Elaboration and Quality of Greek Yogurt (labneh) from Buffalo Milk Supplemented with Plus açaí jelly (Euterpe oleracea Mart.)

Buffalo milk has a high nutritional value, with high fat, protein, and mineral levels. Its derivatives yield exceeds by 40% those derived from bovine milk. As a way to take advantage of this quality, Greek yogurt (Labneh) is an alternative to add value to this important product. Thus, this work aims to prepare Greek yogurt with buffalo milk, added with açaí jelly (Euterpe oleracea Mart.), to carry out physical-chemical, microbiological, sensory, and texture profile analyzes in buffalo milk, Greek yogurt, and in açaí jelly. Natural Greek yogurt had an acceptability index of 90.11% and Greek yogurt with açaí jelly, 93.11%, Journal of Agricultural Studies ISSN 2166-0379 2021, Vol. 9, No. 1 http://jas.macrothink.org 269 which constitutes an alternative for regional raw material valorization, with excellent acceptability, high nutritional value, and outstanding physical-chemical and microbiological quality. Thus, this derivative is indicated for special programs supported by the City Halls and/or Government of Pará state, as a way of generating income and employment for communities producing buffalo milk and açaí.

influenced yogurt consistency, so the percentages of each component are shown in Table 1.

Greek Yogurt Preparation With Aç aí Jelly
The skimmed buffalo milk received heat treatment, in aluminum pans, at a temperature of 95 º C, for 5 minutes, to destroy pathogenic microorganisms and other thermo-resistants. Then, 10% (w/v) of whole milk powder was added to increase the consistency and yield of Greek yogurt, and 4% (w/v) of sucrose, to have enough carbohydrate in the fermentation of sugars by microorganisms. Subsequently, it was cooled to ± 43 º C, in an 'ice bath', and 0.6% (w/v) of lyophilized culture, composed of Lactobacillus acidophilus, Bifidobacterium and Streptococcus thermophilus, was inoculated, fermenting at 43 º C, in an oven of air circulation, until reaching the pH of 4.6 to 4.8.

Journal of Agricultural Studies
With the end milk fermentation, the curd was broken, deposited in cotton fabric, previously sanitized and sterilized, trapped in a properly closed plastic container; then stored at 8 º C, and drained for 12 hours. 10% sour cream, 4% sucrose, 1% modified starch, and 0.03% conservative potassium sorbate were added to the curd, which was homogenized. Aç aí jelly was made with 46.9% fruit pulp at 8 º Brix, 51.6% sucrose, and 1.5% pectin, prepared in a stainless steel pan, where it remained under constant heating and movement until reaches 60 º Brix. Subsequently, it was cooled to complete the aç aí jelly gelation.

Laboratory Analysis
Physical and chemical characterizations of buffalo milk, NGY, and aç aí jelly (AJ) were carried out. And from aç aí jelly, for titratable acidity, hydrogen potential (pH), humidity, fixed mineral residue (ash), crude protein, and soluble solids, according to the Analytical Standards of the Instituto Adolfo Lutz (1985) -Instituto Adolfo Lutz. Total lipids -Bligh-Dyer (Bligh and Dyer, 1959), and total carbohydrates were according to Resolution RDC No. 360, December 23, 2003(Brazil, 2003. Energy value through the Atwater factors, 4 -9 -4 kcal/g, respectively, for proteins, lipids, and total carbohydrates, according to resolution RDC No.360, December 23, 2003(Brasil, 2003. NGY was analyzed in an indicative way, for coliforms at 45 º C and Salmonella sp, with results compared to tolerance parameters required by RDC No. 12, January 2, 2001(Anvisa, 2001, for raw milk, pasteurized milk, NGY, and the jelly. Salmonella sp identification was made for raw milk, pasteurized milk, and NGY. For NGY and aç aí jelly was made filamentous fungi and yeasts identification. All analyses were made according to the methodology of Silva et al. (2001).
Texture profile variables were analyzed for fracturing, hardness, cohesiveness, adhesiveness, elasticity, gumminess, and chewability. In a TA-XT2 texturometer, samples were analyzed under a temperature of 8 º C and the compression was performed with speed in the pre-test at 2.0 mm/s and 2.0 mm/s, with a contact time of five seconds and contact force of 1g (Van Dender et al., 2005). The analyzes were carried out in four replicates, at the Brazilian Agricultural Research Corporation -Embrapa Amazônia Oriental, Belé m, Pará .

Sensory Evaluation
The sensory evaluation of NGY and AJ samples was carried out between 48 and 72 hours after derivative preparation, with UEPA students, teachers and servers. They were untrained, in number of 60, through acceptance test with a nine points' hedonic scale (Dutcosky, 2013), which comprises point 1 (I disliked it a lot) to 9 (I liked it extremely). Also, data were obtained on age, conventional yogurt consumption frequency and purchase attitude of the derivative with aç aí jelly.

Preliminary Tests
Greek yogurt samples, that contained 10 and 15% of the cream, were similar in assigned scores, and because they did not differ, after the Tukey test (p ≤ 0.05), the treatment with 10% was chosen, because it had less cream to keep the texture more consistent, a predominant characteristic in this dairy derivative (Table 2).

Physicochemical Analysis
Data from physical-chemical analyzes of buffalo milk may be different from those found by other authors, since buffaloes, during the lactation period, are influenced by climatic factors, which interfere in forage production and, consequently, in milk production throughout the year; in addition to breeding system influences, such as type of food, pasture or feed, breed, age and management (Simões et al., 2014). Buffalo milk physical-chemical analyzes, followed by standard values indicated in the current legislation are in Table 3.  (Brasil, 2011).
The analysis of soluble buffalo milk solids resulted in 8 º Brix, without parameters in the current legislation. The pH observed in the milk used to make Greek yogurt is similar to that mentioned in the literature (Figueiredo et al., 2010). Simões et al. (2014) indicate seasonal variations in buffalo milk composition, on Marajó Island, Pará , where the pH is 6.87 in the rainy season and 6.86 in the drought.
Fat percentage is included in Ordinance No. 62 (Brasil, 2011), with a minimum of 0.6 and a maximum of 2.9, being classified as "partially skimmed milk". In search of less caloric derivatives, milk skimming is a process favorable to yogurt production. As for protein content, the average value is lower than the literature (Caldeira et al., 2010;Medhammar et al., 2012;Simões et al., 2014). The carbohydrate index supersedes those reported by Figueiredo et al. (2010) and Medhammar et al. (2012), and the energy value is lower than that reported by Figueiredo et al. (2010). Physical-chemical analyzes results of AJ's NGY, followed by legislation standard values, are shown in Table 4. * Results on wet basis. ** NGY -Natural Greek yogurt *** AJ -Greek yogurt with aç aí jam. **** (Brasil, 2007).
Although there are parameters in Brazilian legislation (Brasil, 2007), pH value is following ISSN 2166-0379 2021 Modesto Junior et al. (2016) and diverges as to soluble solids. However, it is similar to that of Mantovani et al. (2012). The moisture percentage of NGY and AJ approaches those determined by Sampaio et al. (2011), Mantovani et al. (2012, and Modesto Junior et al. (2016). The ash contents in the NGY and AJ are under the literature (Lima et al., 2011;Sampaio et al., 2011;Antunes et al., 2015;Modesto Junior et al., 2016). The difference between mineral content in NGY and AJ is due to minerals in aç aí jelly.

Journal of Agricultural Studies
NGY and AJ acidity levels are within the limit of 0.6 and 2% allowed by the legislation for yogurt (Brasil, 2007), and according to Sampaio et al. (2011). This study's protein contents for NGY and AJ are within the Brazilian legislation for fermented milk (Brasil, 2007), with a minimum value of 2.9%. Dry extract percentages differ from those mentioned in the literature (Lima et al., 2011;Mantovani et al., 2012). NGY and AJ fat content in the study meets the minimum standard of 6% of current legislation (Brazil, 2007), which is lower than the literature (Lima et al., 2011;Mantovani et al., 2012).
Acaí jelly total acidity was higher than that described in studies with white aç aí jelly and buriti jelly (Garcia et al., 2017) and lower than that of aç aí purple jelly (Couto et al., 2007). According to Torrezan (1998), jelly's total acidity must be between 0.5 and 0.8%. The moisture content is within the maximum limit of 38% moisture in fruit jellies (Brasil, 1978), with values close to those of Barcia et al. (2010) and Couto et al. (2007). Ash content is similar to that mentioned by Barcia et al. (2010).
Lipid amount in aç aí jelly was higher than those found by Couto et al. (2007) and Barcia et al. (2010), and lower than that of Neto et al. (2013). Aç aí jelly did not have a significant protein value, different from the literature (Couto et al., 2007;Neto et al., 2013;Oliveira et al., 2014). Carbohydrate content determined in aç aí jelly is close to that of Couto et al. (2007), in white aç aí jelly, and surpasses that of Oliveira et al. (2014), in umbu-cajá jelly.

Microbiological Analysis
Microbiological analyzes' results to assess hygienic-sanitary conditions of raw and pasteurized milk are shown in Table 6.  ISSN 2166-0379 2021 Pasteurized milk microbiological analysis has demonstrated milk heat treatment efficiency, before dairy culture inoculation for fermentation, due to the absence of undesirable microorganisms, as required by current legislation. NGY microbiological analysis' results are shown in Table 7. Coliforms at 45º C < 3 NMP/g 10 NMP/g

Filamentous fungi and yeasts
3.37 X 10 -¹ UFC/g -Coliforms' absence at 45 º C in the NGY confirms milk handling and processing efficiency, pre and post-fermentation, as well as Salmonella sp. absence; while filamentous fungi and yeasts' counting does not compromise product integrity. Acaí jelly microbiological analyzes' results are shown in Table 8. Coliforms at 45º C < 3 NMP/g -

Filamentous fungi and yeasts
Absence 10 4 UFC/g Aç aí jelly did not present coliform at 45 º C and neither filamentous fungi and yeasts, due to the high temperature in the elaboration and efficient processing, which favored dairy derivative health.

Sensory Evaluation
Sensory analysis was performed with untrained tasters, where 53% were female and 47% male (Table 9). Regarding yogurt consumption frequency, only 10% of the tasters consumed daily, 51% once or more times a week, and 37% once or more times a month. ISSN 2166-0379 2021  A significant difference was noted in the aroma attributes, since the addition of aç aí jelly to yogurt changed the odor, modified the flavor of NGY, and consequently increased the assigned average, making it more accepted. NGY is usually more acid/sour than AJ, so there was an acceptance of Greek yogurt added with aç aí jam, which had greater global acceptance, due to its sensory characteristics. The scores of the hedonic scale were plotted in percentages on the graphs, to illustrate the distribution between the attributes. The highest score count in the NGY sensory test was 8 (I liked it very much) and 9 (I liked it extremely). The attributes most appreciated by the judges were 'Aroma', with a score 8, of 39%, and score 9, 35%; 'Flavor' with a score 9, of 34% of the tasters, and a score of 9, with 38%; 'Texture', 30% scored 8 and 50%, scored 9; 'Global Assessment', 47% score 8 and 40%, score 9. The NGY presented an acceptability index of 90, for 11% of the tasters and, according to Dutcosky, (2013), the minimum acceptability index is 70%. Thus, the derivative elaborated in the present work has excellent acceptability.

Journal of Agricultural Studies
AJ had a higher score, 9 (I liked it extremely). The 'Color' attribute received a score of 9 from 45% of the tasters; 'Flavor', 68%; 'Texture', 52%; and 'Global Assessment', 61%, while the acceptability index was 93.11% of the tasters. Thus, it can be said that this derivative obtained excellent acceptability, 2% more than the NGY index. Figure  Among the judges, 76% said 'I Would Definitely Buy It', being the derivative with characteristics that are attractive to the consumer, a firmer and more consistent texture, the characteristic flavor of buffalo milk, and the taste and color of aç aí , which is a highly appreciated fruit.

Texture Profile Analysis (TPA)
The results of the texture profile analysis are shown in Table 10, with a comparison between the NGY and AJ profiles. The TPA analysis indicated that the NGY has a high fracturability index, which is the force of the first bite, at the moment of the first compression capable of breaking the food, reflecting ISSN 2166-0379 2021 the low hardness value, which is the force necessary for the food to be deformed between the teeth, tongue or "roof of the mouth" (Bourne, 1978;Steff, 1996;Szczesniak, 1998). Compared to AJ's low fracturability and high hardness, the differences between the samples can be seen due to their proximate compositions (humidity, soluble solids, proteins, among others).

Journal of Agricultural Studies
The degrees of hardness of NGY and AJ are higher than those found in research by Ramos et. al. (2009), who measured the hardness in Greek yogurt with cream and without cream; and those by Souza et al. (2011), in five brands of petit Suisse cheese, which can be compared to Greek yogurt, as it has similar physical characteristics, such as using serum separation techniques, with a hardness between 5.42 and 6.65 kgf.
Cohesiveness indicates the internal forces to the food that determine the extent of the deformation before breaking in the second compression, and that represents the moment of the bite with the molar teeth (Bourne, 1978;Steff, 1996;Szczesniak, 1998). The results found in the present study, for NGY and AJ, are close to those proposed by Ramos et al. (2009) and Silveira et al. (2016), for the degree of cohesiveness of yogurts; and for Souza et al. (2011);Maruyama et al. (2006) and Shamsia and El-Ghannam (2012), in Greek yogurt made from cow's milk.
The adhesiveness of NGY and AJ observed in this work, implies that it is not necessary to apply a lot of force, with the tongue, for example, to overcome the attractive forces between the yogurt and other surfaces, such as teeth and "roof of the mouth" (Bourne, 1978;Steff, 1996;Szczesniak, 1998), which means that AJ and NGY cannot be considered sticky and gummy (Szczesniak, 1998).
Gumminess is the density that allows food to be chewed before being swallowed (Bourne, 1978;Steff, 1996;Szczesniak, 1998). This variable was analyzed in NGY and AJ. Thus, the gumminess was higher than that measured by Ramos et al. (2009), while AJ was characterized as pastier, and due to its greater hardness, this fact could also be due to the degree of cohesiveness, but the values are similar in the two samples.
Chewability is the force exerted to disintegrate food into a suitable state to ingest it. The factors that influence chewability are the hardness, cohesiveness, and elasticity of the food. The evaluation of this variable in the AJ was higher, due to the higher degree of hardness, influenced by the greater addition of soluble solids from the aç aí jelly, and lower degrees of cohesiveness and elasticity (Bourne, 1978;Steff, 1996;Szczesniak, 1998), characteristics that favor the consumption of yogurt.

Conclusion
Greek yogurt made with buffalo milk added with aç aí jelly is a great example of the Journal of Agricultural Studies ISSN 2166-0379 2021 valorization of the regional raw material, as it enhances the chemical properties and the advantages of consuming buffalo milk, as well as highlights the particularities of aç aí . The derivative obtained excellent acceptability, with high nutritional value, protein caloric value, and outstanding physical-chemical and microbiological quality.
The derivative is indicated for a special program supported by the City Halls and/or Government of Pará state, in locations that produce raw materials, to minimize the lack of nutrients, benefiting the health of students from the municipal and state public schools, in addition to generating income and employment in producing communities, by encouraging milk and aç aí production. Thus, Greek yogurt made from buffalo milk with aç aí jam meets the caloric needs recommended by the Student Food Program.