Developing freeze dried snack bites from kefir milk

MINISTRY OF EDUCATION AND TRAINING
HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION
FACULTY FOR HIGH QUALITY TRAINING

CAPSTONE PROJECT
FOOD TECHNOLOGY

DEVELOPING FREEZE-DRIED SNACK BITES FROM
KEFIR MILK

LECTURER: Dr. CAO THI THANH LOAN
STUDENT: NGUYEN THI YEN LINH
DOAN THI UT NHI

SKL 0 0 8 4 5 0

Ho Chi Minh City, December, 2021


HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION
FACULTY FOR HIGH QUALITY TRAINING
FOOD TECHNOLOGY

GRADUATION PROJECT
CODE:2021-17116019

DEVELOPING FREEZE-DRIED SNACK BITES
FROM KEFIR MILK
Advisor: Dr. CAO THI THANH LOAN
Student

ID

NGUYEN THI YEN LINH

17116019

DOAN THI UT NHI

17116025

Ho Chi Minh City, 23th December 2021

ii


i


ii


iii


iv


v

vi


vii


viii


ix


x


xi


Acknowledgement for Thesis
Foremost, we would like to express our sincere gratitude to our advisors Dr. Loan Cao,
visiting lecturer at the Faculty of High Quality at Ho Chi Minh City University of
Technology and Education. During the research and writing of this thesis, Dr. Loan Cao has
enthusiastically supported, guided and given advice from her rich knowledge and rich
experience. Her guidance helped us gain experience and learn many useful things to apply
to the research and development of this thesis.
We would like to thank Dr. Pham Thi Hoan, lecturer at the Faculty of High Quality at Ho
Chi Minh City University of Technology and Education. Her enthusiastic support at any time
helped us complete the research and development of this thesis. We are truly grateful to her
for enthusiastically supporting and imparting knowledge during our study at Ho Chi Minh
City University of Technology and Education

We would like to thank the lecturers of the Faculty of Food and Chemical Technology at
Ho Chi Minh City University of Technology and Education for their enthusiastic support
and providing favorable conditions for us to do research in the laboratory with modern
equipment.
Last but not the least, we would like to thank Kefir Home company for providing
knowledge and materials to research this thesis. We would also like to thank our family and
friends who have always encouraged and supported us to overcome difficulties during the
process of researching this thesis.

xii


Disclaimer
I proclaim that all content presented in this thesis is our own. I declare that all
references in the graduation thesis have been correctly and completely cited in
accordance with regulations.

Ho Chi Minh City, December 23, 2021

xiii


Table of Contents
Acknowledgement for Thesis ........................................................................................... xiii
Abstract ............................................................................................................................. xviii
Chapter 1: INTRODUCTION ............................................................................................ 1
1.1. Rationale .................................................................................................................... 1
1.2. Objection .................................................................................................................... 2
1.3. Object and scope of the study .................................................................................. 2
1.4. Research content ....................................................................................................... 2

1.5. Scientific and practical significance ........................................................................ 2
2.1. Overview about snack foods..................................................................................... 3
2.1.1. Definition ............................................................................................................. 3
2.1.2. Nutritional value of Snack foods ....................................................................... 3
2.1.3. History ................................................................................................................. 4
2.1.4. Types of snack foods ........................................................................................... 5
2.1.5. The snack food market ....................................................................................... 8
2.2. Overview about kefir milk and kefir grains ........................................................... 9
2.2.1. Kefir ..................................................................................................................... 9
2.2.2. Kefir grains ....................................................................................................... 11
2.3. Overview about freeze-drying process .................................................................. 12
Chapter 3: MATERIALS AND METHODS................................................................... 15
3.1. Materials, chemical and equipment....................................................................... 15
3.1.1. Materials ............................................................................................................ 15
3.1.2. Chemicals ......................................................................................................... 20
3.1.3. Equipments ....................................................................................................... 20
3.2. Kefir Milk production............................................................................................. 21
3.2.1. Flowchart........................................................................................................... 21
3.2.2. Process explanation .......................................................................................... 22
3.3. Layout diagram of research procedures .............................................................. 23
3.4. Research methods.................................................................................................... 23
3.4.1. Evaluated the effects of ingredients on the fermentation process and quality
of kefir milk ................................................................................................................. 23
3.4.2 Formulate the milk-kefir snack bites .............................................................. 27
3.4.3. Determine the parameters of the snack bites and evaluate sensory of the
product......................................................................................................................... 29
3.4.4. Determine the storage time and packaging of the snack bites .................... 35
xiv

Chapter 4: EXPERIMENT RESULTS............................................................................ 36
4.1. Evaluated the effects of ingredients on the fermentation process and quality of
kefir milk. ........................................................................................................................ 36
4.1.1. Biomass analysis ............................................................................................... 36
4.1.2. Sensory evaluation ............................................................................................ 36
4.1.3. Physicochemical analysis ................................................................................. 37
4.1.4. Microbiological analysis ................................................................................... 39
4.2. Formulate the milk-kefir snack bites .................................................................... 41
4.3. Determine the parameters of the snack bites ....................................................... 41
4.3.1. Moisture content ............................................................................................... 41
4.3.2. Weight ................................................................................................................ 42
4.3.3. Thickness ........................................................................................................... 43
4.3.4. Hardness ............................................................................................................ 43
4.3.5. Color .................................................................................................................. 47
4.3.6. Sensory evaluation ............................................................................................ 51
4.3.7. Analysis nutrition of snack bites ..................................................................... 52
Chapter 5: CONCLUSION AND RECOMMENDATIONS ......................................... 56
5.1. Conclusions .............................................................................................................. 56
5.2. Recommendations ................................................................................................... 56
REFERENCE ..................................................................................................................... 57
APPENDIX ......................................................................................................................... 65

xv


List of figures
Figure 2.1. Nutrient contents of Commercial Snack Food Products .................................... 4
Figure 2.2. Different shaped snack ....................................................................................... 6
Figure 2.3. Third-generation snacks foods ........................................................................... 7
Figure 2.4. First-generation snack foods ............................................................................... 7

Figure 2.5. Second-generation snack foods .......................................................................... 6
Figure 2.6. Snack food market: Year-on-year Growth Rate (%), Global, 2014-2019 .......... 8
Figure 2.7. Value of the savory snacks market in Vietnam from 2019 to 2026 with
forecasts until 2026. ............................................................................................................... 9
Figure 2.8. Kefir milk ......................................................................................................... 11
Figure 2.9. Kefir grains ....................................................................................................... 12
Figure 2.10. Flowchart of freeze-drying process ................................................................ 13
Figure 3.1. Flowchart of Kefir Milk production…………..........................................……22
Figure 3.2. Layout diagram of research procedures .......................................................... 23
Figure 3.3. Flowchart of snacks production........................................................................ 28
Figure 3.4. Electronic digital caliper................................................................................... 29
Figure 3.5. Snack bites hardness measurement by Texture Profile Analysis (TPA) .......... 30
Figure 3.6. Chroma meter CR- 400 and white calibration plate ........................................ 32
Figure 3.7. Store in 3 types of packaging at room temperature .......................................... 35
Figure 4.1. Growth of a 5-day old culture of yeast grown on DRBC medium. Dilution
factor: 10-2………...........................................................………………………………….39
Figure 4.2. Growth of a 2-day old culture of Lactobacillus spp. grown on MRS medium.
Dilution factor: 10-2 ............................................................................................................. 40
Figure 4.3. The streak culture isolates of Lactobacillus spp. .............................................. 40
Figure 4.4. Trend of hardness of each snack sample for 14 days stored in three different
packaging ............................................................................................................................. 45

xvi


List of tables
Table 3.1. Nutritional information of cow’s milk [50] ....................................................... 15
Table 3.2. Nutritional information per 100 ml Vinamilk .................................................... 16
Table 3.3. Nutritional information per 100 ml DaLat milk................................................. 16
Table 3.4. Nutritional information per 100 ml Pure milk ................................................... 17

Table 3.5. Composition of Powdered sugar ........................................................................ 18
Table 3.6. Ingredient of Milk powder ................................................................................. 19
Table 3.7. Equipments......................................................................................................... 21
Table 3.8. Elements and ingredients recipe for the preparation of kefir milk fermentation 24
Table 3.9. Mixing recipe for snack production ................................................................... 27
Table 3.10. Parameters of snack bites texture measurement .............................................. 30
Table 3.11. White calibration parameters of the handheld colorimeter CR-400/410 ......... 31
Table 3.12. Criteria for evaluate color based on ∆E [74].................................................... 32
Table 3.13. Analysis nutrition of snack bites ...................................................................... 34
Table 3.14. Quantitative methods ....................................................................................... 35
Table 4.1. The results of biomass
analysis………………………………………………….....................................................36
Table 4.2. The result of sensory evaluation ........................................................................ 36
Table 4.3. The result of physical analysis ........................................................................... 38
Table 4.4. The parameters of the snack bites ...................................................................... 42
Table 4.5. The results of the snack hardness for 14 days were stored in three different
packaging ............................................................................................................................. 44
Table 4.6. The results of the snack lightness for 14 days were stored in three different
packaging ............................................................................................................................. 47
Table 4.7. The results of the snack redness for 14 days were stored in three different
packaging ............................................................................................................................. 48
Table 4.8. The results of the snack yellowness for 14 days were stored in three different
packaging ............................................................................................................................. 49
Table 4.9. The results of ∆E of snacks color for 14 days were stored in three different
packaging ............................................................................................................................. 49
Table 4.10. The results of sensory evaluation of snack samples ........................................ 51
Table 4.11. Analysis nutrition of snack bites ...................................................................... 52
Table 4.12. Evaluation of chemical composition between Freeze-dried snack bites from
kefir milk containing gelatin - sugar and Freeze-dried snack bites from yogurt (containing
modified starch) ................................................................................................................... 53

Table 4.13. Quantification of Lactobacillus spp. and total yeast in snack bites ................. 54

xvii


Abstract
In this study, kefir grains were fermented with 3 different types of milk such as Vinamilk,
Da Lat milk, and Greendale Pure Milk Full Cream with the ratio of kefir grains and milk
ratio is 7% (wt/ml) for two periods 16 hours and 24 hours. The products kefir milk after
fermentation is determined quality through sensory testing, pH and moisture measurement,
microbial identification by microbial culture method. The results showed that Vinamilk milk
at 16 hours reached the most optimal level to the quality of kefir milk, from which to conduct
a survey of the mixing formula to choose the best quality product. The quality of the snack
bites will be evaluated through parameters from the method of determining moisture, weight,
thickness, hardness, color, sensory. After mixing and freeze-drying, the weight and thickness
of the samples showed no significant difference between the survey samples, but there is a
clear difference between the survey sample and the control sample. In terms of moisture
content and sensory, the results show differences between samples based on different
ingredients. Moreover, because there is a difference between the properties of the mixing
ingredients, the hardness and color of the product are markedly different. After surveying,
we chose the best quality product, Gelatin- Sugar, to determine nutrition and total microbial
in snack bites products. Furthermore, when storing products in 3 different types of
packaging, the results show that the quality of products preserved by aluminum foil
packaging is no less than vacuum LDPE packaging, but because of its popularity and easy
packaging techniques, we choose aluminum foil packaging as the most optimal packaging.
Keywords: Kefir milk, snack bites, probiotic, freeze-dried.

xviii

Chapter 1: INTRODUCTION
1.1. Rationale
Snack foods have always been a vital element of the food industry and modern life in
recent years, according to the current global trend. The current trend in food selection is for
quick-to-process foods that meet cleanliness, safety, and quality as well as energy
requirements. Snacks have evolved into necessary foods for both children and adults, thanks
to the emergence of hundreds of distinct ingredients. Snack goods can be classed based on
the raw materials used to make them, such as vegetables, fruits, and flour, and they can be
made in a variety of ways to provide full nutrition and a sturdy structure, such as frying,
baking, extruding, roasting, or freeze-drying.
When consumers' health is a top priority, they will look to change their meals to fit a
healthier lifestyle. Kefir is one of the long-standing unique nutritious and tasty components
when it comes to its rich concentration of probiotics, proteins, and digestive aids known to
consumers, is one of the greatest suggestions for consumers. Kefir have high in calcium,
magnesium, vitamins B2, B12, A, D, and K, phosphorus, minerals, amino acids, and
enzymes, as well as other useful bacteria [25]. Kefir contains a high amount of antioxidants
and so has therapeutic benefits. Furthermore, it provides various physiological benefits,
including skin health, digestion, weight loss, and lactase enzyme management [95].
Smoothies and sauces can be made with kefir. These reasons contribute to kefir's gradual
rise in popularity. As a result, during the awareness period, the market is expected to increase
at a significant rate.
The current problems in the snack industry are to provide healthier snacks (mostly by
reducing fat, sodium, and sugar) while maintaining the snack industry's traditional quality
features. One of the safest and effective snack processing methods to create the best quality
snack is freeze-drying. Freeze-drying keeps more nutritional content than other drying
processes, ensuring that whole foods retain their nutritious worth. This method also
preserves the actual shape and color of the original materials, ensuring that consumers feel
real fruits and vegetables in their diets. Another benefit of freeze-drying is the opportunity
to customize it to your specific requirements and project objectives. Frozen ingredients can
be created in a variety of sizes and shapes from fruits and vegetables to a fine flour. The last

product can be easily mixed into any mixture or recipe to give the end product a unique
flavor [39].
The digestive system in humans is a system that has a complex structure, easily disturbed
when we do not fully tolerate nutrients to balance them, especially the digestive system of
children and the elderly when children's stomachs are not yet developed while the elderly
has deteriorated leading to more easily upset digestion. With the special benefit of kefir
containing many beneficial yeast such as Saccharomyces kefiri and Torular kefir [92] these
two enzymes penetrate the mucous membrane where harmful bacteria are formed, forming
Special Weapons And Tactics (SWAT) group that removes harmful bacteria and the
intestinal tract. we have researched a novel product through freeze-drying intending to create
a new rich product nutritious and good for health especially for children and the elderly,
those with poor digestive systems have a nice life and live healthier.

1


1.2. Objection
The purpose of the thesis “Developing freeze-dried snack bites from kefir milk” is to
formulate a healthy freeze-dried foodstuff using kefir as the main ingredients, as well as to
evaluate the sensory and nutrient features of kefir based freeze-dried product.
1.3. Object and scope of the study
The study investigated the influence of different types of milk on the quality of kefir milk
and the changes of kefir milk after mixing with different ingredients. Analysis of the
influence of ingredients on color, moisture, size, texture, and sensory quality of snack bites
after freeze-drying. From there, a suitable method is proposed to produce the best product
while retaining the inherent nutritional value.
1.4. Research content
The topic “ Developing freeze-dried snack bite from kefir milk” includes the following
specific contents:
Experiment 1: Evaluated the effects of ingredients on the fermentation process and quality

of kefir milk. In this study, biomass analysis of kefir grains, sensory evaluation,
physicochemical analysis, and biological analysis of kefir milk were collected.
Experiment 2: Formulate the kefir milk snack bites.
Experiment 3: Determine the parameters (moisture content, weight, thickness, hardness,
color, nutrients, microbiological quantification) of the snack bites and evaluate sensory of
the product.
Experiment 4: Determine the storage time and packaging of the snack bites.
1.5. Scientific and practical significance
The thesis conducts a general research on the process of selecting ingredients and
developing snack bites from kefir milk with different mixing ratios of ingredients. Thereby,
it opens a new research direction on the addition of high biological value ingredients to the
snack production process in the Vietnamese confectionery market. Besides, the addition of
new ingredients is also meaningful in diversifying products and improving the use-value of
snacks.

2


Chapter 2: LITERATURE REVIEW
2.1. Overview about snack foods
2.1.1. Definition
A snack is a food that is smaller than a regular and a less structured meal that the reason
it is usually consumed after meals and does not appear in regular meals such as breakfast,
lunch, or dinner [119]. While some people define snacks as being eaten after meals, others
define snacks depended on the type of food, location, or time consumed during the day [41].
The majority of the snacks on the market are rich in sugar, salt, fat, and energy. Consuming
too many of them can lead to obesity, heart disease and diabetes [31].
In recent years, snack food has been one of the fastest-growing sectors of the food market
with both consumption and value increasing [7] and these products represent an major
segment of the food industry global, especially in developed countries [101]. Factors

contributing to this increase include an increase in one-person households, more school-age
children, and a high proportion of people working in an office. The United States is by far
the largest snack consumer in the world, followed by the United Kingdom, Germany, and
France [101]. Snack foods are a broad category with numerous processing methods. Snacks
are available in a different of forms including fresh ingredients as well as packaged,
processed foods [119]. Fruits, vegetables, yogurt, fish skin, and meat are common
ingredients for dried snack food. Due to the popularity of snacks, many studies of developing
healthy snacks have been increasing, promoting the best diet by consuming more fruits,
vegetables and whole grains and low in total fat (especially solid fats), sodium and refined
sugars [80].
2.1.2. Nutritional value of Snack foods
Snacks are one of the many types of exercise foods energy because they typically contain
substantial amounts of oils and carbs and almost no water. Furthermore, the availability of
vitamins in these food is diminished by thermal processing. Most snacks are salted or
flavored with salt therefore they contain large amounts of sodium [101].
The main energy ingredients in snack foods are lipid (9 kcal), carbohydrate (4 kcal) and
protein (4 kcal).

3


Figure 2. 1. Nutrient contents of Commercial Snack Food Products
2.1.3. History
Snacks have been around for thousands of years, but it wasn't until the commercialization
of snacks and the development of crispy fries that they became popular. Snacks were not all
invented in the United States. However, American processing and marketing skills are
credited with the global popularity of snacks. The original founders’ ingenuity has resulted
in annual global sales of around $ 30 billion [65]. In Europe, the first pack of flavored crisp
4

potato chips appeared 40–45 years ago with cheese and onions, but crisps can now be
purchased crispy fries without the addition of a wide variety of flavors from years before
with a familiar blue bag of salt in every packet [2]. When it comes to snacks, today’s
consumers have a wide variety of flavors to choose from, with cheese and onions, salt and
vinegar, prawn cocktails, chicken/beef and bacon being the most popular in the UK [73].
Among the milestones in the evolution of the current snack foods sector are [65]: The
1800, in 1853: At Saratoga Springs Resort in New York, cook on duty George Crum makes
"crunch potato slices" for Commodore Cornelius Vanderbilt. In 1885, Charles Cretors of
Chicago, Illinois, creates a street-vendor-friendly portable gasoline-powered corn popping
machine with a small peanut roasting. The 1900s — At the St. Louis World's Fair in 1904,
new foods and beverages were introduced, including cotton candy, hamburgers, hot dogs,
and ice cream waffle cones. Lombardi's was America's first licensed pizzeria, opening in
1905. In 1912, America was introduced the Oreo, the world's most famous sandwich cookie.
Pep-O-mint candies were introduced during this decade, while the Tasty Baking Company
started selling Tastykakes, the individually wrapped chocolate that revolutionized on-the-go
munching. Snacking became popular during the Jazz Age, when products like Nestle
Drumsticks, Butterfinger, Mike and Ike, Heath Bars, Reese's Peanut Butter Cups, Mr.
Goodbar, and Oh Henry! were introduced to the market. During the Great Depression, Lay's
Potato Chips, Frito corn chips, Snickers, Twinkies, and Ritz Crackers were all introduced.
Simultaneously, the Girl Scouts' cookie fundraisers grew in popularity to the point where
they had to outsource cookie manufacture to commercial bakers. The United States'
engagement in WWII had the greatest impact on the snacking business and trends of the
1940s. Tootsie Rolls, M&Ms, and other heat-resistant chocolates were popular and practical
additions to soldier's ration packs. Following the war, new items such as Smarties, Junior
Mints, Almond Joys, and Cheetos began to arrive on the market. The 1950s : Pork rinds
made commercially by frying cured pork skins. The 1960s and 1970s were a time of great
change. Following WWII, the economy began to thrive, and Americans witnessed the rise
of fast-food chains, which in a few decades had taken over the world. There were also
munchies like Pringles, Doritos, Apple Jacks, Funyuns, Lucky Charms, and Pop-Tarts, in

addition to hamburgers, pizza, nachos, and tacos. Women began to enter the workforce in
the 1970s, which is why pre-cooked foods packaged in bigger food jars became more
popular. Reese's Pieces, Twix, Pop Rocks, and instant ramen were among the other
wonderful foods available. PCII becomes the Potato Chip/Snack Food Association
(PC/SFA) in 1976. Teddy Grahams, Handi-Snacks, Fruit Rollups, Ranch Doritos, Airheads,
SnackWells Devil's Food Cookies, Bagel Bites, and many more are thanks to the 1980s and
1990s. 1995: Sales of low- and no-fat snack items undergo a surge. Seventy-five percent of
full-line snack food manufacturers responding to industry surveys said they introduced lowor no-fat items this year. 1997: Advances in flavor technology result in a wider range of
snack food products. Snacks have had access to a broader variety of snack items than ever
before in the twenty-first century. In the United States, gross-out candies have become the
fastest-growing confectionery market sector. Hershey's, Quaker, Smucker's, Cheerios,
Pillsbury, Frito-Lay, and a slew of other snack companies are among the most well-known.
2.1.4. Types of snack foods

5