Storage Quality and Oxidative Stability Attributes of Jackfruit (Artocarpus heterophyllus L.) Seed Powder fortified Ghee Residue Burfi

Ghee residue is one of the important by-products of the dairy industry, the potential of which has not been commercialised and is otherwise discarded, which leads to loss of many nutrients, anti-oxidants and flavour compounds. Recognizing its vital importance, the present study was carried out to standardize the formulation and to evaluate the acceptability of the burfi. Initially, burfi was prepared by incorporating ghee residue in the proportion of 10%, 20%, 30%, 40% and 50% by replacing respective proportions of khoa from which 40% ghee residue and 60% khoa was optimised in the formulation. Further, different levels of gram flour (3%, 6% and 9%) were tried in the formulation of ghee residue burfi. Based on sensory parameters, optimum level of gram flour was found to be 3%. The addition of gram flour enhanced the textural attributes of the product. Further, jackfruit seed powder (JSP) was added at 1%, 2% and 3% and shelf-life studies were undertaken. The various levels of JSP non significantly decreased the pH, TBARS and FFA content of the burfi samples. An increase in the most of sensory parameters was seen at 3% of gram flour. The total phenol and total flavonoid content were found to be in the range of (1.71-3.34 mg/g GAE) and (0.46-6.12 mg/g Quercetin) respectively. The shelf-life of the products were reported to be 15 days without any marked loss of physico-chemical, microbial and sensory quality. Considering the nutritional content of the product, it shall prove to be beneficial in providing energy and protein content to the malnourished section of the society.

India is the largest and one of the most economical milk producers in the world, with an average production of 155.5 Million tonnes per annum (NDDB, 2015-16); Nearly 56 per cent of total milk produced in India is utilized for preparation of variety of traditional milk products i.e., Ghee, Curd, Khoa, Butter, Milk powder, Paneer, Chhana etc. Out of total milk produced, 6.5 per cent is utilized for Khoa making (Anonymous, 2016). Ghee residue is a by-product obtained during manufacture of ghee. About 30-35% of the milk produced in India is converted into ghee (Gandhi et al., 2013). When cream is heated into ghee, a brownish residue/ghee residue settles down after molten ghee is strained out. It has high nutritional value and is a rich source of lipids, proteins, antioxidants and flavour compounds. Most of the times, it is considered as a waste and is used at the industry level for the production of lipase being a potential source of the lipids (35-70%) and in the baking industry as flavour enhancer. However, at commercial level it has not been utilized by food industries. At the domestic levels it is used for samosa filling or spreading over chappaties etc. Consumption of dairy sweets is closely related with our traditional rituals and festivals. Most dairy food delicacies are value added products generating high profits. Burfi, a khoa based sweet delicacy is popular in all parts of the country. The remarkable adaptability of khoa to amalgamate with different ingredients has craved out methodologies of large burfi varities. The market for traditional dairy products in India is estimated to be US $ 10 billion, being the largest and fastest growing segment of the Indian dairy industry (Pal et al., 2006). Although manufacture of traditional products are gaining popularity yet the limitation of shorter shelf life due to microbial contamination is a matter of concern. Development of rancidity arising out of lipid degradation reduces the shelf-life of the product, which ultimately affects consumer acceptability (Nerin et al., 2008). Advancement in the preservation of food items now inclines more towards the use of biopreservatives for shelf life extension which also provides additional health benefits of the natural antioxidants. Artocarpus heterophyllus (Jackfruit) trees belong to mulberry family Moraceae (Rahman et al., 1999). Jackfruit seeds contains 6.6-7 % protein, 38% carbohydrate, 1-1.5% fiber and 0.4% fat. Converting seeds into flour overcomes the problem of shorter life span and also allows adjunction with wide arrays of flours to be used for value addition while providing extra advantage of nutrients and polyphenolic compounds. Antimicrobial effects of jackfruit seed powder has also been reported by several researchers in the recent times. Therefore, present study was carried out of evaluate physico-chemical attributes of ghee residue collected by direct cream method and its conversion into burfi type confection. Further, shelf-life studies were undertaken with the incorporation of jackfruit seed powder.

Collection and processing of ghee residue
Cream collected over a span of time and kept under freezer condition was heated uniformly on a low heat with continous stirring to avoid scorching at the base of container. Ghee was filtered out and sediment (ghee residue) was hand pressed in sieve to obtain ghee residue. Further, the ghee residue was treated as recommended by Prahlad (1954) with slight modifications. Ghee residue was tied in a muslin cloth and then kept in warm soda bicarbonate solution (1%) for 15 minutes to neutralize the acidity.

Preparation of khoa
The khoa was prepared from milk by continous stirring cum scrapping till it attained pasty consistency as described by De (2004).

Preparation of control burfi
Freshly prepared khoa was spread over the karahi and crystal sugar @30g was added following which the mixture was worked upon with wooden ladle for 5-10 minutes. The mass was transferred to the greased trays, flattened and allowed to cool under room temperature. It was later cut into the desired rectangular shape.

Preparation of experimental burfi and JSP added burfi
Experimental burfi was prepared with khoa, ghee residue and gram flour. Sugar @30g was added. Jackfruit seed powder was added at three different levels viz 1%, 2% and 3% for the preparation of JSP added burfi.

Physico-chemical properties
The pH of ghee residue burfi was measured soon after its preparation by the method of Keller et al. (1974) by using a digital pH meter (Systronics Digital pH Meter 803). The proximate components viz., moisture, crude protein, crude fat, total ash contents and Titratable acidity and peroxide values were determined by using standard procedures prescribed by AOAC (1995). Water activity of the samples was determined using water activity meter (Aqua Lab-Series 3 TE). Lactose percent in the samples was done as per Lane-Eynon volumetric method (Adriano et al., 1934). Total cholesterol in the lipid extracts was determined by adopting the Tschugaeff reaction as modified by Hanel and Dam (1995).

Storage studies
TBARS value of the samples was determined as per method described by Witte et al. (1970). Free Fatty Acid value of the samples was determined as per method of Koniecko 1979. The microbiological characteristics viz., total plate count, psychrophillic count, coliform count and yeast and mould count were determined by methods of APHA (1984).

Antioxidant assays
Total Phenol content-Phenol content of the samples was determined as per method of Singleton et al. 1999. Total Flavonoid Content-The content of flavonoids in the examined samples was determined using spectrophotometric method (Quettier et al., 2000).

Sensory evaluation of ghee residue burfi
The burfi was evaluated for its sensory parameters at regular intervals by semi-trained experienced sensory panel consisting of 7 scientists of the Faculty of Veterinary Sciences and Animal Husbandry on a 9-point hedonic scale with slight modification (Pal and Gupta, 1985) wherein a score of 1 represented 'dislike extremely' and score of 9 represented 'like extremely'. Water was provided to the panellists for oral rinsing between two sample testing.

Statistical analysis
The results were analysed statistically for analysis of variance and least significant difference tests using the software of statistical package for social sciences (SPSS 16.0) and as per Snedecor and Cochran (1980).

Sensory evaluation of ghee residue burfi of different ratio
The basic formulation of burfi was optimized for the levels of ghee residue and levels of khoa. For this purpose, different proportions of ghee residue and khoa viz. 10:90, 20:80, 30:70, 40:60 and 50:50 were used in the preparation of ghee residue burfi keeping the fixed level of sugar i.e. 30g (as per standard texts) to optimize the levels of ghee residue and khoa. The 0:100 combination served as control. The products were judged for colour and appearance, body and texture, flavour and overall acceptability. The results of sensory evaluations are presented in table 1.
Results showed that with increase in the levels of ghee residue, no significant difference was observed upto 40:60 level thereafter, a significant (P<0.05) decrease was observed. This could be attributed to the brown colour of the ghee residue and so could be incorporated upto 40% level. This is in accordance with the study of Borawake and Bhosale (1996), where it was reported that increasing levels of replacement of fat with GR decreased the colour and appearance scores in nankhatai type cookies and sponge cakes. The scores for flavour increased nonsignificantly (P>0.05) with the increase in the inclusion of ghee residue. This is probably because of the high flavour potential of GR due to the presence of high FFA, carbonyls and lactones Wadhwa, 1991a and1991b). Similar findings were observed by Subbulakshmi et al. (1990), who concluded that ghee flavour in the residue improves the aroma of the products there by improving the overall acceptability. Overall acceptability of burfi containing 40:60 combination although low was comparable with the control. Based on above observations, 40% ghee residue and 60% khoa proportion was selected for further studies.

Sensory evaluation of ghee residue burfi incorporated with different levels of gram flour
In this part of the study, different levels of gram flour (GF) i.e. (3, 6 and 9%) were utilized in the formulation of burfi by replacing the respective proportion of khoa. Product containing 0% gram flour served as control. The mean values for sensory parameters are presented in table 2. The mean sensory scores for burfi made with 9% gram flour were significantly (P<0.05) lower than the burfi prepared with 3% gram flour and control burfi, however the latter two were comparable with each other. The scores for colour and appearance decreased after 3% level because at higher amounts, it gave darker colour to the product and did not appeal the judges. The scores of flavour for burfi also decreased after 3% level because of the flour taste which replaced the original flavour and taste of burfi when used in greater amounts. Higher values of overall acceptability might be due to higher scores for other sensory attributes for the formulation containing 3% gram flour. Hence, 3% gram flour was found optimum in the development of gram flour incorporated ghee residue burfi (GFb).

Proximate composition of designed burfi
The proximate composition of burfi designed with ghee residue, khoa and gram flour is presented in Table 3.

Physico-chemical and sensory evaluation of optimized burfi with different levels of Jackfruit Seed Powder (JSP)
Three different levels of Jackfruit seed powder (1%, 2% and 3%) were added into gram flour based ghee residue burfi and the product was analysed for storage parameters at weekly interval upto 21 days.

Physico-chemical parameters
The mean values for various physico-chemical attributes of ghee residue burfi (containing 3% gram flour) and incorporated with different levels of Jackfruit seed powder are presented in Table 4. The mean values of pH in control (GFb) as well as burfi treated with different levels of JSP decreased significantly (P<0.05) with the progressive storage interval. The decline in the pH of gram flour burfi with jackfruit seed powder could be attributed to the acidic pH of Jackfruit seed powder (Swami et al., 2012). TBARS followed a significant (P<0.05) increasing trend from day 0 to 21 in case of both control as well as burfi with added jackfruit seed powder. This is in accordance with findings of Kumar et al. (2010) who reported a significant increase in TBA values with increase in time in stored khoa samples containing antioxidants. The FFA content showed a non-significant increase throughout the storage period in control as well as treated burfi samples. Increase in FFA was within desirable limits when compared to BIS (1966) as per IS: 3508 rules maximum limit for FFA is 3.0 in ghee and all ghee residue products showed lower levels in comparison to PFA recommendations. The results are also in agreement with Janghu et al. (2014) who studied the effect of storage on free fatty acid content of candy and chocolate made from ghee residue. Water activity (a w ) of the products decreased with the advancement in the storage interval; however the scores for GFb with 3% JSP were higher than the control on all days of storage.
Peroxides were not detected till 14 days of refrigerated storage, however they were detected on day 21.

Total Phenol content (mg/g GAE)
Total phenolic content of samples (with optimized levels of flours) treated with varying levels of JSP and stored at refrigeration temperature (7±1ºC) is presented in Fig. 1. The results showed that there was non-significant decrease (P<0.05) in phenolic content of control, GFb with 2% JSP and RWFb with 2% JSP upto day 14 and thereafter a significant (P<0.05) decrease was observed on day21 of refrigerated storage. Shanmugapriya et al. (2011) studied total phenolic contents of Artocarpus heterophyllus (Jackfruit) seeds and reported that it has effective antioxidant activity due to presence of phenolic compounds in the range of 2-4.2 mg/g extract. However, low content of phenols were detected in burfi which might be due to processing losses. The results showed that there was non-significant (P>0.05) decrease in values for GFb with 2% JSP upto 14 th day of storage after which a significant (P<0.05) decrease was observed on day 21 of refrigerated storage. For rest of the treatments, a non-significant difference (P>0.05) was observed. Shanmugapriya et al. (2011) studied total flavonoid contents of Artocarpus heterophyllus (Jackfruit) seeds and reported that it has high flavonoids content in the range of 1-4 mg/g extract. However, content of flavonoid detected were low in burfi which might be due to processing losses and destruction of flavonoids during preparation of product.

Microbiological Parameters
The mean values expressed as cfu/g for various microbiological attributes of ghee residue burfi incorporated with optimized level of gram flour (3%) are presented in Table 5. Total plate count (TPC) followed a linear increasing trend from day 0 to 21 in control as well as JSP added burfi samples. The values were non-significantly (P<0.05) lower in case of GFb with added 3% JSP on all days. This might be because of the low concentration of the JSP. However, counts remained under acceptable range until 14 days of refrigerated storage. The increase in TPC with progressive storage may be attributed to the post process contamination during handling. Reddy (1985), also found that burfi made from concentrated milk and mixture of cane sugar and corn-syrup and stored at 5 °C had a total viable count of 2×10 2 and 6×10 3 /g on the first day and after 190 days, respectively. The psychrophillic count was not detected at day 0 and 7 but appeared at 14 day of storage with significant (P<0.05) increase on day 21. The appearance of psychrophilles after such a long gap might be caused by sufficient heat treatment during processing, which drastically injured and killed the psychrophillic population reducing the number of surviving injured and resistant ones and hence donot form any colony. A detectable count on day 14 onwards while nil on preceding observations might be attributed the fact that bacteria generally need some lag phase before active multiplication is initiated (Jay, 1996). No anti-fungal effect could be seen in any sample incorporated with jackfruit seed powder on any day of storage.

Sensory parameters
The mean values for various sensory attributes of ghee residue burfi incorporated with optimized level of gram flour (3%) are presented in Table 6. The values of colour and appearance and mouthfeel for control as well as JSP added burfi samples were comparable upto 14 day of storage. Decrease in colour scores with advancement of storage days might be attributed to oxidative fading, moisture loss and non-enzymatic browning from reaction between lipid oxidation products and amino acids (Chandralekha et al., 2012). The scores for flavour in case of control GFb decreased non-significantly upto 7 th day and thereafter a significant decline was observed. Decline in textural scores on 21 st day of storage might be attributed to proteolytic and disulphide bond changes (Santamaria et al., 1992). Similar trend was observed by Reddy (1985) and Kamble (2010). There was dryness of the surface, reduced freshness, dull appearance and faded colour with advanced storage period. The observations present study indicated that both control and JSP added burfi samples retained acceptable physico-chemical characteristics, colour values, microbiological counts and good to very good sensory rating during storage under refrigerated temperature at 7±1ºC for 14 days. Hence, formulated burfi samples evolved in this study could be safely stored up to 14 days of storage at 7±1ºC without any marked loss of physico-chemical, colour, microbiological and sensory quality. concluded that ghee residue can be very well utilized for preparation of palatable and economical burfi by blending 40 per cent ghee residue and 60 per cent khoa on weight basis. The level of gram flour in the formulation of ghee residue burfi was standardized at 3%. The addition of flour improved the textural properties of the burfi. The storage quality of the developed products was further studied and both control and jackfruit seed powder enriched burfi maintained acceptable oxidative stability, microbial profile and sensory acceptability upto 14 th day of refrigerated storage (7±1ºC).