Effect of market setting and time of purchase on quality of beef in vietnam

The objectives of this study were: 1 to exam the effect of three market types and two sampling times on off-odors/off-flavors in beef in Vietnam; 2 to exam the effect of two above factor

ĐẠI HỌC QUỐC GIA TP HCM

TRƯỜNG ĐẠI HỌC BÁCH KHOA

-

VŨ THỊ THANH PHƯƠNG

EFFECT OF MARKET SETTING AND TIME OF PURCHASE ON

QUALITY OF BEEF IN VIETNAM

Chuyên ngành: Công nghệ Thực phẩm

Mã số: 60 54 01 01

LUẬN VĂN THẠC SĨ

TP HỒ CHÍ MINH, tháng 12 năm 2015

CÔNG TRÌNH ĐƯỢC HOÀN THÀNH TẠI TRƯỜNG ĐẠI HỌC BÁCH KHOA - ĐHQG - HCM

Cán bộ hướng dẫn khoa học: PGS.TS Nguyễn Hoàng Dũng

Cán bộ chấm nhận xét 1: TS Hoàng Kim Anh

NHIỆM VỤ LUẬN VĂN THẠC SĨ

I Tên đề tài

EFFECT OF MARKET SETTING AND TIME OF PURCHASE ON

QUALITY OF BEEF IN VIETNAM

II Nhiệm vụ và nội dung

Nhiệm vụ: Đánh giá ảnh hưởng của ba loại hình chợ (siêu thị, chợ có mái che, chợ

không mái che) và hai thời điểm mua mẫu lên chất lượng thịt bò

 Khảo sát ảnh hưởng của loại chợ và thời gian lên số lượng vi khuẩn hiếu khí,

E.coli và coliforms phát triển trên bề mặt thịt bò

III Ngày giao nhiệm vụ: 19/01/2015

IV Ngày hoàn thành nhiệm vụ: 20/12/2015

V Cán bộ hướng dẫn: PGS TS Nguyễn Hoàng Dũng

Tp Hồ Chí Minh, ngày 21 tháng 12 năm 2015

Trưởng khoa Kỹ Thuật Hóa Học

ĐẠI HỌC QUỐC GIA TP HỒ CHÍ MINH

TRƯỜNG ĐẠI HỌC BÁCH KHOA

-

CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM

Độc lập – Tự do – Hạnh phúc -

Tp Hồ Chí Minh, ngày 21 tháng 12 năm 2015 Sinh viên thực hiện

VŨ THỊ THANH PHƯƠNG

TÓM TẮT LUẬN VĂN

Chất lượng thịt bò tươi được quyết định bởi nhiều yếu tố Sự oxy hóa được xem là yếu

tố quan trọng ảnh hưởng đáng kể đến chất lượng thịt, đặc biệt là sự oxy hóa chất béo Nhiều hợp chất thứ cấp được tạo ra từ quá trình oxy hóa chất béo dẫn đến sự hình thành mùi và vị lỗi của thịt như: mùi ôi dầu, mùi cỏ, mùi carton, mùi gan, vị chua Ngoài ra, chất lượng thịt còn bị ảnh hưởng bởi số lượng vi khuẩn hiếu khí hình thành trên bề mặt thịt Những vi sinh vật này phát triển trên bề mặt thịt làm độ nhớt, màu sắc của thịt bị biến đổi Tuy nhiên, thịt tươi tồn tại nhiều chất chống oxy hóa nội tại, bao gồm vitamin A, E, và các enzyme chống oxy hóa có hoạt tính chống oxy hóa (TAC) Những hợp chất này đóng vài trò quan trọng trong sự ngăn chặn sự oxy hóa chất béo trong thịt Do đó, chất lượng thịt được đánh giá dựa trên các chỉ tiêu sau: mùi mỗi, vị lỗi, chỉ số hóa lý, và tổng số vi sinh vật hiếu khí

Sự oxy hóa chất béo và sự phát triển của vi sinh vật hiếu khí trên bề mặt thịt bò bị ảnh hưởng bởi các yếu tố bên ngoài như điều kiện môi trường (nhiệt độ, ánh sáng mặt trời,

độ ẩm, và nồng độ oxy) và thời gian thịt được bày bán trên thị trường Nghiên cứu này khảo sát điều kiện môi trường thông qua ba loại hình chợ gồm siêu thị (SM), chợ có mái che (IM), và chợ không có mái che (OM) Đối với thời gian bày bán, thịt bò được mua tại hai thời điểm, thời điểm 1 là thời gian mở cửa chợ (T0) và thời điểm 2 là thời điểm cách thời điểm 1 bốn tiếng (T4) Mục đích của nghiên cứu bao gồm: 1) khảo sát ảnh hưởng của ba loại hình chợ và 2 thời điểm mua thịt lên mùi và vị lỗi trong thịt bò, 2) khảo sát ảnh hưởng của hai yếu tố trên lênsự oxy hóa chất béo dựa trên hoạt tính chống oxy hóa tổng và sản phẩm bậc hai của quá trình oxy hóa, và 3) khảo sát tổng số lượng vi khuẩn hiếu khí phát triển trên bề mặt thịt ảnh hưởng bởi hai yếu tố trên

Mẫu thịt thăn bò được mua từ ba thành phố của Việt nam gồm Hồ Chí Minh, Đà Nẵng,

và Hà Nội Các mẫu để kiểm tra vi sinh được đặt trong túi vô trùng Whirl-Pak Các mẫu để kiểm tra hóa lý và cảm quan được đặt trong túi có khóa kéo Tất cả mẫu được bảo quản trong thùng đá (Igloo, Katy, TX) có túi đá khô để giữ lạnh và được vận chuyển về trường đại học Bách khoa

Hội đồng mô tả đã thống nhất được ba mùi lỗi và hai vị lỗi bao gồm mùi gan (liveryR), mùi chua (sourR), mùi ngọt (sweetR), vị chua (sourC), và vị gan (liveryC) Loại chợ ảnh hưởng có nghĩa lên thuộc tính liveryR (P ≤ 0.05) Giá trị liveryR của mẫu thịt bò mua tại IM cao hơn khi mua tại OM (P = 0.004) Trong khi đó, giá trị liveryR mua ở SM không khác biệt có nghĩa so với OM và IM (P = 0.061 và 0.292, tương ứng) Giá trị sourR và liveryC của mẫu thịt mua tại thời điểm T0 thấp hơn tại thời điểm T4 (P = 0.019 và 0.032, tương ứng) Ảnh hưởng của loại chợ và thời gian lên thuộc tính sweetR và sourC là tượng tự nhau (P ≥ 0.09) Nhìn chung, loại chợ và thời gian bày bán có ảnh hưởng lên thuộc tính cảm quan mùi và vị lỗi của thịt bò Phương pháp FC (Folin-Ciocalteu), phương pháp TEAC (trolox equivalent antioxidant capacity), và phương pháp FRAP (ferric reducing antioxidant power) được sử dụng rộng rãi để xác định hoạt tính chất chống oxy hóa của các chất chống oxy hóa nội tại

có trong thịt Cả hai phương pháp FC và TEAC đều thể hiện ảnh hưởng của loại chợ lên hoạt tính chống oxy hóa của thịt (P ≤ 0.05) Trong đó, hoạt tính chống oxy hóa của thịt mua tại OM cao nhất so với hai chợ còn lại (P < 0.0001) Hơn thế nữa, phương pháp FC còn chứng minh được rằng thời gian bày bán ảnh hưởng có nghĩa lên hoạt tính chống oxy hóa (P ≤ 0.05), cụ thể tại thời điểm T4 hoạt tính chống oxy hóa có giá trị cao hơn so với thời điểm T0 (P = 0.04) Ngược lại, phương pháp FRAP không chứng minh được ảnh hưởng của loại chợ và thời gian lên hoạt tính chống oxy hóa của thịt Ngoài việc xác định hoạt tính chống oxy hóa của thịt, nghiên cứu này còn xác định sản phẩm bậc hai của quá trình oxy hóa chất béo bằng phương pháp TBARS (thiobarbituric acid reactive substances) Giá trị TBARS của mẫu thịt mua tại SM là cao nhất so với IM và OM (P = 0.003 và 0.04, tương ứng) Do đó, loại chợ và thời gian cũng có ảnh hưởng có nghĩa lên sự oxy hóa của thịt thông qua hai chỉ số: hoạt tính chống oxy hóa và sản phẩm bậc hai của quá trình oxy hóa

Mặt khác, nghiên cứu này xác định ảnh hưởng của loại chợ và thời gian lên số lượng

vi sinh vật hiếu khí (vi khuẩn hiếu khí (APC), E.coli, và Coliforms) phát triển trên bề

mặt thịt Kết quả cho thấy loại chợ và thời gian bày bán ảnh hưởng có nghĩa lên số lượng vi khuẩn hiếu khí (P = 0.06 và 0.03 (P ≤ 0.1), tương ứng) Số lượng coliforms bị ảnh hưởng bởi loại chợ (P = 0.005) Loại chợ và thời gian không ảnh hưởng lên số

lượng của E.coli (P = 0.38 và 0.84, tương ứng) Tuy nhiên, có sự tương tác giữa loại

chợ và thời gian có ý nghĩa thống kê (P = 0.03)

Nhìn chung, loại chợ và thời gian bày bán có ảnh hưởng có nghĩa lên sự oxy hóa chất béo của thịt thông qua những biến đổi của các thuộc tính cảm quan, chỉ số hoạt tính chống oxy hóa và chỉ số TBARS Thêm vào đó, số lượng vi khuẩn hiếu khí và coliforms cũng bị ảnh hưởng có ý nghĩa thống kê bởi hai yếu tố loại chợ và thời gian

ABSTRACT

Lipid oxidation is one the most important factors that can affect in quality of fresh beef meat during postmortem period Many secondary compounds formed by lipid oxidation can cause off-odor and off-flavor production in meat Besides, the meat quality also affected by the aerobic microorganisms formed on surface of meat during storage However, fresh meat subsists several intrinsic antioxidants, including tocopherol, carotene, and antioxidants enzymes with their total antioxidant capacities (TACs) These compounds play a role to prevent influences of lipid oxidation in meat The oxidative changes in beef meat depend on environmental conditions (e.g temperature, sunlight, moisture, and oxygen) and display time of meat The beef quality is evaluated based on off-odors, off-flavors, physicochemical indicators, and microbial indicators This study examined the environmental conditions through three market types, including supermarkets (SM), indoor markets (IM), and open markets (OM) For examining display time, the beef was purchased at two sampling times at each market The opening time (T0) was the opening of individual markets, and the closing time (T4) was 4 h after opening The objectives of this study were: 1) to exam the effect of three market types and two sampling times on off-odors/off-flavors in beef in Vietnam; 2) to exam the effect of two above factors on the lipid oxidation through two indicators known as total antioxidant capacities and secondary products of oxidation; and 3) to evaluate the counts of aerobic bacteria quantity grown on meat surface affected by different market types and sampling times

Longissimus muscle beef samples were purchased from three areas, including Ho Chi

Minh City, Da Nang, and Ha Noi reached adequate representation of Vietnam The samples were placed separately in sterile Whirl-Pak® bags (Nasco, Fort Atkinson, WI) for microbial test and placed in zip bags for the sensory and physicochemical tests Samples were stored in an Igloo Super Tough Sportsman ice chest (Igloo, Katy, TX) with frozen ice packs and transported back to a local university in each region

Three off-odors and two off-flavors were formed such as raw livery odor (liveryR), raw sour odor (sourR), raw sweet odor (sweetR), cooked sour flavor (sourC), and

cooked livery flavor (liveryC) from descriptive panel Market type significantly affected liveryR (P ≤ 0.05) LiveryR of beef samples from IM was higher than that from OM (P = 0.004) Whereas liveryR in beef from SM was not significantly different that from OM and IM (P = 0.061 and 0.292, respectively) SourR and liveryC

of beef samples at T0 had less than that at T4 (P = 0.019 and 0.032, respectively) The effect of market type and display time on sweetR and sourC were similar to that of the raw beef (P ≥ 0.09) Overall, the market type and display time have to impact on off-odor and off-flavor descriptors of beef meat

Folin-Ciocalteu (FC) method, trolox equivalent antioxidant capacity (TEAC) method, and ferric reducing antioxidant power (FRAP) method were widely used to determine TCAs of intrinsic antioxidants in beef meat In both the FC and TEAC methods indicated the significant effect of market type on TAC in beef meat (P ≤ 0.05) in which OM had the highest TAC compared to IM and SM (P < 0.0001) except FRAP method Moreover, FC method also showed that the significant effect of display time

on TAC (P ≤ 0.05) specifically TAC of beef at T4 had the highest (P = 0.04) except FRAP method In addition, determining the lipid oxidation extent of beef meat also based on the secondary oxidation products through thiobarbituric acid reactive substances (TBARS) value TBARS value of beef meat collected from SM were the highest compared to that from IM and OM (P = 0.003 and 0.04, respectively) Therefore, the market type and display time of beef affected significantly on the lipid oxidation through TAC and TBARS indicators of beef meat

On the other hand, this study also determined the effect of market type and display time on microbiological quality The market type and display time had to impact significantly on aerobic plate count (P = 0.06 and 0.03 (P ≤ 0.1), respectively) The coliforms counts were affected by the market type (P = 0.005) There was not market

type and display time affected on E.coli counts (P = 0.38 and 0.84, respectively)

However, the market type x display time interaction was significant (P = 0.03)

The general, the market type and display time were significantly effective the lipid oxidation of beef meat through off-odor and off-flavor descriptors, and TAC and TBARS indicators In addition, counts of aerobic bacteria and coliforms were affected

by the market type and display time

LỜI CAM ĐOAN

Tôi xin cam đoan rằng các số liệu và kết quả nghiên cứu trong luận văn là công trình nghiên cứu thực sự của tôi và được tiến hành dưới sự hướng dẫn của PGS.TS Nguyễn Hoàng Dũng

Các kết quả được trình bày trong nghiên cứu là trung thực và chưa được công bố dưới bất kỳ hình thức nào

Tôi hoàn toàn chịu trách nhiệm về nghiên cứu của mình

Học viên thực hiện

Vũ Thị Thanh Phương

CONTENTS

CHAPTER 1: INTRODUCTION 1

References 4

CHAPTER 2: EFFECTS OF MARKET SETTING AND TIME OF PURCHASE ON OFF-ODOR AND OFF-FLAVOR DESCRIPTORS IN BEEF (Longissimus Muscle) IN VIETNAM 7

Abstract 8

Introduction 9

Materials and Methods 10

Sample Collection 10

Sample Preparation 11

Result and Discussion 18

Beef Odor Descriptor 18

The effects of Market Type and Time Point 20

Descriptor Patterns (PCA) 23

Conclusion 24

References 25

CHAPTER 3: EFFECTS OF MARKET SETTING AND TIME OF PURCHASE ON THE TOTAL ANTIOXIDANT CAPACITY (TAC) AND THIOBARBITURIC ACID REACTIVE SUBSTANCES (TBARS) VALUE OF BEEF (Longissimus Muscle) IN VIETNAM 28

Abstract 29

Introduction 30

Materials and Methods 32

Sample collection 32

Chemicals 32

Statistical analysis 35

Result and discussion 35

The total antioxidant capacity (TAC) determined by FC, FRAP, and TEAC methods 35

The TBARS value determined through TBARS method 40

Conclusion 42

References 43

CHAPTER 4: EFFECTS OF MARKET SETTING AND TIME OF PURCHASE ON COUNTS OF AEROBIC BACTERIA, ESCHERICHIA COLI, AND COLIFORM OF OF BEEF (Longissimus Muscle) IN VIETNAM 47

Abstract 48

Introduction 49

Materials and methods 50

Sample preparation 50

Microbiological Analysis 50

Result and discussion 52

Conclusion 57

References 58

CHAPTER 5: SUMMARY AND CONCLUSIONS 61

APPENDICES 63

Appendix A 63

Appendix B 67

LIST OF TABLE

Table 2.1 Characteristics used to classify supermarkets (SM), indoor markets (IM), and open markets (OM) across three regions of Vietnam 10Table 2.2: Basic taste concentrations in aqueous phase used for detection test 13Table 2.3: References initially used to train the panelists 14Table 2.4: Definitions and References for raw fresh beef odor descriptors (n=3) and cooked beef flavor descriptors (n=2) 19Table 2.5: Effect of market type on off-odors and off-flavors of beef samples from supermarkets (SM), indoor markets (IM), open markets (OM) across three regions

of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 21Table 2.6: Effect of display time on off-odors and off-flavors of beef samples at the market opening (T0) and 4 h after the opening (T4) across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 22Table 3.1: Effect of market type on chemical values of beef samples from supermarkets (SM), indoor markets (IM), open markets (OM) across three regions

of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 37Table 3.2: Effect of display time on chemical values of beef samples at the market opening (T0) and 4 h after the opening (T4) across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 37Table 4.1: Effect of market type on bacterial counts in beef procured from supermarkets (SM), indoor markets (IM), open markets (OM) across three regions

of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 54Table 4.2: Effect of display time on bacterial counts in beef procured at the market opening (T0) and 4 h after the opening (T4) across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) 55

LIST OF FIGURES

Fig 2.1: Principle component plot of five descriptors of raw fresh beefs and cooked beefs 24Figure 3.1 TAC of raw beef determined through FC, FRAP, and TEAC methods bought market types 35Figure 3.2 TAC of raw beef determined through FC, FRAP, and TEAC methods bought at two display times 36Figure 3.3 TBARS value of raw beef determined by TBARS method bought three market types 40Figure 3.4 TBARS value of raw beef determined by TBARS method bought at two display time 41

Figure 4.1: Aerobic Plate Count (APC), E coli, and coliforms bacterial count of

beef purchased at the supermarket (SM), indoor market (IM), and open market (OM), across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi) Within a category of bacterial count, means without common letters differ, (Pmarket type = 0.060, 0.380, 0.005, respectively) 52

Figure 4.2: Aerobic Plate Count (APC), E coli, and coliforms bacterial count of

beef purchased at two sampling times (opening - T0 and 4 h after opening - T4) Within a category of bacterial count, means without common letters differ, (Ptime = 0.034, 0.837, 0.196, respectively) 53Figure 4.3: E coli determination at market type × sampling time interaction of log CFU/g at supermarket (SM, P = 0.074) and indoor market (IM, P = 0.052) 57

CHAPTER 1 INTRODUCTION

Meat is a complex matrix which is a highly nutritious food, rich in proteins, amino acids, vitamins (vitamin A, C, E; especially vitamin B complex), and minerals (zinc and iron), hence it is highly perishable Lipids are vital components of meat, which plays important role in consumer’s acceptance reflecting several desirable characteristics of meat such as color, flavor, tenderness, and juiciness The presence of oxygen and metals such as iron may be brought about by a high intake of oxidized lipids or polyunsaturated fatty acids (Olsen et al., 2005) Furthermore, lipid oxidation

is one of the most important factors that affect the quality of meat, especially in beef meat Many volatile compounds such as aldehydes were formed, which are responsible for off-odor (Ahn et al., 1998, Ahn and Lee, 2002), off-flavor (Dietze et al., 2007) and rancidity (Campo et al., 2006; Ahn et al., 2002; Byme et al., 2002), and change meat color (Guillen-Sans and Guzman-Chozas, 1998) Lipid oxidation can occur in both fresh and cooked meats (Min and Ahn, 2005; Jo et al., 2006)

In addition, other factors also play different roles in the change of meat quality that is strongly linked to microorganisms, especially in case of the meat displayed in the market The microbiological quality of meat depends on the physiological status of the animal at slaughter, the spread of contamination during slaughter and processing, the temperature and other conditions of storage and distribution In fact, some of the microorganisms originate from the animal’s intestinal tract as well as from the environment with which the animal had contact at some time before or during

slaughter (Koutsoumanis and Sofos, 2004) E coli, coliforms, and aerobic plate count

are indicators of fecal contamination, environmental contamination, and overall hygienic conditions

Raw meat is associated with intrinsic antioxidants such as α-tocopherol (vitamin E), carotene (vitamin A), ascorbic acid (vitamin C), glutathione, and antioxidant enzymes (glutathione peroxidases, superoxide, dismutases and catalase) These compounds retard lipid oxidation in fresh and stored meat, and preserve the beef color and beef

β-odor quality as well The antioxidants are incorporated within cell membranes and protect tissues against oxidation from reactive oxygen species This maintains the overall quality of meat and secondary products The antioxidant potential in meat is determined by the antioxidant composition and the antioxidative properties of constituents By definition, the antioxidant activity (AOA) is the capability of a compound to inhibit oxidative degradation, e.g lipid peroxidation The antioxidant capacity gives information about the duration of antioxidative action, the reactivity characterizes the starting dynamics of antioxidation at a certain concentration of an antioxidant or antioxidant mixture Individual antioxidants can react as chain-braking

of oxidative reactions and the activity is related to the reactivity of the antioxidants to free radicals (Roginsky and Lissi, 2005) Recently, researchers have been interested in the methods for determining total antioxidant capacity from raw meat (Abu-Salem et al., 2014; Gatellier et al., 2004) The authors have developed the different measurement methods, including Ferric Reducing Antioxidant Power (FRAP) method (Benzie and Strain, 1996; Pulido, Bravo, and Saura-Calixto, 2000), Trolox Equivalent Antioxidant Capacity (TEAC) method (Re et al., 1999), and Folin-Ciocalteu (FC) method (Stratil et al., 2006; Lee et al., 2014) Besides, Sørensen and Jørgensen, (1996) has developed Thiobarbituric Acid Reactive Substances (TBARS) method to determine secondary oxidation products such as carbonyls (ketones and aldehydes), alcohols, hydrocarbons (alkane, alkene), and furans

Many factors impact on the development of lipid oxidation in fresh meat such as external factors and internal factors The internal factors include fat conten, fatty acid composition, and antioxidants, heme pigments and iron content (Addis, 1986; Du et al., 2000; Choe and Min., 2006; Min et al., 2008), and metal catalysts and degree of polyunsaturation in the lipids of meat play the most important roles (Gray and Pearson, 1987; Calkins and Hodgen 2007) The external conditions such as processing, environmental factors, exposure time of raw meat without package, packaging (Kumar et al., 2015; Esmer et al., 2011; Khairy 2010) and stogage conditions also considerably contribute to lipid oxidation process (Ahn et al., 2009)

temperature and sunlight play a major important part on the lipid oxidation development

The objectives of this study hence are: 1) to exam the effect of three market types and two sampling times on off-odors/off-flavors in beef in Vietnam; 2) to exam the effect

of two above factors on the lipid oxidation through two indicators known as total antioxidant capacities and secondary products of oxidation; and 3) to evaluate the counts of aerobic bacteria quantity grown on meat surface affected by different market types and sampling times

References

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Appl Muscle Biol Meat Sci page: 227-246

Ahn, D U., and Lee, E J 2002 Production of off-odor volatiles from liposome-

containing amino acid homopolymers by irradiation J Food Sci 67 (7): 2659-

2665

Abu-Salem, F., M Mahmoud, M El-Kalyoubi, A Gibriel & A A.-A Arab (2014)

Antioxidant and A ntimicrobial Properties of Peptides as Bioactive Components

in Beef Burger International Journal of Biological, Food, Veterinary and Agricultural Engineering, 8

Benzie, I F F & J J Strain (1996) The Ferric Reducing Ability of Plasma (FRAP) as

a Measure of ―Antioxidant Power‖: The FRAP Assay Analytical Biochemistry, 239, 70-76

Byrne, D V., Bredie, W L P., Mottram, D S., & Martens, M (2002) Sensory and

chemical investigations on the effect of oven cooking on warmed-over flavour development in chicken meat Meat Science, 61(2), 127-139

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CHAPTER 2

EFFECTS OF MARKET SETTING AND TIME OF PURCHASE ON

OFF-ODOR AND OFF-FLAVOR DESCRIPTORS IN BEEF (Longissimus Muscle) IN

VIETNAM

Phuong T T Vu1, April K McCain2, Tran H B Cao1, Cam T H Tran3, Man V V Le1,

Dung H Nguyen1, and Thu T N Dinh2 1

Chemical Engineering, HCMC University of Technology, Ho Chi Minh City, Vietnam 2

Animal and Dairy Sciences, Mississippi State University, Mississippi State, Mississippi,

U.S.A

3

Faculty of Food Technology, HCMC University of Food Industry, Ho Chi Minh City,

Vietnam

Abstract

Beef quality is an important driver of purchase decision by Vietnamese consumers This study was to evaluate the influence of type of markets, and time of purchase on the sensory quality of beef across three regions of Vietnam

Beef Longissimus muscle samples were collected in Ha Noi, Da Nang, and Ho Chi

Minh City to represent regional variation in meat mechandizing in Vietnam Five beef samples were randomly purchased at each of two open markets (OM), two indoor markets (IM), and two supermarkets (SM) in each region at the opening of the markets (T0) and 4 h after the opening (T4) Beef samples were evaluated for raw and cooked descriptive off-odors by trained panelists The descriptive panel was trained to identify, define, and evaluate the intensity of raw livery, raw sweet, raw sour, cooked livery, and cooked sour odors on a 6-point scale (0 = totally lacking; 5 = very intensive) A generalized linear mixed model was used to analyze the variances with market type, sampling time, and their interaction as fixed effects and region as a random effect in a randomized complete block design Statistical significance was

0.061 and 0.292, respectively) Beef samples at T0 had less raw sour odor and cooked

livery flavor than those at T4 (P = 0.019 and 0.032, respectively)

These results indicate that raw livery odor varied by market types In addition, raw sour and cooking livery odors increased as beef was purchased later in the day (T4 vs T0) The findings of this study provided useful information to predict purchase decision by beef consumers and to devise a strategy to manage beef quality at various markets in Vietnam

Keywords: beef quality, Longissimus muscle, odor, descriptive, sensory quality

Introduction

Sensory evaluation is the multidisciplinary approach using human senses as instruments for assessing food quality In terms of qualitatively and quantitatively assessing a food using trained panels, it is referred to descriptive test (1992, 1992).The beef quality is a complex concept assessed based on consumer requirements and acceptance It is defined by sensory attributes, instrumental and chemical attributes of beef (Spanier et al., 1992), (Cardello, 1995), (Molnár, 1995) Beef sensory attributes include three main groups: flavor (e.g., aroma, taste), texture (e.g., tenderness, juiciness), appearance (e.g., color, appeal, size) (Molnár, 1995), (St Angelo, 1996) (Stelzleni and Johnson, 2008), (Calkins and Hodgen, 2007) showed that flavor is a very complex attribute to be used to define taste and aroma

The flavor of beef depends on factors such as diet (Shahidi, 1986), (Sitz et al., 2005), the polyunsaturated fats content (PUFAs) (Baublits et al., 2009), the post-mortem aging period (Sitz et al., 2005), (Spanier et al., 1997), (Ba et al., 2014), and end-point cooking temperature (Spanier and Miller, 1996)

Besides, (St Angelo, 1996) showed that the basic chemical reactions focusing on lipid oxidation had impact on beef flavor quality through chemical analysis by the TBA test and sensory analysis by descriptive panel (Gray et al., 1996) also described that lipid oxidation is one of the important periods of quality deterioration in beef samples and further stated that the negative characteristics of changes in quality were the indicators

of the off-flavor formations Besides, (Gray, 1987), (Gray et al., 1996), (Campo et al.,

2006), (Hansen, 2007), (Khan, 2014) pointed out that lipid oxidation was one of the main causes that affected beef sensory quality by forming off-flavors and off-odors Furthermore, the previous studies (Savell et al., 1987), (Spanier and Miller, 1996), (Robbins et al., 2003) showed that off-flavors were fully reflected the beef quality and was one of the significant factors affecting consumer purchasing decisions

Meat packing such as modified atmospheric packaging (MAP), vacuum packaging (VP), control atmosphere packaging (CAP) protects meat from external effects as concentrated CO2, O2, level of surface exposure to atmosphere which are the major causes of lipid oxidation In addition, the environmental conditions as sunlight, temperature, humidity, display condition also affected lipid oxidation Some previous

studies indicated that packing process effected on level of exposure (Spanier et al.,

1992), package type (Khan, 2014)

In Vietnam, fresh meat is displayed at supermarket (SM) in expanded polystyrene tray wrapped PVC film at refrigerated temperature (0 – 40C) At indoor market (IM) and open market (OM), raw materials are directly exposed of sunlight, in varied temperature without being packed Moreover, taste and aroma is one of the most important sensory traits affecting acceptance of comsumer (Robbins et al., 2003), (Kerth et al., 1995), Feuz et al., 2004)

Therefore, it is important to investigate the market type and display conditions impacted on meet flavor The objective of this study found out the influence of market type and display time on sensory beef quality across three regions of Vietnam through off-odor and off-flavor descriptors

Materials and Methods Sample Collection

Meat samples for training were obtained from local grocery stores in Ho Chi Minh City (HCMC) Those for the final experiment were obtained from the three representative regions of Vietnam, HCMC, Da Nang (DN), and Ha Noi (HN) The three types of markets (supermarket (SM), indoor market (IM), and open market (OM)) were classified according to their characteristics (the availability of refrigeration, the availability of air conditioning, and the architectural exterior of the markets such as walls and roofs (Table 2.1)

Table 2.1 Characteristics used to classify supermarkets (SM), indoor markets (IM), and open markets (OM) across three regions of Vietnam

In each market type, the number of markets was two that resulted in six markets per region Two sampling times were selected to collect samples at each market The opening time (T0) was individually selected corresponding to the opening schedule of

individual markets and the closing time (T4) was 4 h after the opening Longissimus muscle was chosen for use in this study Five 300-g Longissimus muscle samples were

collected aseptically from various vendors, so there were 180 samples Vendors were randomly selected when sampling If a market had less than five vendors, at least one vendor was sampled repeatedly in the rotating order There was no vendor choice in the SM because each SM was the only meat vendor Those samples were purchased separately and from different sub-primals At T4, in general, samples were purchased again at the original vendors selected at T0 The vendor randomization process was executed in the similar manner The samples were placed isolatedly in zip plastic bags and were coded with ―B‖ for ―beef‖ and three-digit number from 001 to 180 The bags were zipped immediately after meat was put Samples were stored in the Igloo Super Tough Sportsman ice chest (Igloo, Katy, TX) with ice packs

Sample Preparation

Beef samples in the ice chests were transported back to a local university in each region After vacuum-packed by a household vacuum machine (DZ 300A), the samples were immediately stored at -200C in a freezer (Sanaky VH365A1 in HCMC, Sanyo MDF-U333 in DN, or Alaska HB 490 490L in HN) until ready to be evaluated The samples were removed from the freezer 24 h prior to cook and allow to thaw in the refrigerator (40C) (Adhikari et al., 2011) Samples for both training and the final experiment were prepared in the same procedure The samples were cut into equally two parts of which the piece for fresh sample test is approximately 50-g and the piece for cooked is approximately 250-g

To raw fresh samples test, samples were milled by grinder (Pensonic Grinder 6000) and put into dark glass jars coded with random three-digit numbers The panel only evaluated samples when the samples were inside the jars at least 5 mins

PB-To cooked samples, samples were wrapped in aluminum foil and broiled by an electric oven (Sanaky VH-368N) which was preheated at least 5 min at 2500C Sample was recorded at its internal temperature (using the Fisher Scientific™ Traceable™ Infrared

Thermometer Gun (Fisher Scientific, Waltham, MA) with a fast-responding temperature probe) The probe was inserted horizontally from the side to the center sample The meats were broiled until the target internal temperature was reached The internal temperature target was 770C (Gomes et al., 2014) After cooked, samples were cut into approximately 2.5 cm cubes, wrapped in aluminum foil, coded with random three-digit number, and served to the panelists at approximately 600C (Muchenje et al., 2010) The evaluations were done under red light to minimize bias which could occur due to the color and the appearance of the beef samples

Descriptive Panel Development (ISO 8586-1, 1993)

Panel Recruitment

Recruitment is an important starting point in forming a panel of selected assessors (8586-1, 1993) Panel recruitment memo was sent to food technology department students through email Candidates had to answer the first screening questionnaire that sought out their beef eating habit, any beef allergies, and availability for the long-term project (lasting at least 6 months) Qualified candidates took the next screening The next screening included two test sessions The first session comprised five base taste detection test, and triangular test on sweet taste The second session included odor description test, odor matching test, and triangular test on rancid odor During the next screening, each sample was coded by the random three-digit number Candidates were asked to detect samples among the five basic tastes in water (bitter, salty, sour, sweet, and umami) and describe the seven odor of meat (fishy, rancid, grassy, metallic, cardboard, livery, sour dairy) They are presented with one sample of each type and are allowed to familiarize themselves with them (6658, 1985) Thereafter, these samples were coded with random three-digit number and presented at the same time Candidates are asked to match each of them to one of the original set and to describe the sensation they are experiencing (8586-1, 1993) They were also given two sets of three samples with the two same samples, one different sample on sweet taste and rancid odor, respectively, and asked to find this different sample The basic five taste concentrations used for detection test are showed in Table 2.2

Table 2.2: Basic taste concentrations in aqueous phase used for detection test

(%)

Concentrati

on in water (g/l)

Descriptor Development

Before training phase, panelists shall be instructed not to use perfumed cosmetics prior to or during sessions They shall also be asked to avoid contact with tobacco or with strong tastes or odors for at least 60 min prior to such sessions (8586-1, 1993) In the first phase, panelists were supplied basic knowledge of beef odors by familiarizing with the different oxidative levels of raw fresh samples and cooked samples, respectively through the attributes that appeared frequently in prior studies of oxidized meat These initial attributes was chosen to develop into sensory descriptors Then (Table 2.3) through the tests such as detection, matching, recognition, paired comparison, triangular tests

Table 2.3: References initially used to train the panelists.

Rancid The aromatics associated with oxidized fat and oils.1 Microwaved Wesson vegetable oil (3 or 5 min at high).1

Cardboard

Flavor associated with wet cardboard and stale.3

CuSO4 1% 0.2 mL in ground meat4Wet cardboard2

0.04, 0.08, and 0.16 g ferrous sulfate in strip loin beef4

Fishy

Flavor associated with fish3

Addition of omega-3 fatty acids to ground meat (hamburger)2

Fish stock in boiling water4

Grassy Flavor associated with fresh grass

3

Aromatic found in grass-fed animals4

Add 20 mg of hexanal in ground meat (hamburger)4

1 drop hexanal in 300 g beef 4

1 drop hexanal in 100 g beef 4

3 drops hexanal in 100 g beef 4

Fresh calf liver, cooked to 70 °C on open hearth grills440% cow liver in ground beef 4

75% cow liver in ground beef 4100% liver 4

2.0% sucrose solution1Sucrose 1 g/l aqueous soln4

1

(Adhikari et al., 2011), 2(Johnson and Civille, 1986), 3(Campo et al., 2006), 4(Maughan, 2011), 5(O'Sullivan et al., 2003)

The panelists were asked to assess beef samples with the different oxidative level to confirm samples which were most applicable to this study The purpose of this step helped the panel improve their ability in detecting and distinguishing sensory characteristics of raw fresh and cooked beef, based on the descriptors in Table 2.3 At this phase, discussions were opened for panelists to decide which attributes were most useful in describing lipid oxidation in various meat products These terms were then discussed and voted upon by the panelists

Raw fresh and cooked meat samples were used for the descriptor development, with various oxidation levels adjusted on the samples All samples were cooked to the same internal temperature of approximately 770C for safety purposes The panelists were also asked to expectorate all cooked samples after finishing evaluation for safety Coffee powder was used to refresh the olfactory between raw fresh samples To cooked samples, the panelists were asked to cleanse the palate between samples with unsalted crackers and flavorless water

Training on the scale

This part of the training took approximately 72 hours in total The panelists were trained to estimate intensity of the odor attributes in beef on the 6-point intensity The 6-point scale is an intensity measure from 0 to 5 in which point 0 indicates samples with no odor and point 5 indicates samples with the highest odor intensity All attributes should be evaluated equally on the same intensity scale; for example, a 3-point in livery should be equal to a 3-point in sour This training phase allowed the panelists to become familiar with the mechanics of the scale, and various intensity anchors on the scale They were introduced to different odor attributes commonly found in beef If there is no consensus, panelists will discuss to reach an agreement which is then used to establish intensity anchors Training panel continued until the panelists agreed on all of the descriptors which appeared in almost meat samples Panelists were considered highly trained when they showed reproducibility between replications of the same sample, and had ratings consistent with the rest of the panel (Maughan, 2011) Panelists had at least 30 hours of training on the descriptors and

The panelist’s ability was assessed through the identification and quantification of different attributes of the meat samples The time between evaluation times was long, hence panelists received additional training to avoid performance degradation

Descriptive Panel Evaluation

The descriptors were established and the panelists were fully trained Panelists were able to apply the descriptor to the final evaluation experiment The numbers of samples in each region was 60 The total was 180 samples for the three regions Therefore, there were 18 evaluation sessions in each of which was assessed 10 random samples of the same region

The assessment followed sensory procedures After thawed, all samples were cooked without flavoring in an electric oven and the internal temperature was checked using a highly accurate thermometer Samples were cut into 2.5 cm cubes, wrapped in aluminum foil, coded with the random three-digit number, and served to the panelists

at approximately 600C The evaluations were done under red light to minimize bias that could occur due to the color and appearance of the beef samples, with a 15-min break between replicates The samples were presented in a complete block design, in a random and balanced order, with random three-digit number code on sample container

Statistical significance was concluded when p ≤ 0.05 The panelist ratings were

analyzed using Principal Component Analysis (PCA) (Maughan, 2011) PCA was performed on the mean scores of sensory attributes of raw fresh samples and cooked samples to investigate correlation between attributes of two sample types The analyses were performed using SAS version 9.4 (SAS Institute, Inc., Cary, NC, USA)

Result and Discussion Beef Odor Descriptor

A total of 5 descriptors were developed to describe the oxidative process of beef Definitions, references and evaluating procedure for each descriptor were determined

by the consensus of panelists Besides, they were built based on some of the previous references modified during the training There were three off-odor descriptors for raw fresh sample description and two off-flavor terms for cooked samples The final descriptors, definitions, anchors and scale values are indicated in Table 2.4 Each descriptor was anchored with two reference points at two ends of the scale

The reason for sampling in various type markets at different two sampling times was

to determine the most common odor corresponding to the phase lipid oxidation of beef Samples with defects and beef packed using different methods had higher frequency of livery descriptor (Adhikari et al., 2011) Beef flavor decreased as display time increased (Campo et al., 2006) Furthermore, livery flavor was also highly influenced by display (Campo et al., 2006) A complete list of the lexicon for beef flavor applied in many other studies to date was developed by (Adhikari et al., 2011), (Luchsinger et al., 1997) Other references were replaced based on the experiences and consensus of the panel until a total of descriptors were described particularly Some other important attributes present only in selecting samples depending on the group characteristics were liver-like, sour dairy (Adhikari et al., 2011) Moreover, (Muchenje et al., 2010) found out that the most frequent off-flavor descriptors were livery and sour

Table 2.4: Definitions and References for raw fresh beef odor descriptors (n=3) and cooked beef flavor descriptors (n=2)

100% concentrated sugarcane water

0

5

Raw sour

1% raw vinegar in water 20% raw vinegar in water

0

5 Cooked livery

0% pork liver in strip loin beef 100% pork liver

0

5 Cooked sour

0.7% raw vinegar in water 1,3% raw vinegar in water

0

5

As previously mentioned results, the references of sweetR, sourR and sourC were adapted into the new ones more relevant to nature of evaluated samples The final descriptors consented by the panel consisted of 3 off-odor terms (livery, sour and sweet for raw fresh samples) and 2 off-flavor terms (sour and livery for cooked samples) In previous studies, some of the references were reflected so that they represented products locally Therefore, applying these references is not suitable for the tested beef samples Moreover, these references did not accurately reflect what panelists perceived from the samples For instance, the reference used regularly for sour flavor was citric acid while the panelists consented with the chemical similar reference acetic acid from vinegar It was the same way for sour odor Besides, the reference of sweet odor base on most ideas under the consensus of panelists

The effects of Market Type and Time Point

The results are demonstrated in Table 2.5, Table 2.6

The effects of market type and time point on the meat quality were indicated by the five descriptors The result showed significant differences P = 0.013 (P ≤ 0.05) in the

market type of liveryR Time point impacted on sourR (P = 0.019), liveryC (P = 0.032) with significant differences (P ≤ 0.05) At sweetR has a significant (P ≤ 0.1) impacted on the time point (P = 0.09) The effect of market type on sourR, sweetR,

sourC and liveryC were not significant (P ≥ 0.05) Time point did not significantly (P

≥ 0.05) impacted on liveryR and sourC There were no significant differences (P ≤ 0.05) in the time point of liveryR and sourC Table 2.6 shows the Least Squares Means (LS-means) for each effect (market type and time point) and each descriptor For each descriptor, the effects that had the same superscript letters are not significantly different (P ≤ 0.05) IM and OM were significantly different for the liveryR For the sourR and liveryC, T0 and T4 were significantly different As expected, the increasing of sampling time made liveryR, sourR and liveryC intensities increase and sweetR and sourC decrease However, this decreasing was not significant differences

Table 2.5: Effect of market type on off-odors and off-flavors of beef samples from supermarkets (SM), indoor markets (IM), open markets (OM) across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi).

ab LS means with like letter do not differ (P < 0.05)

SEM: standard error of the mean

*P ≤ 0.05

Table 2.6: Effect of display time on off-odors and off-flavors of beef samples at the market opening (T0) and 4 h after the opening (T4) across three regions of Vietnam (Ho Chi Minh City, Da Nang, and Ha Noi).

LS means with like letter do not differ (P < 0.05)

SEM: standard error of the mean

*

P ≤ 0.05, **P ≤ 0.1

The characteristics of market type assessed through two factors as lighting and temperature For the SM, fresh beef were stored at 0 – 40C under the fluorescent light

At the IM, they were kept staying out of direct sunlight by roof at natural temperature, especially, at the OM, raw beef directly exposed to sunlight at natural temperature The most essential single factor for microbial growth is temperature (Haines, 1937) Optimal temperature for aerobic microbial development is 320C (Haines, 1937) In this case study, meat was directly contacted with Vietnamese tropical environment temperature which was also the same optimal microbial temperature Off-flavors are produced mainly by microbial causes Besides, lighting also is an important role in the microbial development In addition, the light intensity intensifies lipid oxidation For example, (Djenane et al., 2001) indicated that the type of lighting substantially impacted the off-flavor, off-odor of fresh beef packaged in MAP and displayed for retail sale In general, market type was one of factors contributing to the formation of off-flavor

The longer display time is, the more beef surface directly exposes the physical agents that cause the formation of off-flavor Display time had a large influence on the descriptors, especially liveryC (Campo et al., 2006) and sourR significantly influenced Therefore, display time is main factor increased the off-flavor

Descriptor Patterns (PCA)

Principal components analysis (PCA) (Figure 2.1) indicated the differences between raw fresh samples and cooked samples in terms of sensorial descriptors

The principal component I (PC I) explained 60.87% of the variation in the samples, while the principal component II (PC II) explained 39.13% of the variability Based

on the positions of the descriptors on the plot, most of the descriptors were helpful in discriminating different beef samples as some of the points were placed away from the origin PC I was primarily composed by liveryR and sourR (0.80 and 0.75), respectively PC II was primarily composed by livery (0.81) Therefore, the PCA plot indicated that raw fresh samples were mainly characterized by liveryR and sourR, and cooked samples were mainly characterized by liveryC

Fig 2.1: Principle component plot of five descriptors of raw fresh beefs and cooked beefs

These results are in accordance with (Haines, 1937) who expressed that the decomposition product of sugars and other small molecules determined sour odor of fresh meat Besides, (Adhikari et al., 2011) showed that liveryC was one of the negative flavors characterizing lipid oxidation appeared with high frequency Moreover, in a lexicon for cooked beef, liveryC constantly presented in studies as (Campo et al., 2006), (Adhikari et al., 2011), (Maughan, 2011), (Muchenje et al.,

2010)

Conclusion

The results of this study portrayed that off-odors and off-flavors represented lipid oxidation of raw beef and cooked beef The previous studies lack of research off-flavors of fresh beef displayed at retail phase, especially research in developing countries Moreover, this study indicated that market type and display time had a big influence on the beef quality, altered characteristic flavor of beef Finally, the attributes like liveryR, sourR and liveryC represented fresh beef and cooked beef,

liveryR sourR

sweet R

sourC liveryC

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