Sample Questions

1
Sample Questions

• Some foods can be rapidly pre-dried to remove
  Type III water prior to the use of an approved
  analytical method for moisture (Adv or
  Disad...??)
• Food analysts commonly express their data on a
  fresh weight and dry weight basis.How/Why
• Which governmental agencies have enforcement and
  inspection authority over our food supply?
• Describe why Type I water is more difficult to
  remove from a food than Type II water..Type III.

2
4 Juice Blend

• You are the newly hired Quality Control Manager
  for a fruit juice processing plant. Your
  processing plant has 4 large holding tanks for 4
  different fruit juices and 1 tank that is used
  for mixing the 4 juices into the final product.
• As you begin this job, you realize that no
  samples are being taken for quality control
  purposes, a fact that you want to remedy.
• Provide a written description to your employees
  detailing how these samples will be obtained and
  the handling practices associated with the
  samples.

3
Sample Questions

• A solution is made by dissolving 40 g of sucrose
  (MW342) up to a final volume of 500 mL. What is
  the concentration of sucrose (in water) in parts
  per million (ppm)?
• 40g/500mL 80g/L 80,000 mg/L (w/v)
• A solution is made by dissolving 40 g of sucrose
  (MW342) in 500 mL.
• 40g/540mL 74.074g/L 74,074 mg/L (w/v)

4
Sample Questions

• You are given an excess of a 19.2 aqueous
  solution of acetic acid (MW 48). You job is to
  prepare exactly 400 mL of a 2M aqueous acetic
  acid solution. Show how you would prepare this in
  the laboratory.
• Think first, units of concentration must match
• 1M acetic acid 48g/L or 4.8
• Therefore, 19.2 acetic 4M
• (400 mL) x (2M) (? mL) x (4M)? 200 mL
• Therefore, to make this solution you would add
  200 mL of 4M acetic acid to 200 mL of water
• More simply Just dilute by half

5
Chapters 1-3

• Sample selection criteria
• Official methods
• Governmental regulations and food analysis
• Topics specifically relating to food analysis,
  methodology, sampling, sample preparation, and
  related topics

6
Food Analysis-More Theory and More
PracticePROXIMATE ANALYSIS ()

• Moisture
• Crude Protein (nitrogen)
• Crude Fat
• Ash
• Carbohydrates

______________________
Total 100
7
Some Numbers ?

• Average or Mean is sum of measurements divided by
  number of measurements.
• Standard Deviation measure the spread of the data
• Coefficient of Variation (CV) gives the standard
  deviation in relation to average (SD/mean)
• Standard Error (of the mean) is used to establish
  confidence intervals for the mean. Most often,
  the stderr is reported in scientific work to
  denote the relative spread in a data set.
  (SD/(n)1/2 )

SD
8
Behind the Numbers

• What do these values tell you about your
  analyses?
• Quality of the data?
• Repeatability?
• Individual running the assay?

9
Practice Problems

• Acid-Base neutralization
• Solute concentrations (w/v or v/v)
• Dilutions and dilution factors
• Slopes, standard curves, determining unknowns
• You will not need to calculate a slope

10
The Nature Sampling

• We can not examine all products
• Needed to take a portion of the population
• A sample should represent the population
• Selections
• What is the population?
• How do you estimate that population?
• Analysis method should reflect the sampling
  procedure

11
Sampling

• Why is sampling so important?
• Can sampling save you in a legal battle?
• Importance of record keeping.
• Importance of standard methods for sampling.

12
pH-TA Lab

• What is difference between pH and TA?
• What lab components you you need to determine the
  TA of a food?
• What is the importance of knowing the EXACT
  concentration of the base you are titrating with?
• Is there a difference between using an indicator
  dye and a pH meter for determining the endpoint?
• Concepts of acid dissociation
• Calculations

13
Analysis for Water

• Water can be gained or lost during sample
  preparation
• Analysis time and temperature vary. Why?
• Endpoint is when consecutive weightings are
  identical.
• Moisture ovens
• Special considerations for moisture

14
Analysis for Ash

• Special considerations for ash
• Sample composition
• Type of crucible
• Dry vs Wet (merits of each..order of analyses)

15
Common Concentration Units

• 1 g / 100 g _____
• 1 mg / kg parts per _____
• Lab calculations
• Concentrations
• Weight per volume
• Volume per volume
• V1C1V2C2
• Key laboratory concepts

16
Protein Lab

• Use of a standard curve
• Dilutions and concentrations
• General reaction scheme
• Why can we use BSA to quantify soluble protein in
  a product such as beer? (external standard)
• Could we also have used the standard addition
  method or an internal standard in this assay

17

• EXAM 1
• Bring your calculator !!!!!!!
• Bring a PEN..no pencils
• WRITE neatlyI wont guess