added at a rate of 30 g and 0.1 g, respectively per 100 g of khoa, respectively with continuous stirring and scraping till brown colour developed. The colour of khoa manufactured by conical vat process and determined by lovibond tintometer was reported to have 1.68y þ 0.3R (Rajorhia, Pal, Garg, & Patel, 1991). The contents of the pan were then removed and transferred into a stainless steel tray for cooling to room temperature (30 C) and finally ball forming (20 g each with an approximate 3 cm diameter) was done manually using palms. The proximate composition of the brown peda in terms of moisture (IS: 2785, 1964), fat (IS: SP (Part XI), 1981), protein (Meneffee & Overman, 1940), lactose, sucrose (IS: SP (Part XI), 1981) ash (AOAC, 1975) and free fat (Hall & Hedrick, 1971) is given in Table 1. For estimation of free fat, about 10 g of brown peda was accurately weighed into a 250 ml glass stoppered conical flask and to it was added 100 ml of petroleum ether (40e60 C). The flask was shaken vertically 10 times, then allowed to settle for 15 min and then filtered through Whatman No. 42 filter paper into a previously weighed Mojonnier fat dish. The procedure was repeated twice for extraction. Ether was evaporated and the free fat (residue) was weighed. The results were expressed as g/100 g of total fat. About 500 g of the prepared brown peda were packed in two different packaging systems viz. vacuum packaging and Table 1 Proximate composition of the brown peda. Component Content (g/100 g) Moisture Fat Protein Lactose Sucrose Ash Free fat (on total fat basis) Mean SD; n ¼ 3. modified atmosphere packaging (MAP). A 5-layer nylon (LLD/BA/ Nylon-6/BA/LDPE) (thickness: 110 m; WVTR: 3.96 g/m 2-24 h; OTR: 36 ml/m 2-24 h) procured from M/s Hitkari Industries Ltd., Noida (India) was used for MAP by flushing nitrogen and carbon dioxide gases both at 1 bar pressure for 3 s (P 2 ) and vacuum packaging (M/s REEPACK SRI, Italy) under a vacuum of kpa for 7.5 s (P 3 ) while brown peda packaged in cardboard boxes lined with butter paper was treated as control (P 1 ). Prior to filling, the packaging materials were sterilized by exposing to ultraviolet (UV) light in a UV chamber for 30 min. All the three treated brown peda samples (P 1, P 2 and P 3 ) were stored at 30 1 C and analyzed at an interval of 10 days for 40 days. All the trials were carried out in triplicate Sensory evaluation Sensory evaluation of fresh and stored samples of brown peda was carried out by a panel of nine (discriminative and communicative) judges selected from the Faculty and Research Scholars of Dairy Technology Division of the Institute. The panelists have not been trained for the present study but they are dairy professionals having adequate knowledge about the sensory evaluation methods and the product attributes. All the samples were evaluated for sensory attributes such as flavour (10), body and texture (10) and colour and appearance (5) and overall acceptability (25) using a 50 point score card developed for this delicious sweet (the maximum score for each attribute is given in parenthesis against each attribute). Based on the overall perception of the samples, the overall acceptability scores of brown peda were given by the panelists. A minimum score of 65% of total score for each attribute i.e. 6.5 for flavour and body and texture, 3.3 for colour and appearance and 16 for overall acceptability was considered acceptable Physico-chemical analysis Determination of moisture Mojonnier method as described in Indian Standards for determination of moisture in hard cheese (IS: 2785, 1964) was used for brown peda with slight modifications. About 20 g of previously washed and dried sand was weighed into an aluminium dish, allowed to dry further in an oven at 100 C and weighed to the nearest of 1 mg constant weight. Five gram of brown peda was transferred into the dish and 5 ml of distilled water was added to it. The contents were mixed thoroughly into a paste with the help of glass rod. The dishes were then transferred to thermostatically controlled water bath at 100 C 1 C for 30 min and later transferred to a hot air oven maintained at 100 C 1 C. Drying was continued till the solid mass of the dishes turned to be light brown and difference between the two successive weighings was not more than 1 mg. The results were expressed as percent moisture Titratable acidity and ph The titratable acidity in terms of percent lactic acid was determined following the method as described by AOAC for cheese (AOAC, 1975) which was adopted for misti dahi (caramel coloured

3 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e sweetened set-type yoghurt) (Raju & Pal, 2009; Raju & Pal, 2011). Two grams of sample was taken in a porcelain dish and mixed homogenously by adding 20 ml hot distilled water (65 C). This was followed by addition of 10 ml of 0.1 mol eq/l sodium hydroxide and 1 ml of 0.5 g/100 ml phenolphthalein indicator. The mixture was titrated against 0.1 mol eq/l hydrochloric acid with continuous stirring till the pink colour disappeared completely. The ph of the fresh and stored samples was determined using a digital ph metre (Model: Lab India) Water activity Water activity was measured using water activity metre Aqua Lab (Model Series 3 TE) supplied by Decagon Devices, WA, USA. Prior to the measurement the samples were tempered to 25 C Colour The colour of brown peda was measured using a Colorflex colourimeter supplied by Hunterlab (Hunter Associates Laboratory, Inc., Reston, VA, USA) along with the software (version 4.10) and the results were expressed in terms of CIELAB system. Before the test, the instrument was calibrated with standard black and white tiles as specified by the manufacturer. The light source was dual beam xenon flash lamp. Data was received through the software in terms of L* (lightness), ranging from 0 (black) to 100 (white), a* (redness), ranging from þ60 (red) to 60 (green) and b* (yellowness), ranging from þ60 (yellow) to 60 (blue) values. For measuring the colour of brown peda, the intact brown peda samples were transferred into the sample container attached with the Colorflex instrument for taking the readings. Readings were taken in triplicate for each sample Biochemical analysis Free fatty acids The method prescribed by Deeth, Fitz-Gerald, and Wood (1975) was used to estimate the free fatty acids (FFA) content of brown peda. The method consisted of accurate weighing of 5 g of brown peda sample into a 60 ml stoppered test tube. Ten millilitre of extraction mixture (Iso propanol: petroleum ether: 4N sulphuric acid in the ratio of 40:10:1) was added and mixed thoroughly. This was followed by the addition of 6 ml petroleum ether and 4 ml distilled water. The test tube was stoppered and tempered at 40 C for 10 min and the contents were vigorously shaken for 20 s. The two layers were allowed to separate for 10e15 min and an aliquot of the upper layer (5e8 ml) was withdrawn and titrated against 0.02 mol eq/l methanolic KOH solution using 1 g/100 ml methanolic phenolphthalein indicator. A blank, in which brown peda was replaced with distilled water, was also simultaneously run. The results were expressed as m eq of oleic acid/g Peroxide value The peroxide value was determined by using iodometric method as described in Indian Standard (IS: 3508, 1966). Accurately one gram of extracted fat sample was weighed into a test tube and 1 g of powdered potassium iodide and 20 ml of the solvent mixture were added. The contents of the tube were boiled in a steam bath for not more than 30 s. As the solvent vapours began to escape from the hole in the bung, the opening was closed with a glass rod. Then the contents were cooled immediately under a running tap and transferred into a conical flask containing 20 ml of 5 g/100 ml aqueous solution of potassium iodide and washed out the test tube twice with 25e30 ml of distilled water. The solution was titrated against sodium thiosulphate solution (0.002 mol eq/l) using starch indicator for achieving the end point. A blank test was also performed simultaneously. The results were expressed as meq of oxygen per kg fat Hydroxy methyl furfural Hydroxy methyl furfural (HMF) in brown peda samples was determined by the method described by Keeney and Bassette (1959) with slight modification. Three gram of brown peda was thoroughly mixed with 7 ml distilled water followed by 5 ml of 0.3 mol eq/l oxalic acid and the tubes were kept in a boiling water bath for 60 min. The contents of the tubes were then cooled and 5 ml of 40 g/100 ml trichloroacetic acid solution was added. The precipitated mixture was then filtered through Whatman No. 42 filter paper. About 0.5 ml of the filtrate was pipetted out into a 5 ml test tube and 3.5 ml of distilled water and 1 ml of 0.05 mol/l thiobarbituric acid solution (aq) were added and mixed well. The tubes were kept in a water bath at 40 C for 50 min. After cooling to room temperature, absorbance of the samples was measured at 443 nm. Simultaneously, a blank test was also carried out using distilled water. The results were expressed as m mol/l Textural profile analysis Texture profile analysis (TPA) was carried out using a texture analyzer, TA-XT2i (M/s Stable Micro Systems, UK) fitted with a 25 kg load cell and was calibrated with 5 kg standard dead weight prior to use. For determining the TPA parameters, the samples which were previously tempered to 25 C were cut into cylindrical shape of height 1 cm and were subjected to monoaxial compression of 0.8 cm/cm of the initial sample height using a probe (P-70) during the first stage of the two-bite test with a cross head test speed of 2.5 mm/s. From the resulting force-time curves, various textural characteristics such as hardness, cohesiveness, adhesiveness, springiness, gumminess and chewiness were calculated using the Texture Expert Exceed software (v 2.55) supplied by the manufacturer along with the instrument. A minimum of five replicates per sample was run Microbiological analysis Microbiological analysis of brown peda samples during storage was examined for total viable count, yeast and mould counts and coliform count as per the standard methods described in Manual of Dairy Bacteriology (ICAR, 1982). The data on microbiological quality is presented in log 10 values Statistical analysis The data obtained in the present study was analyzed (ANOVA) by Least Square Design using SYSTAT software (version ) procured from SYSTAT Software Inc (CA, USA). 3. Results and discussion 3.1. Changes in sensory quality of brown peda during storage The sensory scores showed a decreasing trend during storage in all samples of brown peda irrespective of packaging techniques (Fig. 1). Statistical analysis results also showed highly significant (P < 0.01) effect of both packaging techniques and storage period on all the sensory attributes of brown peda during storage (30 1 C). There was not much change in the sensory attribute scores up to 20 days in vacuum packaged (P 3 ) samples, thereafter there was nominal decrease in the scores during further storage. The rate of decrease in sensory scores for the samples packaged in cardboard box (P 1 ) was more rapid as compared to the samples in

4 120 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e125 Fig. 1. Effect of packaging techniques on sensory attributes of brown peda during storage at 30 C (A: Flavour; B: Body and texture; C: Colour and appearance; and D: Overall acceptability) ( ¼ cardboard box lined with butter paper (P 1 ); ¼ modified atmosphere packaging in 5-layer nylon (P 2 ); ¼ vacuum packaging in 5-layer nylon (P 3 )). MAP (P 2 ) and vacuum (P 3 ) packaging. This might be due to rapid loss of moisture from the product packaged in cardboard box (P 1 ). Despite decreasing trend the samples were found to score well over the minimum acceptable limit (65% score of the total score) during the entire storage study. None of the judges reported the presence of any objectionable off flavour such as oxidized, rancid, acidic etc. during the entire period of storage. The decrease in flavour scores may be attributed to slight loss of freshness, which is inherent with any food product. The findings of the present study are in accordance with the report of Biradar et al. (1985). Sharma, Singhal, and Kulkarni (2003) also reported the decrease in mean flavour and body and texture scores of the control and MAP packaged malai peda samples in flexible packaging material at room temperature. The reduction in flavour and body and texture score for control (without MAP) was much rapid than for MAP samples. Similar observation was reported by Kumar et al. (1997). In vacuum packaged (P 3 ) samples slight increase in colour and appearance score after 10 days of storage (Fig. 1) was observed. Oozing out of free fat on the surface and making the texture compact of brown peda samples packaged under vacuum could be responsible for improving the appearance of the product. This indicates that the appearance of vacuum packaged samples was highly acceptable at the end of the respective storage period Changes in physico-chemical attributes of brown peda during storage The changes in physico-chemical attributes of brown peda during storage are given in Fig. 2.The loss of moisture during storage is a common observation for brown peda. Level of moisture in the product plays a significant role on quality of the product during storage as far as bacterial activity, yeast and mould growth, browning reaction and the acceptability of khoa-based sweets are concerned. Therefore, the packaging materials and packaging techniques are carefully selected to check the moisture loss during storage of such sweet especially at high temperature. A decreasing trend in moisture, ph and water activity of brown peda during storage was observed (Fig. 2). Maximum decrease in moisture, ph and water activity in 20 days was observed in samples packaged in cardboard box (P 1 ) and stored at 30 1 C as compared to the samples packaged under MAP (P 2 ) and vacuum (P 3 ). The higher moisture loss in P 1 may be attributed to poor barrier property in respect of water vapour transpiration rate of cardboard lined with butter paper. In case of MAP and vacuum the lower rate of moisture loss was due to the use of 5-layer nylon packaging material which provided better barrier to moisture loss during storage. During storage the highest increase in acidity took place in control samples packaged in cardboard box (P 1 ) on the 20th day of storage. The corresponding increase in acidity of the samples packaged in MAP (P 2 ) was 1.12% after 30 days of storage whereas in samples packaged under vacuum (P 3 ) increase in acidity was 1.24% from the initial value of 0.76% after 40 days (Fig. 2). These results can also be corroborated with the sensory results, which showed the decrease in body and texture score of brown peda at higher rate in P 1 package than in P 2 and P 3. Analysis of variance showed highly significant (P < 0.01) difference for moisture, ph and water activity between packaging techniques and among intervals of storage. Earlier several workers have also reported considerable loss of moisture and ph in peda during storage which made the product dry and hard and thus sensorily unacceptable. Bhatele (1983) reported that the rate of moisture evaporation from burfi samples was different from samples packaged in different packaging materials. Lowest

5 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e Fig. 2. Effect of packaging techniques on physico-chemical attributes of brown peda during storage at 30 C (A: Moisture; B: Acidity; C: ph; and D: Water activity) ( box lined with butter paper (P 1 ); ¼ modified atmosphere packaging in 5-layer nylon (P 2 ); ¼ vacuum packaging in 5-layer nylon (P 3 )). ¼ cardboard moisture loss was noticed in peda samples packaged in MAP as compared to control reported by Sharma et al. (2003). The changes in ph can not be directly correlated with change in acidity; still it was found that with the increase in acidity, the ph went on decreasing (Fig. 2). Kumar et al. (1997) also reported a decrease in ph of peda during storage for 180 days at 20 C. The changes in the colour of fresh and stored samples of brown peda packaged using different packaging techniques and stored (30 1 C) in terms of lightness (L*), redness (a*) and yellowness (b*) values are given in Table 2. It can be seen that the L* values of brown peda samples in all three packaging techniques did not show similar trend during storage at 30 1 C. Samples packaged in cardboard box (P 1 ) and MAP (P 2 ) showed increasing trend of lightness, but the rate of increase was more rapid in cardboard box (P 1 ) where the initial value of L* increased from to after 20 days of storage. Quite slower rate of increase was observed in MAP (P 2 ) where value increased from to after 30 days of storage. This indicates that the brown peda packaged in cardboard became lighter in colour during storage as compared to that packaged in MAP conditions. On the contrary decreasing trend in L* values was noticed for the samples packaged in vacuum (P 3 ) where the value from on zero day decreased to after 40 days of storage. It indicates that the vacuum packaged product became dark in colour towards the end of storage period. The reason behind this could be oozing of fat on the surface of product due to vacuum which improved the glossiness of the product. Statistical analysis of the data on L* values of the stored brown peda samples revealed that the packaging techniques exerted highly significant (P < 0.01) effect while intervals of storage were observed to be significant (P < 0.05). All the fresh samples showed almost similar a* values but with the progress in storage period, a* values showed different trend towards the end of storage period (Table 2). Brown peda samples packaged in cardboard box (P 1 ) and MAP (P 2 ) showed decreasing trend in a* values during storage. The rate of decrease was very fast in case of P 1 where the initial value of decreased to after 20 days of storage. The decrease was quite slow P 2 samples where the initial a* value of decreased to after 30 days of storage. The reverse trend was observed in case of P 3 samples wherein a* values showed increasing trend i.e. from on zero day, it increased to towards the end of 40 days of storage. The effect of packaging technique and storage period on a* (redness) values of brown peda was found to be significant (P < 0.01) (Table 2). Highly significant effect (P < 0.01) of different packaging techniques was found on the b* values of brown peda. Although brown peda samples packaged in both cardboard box (P 1 ) and MAP (P 2 ) showed increasing trend in b* values, the rate of increase was quite high in case of P 1 wherein the b* value increased from initial value of to after storage of 20 days. In case of P 2 the b* values increased from initial value of to at the end of 30 days. However, the b* value of P 3 samples showed slight decreasing trend where the b* values decreased from initial value of to after 40 days of storage. It is well established that the Maillard reaction is incredibly complex. However, it has been simplified into three schemes of reactions viz. initial stage reactions, intermediate stage reactions and final stage reactions. The intermediate and final stage reactions yield products that are either colourless or yellow and highly coloured, respectively (Nursten, 2005). The decreased a* values of brown peda in P 2 and P 3 could be due to degradation of coloured compounds into

6 122 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e125 Table 2 Effect of packaging treatments on the instrumental colour and textural attributes of brown peda during storage at 30 C. Parameter Storage Interval Colour parameters Lightness (L*) P P P Redness (a*) P P P Yellowness (b*) P P P Textural attributes Hardness (N) P P P Cohesiveness P P P Adhesiveness (N.m) P P P Springiness P P P Gumminess (N) P P P Chewiness (N) P P P Mean SD; n ¼ 3. P 1 ¼ cardboard box lined with butter paper; P 2 ¼ modified atmosphere packaging in 5-layer nylon; P 3 ¼ vacuum packaging in 5-layer nylon. colourless compounds during storage in the restricted permeation of oxygen through packaging material in P 2 and presence of vacuum in P Biochemical changes in brown peda during storage During storage the highest increase in free fatty acidity (FFA), peroxide value and total HMF (Fig. 3) took place in control samples packaged in cardboard box (P 1 ) on the 20th day of storage. The rate of increase in FFA was highest in P 1 samples wherein FFA increased from an initial value of 5.73 to a final value of m eq g 1 after 20 days of storage. The rate of increase was, therefore, lowest in vacuum packaged samples which may be ascribed to slower microbial growth particularly of aerobic type microflora. From the consideration of acidity, FFA, peroxide value and total HMF, the effect of all the packaging techniques and intervals of storage were found to be significant (P < 0.01) during storage. Despite gradual increase in acidity, FFA, peroxide value and total HMF none of the samples tasted sour, oxidized and rancid and the acidity level were within the acceptable limits. In the present study, the slow rate of increase in FFA, peroxide value and HMF contents in 5-layer nylon (P 2 ) and vacuum packaged samples (P 3 ) could also be ascribed to the reduced oxygen permeation due to high barrier for oxygen and absence of oxygen, respectively. Several earlier workers observed similar trends in acidity, FFA, peroxide value and total HMF of different products during storage. Goyal and Srinivasan (1989), Kumar and Srinivasan (1983) and Sharma et al. (2001) reported in khoa. Similarly, Palit and Pal (2005) and Sachdeva and Rajorhia (1982) in burfi whereas, Kumar et al. (1997) and Sharma et al. (2003) in peda and Navajeevan and Rao (2005) in retort processed kunda during storage at 37 C Textural changes of brown peda during storage The changes in textural quality of brown peda in terms of texture profile analysis (TPA) during storage packaged under different packaging conditions are given in Table 2. TPA comprises a two-bite test that gives textural properties of food products in terms of hardness, adhesiveness, cohesiveness, springiness and gumminess (Bourne, 2002). The force necessary to attain a given deformation, called as hardness, is commonly evaluated parameter while determining the texture of milk products. It is the height of the peak force on the first compression cycle (first bite). In the present study, a gradual increase in hardness of all brown peda samples irrespective of the packaging techniques was observed. The rate of increase was highly significant (P < 0.01) in P 1 samples compared top 2 and P 3 samples (Table 2). The increase in hardness of all brown peda samples during storage could be attributed to the difference in moisture content. From Table 2, an inverse relationship between the moisture content of samples and their hardness can be established as the hardness increased with the decrease in moisture content. Gupta, Patil, Patel, Garg, and Rajorhia (1990) observed that hardness of khoa (a heat desiccated milk product) was highly correlated with total solids and increasing total solids resulted in higher hardness. Similar findings were reported by Bhatele (1983) and Sachdeva (1980) in burfi samples. They observed that when burfi was packaged in parchment paper, its hardness continuously increased with the progress of storage period due to high amount of moisture loss. Adhesiveness is the negative force of the first bite representing the work necessary to pull the compressing plunger away from the sample. The adhesiveness values of P 1 samples showed rapid decrease from initial value of to g s. after 20 days storage. On the contrary, the adhesiveness values of P 2 and

7 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e Fig. 3. Effect of packaging techniques on biochemical and microbiological parameters of brown peda during storage at 30 C (A: Free fatty acids; B: Total hydroxyl methyl furfural; C: Peroxide value; D: Total viable count; and E: Total yeast and mould count) ( ¼ cardboard box lined with butter paper (P 1 ); ¼ modified atmosphere packaging in 5-layer nylon (P 2 ); ¼ vacuum packaging in 5-layer nylon (P 3 )). P 3 samples showed increasing trend (P < 0.01). Cohesiveness is molecular attraction by which the particles of a body are bounded throughout the mass. Cohesiveness may be defined sensorily as the degree to which a substance is compressed between the teeth before it breaks. Instrumentally, it is measured by calculating the ratio of the area of second bite to that of first bite (A 2 /A 1 )(Bourne, 2002). It was found that the samples packaged in cardboard box (P 1 ) showed rapid increase in cohesiveness from initial value of to towards the end of 20 days storage followed by samples packaged in vacuum (P 3 ) which increased from to after 40 days of storage. However, the cohesiveness of samples packaged in MAP (P 2 ) was almost unchanged up to 20 days and thereafter marginal increase was observed from initial value of to towards the end of 30 days of storage. Table 2 reveals that the type of packaging techniques and intervals of storage contributed significantly (P < 0.01) towards the change in cohesiveness during storage. Similar findings were recorded by Palit (1998) in burfi samples who reported increasing trend in cohesiveness value during storage irrespective of type of packaging. It was also

8 124 G. Londhe et al. / LWT - Food Science and Technology 47 (2012) 117e125 Table 3 Pearson s correlation coefficients between sensory attributes, instrumental colour and biochemical constituents. FL BT CA OA L* a* b* FFA PV HMF Flavour (FL) Body and texture (BT) 0.844** Colour and appearance (CA) 0.543** 0.637** Overall acceptability (OA) 0.924** 0.960** 0.754** Lightness (L*) 0.312* 0.567** 0.841** 0.593** Redness (a*) 0.329* 0.576** 0.796** 0.593** 0.928** Yellowness (b*) 0.421** 0.572** 0.396** 0.532** 0.337* 0.409** Free fatty acids (FFA) 0.872** 0.982** 0.687** 0.974** 0.580** 0.593** 0.583** Peroxide value (PV) 0.946** 0.872** 0.509** 0.908** 0.293* 0.336* 0.495** 0.879** Hydroxy methyl furfural (HMF) 0.866** 0.816** 0.777** 0.914** 0.619** 0.595** 0.417** 0.830** 0.846** * Correlation is significant at 0.05 level (P < 0.05); **Correlation is significant at 0.01 level (P < 0.01). reported that the rate of increase was slow in case of vacuum packaged samples as compared to control. The distance that the food recovered its height during the time that elapsed between the end of the first bite and the start of the second bite was defined as springiness (Bourne, 2002). During storage all samples showed increasing trend in springiness values irrespective of packaging technique. However the rate of increase differed in each packaging technique. Rapid increase in springiness value was observed in P 1 samples followed by P 3. Samples packaged in MAP (P 2 ) showed the slower rate of increase as compared to cardboard box and vacuum packaging (P < 0.01). Earlier workers (Adhikari, Mathur, & Patil 1994; Gupta et al., 1990) reported that springiness was the only textural attribute which had no correlation with any of the compositional parameters of khoa. Palit (1998) reported an increase in springiness value of burfi during storage irrespective of type of packaging. Two other parameters viz. gumminess and chewiness were derived by calculation from the measured parameters. Gumminess was defined as the product of hardness and cohesiveness while chewiness was defined as the product of gumminess and springiness (Bourne, 2002). Gumminess character depends upon hardness and cohesiveness of the product. Gumminess of the fresh brown peda samples packaged in cardboard box (P 1 ) was N and that of packaged in MAP (P 2 ) and vacuum (P 3 ) samples were N and N, respectively. All the samples showed an increasing trend during storage but the rate of increase varied in all packaging techniques (Table 2). The rate of increase was more rapid in case of P 1 samples compared to P 2 and P 3 (P < 0.01). Chewiness is the product of gumminess and springiness. A gradual increase in chewiness of all brown peda samples irrespective of packaging techniques was noticed during storage (Table 2). The rate of increase was very high in samples packaged in P 1 followed by quite lower rate of increase in P 3. However, negligible increase in chewiness value was observed in MAP (P 2 ) samples during storage. This increasing trend in gumminess and chewiness in all brown peda samples during storage could be attributed to increase in hardness and cohesiveness and gumminess and springiness values, respectively. These findings are in agreement with the findings of Palit (1998) who observed that the gumminess and chewiness of burfi increase with the progress of storage period irrespective of type of packaging. Patil, Patel, Garg, and Rajorhia (1991) observed that soft burfi was significantly less gummy than hard burfi Microbiological changes in brown peda during storage The microbiological changes in brown peda packaged under different packaging conditions during storage are given in Fig. 3. Initial total viable count in all the samples ranged from 2.40 to 2.56 per gram (log 10 ). During storage all the samples showed an increasing trend in total viable count. The rate of increase was higher in case of P 1 samples compared P 2 and P 3. This trend demonstrates that vacuum packaging followed by MAP retarded the overall bacterial growth during storage (P < 0.01). Earlier workers also reported increasing standard plate counts of burfi during storage (Garg & Mandokhot, 1987; Misra & Kuila, 1988; Sachdeva, 1980). But Kumar et al. (1997) in his study on the extension of shelf life of peda did not observe increase in the microbial growth during storage in the product packaged under MAP with oxygen scavengers. Palit and Pal (2005) reported that the rate of increase of total viable counts in control sample of burfi was higher than that of vacuum packaged burfi. For most of the intermediate Indian dairy foods such as peda, burfi, kalakand etc. mould growth tends to be a major problem and often most important single factor limiting their shelf life. In the present study, yeast and mould counts were not detected in fresh brown peda samples packaged in cardboard box (P 1 ). During storage all the samples of brown peda showed the presence of yeast and mould count which increased with the progress of storage period (Fig. 3). Among all the samples, P 1 spoilt after 20 days of storage due to surface mould growth and were withdrawn from further storage. Due to same reason, P 2 samples packaged in MAP spoilt after 30 days of storage whereas, vacuum packaged samples (P 3 ) spoilt mainly due to the growth of gas producing organisms after 40 days of storage. Highly significant (P < 0.01) effect of different packaging techniques and intervals of storage on total viable count and yeast and mould counts was revealed Correlation between sensory, instrumental colour and biochemical constituents It can be seen from Table 3 that sensory flavour (r ¼þ0.924, P < 0.01), body and texture (r ¼þ0.960, P < 0.01) and colour and appearance (r ¼þ0.754, P < 0.01) very well correlated with overall acceptability of brown peda. L* negatively correlated (r ¼ 0.928, P < 0.01) with a* but positively correlated with b* (r ¼þ0.337, P < 0.05). The sensory flavour was highly negatively correlated with FFA (r ¼ 0.872, P < 0.01), peroxide value (r ¼ 0.946, P < 0.01) and HMF (r ¼ 0.866, P < 0.01). Similar correlations were observed for overall acceptability of brown peda with FFA (r ¼ 0.974, P < 0.01), peroxide value (r ¼ 0.908, P < 0.01) and HMF (r ¼ 0.914, P < 0.01). The FFA content was highly correlated with peroxide value (r ¼þ0.879, P < 0.01) and HMF content (r ¼þ0.830, P < 0.01). 4. Conclusion The present study attempted to improve the shelf life of brown peda, an Indian milk-based confection, by packaging interventions. From the results obtained, it is clear that there was a progressive decrease in moisture and increase in lactic acidity, free fatty acid, peroxide value, hydroxyl methyl furfural at different rates in all the samples packaged in different packaging techniques. Accordingly, the shelf life of the product was found to differ considerably with

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