Sensory evaluation and consumer acceptability of buffalo curd prepared at 37 °C incubation temperature with various lactic starter cultures under refrigerated storage conditions

The major objective\r\nof this work is to determine the\r\nsensory properties of lactic cultures inhabiting buffalo curd. Commercially available indigenous starter cultures\r\nwere used to prepare buffalo milk curd. Buffalo Milk was adjusted to contain 5% fat and 9% SNF levels using the Pearson\r\nsquare method. All the above samples were incubated at 37 °C separately to study the effect of incubation temperature on the sensory\r\nproperties of buffalo curd. All curd samples were compared with the control\r\ncurd sample by sensory evaluation to select the best starter culture\r\ncombination with higher sensory score. The sensory scores\r\nfor buffalo milk curd samples prepared using Buffalo milk curd prepared by Lactococcus\r\nlactis subsp. lactis +\r\nLactococcus lactis subsp. cremoris + Lactococcus lactis subsp.\r\nlactis biovar diacetylactis inoculation and incubated at 37 °Ccombination of starter cultures were higher than\r\nthe control and other treatments in terms of flavour, body and texture, colour\r\nand appearance, overall acceptability (8.88 ±0.01, 8.76 ±0.01, 8.84 ±0.01, 8.87\r\n±0.01) on day 0 and lowest flavour, body and texture, colour and appearance,\r\noverall acceptability scores (7.52 ±0.01, 7.13 ±0.01, 8.03 ±0.01, 7.50 ±0.01)\r\nwere observed for buffalo milk curd sample prepared using Buffalo milk curd prepared by Lactococcus\r\nlactis subsp. cremoris inoculation and incubated at 37 °C starter culture on day 0. Results showed that starter cultures, and incubation temperatures\r\nsignificantly influenced the sensory characteristics of buffalo curd.

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Introduction

Starter cultures and fermentation temperature are key factors affecting sensory characteristics of curd. The starter cultures confer distinct textural and flavour properties and are also used to promote acid development during curd manufacturing process. (McSweeney and Sousa, 2000) [14] . Composition of milk is influenced by species, breed, individuality, nutritional status, health, and stage of lactation of milch animals. (Fox et al., 2000) [9] . Buffalo milk is rich in fat, lactose, caseins, calcium, magnesium, and phosphate compared with cow milk (Fundora et al., 2001; Ahmad et al., 2008) [10,1] and, because of its chemical composition, buffalo milk offers excellent opportunities for the development of different dairy products (Murtaza et al., 2008) [15] . Curd is a fermented dairy product that undergoes a complex series of chemical, bacterial, and enzymatic reactions during ripening (Singh et al., 2003; Farkye, 2004) [20,8] , which are responsible for the development of sensory characteristics (Pollard et al., 2003; Smit et al., 2005; Azarnia et al., 2006) [17,21,2] . Fermentation of curd is time-consuming lengthy process (Law, 2001; Murtaza et al., 2012) [13, 16] use of variety of starter cultures in different combinations (Lee et al., 1990), and incubation temperatures (Rehman et al., 2000) [18] . Attempts to shorten the fermentation time using a range of ripening systems have had varying degrees of success (Wilkinson, 1993; Law, 2001) [22,13] . Grading and judging are used extensively for sensory evaluation of dairy products (Bodyfelt et al., 1988) [3] ; Assessment of the sensory characteristics of curd and various sensory characteristics is an important part of cheese quality evaluation and currently involves the use of trained sensory panelists or individuals (Downey et al., 2005) [6] . A product is evaluated based on the presence or absence of specific attributes and on overall quality score. These quality scores are usually based on the opinions of one individual, and the quality score is subjective rather than specifically defined (Drake et al., 2005; Caspia et al., 2006) [7,4] . The study was designed with the objective determine the sensory properties of lactic cultures inhabiting buffalo curd prepared at 37 °C incubation temperature under refrigerated storage conditions and its consumer acceptability.

Materials and Methods

Buffalo milk curd were prepared and incubated at 37 °C using 5 per cent fat and 9 per cent SNF combination by means of pearson square standardization using the starter culture combination listed in table 1.

B1C	Control buffalo curd prepared by curd culture incubated at 37 °C
B1Ll	Buffalo milk curd prepared by Lactococcus lactis subsp. lactis inoculation and incubated at 37 °C
B1Lc	Buffalo milk curd prepared by Lactococcus lactis subsp. cremoris inoculation and incubated at 37 °C
B1Ld	Buffalo milk curd prepared by Lactococcus lactis subsp. lactis biovar diacetylactis inoculation and incubated at 37 °C
B1Ll+Ld	Buffalo milk curd prepared by Lactococcus lactis subsp. lactis and + Lactococcus lactis subsp. lactis biovar diacetylactis inoculation and incubated at 37 °C
B1Lc+Ld	Buffalo milk curd prepared by Lactococcus lactis subsp. cremoris + Lactococcus lactis subsp. lactis biovar diacetylactis inoculation and incubated at 37 °C
B1Ll+Lc+Ld	Buffalo milk curd prepared by Lactococcus lactis subsp. lactis + Lactococcus lactis subsp. cremoris + Lactococcus lactis subsp. lactis biovar diacetylactis inoculation and incubated at 37 °C
B1Lnl	Buffalo milk curd prepared by Leuconostoc lactis inoculation and incubated at 37 °C
B1Lnm	Buffalo milk curd prepared by Ln.mesenteroides subsp. cremoris inoculation and incubated at 37 °C
B1Lnl+Lnm	Buffalo milk curd prepared by Leuconostoc lactis + Ln.mesenteroides subsp. cremoris inoculation and incubated at 37 °C
B1Lp	Buffalo milk curd prepared by Lactobacillus plantarum inoculation and incubated at 37 °C
B1Lpp	Buffalo milk curd prepared by Lactobacillus paraplantarum inoculation and incubated at 37 °C
B1St	Buffalo milk curd prepared by Streptococcus salivarius subsp. thermophilus inoculation and incubated at 37 °C

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Starter cultures and their combinations

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Sensory evaluation curd

The panel of judges assessed the coded curd samples at random, according to the methodology described by Indian standards (IS, 1971). Sensory evaluation of samples was carried out with a 12-member and the panelists had a good knowledge on the sensory evaluation of dairy products and participated previously in such evaluations. Curd samples, in the plastic containers were conditioned at room temperature for 15 min before testing. Sensory evaluation of the samples was carried out in the sensory evaluation room under appropriate fluorescent lighting. Each panellist was asked to taste the curd samples labelled with code and rate the sensory parameters on a 9-point hedonic scale. According to the 9-point structured hedonic scale, the acceptance test was carried out for the attributes of colour and appearance, body and texture, flavour and overall acceptability. For all the attributes, 9-point scale was defined as that the highest value indicates the highest degree of preference. Panellists were also requested to give the scores and comments on a sensory evaluation score card. Water was provided to rinse the palate before and after tasting the sample. The various starter cultures and their combinations above were used to prepare buffalo milk curd samples with 5% fat and 9% SNF combinations. The sensory scores of buffalo curd samples prepared with various combinations of starter cultures by incubating at 37 °C and stored at refrigeration temperature are shown in Tables 1,2, 3 and 4 respectively.

Results

The sensory scores of buffalo milk curd samples prepared with various combinations of starter cultures by incubating at 37 °C and stored at refrigeration temperature 5.00 ± 0.5 ºC are shown in Tables 2,3, 4 and 5, respectively. The various starter cultures and their combinations as in Table 1 were used to prepare buffalo milk curd samples with 5% fat and 9% SNF combinations by incubating at 37 °C. All buffalo milk curd samples were compared with the control curd sample by sensory evaluation to select the best starter culture combination with extended shelf life. The sensory scores for buffalo milk curd samples prepared using B1Ll+Lc+Ld Lactococcus lactis subsp. lactis + Lactococcus lactis subsp. cremoris + Lactococcus lactis subsp. lactis biovar diacetylactis inoculation and incubated at 37 °C were higher than the control and other treatments in terms of flavour, body and texture, colour and appearance, overall acceptability (8.88 ±0.01, 8.76 ±0.01, 8.84 ±0.01, 8.87 ±0.01) on day 0 and lowest flavour, body and texture, colour and appearance, overall acceptability scores (7.52 ±0.01, 7.13 ±0.01, 8.03 ±0.01, 7.50 ±0.01) were observed for buffalo milk curd sample prepared using Lactococcus lactis subsp. cremoris inoculation and incubated at 37 °C (B1Lc) starter culture on day 0. (Table 2345). The flavour, body and texture, colour and appearance, overall acceptability scores (6.92 ±0.01, 6.67 ±0.01, 7.05 ±0.01, 7.04 ±0.01) were higher than the control and other treatments for the buffalo milk curd samples prepared using B1Ll+Lc+Ld (Table 2345) starter culture combinations and incubated at 37ºC on day 6 of storage at 5.00 ± 0.5ºC and whereas flavour, body and texture, colour and appearance, overall acceptability scores were lower than the control and other treatments for the buffalo milk curd sample prepared using Buffalo milk curd prepared by (B1St) Streptococcus salivarius subsp. thermophilus inoculation and incubated at 37 °C starter culture (3.89 ±0.01, 3.65 ±0.01, 6.16 ±0.01, 4.04 ±0.02) on day 6 of storage at 5.00 ± 0.5 ºC.

Discussion

Buffalo Curd sample containing Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis biovar diacetylactis starter cultures had significantly high sensory scores compared to other starter cultures. These findings are in close agreement with Shekhar et al. (2013) [19] who investigated about the effect of different cultures on physico-chemical and sensory properties of buffalo curd incubated at 30ºC and 42ºC found that the sensory scores of buffalo curd ranged as 6.76 to 7.78. Khedar et al. (2016) reviewed that homofermentative L. lactis subsp. lactis is able to produce free amino acids, which are believed to stimulate the growth of Lac.lactis subsp. cremoris strains. Another important species in the mesophilic starter category is the homofermentative L. lactis subsp. lactis biovar diacetylactis, which is able besides lactic acid production of fermenting citric acid into a number of other compounds such as diacetyl and carbon dioxide. However, at a pH below 5, carbon dioxide and a number of compounds similar to diacetyl, but non-aromatic, are produced. Homofermentative thermophilic starter microorganisms, like L. delbrueckii subsp. bulgaricus and Str. salivarius subsp. thermophilus are used to obtain mildly sour dahi. These starters play an important role in producing a good quality dahi having a firm and uniform consistency with a sweet aroma and acidic taste. (Chatterjee et al.,2022) [5] The lower sensory scores for some starter culture is explained by Ghosh and Rajorhia (1990) [11,12] recorded that certain curd samples scored low flavor ratings because of the heterofermentative nature of the bacterial culture and known to produce small amounts of formic acid and CO 2 imparts a sharp taste to the product.

Conclusion

Conclusively, the results of the present study suggest that the buffalo milk curd prepared with Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis biovar diacetylactis incubated at 37 ºC could be stored at refrigeration temperature for up to 6 days had good consumer acceptability.

Acknowledgement

AcknowledgementsAuthors sincerely thank Tamil Nadu Veterinary and Animal Sciences University for providing necessary facilities to carry out this research work.

Figures and tables from the paper

Storage period in Days	Starter cultures	—	—	—	—	—	—	—
	B1C	B1Ll	B1Lc*	B1Ld	B1Ll+Ld	B1Lc+Ld	B1Ll+Lc+Ld	B1St
0	8.74cA±0.10	8.76bA±0.10	7.52eA±0.10	8.77 bA±0.10	8.88aA±0.10	7.57dA±0.10	8.88aA±0.10	7.57dA±0.10
2	8.05dB ±0.10	8.04dB±0.10	7.07eB±0.10	8.38bA±0.10	8.28cB±0.10	7.07eB±0.10	8.47aA±0.10	7.07eB A±0.10
4	6.55cC±0.10	6.05dC±0.10	6.07dC±0.10	7.08bB±0.10	7.09bC±0.10	6.08dC±0.10	7.58aB±0.10	6.57cC±0.10
6	4.97bD±0.10	4.96cD±0.10	4.98cD±0.10	4.97cC±0.10	4.96cD±0.10	4.98cD±0.10	6.92aC±0.10	3.89dD±0.10
8	3.92bE±0.10	3.93bE±0.10	3.92bE±0.13	3.93bD±0.10	3.99bE±0.13	3.99bE±0.13	5.17aD±0.13	2.96cE±0.10
10	2.94bF±0.10	3.00aF±0.10	2.95bF±0.10	2.96bE±0.10	3.00aF±0.10	2.94bF±0.10	3.00aE±0.10	3.01aE±0.10

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Flavour scores of buffalo milk curd with various starter cultures incubated at 37 °C during refrigerated storage

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Storage period in Days	Starter cultures	—	—	—	—	—	—	—
	B1C	B1Ll	B1Lc*	B1Ld	B1Ll+Ld	B1Lc+Ld	B1Ll+Lc+Ld	B1St
0	8.68cA±0.10	8.69cA±0.10	7.13dA±0.10	8.70 bA±0.10	8.72aA±0.10	7.15dA±0.10	8.76aA±0.10	7.15dA±0.10
2	7.63dB ±0.10	7.63dB±0.10	6.65eB±0.10	7.96bB±0.10	7.86cB±0.10	6.65eB±0.10	8.05aB±0.10	6.65eB±0.10
4	6.13cC±0.10	5.54dC±0.10	5.55dC±0.10	6.66bC±0.10	6.67bC±0.10	5.67dC±0.10	7.16aC±0.10	6.15cC±0.10
6	4.54dD±0.10	4.63cD±0.10	4.65bD±0.10	4.66aD±0.10	4.65bD±0.10	4.66aD±0.10	6.67aD±0.10	3.65eD±0.10
8	3.63bE±0.10	3.63bE±0.10	3.65bE±0.13	3.66bE±0.10	3.67bE±0.13	3.67bE±0.13	4.87aE±0.13	2.87cE±0.10
10	3.05bF±0.10	2.69cF±0.10	2.65cF±0.10	2.66cF±0.10	2.68cF±0.10	2.66cF±0.10	3.72aF±0.10	2.69cE±0.10

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Body and texture scores of buffalo milk curd with various starter cultures incubated at 37 °C during refrigerated storage

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Storage period in Days	Starter cultures	—	—	—	—	—	—	—
	B1C	B1Ll	B1Lc*	B1Ld	B1Ll+Ld	B1Lc+Ld	B1Ll+Lc+Ld	B1St
0	8.75cA±0.10	8.77bA±0.10	8.03dA±0.10	8.78 bA±0.10	8.83aA±0.10	8.14dA±0.10	8.84aA±0.10	8.07dA±0.10
2	8.48dB ±0.10	8.68cB±0.10	7.99eA±0.10	8.66cA±0.10	8.77bA±0.10	8.08eA±0.10	8.77aA±0.10	8.02eA±0.10
4	7.52bC±0.10	7.02dC±0.10	7.05dB±0.10	7.03dB±0.10	7.04dB±0.10	7.03dB±0.10	7.53aB±0.10	7.22cB±0.10
6	6.87bD±0.10	5.74cD±0.10	5.81dC±0.10	5.80dC±0.10	5.79dC±0.10	5.85dC±0.10	7.05aB±0.10	6.16cC±0.10
8	5.28cE±0.10	5.25cD±0.10	5.31cC±0.13	5.24cD±0.10	5.26cD±0.13	5.25cD±0.13	6.84aC±0.13	5.83bD±0.10
10	5.14cF±0.10	3.17cE±0.10	5.21cD±0.10	5.15cD±0.10	5.08cD±0.10	5.11cD±0.10	6.06aD±0.10	5.54bD±0.10

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Colour and appearance scores of buffalo milk curd with various starter cultures incubated at 37 °C during refrigerated storage

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Storage period in Days	Starter cultures	—	—	—	—	—	—	—
	B1C	B1Ll	B1Lc*	B1Ld	B1Ll+Ld	B1Lc+Ld	B1Ll+Lc+Ld	B1St
0	8.72cA±0.10	8.83bA±0.10	7.50dA±0.10	8.82bA±0.10	8.85aA±0.10	7.52dA±0.10	8.87aA±0.10	7.51dA±0.10
2	8.02dB ±0.10	8.02dB±0.10	7.00eA±0.10	8.33bB±0.10	8.23cB±0.10	7.03eA±0.10	8.43aA±0.13	6.96fB±0.10
4	6.52cC±0.10	6.03dC±0.10	6.01dB±0.10	7.03bC±0.10	7.05bC±0.10	6.03dB±0.10	7.54aB±0.10	6.54cC±0.10
6	6.04bD±0.10	5.03cD±0.10	5.02cC±0.10	5.02cD±0.10	5.03cD±0.10	5.04cC±0.10	7.04aC±0.10	4.04dD±0.13
8	4.02bE±0.10	4.04bE±0.10	4.02bD±0.13	4.03bE±0.10	4.05bE±0.13	4.04bD±0.13	5.26aD±0.13	3.02cE±0.10
10	3.01bF±0.10	3.04aF±0.10	3.01bE±0.10	3.01bF±0.10	3.03aF±0.10	3.01bE±0.10	3.04aE±0.10	3.02bF±0.10

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Overall acceptability scores of buffalo milk curd with various starter cultures incubated at 37 °C

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