Chapter 3. Sensory testChapter 3. Sensory test

1. Introduction 1. Introduction

• The overall quality of food can be divided into three main categories: quantitative, hidden and sensory.

• Some quantitative aspects of food quality are primarily of interest to the process, e.g., yield of product obtained from a raw material.

• Hidden quality attributes include the nutritional value of a food or the presence of toxic compounds that, generally, cannot be determined by sensory evaluation.

• Definition: The color, aroma, flavor and shape of a food are tested by person’s sensation: taste, olfaction, visual sensation and touch, and then evaluated with word, symbol or data.

• The selection, acceptance, and digestibility of a food are largely determined by its sensory properties.

• According to Kramer sensory include (1) appearance (color, size, shape, absence of defects, and the consistency of liquid and semisolid products); (2) kinesthetics (texture, consistency, and viscosity), and (3) flavor (taste and odor).

• Aim:1) Evaluate acceptance of food

2) Determine quality of food

• Sensory evaluation have been widely used in examination of food quality, purchase of raw material, change of technical process, storage of food, R&D of new product, and market investigation.

2. Category of sensory test2. Category of sensory test

• Visual sensation• Olfaction • Taste • Touch

2.1 Visual sensation2.1 Visual sensation

• Observe appearance by eyes.

Color is an important appearance factor. In agriculture, color development or color changes are used in assessing the maturity of fruits and vegetables.

The color of food often affects our phychology. Discoloration or fading of color is often accompanied or identified by consumers as being associated with undesirable changes in texture and flavor.

• Appearance characteristics of gloss, transparency and turbidity are often important.

2.2 Olfaction2.2 Olfaction

• There is a number of relationship between food odor and its fresh degree, and processing manner.

• Odor in foods is most commonly attributed to compounds containing sulfur, nitrogen, and certain halogens.

• Affection of temp. on odor

• Olfaction fatigue

2.3 Taste2.3 Taste

• Four basic taste modalities: sweet, sour, salt, and bitter.

Sweet: produced by a variety of nonionized aliphatic hydroxy compounds, the most important of which are sugars.

Sour: not all acids are sour; indeed some amino acids are actually sweet. Sugar may enhance or depress the perception of sourness.

• Salt: a pure salty taste is typified in foods by sodium chloride. Generally, other salts give a mixed taste.

• Bitter: the typical bitter stimuli are given by alkaloids such as caffeine or quinine; also some amides are bitter. Tannins contribute to both bitter and astrigency.

• Taste sensations and threshold ate affected by many factors, including food temp., overall food composition, concentrations of individual components, and age, illness and hunger among tasters.

• Taste fatigue

Test order: weak→strong ; wash mouth with warm water ; proper rest

2.4 Touch 2.4 Touch

• 借助手、皮肤等器官的触觉神经来检验食品的弹性、韧性、紧密程度、稠度等

• → →视觉检验 嗅觉检验 味觉检验和触觉检验

3. Basic requirements of sensory 3. Basic requirements of sensory testtest

• 3.1 requirements of sensory lab

Quiet, sound proof, neat, no off-flavor, natural color: decrease the disturb to assessor, make person comfort to fix his attention on testing.

Two basic part: test section, and sample preparation section

3.2. Selection of assessor3.2. Selection of assessor

Favorite assessor： 1） evaluate the acceptance of foods; 2） No need training; 3） number should more than 100; 4） personnel composition should present the whole of consumers.

Analysis assessor： test foods quality, must be selected and trained.

• Primary assessor：初级评价员• Selected assessor：优选评价员• Expert：专家• Panel：评价小组

Conditions for analysis assessorsConditions for analysis assessors

• Age: 20-50, men or women• No addiction of smoking and drinking• Health• Sense organs are good• Be interested in food sensory evalutaion• Good discrimination of different foods• Have responsibilty• Good description for sensory content

Test for assessorsTest for assessors

• Test for taste ability

• Test for olfaction ability

3.3. preparation of sample3.3. preparation of sample

• 1） Amount of sample

• 2） Temperature of sample

• 3） Vessel of sample

• 4) Number of sample

3.4 choice of time3.4 choice of time

• 2-3 hours after eating

• No smoking and no thrill foods before half hour of testing

4. Methods of sensory test4. Methods of sensory test

• 4.1. difference test (差别检验 )：用于确定两种样品之间是否存在差别

1） paired comparison test (成对比较检验 )：把 A、 B两个样品进行比较，判断两者之间是否存在差别。

• 样品提出形式为： AB、 BA、 AA或 BB

2） triangular test (三点检验法 )• 3个样品，其中两个是相同的，要求找出第 3个不同的样品。

• 适用于鉴别两个样品之间的细微差别，也可用于评价员的挑选和培训

3 “） A” or “ not A” test• 评价员熟悉 A后，再从一系列样品中找出哪些

“是 A” “，哪些是 非 A”。• 适用于确定由于原料、加工、处理、包装、贮藏等环节的不同所造成的感官特性的差异

4.2. scale and classification test4.2. scale and classification test标度和类别检验标度和类别检验

• 1） ranking test (排序法 )• 比较数个样品，按某种指标（如咸味、甜味、风味、喜好程度等）排出顺序。

• 不要求评价样品间差异的大小• 可用于消费者的可接受性调查• 也可作为粗选• →例：甜味最强 甜味最弱

• 2） scoring test (评分法 )• 对样品的某种品质特性进行评分• 可以同时鉴评一种或多种产品的一个或多个指标的强度及其差异

• 应用广泛，如鉴评新产品，评比评优

4.3. descriptive test4.3. descriptive test描述性检验描述性检验

• 检验人员用合理的、清楚的文字对食品的某些指标进行准确的描述

• 如外观、颜色、风味、组织等• 定性描述，定量描述