KỸ THUẬT SỬ DỤNG PHỤ GIA ỔN ĐỊNH và CẢI THIỆN TÍNH CHẤT CẢM QUAN CHO THỰC PHẨM

CHỦ ĐỀ 3: KỸ THUẬT SỬ DỤNG PHỤ GIA ỔN ĐỊNH & CẢI THIỆN TÍNH CHẤT CẢM QUAN CHO THỰC PHẨM Phần 1: PHỤ GIA ỔN ĐỊNH & CẢI THIỆN TRẠNG THÁI, CẤU TRÚC CHO THỰC PHẨM – PHỤ GIA ỔN ĐỊNH - TẠO ĐẶ

CHỦ ĐỀ 3:

KỸ THUẬT SỬ DỤNG PHỤ GIA ỔN ĐỊNH & CẢI THIỆN TÍNH CHẤT

CẢM QUAN CHO THỰC PHẨM

Phần 1: PHỤ GIA ỔN ĐỊNH & CẢI THIỆN TRẠNG THÁI, CẤU TRÚC CHO THỰC PHẨM – PHỤ GIA ỔN ĐỊNH - TẠO ĐẶC – TẠO GEL

1 KHÁI QUÁT CHUNG

• Phân biệt các thuật ngữ

• Quá trình tạo đặc và tạo gel

1.2 ĐẶC ĐIỂM QUÁ TRÌNH TẠO ĐẶC & TẠO

GEL CỦA CÁC PHỤ GIA THỰC PHẨM

• Cơ chế

• Các yếu tố ảnh hưởng

1.2.1 THICKENING

• The process of thickening involves the

nonspecific entanglement of conformationally disordered polymer chains; it is essentially a polymer-solvent interaction.

• Thickening occurs above a critical

concentration known as overlap concentration (C*) Below this, the polymer dispersions

exhibit Newtonian behaviour but show a Newtonian behaviour above this concentration

non-CÁC YẾU TỐ ẢNH HƯỞNG ĐẾN HIỆU QUẢ

– The food system in which it is used

– The pH of the food system, and

– Temperature

1.2.2 GELATION

• Gel formation is the phenomenon

involving the association or cross-linking

of the polymer chains to form a three

dimensional network that traps or

immobilises the water within it to form a rigid structure that is resistant to flow

Classification of food gels

• Căn cứ vào nhiệt độ tạo gel

• Căn cứ vào đặc điểm của hệ mà từ đó gel được hình thành – Mức độ trật tự của các đại phân tử trước và sau khi tạo gel

• Căn cứ vào đặc tính của hệ gel được hình thành – Based on macroscopic behavior

CĂN CỨ VÀO NHIỆT ĐỘ TẠO GEL

• ‘Cold-setting’, gelation is induced by

cooling, and includes those biopolymer

gels that occur in nature and provide

structures in biological systems

• ‘Heat-setting’, gelation occurs by heating, and includes those systems where gelation involves extensive denaturation of the

biopolymer, e.g thermally unfolded

globular proteins

chemical action.

CĂN CỨ VÀO ĐẶC ĐIỂM CỦA HỆ GEL

• Gels are free-standing as a consequence of the development of the three-dimensional network, called ‘true gels’,

• Gel are characterized by a tenuous gel-like

network which is easily broken when submitted

to a high enough stress, called ‘weak gels’

• ‘Strong gels’ are those networks that have

‘finite energy’, and ‘weak gels’ are those

systems that are transient in time.

Gel point and sol–gel transition

• During gel formation, a polymer undergoes a phase

transition from a liquid to a gel The sol–gel transition is

a critical point where one characteristic length scale (viz the size of the largest molecule) diverges It is a

transition in connectivity between a sol where the

‘monomers’ are not connected, to a gel where they are connected Therefore, irrespective of the system studied

or the mechanism involved, gelation is a critical

phenomenon where the transition variable will be the

connectivity of the physical or chemical bonds linking the basic structural units of the material (Lopes da Silva et al., 1998).

• Gelation requires a critical minimum concentration of polymer

molecules, C 0 , to form a gel matrix

• When a gelling polymer concentration is above C 0 , one may think

about gel point either as an instant in time, tc, or as a specific

temperature, Tgel

• Before the gel point the connectivity is small and the material typically relaxes rapidly

• Near the gel point the relaxation time rises sharply and at the gel point

it diverges to infinity (or at least to very long times for a finite sample);

in addition, the relaxation spectrum no longer contains a characteristic time

• After the gel point, if the network has reached a high degree of

development, the maximum relaxation time of the final network is also very short (Lopes da Silva et al., 1998).

CÁC YẾU TỐ ẢNH HƯỞNG ĐẾN HIỆU QUẢ

SỬ DỤNG PHỤ GIA TẠO GEL

2 PHỤ GIA TẠO ĐẶC & TẠO GEL

• Phân loại

• Danh mục

• Đặc điểm và tính chất đặc trưng

• Theo bản chất hóa học

– Protein

• Gellatin

• Milk proteins – Cacborhydrate

• Tinh bột

• Pectin

• Marine biopolymer: Carrageenan, Alginate, Agar

• Gum: Acacia gum, Carob Bean Gum, Curdlan , Gellan Gum, Konjac Flour …

• Theo chức năng công nghệ:

– Thickeners

– Gelling agents

– Stabilizers

2.2 DANH MỤC PHỤ GIA

• Danh mục các phụ gia:Thickeners, Gelling agents và Stabilizers có thể tra cứu tại địa chỉ:

1 http://www.fao.org/food/food-safety-quality

/scientific-advice/jecfa/jecfa-additives/en /

2 http://www.codexalimentarius.net/gsfaonlin

e/additives/results.html?ins=270&searchBy= add&lang=en

LƯU Ý

• Ở trang web thứ nhất phụ gia thuộc nhóm

2.4 ĐẶC TÍNH CỦA PHỤ GIA TẠO ĐẶC &

TẠO GEL

• Đặc tính chung

• Đặc tính riêng

2.4.1 ĐẶC TÍNH CHUNG

• Food hydrocolloids/hydrophilic colloids

– Long chain polymers

– Presence of a large number of hydroxyl (-OH) groups

• Functional properties are obtained by

mixing them with water

2.5.1 TINH BỘT & TINH BỘT BIẾN TÍNH

• Native starches

• Modified starches

CÁC YẾU TỐ ẢNH HƯỞNG ĐẾN KHẢ NĂNG

TẠO ĐẶC & TẠO GEL CỦA TINH BỘT

The swollen granules act like ‘balloons’ which fill a space or volume and it is the inability to move around easily that gives

viscosity

• The starch granules have broken down and the amylose and amylopectin chains are free in solution and can associate to form a gel.

• Generally with fairly rapid cooling a gelled network is formed but if the cooling is done more slowly, or if there is a higher concentration of starch or low levels

of other ingredients that can interact, a process

called retrogradation can occur where the starch

polymers align to give small, discrete, insoluble

particles.

• Starches with a higher amylose content are more

likely to gel or retrograde but these processes can be avoided by using the 100% amylopectin starches.

MODIFIED STARCHES

• Phân loại tinh bột biến tính

• Tính chất công nghệ của các loại tinh bột biến tính

MODIFICATION OF STARCH

Using enzymes to modify starch

CHEMICAL & BIOCHEMICAL MODIFICATION OF STARCH

2.5.2 PECTINS

• Pectin is the general term for a group of

polyuronans that occur as the structural

components of plants

• Commercial pectins are obtained from the pomace of apple or the peel of citrus fruits following hydrolysis, which renders the

pectin water soluble

• Pectin molecules consist of linear chains of (1,4)-α

galacturonic acid residues up to 80% of which occur

as the methyl ester together with up to 4% rhamnopyranose units which are distributed along

(1,2)-α-the chain giving rise to kinks

• L-Arabinose, D-galactose and D-xylose (10–15%) are linked to the rhamnose units forming ramified side- chains which are referred to as ‘hairy regions’ along the otherwise smooth galacturonan backbone.

• If the degree of esterification (DE) is

more than 50% it is referred to as high methoxyl (HM) pectin

• De-esterified pectin with DE of less than 50% is produced by mild acid or alkali treatment and is referred to as low

methoxy (LM) pectin

• Both HM and LM pectins form gels

For HM pectin (DE 60–75%)

• Gelation occurs at high soluble solids content (typically 50–75% sugar) and at pH <3.5 over

a period of time

• The gels are not thermoreversible

• Junction zone formation is believed to be as a consequence of hydrophobic association

between ester groups coupled with

intermolecular hydrogen bonding between

hydroxyl groups on the galacturonan backbone

For LM pectin (DE typically 20–40%)

• Gelation is brought about by the addition

2.5.3 GUM ARABIC

• The gum is a complex polysaccharide consisting of galactopyranose (~44%), arabino-pyranose and

furanose (~25%), rhamnopyranose (14%),

glucuropyranosyl uronic acid (15.5%) and

4-Omethylglucuropyranosyl uronic acid (1.5%)

• It also contains a small amount (~2%) of protein

as an integral part of the structure

• Analysis of the carbohydrate structure has shown that it consists of a core of β-(1,3)-linked galactose units with extensive branching at the C6 position

• The branches consist of galactose and arabinose and terminate with rhamnose and glucuronic acid.

2.5.4 GALACTOMANNAN SEEDS GUMS

• Gồm: Locust bean (or carob), tara and guar

gums

• They consist of a linear main chain of

β-(1,4)-linked mannopyranosyl units with

galactopyranosyl units linked α-(1,6) to varying degrees and have a molecular mass of the order

of 10 6

• The mannose to galactose ratio, (M/G), is

approximately 4.5:1, 3:1 and 2:1 for locust

bean, tara and guar gums, respectively

• The galactose residues have been shown to be non-uniformily distributed along the mannan

chain

• The presence of galactose tends to inhibit

intermolecular association; hence, hereas guar gum is readily soluble in cold water, tara and locust bean gums have to be heated to high

temperatures to achieve complete dissolution

• Once dissolved, all three yield highly viscous

solutions.

• Locust bean gum will self-associate in solution and can form thermally irreversible gels on

• Locust bean gum also forms strong

thermoreversible gels with xanthan gum

2.5.5 XANTHAN GUM

• The gum is obtained from the genus Xanthomonas, notably

X campestris, by aerobic fermentation

• The xanthan molecules have a β-(1,4)-linked glucopyranose backbone as in cellulose and in addition have a

trisaccharide side-chain on every other glucose residue

linked through the C3 position

• The side-chain consists of two mannopyranosyl residues

linked on either side to a glucuropyranosyl uronic acid

group

• The inner mannose residue connected to the backbone may

be acetylated while the terminal mannose residue may be pyruvated.

• The molecular mass of the xanthan molecules is very high (>3 × 10 6 ) and the gum dissolves in water to

yield highly viscous solutions

• The xanthan molecules undergo a thermoreversible coil–helix transition in solution, which is shifted to

higher temperatures by the addition of electrolyte

• In the disordered coil form the side-chains are

envisaged as protruding away from the backbone into solution, while in the ordered form the molecules form

a stiff five-fold helical structure with the side-chains folded in and associated with the backbone

2.5.6 CARRAGENAN

• The three major types are kappa, iota and

lambda carrageenan

• The temperature of gelation increases with

increasing electrolyte concentration.

• It has been shown that potassium, rubidium

and caesium ions specifically bind to the helical structure of kappa carrageenan and hence

promote helix formation and gelation at much lower concentrations than other electrolytes

• As a consequence kappa carrageenan gels are much stronger in the presence of potassium

chloride compared with, say, sodium chloride

• This ion specificity is not observed for iota,

which forms weaker, more elastic gels than

kappa

• This is probably due to the fact that the

increased charge on the iota carrageenan chains reduces the extent of helix self-association.

2.5.7 GELATIN

• Gelatin is denatured collagen, which is a protein and the major constituent of the white fibrous connective tissue occurring

in the hides, skins and bones of animals

• Type A (acid treatment) and Type B

(alkaline treatment) gelatins The main amino acids are glycine, proline, alanine and 4-hydroxyproline for both types

• Type A gelatin contains lower amounts of

glutamic and aspartic acids and hence the

isoelectric point for Type A is in the range 7– 9.4 while for Type B it is in the range 4.8–5.5

• In solution above ~40 ºC the gelatin

molecules are in the form of random coils but

on cooling the chains tend to order and form collagen-like triple helices which aggregate to form optically clear elastic gels.

• It is now generally recognised that the helix

is double stranded

rise to highly shear thinning rheological

properties and unlike other polyelectrolytes, the viscosity of xanthan solutions can

actually increase rather than decrease on

addition of electrolyte since the electrolyte will promote helix formation and association.

3 KỸ THUẬT SỬ DỤNG PHỤ GIA TẠO

GEL & TẠO ĐẶC

• Căn cứ lựa chọn phụ gia tạo đặc, tạo gel

• Kỹ thuật lựa chọn

• Kỹ thuật sử dụng

CĂN CỨ LỰA CHỌN

• Tính chất của phụ gia

– Tham khảo tài liệu

• Đặc điểm của thực phẩm

– Công thức phối liệu

– Yêu cầu chất lượng của sản phẩm

– Cách thức sử dụng sản phẩm

• Đặc điểm của quá trình sản xuất, bảo

quản, phân phối

CẦN PHÂN TÍCH ĐƯỢC CÁC YẾU TỐ ẢNH HƯỞNG ĐẾN KHẢ NĂNG TẠO ĐẶC & TẠO GEL CŨNG NHƯ ĐỘ BỀN CỦA HỆ

Methods of starch selection

• What is the desired function of the starch you are adding?

• What is the method of processing you anticipate using?

• What is the food system pH?

• Does the process contribute high shear?

• What percent of water soluble materials will be present?

• Ingredients that hydrate water limit the available water for granule

• Is one or more of the following used: fat(s), salt(s) and

gums?

• Is the finished product subjected to post processing?

• How will the product be stored?

TÀI LIỆU THAM KHẢO

• Food stabilisers, Thickeners and gelling agents

• Starch in food: Structure,function and applications – Chapter 12 & 13

• Texture in Food: Volume 1 (Semi-solid Food) – Chapter 11