yogurt production process

At the heart of yogurt fermentation lies the lactic acid bacteria, particularly Lactobacillus and Streptococcus species, which convert lactose into lactic acid, causing the milk proteins

NONG LAM UNIVERSITY, HO CHI MINH CITY

FACULTY OF CHEMICAL ENGINEERING & FOOD TECHNOLOGY

te£LÌœ

TOPIC:

Discuss the processing technique(s) or method(s) on the quality

of specific food products

Full Name: Tran Mai Trang Class: DH22TP

Student’s ID: 21125531 Instructor: Assoc Prof., Dr Kha Chan Tuyen

Ho Chi Minh City, 06" April 2024

YOGURT PRODUCTION PROCESS

1 ABSTRACCT s G G0 3 0.3 1 TY TH I0 04 9 0004 010004 1 0 000.04998 1

2, INTRODUCTION co HH cọ HT TH nọ g TH 4 TH g0 08 1

3 YOGURT PRODUCTION PROC ES cà HT TH HH ng 2 3.1 Materials, equipments and methods for yogurt fermentafion - 2

3.3 Mechanism ofyogurt Íermenfation 2: 21121 2122111111111 111182111182 key 6 3.4 Set Yoghurt Manufacturing Process€§ 02102012 2c ng Hà Hy 7

4 SUMMARY AND RECOMMENDATHIONS uc cu HH ng nhưng 16

4.2 Recommendat1ions +: 222221112111 1211121 11111151 11211211 1111111101111 16

5 REFERENCES, cccsssscssssccsssscssssscssssecssssecsessessessesssnsssesansssnnesssnnscssanscennesessnasssnsesseees 16

LIST OF FIGURES

Figure 1 Pyruvic acid converted into Lactic acid ccc ccceccecceseseesesecteeneeseteeneens 7 Figure 2 Pyruvic acid mto Acetie alhehyde 02c 2212212212111 xe re 7 Figure 4 Milk from the cow is measured in-line

and then sent to a bulk cooling tanK - - 2222212221131 15111511111 111 11511111 re 8

Figure 5 Engineering flow sheet of set yoghurt production 0.0.00 0 cere 9 Figure 6 HoIIOB€TIZ€T, Q2 2020121221251 151 22111211511 11121111 2111110112012 11015 11211 1 1H rg 10 Figure 7 Yogurt PackagIng 1c n2 12115115251 151 25112111211 211 1012112112112 1 0 tr rkg 11

LIST OF TABLES

2090115

e900991 1 ae

Table 3 Microorganisms used in the production

of yogurt from milk (Oberman

1998) uc nen HH eo H & Libudzsz Z., 5

1 ABSTRACT

Yogurt production involves the fermentation of milk through a carefully controlled process that blends traditional practices with scientific precision The quality of the raw milk, with specific requirements for fat, non-fat dry matter, and microbial levels, is crucial for successful fermentation The addition of sugars, fruits, and other permitted additives can enhance the flavor and characteristics of the final product At the heart of yogurt fermentation lies the lactic acid bacteria, particularly Lactobacillus and Streptococcus species, which convert lactose into lactic acid, causing the milk proteins to coagulate and imparting the distinctive texture and taste The intricate interplay between biochemical changes, microbial activity, and stringent quality control measures during the fermentation process showcases yogurt as both a culinary delight and a scientifically intricate endeavor, exemplifying the harmonious fusion of tradition and modem techniques in food production The main objective of this study is to provide insight into yogurt production; discuss the main ingredients, how to operate the main equipment, and equipment used in yogurt production

Keywords: yogurt production, fermentation, fermentation process, milk processing, quality control

2 INTRODUCTION

The craft of tuming milk into yogurt through fermentation is a respected custom enjoyed

by various societies, known for its long history and health benefits Yogurt, a smooth dairy product known for its tart taste and health benefits from probiotics, is valued in cooking customs around the globe The yogurt fermentation process, essential in dairy production, combines traditional skill with scientific accuracy Yogurt production relies

on the quality of fresh milk, which can be sourced from different forms such as fresh milk, powdered milk, condensed milk, reconstituted milk, or recycled milk The strict requirements for fresh milk include low levels of microbes, no presence of bacteria, antibiotics, enzymes, or chemical residues from cleaning, to guarantee the best fermentation results

The fat and non-fat dry matter content are two important factors to consider when evaluating raw milk, with the non-fat dry matter content required to be at least 8.2% according to WHO/FAO guidelines Studies show that enhancing non-fat dry matter, especially by increasing casein and whey protein levels, improves the overall structure of yogurt and reduces serum separation, a common problem in traditional yogurt making (Hui, 1992)

Producers can add sugars like glucose or sucrose while processing to increase sweetness

In other words, fruit purees like strawberry, blueberry, or apple can also be added, with sugar typically making up around 50-55% of the puree Furthermore, certain yogurt items may be fortified with flavorings and coloring agents, following national guidelines on allowed additives and maximum amounts

The important microbial community needed for yogurt fermentation consists of a variety

of bacteria and fungi Lactic acid bacteria, particularly certain types of Lactobacillus and Streptococcus, lead the lactic fermentation process by converting lactose into lactic acid, which plays a crucial role in determining the flavor and texture of yogurt

At the core of lactic fermentation is the transformation of lactose into glucose and galactose, then glycolysis and conversion of pyruvic acid into lactic acid by lactate dehydrogenase enzymes The pH dropping causes milk proteins, especially casein, to clot, resulting in the gel-like texture of yogurt

Essentially, the intricate relationship between biochemical changes, microbial cooperation, and precise quality control during yogurt fermentation showcases its dual role as a common food item and a scientific project.The art of fermenting milk into yogurt is a time-honored tradition celebrated across cultures, characterized by its rich history and nutritional significance Yogurt, a creamy dairy product renowned for its tangy flavor and probiotic benefits, holds a cherished place in culinary traditions worldwide

Table 1 Chemical composition of yogurt

Stain pH Prot(%) Casein(%) WSEs(%) Fat (g/100 2) Lactic acid

(g/L)

1 Day

CNT 4194001 3.284011 2454011 O1540.01 2.684017 3.98+40.35 LpwCFS1 4.0740.02 3.4340.11 2414011 0.194001 3.754039 4.43+40.65 Lp8328 4.284001 3.354023 25940.16 0.194001 4054013 465+41.04

14 Days

CNT 4.254001 3.0340.00 2424000 O1140.01 4434010 4904081 LpwCFS! 4.1840.01 2.9540.11 2.344011 0.1040.00 4484010 5.05+40.04 Lp8328 4134001 3.194000 2.274014 0.124000 4454006 5.434051

28 Days

CNT 4.224001 1.994011 1614£0.07 0.104000 434020 5.1440.23 LpWCFSI 4.17+0.0I1 2.8740.00 2241+002 0.104000 444000 5.46+0.62 Lp8328 4214001 2.9540.11 2.134011 0.124000 434020 5441+0.26

3 YOGURT PRODUCTION PROCESS

3.1 Materials,

fermentation

Materials

Source: Vittorio Capozzi

yogurt

The yogurt production process begins with securing the essential material - fresh milk of superior quality This raw milk can originate from various sources, including freshly obtained milk straight from the dairy animal, powdered milk, condensed milk, reconstituted milk, or even milk recycled from previous dairy processes Regardless of

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the source, the milk must adhere to stringent requirements to ensure optimal fermentation conditions It should exhibit low microbial levels and be entirely free from pathogenic bacteria, antibiotics, enzymes, and any chemical residues that may have originated from cleaning agents used in dairy facilities The presence of such contaminants could potentially mhibit or adversely alter the fermentation process, ultimately compromising the quality and safety of the final yogurt product

Table 2 Milk chemical composition

Source: The Essential Guide to Nutrient Requirements — Institute of Medicine of the national acedamies — USA Two critical factors that demand careful consideration are the fat content and the non-fat dry matter (NFDM) levels present in the raw milk According to guidelines set forth by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO), the NFDM content should be at least 8.2% Notably, a higher NFDM level, particularly an increased concentration of casein and whey proteins, has been scientifically demonstrated to enhance the structural integrity of the yogurt, thereby reducing the likelihood of whey separation, a common challenge in traditional yogurt production methods

In addition to the milk itself, other ingredients may be incorporated to impart desired flavors and characteristics to the yogurt Sugars such as glucose or sucrose can be added

to enhance the overall sweetness profile, while fruit purees like strawberry, blueberry, or apple can lend natural flavors and vibrant colors to the final product These fruit purees typically contain 50-55% sugar Furthermore, permitted food flavorings and colorants, adhering to national regulations on permissible additives and their maximum levels, may also be introduced to create unique and appealing yogurt varieties

For some products, people use stabilizers to help the yogurt have the required viscosity structure as required Commonly used stabilizers are gelatin, pectin, agar-agar they are hydrophilic and can bind with water The type of stabilizer and optimal use content for each product will be determined by experimental methods

Equipments

- Milk Reception Units: These systems are equipped with storage tanks and transfer pumps specifically designed to receive and unload fresh milk Their primary function is to maintain the integrity and quality of the milk product throughout the reception process

- Homogenization Equipment: The homogenization machine operates as a piston pump, featuring a homogenization valve on the pressure-boosting tube The subdivision of fat globules is a result of the abrupt change in milk velocity as it passes through the valve The sudden alteration in the flow cross-section leads to a significant increase in velocity As the fat globules transition from a low-velocity zone to a high-velocity zone, they experience tension, causing them to be torn apart and reduced in size The homogenization process occurs at a temperature of 64°C upon entry and 67°C upon exit Homogenization pressure is regulated at two levels: level 1 at 2700psi (~ 18.62 MPa) and level 2 at 500psi (= 3.44738 Mpa)

- Filling Machine: The filling machine operates according to pre-set programs and

is entirely enclosed The filling environment is ensured to be entirely sterile The product is filled and packaged in a sterilization process using a Tetra Bnk Aseptic filling machine Upon completion of tube attachment, shrink wrapping, and box sealing, the product awaits shipment

- Pasteurizers: These thermal treatment equipment are designed to heat the milk to

a specific temperature, effectively destroying any pathogens and undesirable enzymes present The goal is to ensure the safety of the milk while preserving its sensory and nutritional properties essential for yogurt production

- Mixing Systems: These process platforms come equipped with stirring and mixing devices that enable the uniform incorporation of additional ingredients into pasteurized milk Ingredients such as fruits, flavors, and sweeteners are blended seamlessly to achieve the desired yogurt formulation

- Mixing Systems: These process platforms come equipped with stirring and mixing devices that enable the uniform incorporation of additional ingredients into pasteurized milk Ingredients such as fruits, flavors, and sweeteners are blended seamlessly to achieve the desired yogurt formulation

- Refrigeration Equipment: The second-stage refrigeration machine employs an indirect heat exchange method, where the milk is cooled down through heat exchange with a thermal medium, using glycol as an indirect refrigerant The inlet temperature of the milk is 30°C, and the outlet temperature is 4°C

- CIP and SIP; Clean in place (CIP) and sterilization in place (SIP) systems that use chemical solutions and/or steam at high temperatures to effectively clean and disinfect production equipment, ensuring optimal sanitary conditions for yogurt manufacturing

Methods for yogurt fermentation

In yogurt production, one common method of fermentation involves inoculating the milk with specific starter cultures, typically consisting of Lactobacillus bulgaricus and Streptococcus thermophilus (Tamime & Robinson, 2007) These bacterial strains are carefully selected and cultured under controlled conditions to ensure their viability and effectiveness in the fermentation process (Chandan & Kilara, 2013)

To initiate fermentation, a predetermined amount of these starter cultures is added to the milk The inoculated milk is then incubated at a controlled temperature, usually around 40-45°C, to create optimal conditions for bacterial growth and activity (Walstra et al., 2006) This controlled environment ensures that the fermentation process proceeds efficiently and consistently

Compared to spontaneous fermentation, where natural microbial populations ferment the milk, using starter cultures offers several advantages Firstly, it allows for greater control over the fermentation process, ensuring the desired microbial activity and resulting product characteristics (Chandan & Kilara, 2013) Secondly, using selected starter cultures helps standardize the fermentation process, leading to more consistent product quality and flavor profiles

Throughout the fermentation period, the temperature and pH of the milk are closely monitored and regulated to maintain optimal conditions for the growth and activity of the starter cultures This meticulous control helps ensure the successful conversion of lactose into lactic acid, which is crucial for acidification and coagulation of the milk proteins (Tamime & Robinson, 2007)

The fermenting milk with selected starter cultures offers a controlled and standardized approach to yogurt production By carefully managing the fermentation process, producers can achieve consistent product quality and desirable sensory attributes, ultimately meeting consumer expectations for delicious and nutritious yogurt (Chandan & Kilara, 2013)

3.2 Microorganisms

Table 3 Microorganisms used in the production of yogurt from milk (Oberman H &

Libudzsz Z., 1998)

Microorganisms | species

Bacteria

Lactobacillus L.delbrueckn

L.delbrueckii ssp lactis L.delbrueckii ssp bulgaricus L.helveticus

L.acidophilus L.casei L.kefir Lactococcus L.lactis ssp lactis

L.lactis ssp lactis var diacetylatis

L lactis ssp cremoris

Leuconostoc L.mesenteroides

Stretococcus L.mesenteroides ssp dextranicum

Pediococcus L.mesenteroides ssp cremoris

Acetobacter S.thermophilus

P.pentosaceus P.acidilactis A.aceti

Yeast

Kluyveromyces | K.marxianus ssp marxianus

Candida K marxianus ssp bulgaricus

Saccharomyces | K.lactis

Torulaspora C.kefr

S.cerevisiae S.lactis T.delbrueckn Filamentous Fungi

Geotrichum | G.candidum

3.3 Mechanism of yogurt fermentation

Theoretical basis

Lactose is considered the essential energy source for bacterial metabolism and serves as the precursor for a plethora of synthesis reactions Within dairy products, particularly those derived from milk, three primary fermentation types are observed: alcoholic fermentation, lactic fermentation (most common), and butyric fermentation

Additional fermentation types may occur during yogurt production, resulting from the interaction of the primary fermentation types Furthermore, specific fermentation processes tailored to each product may also occur, such as acetic fermentation, propionic fermentation, among others

These fermentation processes are orchestrated by various microbial _ strains, predominantly lactic acid bacteria (LAB), which metabolize lactose to produce lactic acid

as the primary end product This conversion not only contributes to the characteristic tangy flavor of yogurt but also plays a crucial role in its texture and preservation (Chandan & Kilara, 2013; Tamime & Robinson, 1999)

Furthermore, LAB strains such as Lactobacillus bulgaricus and Streptococcus thermophilus are commonly employed in yogurt production due to their ability to thrive

in the elevated temperatures typically utilized durmg fermentation This symbiotic relationship between LAB injections contributes to the overall quality and consistency of the yogurt product (Walstra et al., 2005)

Lactic Fermentation

Lactic fermentation, a hallmark process in yogurt production, is primarily catalyzed by lactic acid bacteria (LAB) (Tamime & Robinson, 1999; Walstra et al., 2005) This fermentation process can be classified into two main types: typical and atypical lactic fermentation, depending on the specific composition of the fermentation products

In the lactose-rich environment of milk, LAB initiate lactose metabolism by synthesizing lactose enzymes The metabolic pathway involves the conversion of galactose into glucose through a series of enzymatic reactions Subsequently, glucose undergoes further metabolic transformations, ultimately producing pyruvic acid via the glycolytic pathway

of Embden-Meyerhof (Walstra et al., 2005)

Galactose + ATP D Galactose — | — phosphate + ADP

Galactose — 1 — phosphate D Glucose — 1 —phosphate

Glucose — | — phosphate D Glucose — 6 — phosphate

Glucose — 6 — phosphate D Glucose + H3PO,

Under the catalytic action of lactate dehydrogenase enzyme, pyruvic acid is then converted into lactic acid, the primary acidulant in yogurt Additionally, LAB possess decarboxylase enzymes that can also catalyze the conversion of pyruvic acid into acetic aldehyde, contributing to the flavor profile of the final product

H,C“ `COOH H.C `COOH

CH3 CH3 pyruvic acid lactic acid | Decarboxylase |

H,C COOH -THỊ H,C COOH

Figure 1 Pyruvic acid converted into Lactic acid Figure 2 Pyruvic acid into Acetic alhehyde

The coagulation mechanism in yogurt production is profoundly influenced by the presence of lactic acid Normally, casein micelles in milk possess a negative charge, resulting in electrostatic repulsion and maintaining a colloidal state However, as the pH

of milk decreases to the isoelectric point (pl) of casein (around 4.7), the micelles neutralize, leading to aggregation and gel formation (Lucey, 2015) This gelation process

is vital in yogurt manufacturing, where fermentation is typically halted at a pH of approximately 4.7 for Greek yogurt and around 4.1 for unstrained yogurt

Moreover, lactic acid plays a crucial role in interacting with calcium caseinate to form a curd structure This reaction involves the formation of calcium lactate and the dissolution

of calcium phosphate, resulting in the release of Ca” ions These calcium ions contribute

to the stability and firmness of the coagulum, ultimately influencing the texture and quality of the yogurt product (Tamime & Robinson, 1999)

3.4 Set Yoghurt Manufacturing Processes

The yogurt production process employing fermentation with starter bacteria, as elucidated previously, stands as a conventional and widespread practice in the yogurt manufacturing realm This method facilitates precise regulation of fermentation

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parameters, including temperature, duration, pH levels, and starter bacteria proliferation Such meticulous control is instrumental in upholding uniformity in the quality, flavor, and attributes of the eventual yogurt output Adhering to these procedural steps is paramount

in yielding safe, premium-quality yogurt items that align with consumer expectations

Milk Receiving Pretreating Separating

Collecting, Transpoting >| Testing and Sampling |= ° 50°C and 3%fat

90°C and 10 minuets >37°C and 2500psi 35°C — 45°C

42°C - 43C — 42°C — 43°C = _——

Figure 3 Process block diagram of set yogurt production

Milk Receiving and Pretreating

Upon reception, milk undergoes stringent protocols to maintain its quality and integrity, especially considering potential bacterial growth during transportation (Walstra et al., 1999) Milk may arrive in cans or tankers, with temperatures typically ranging from

>10°C to 20-30°C, depending on climatic conditions The duration between milking and arrival at the dairy can span up to a day, allowing for bacterial proliferation influenced by milking hygiene, temperature, and storage duration (Walstra et al., 1999) Mesophilic bacteria, primarily responsible for spoilage, often induce lactic acid fermentation, while contamination with polluted water, notably pseudomonads, can lead to nonsouring spoilage (Walstra et al., 1999) Upon arrival, milk is promptly cooled to <6°C to stabilize its bacteriological quality for up to 2 days (Walstra et al., 1999)