Transcript Standard methods for the estimation of natural juice_Ms Frutosx

STANDARD METHODS
FOR THE ESTIMATION
OF NATURAL JUICE
Dr. María José Frutos Fernández
Agro-Food Technology Department
Miguel Hernández University
Orihuela (Alicante) Spain
E-mail: [email protected]
WORKSHOP ON ESTIMATION OF NATURAL JUICES IN NECTARS
Cairo, egypt 10-11 november 2014
EUROPEAN LEGISLATION ON FRUIT
JUICES AND NECTARS
COUNCIL DIRECTIVE 75/726/EEC
COUNCIL DIRECTIVE 93/77/EEC
COUNCIL DIRECTIVE 2001/112/EC
COUNCIL REGULATION (EC) No 1182/2007
COUNCIL REGULATION (EC) NO 1332/2008
COMMISSION DIRECTIVE 2009/106/EC
COUNCIL DIRECTIVE 2012/12/EU (Amending Council Directive 2001/112/EC)
LAST MODIFICATIONS OF EU DIRECTIVE
o New composition requirements of fruit juices and nectars
o Modification of specific labelling requirements
o To inform consumers adequately
1.
Addition of sugars to juices is not allowed (only nectars and special products according to
Council directive 2001/112/CE)
2.
The facultative incorporation in juices and nectars of flavours from the same fruit specie
(tomato juice is included in the new directive)
3.
Definition of fruit is included (to clarify that fruits subjected to post-harvest treatments can
be use in the juice production)
METHODS OF ANALYSIS AND SAMPLING
(CODEX STAN 247-2005)
PRINCIPLE
Enzymatic determination
HPLC
Indophenol method
Fluorescence spectrometry
Gravimetry
Deuterium Nuclear Magnetic
Resonance (Deuterium NMR)
Spectrometry
Stable isotope mass spectrometry
Trititmetry (back titration after
precipitation)
Capillary gas chromatography
Centrifugation % value
Electrochemical Tritimetry
PRINCIPLE
Scott distillation, titration
Distillation and direct Reading of the
volume determination
Microbiological method
Potentiometry
Photometric determination
Colorimetric
Digestion /titration
Microfluorometry
Scott distillation, titration
Distillation and direct Reading of the
volume determination
Microbiological method
Potentiometry
STANDARD METHODS
IFU
AOAC
EN
ISO
NMKL
UNE-ENV
STANDARD METHODS ACCORDING TO
PRINCIPLE
HPLC
ENZYMATIC DETERMINATION
Anthocyanins
Acetic acid
Sulphur dioxide
Alcohol (etanol)
Lactic acid D and L
Citric acid
Malic acid
Benzoic acid as marker in
orange juice
Glucose-D and
Fructose-D
L-malic/total malic acid
ratio in Apple juice
Benzoic acid and its salts,
sorbic acid and its salts
Gluconic acid
Malic acid D and L
Glycerol
Isocitric acid-D
Sorbitol D
Sucrose
Ascorbic acid
Citric acid
Fumaric acid
Glucose and Fructose and
saccharose
Hesperidin and naringin
Hydroxymethyl furfural
Malic acid
L-malic/total malic acid ratio
in Apple juice
Malic acid D in Apple juice
Naringin and neohesperidin
in orange juice
Quinic, malic and citric acid in
cranberry juice cocktail and
Apple juice
Sucrose
Tartaric acid in grape juice
STANDARD METHODS ACCORDING TO
PRINCIPLE (CODEX STAN 247)
GRAVIMETRIC
STABLE ISOTOPE MASS SPECTROMETRY
Ash in fruit products
Total solids
(Microwave oven
drying)
DEUTERIUM NUCLEAR
MAGNETIC RESONANCE
(NMR)
Beet sugar in fruit juices
C13/C12 ratio of etanol derived from fruit juices
Carbon stable isotope ratio of orange juice
Carbon stable isotope ratio of Apple juice
Stable carbon isotope ratio in the pulp of fruit juices
Stable carbón isotope ratio of sugars from fruit juices
Stable hydrogen isotope ratio of water from fruit juices
Stable oxygen isotope ratio in fruit juice water
STANDARD METHODS ACCORDING TO
PRINCIPLE (CODEX STAN 247)
Microbiological:
Fermentability
OTHER METHODS
Titrimetry: Carbon dioxide, sulphur dioxide, titrable
acids, total.
Indophenol: Ascorbic acid –L
Indirect by refractometry: soluble solids
Pycnometry or Densitometry: Relative density
Atomic Absorption Spectroscopy: Na, K, Ca, Mg in
fruit juices.
Spectrometry: Benzoic acid and its salts,
Hydroxymethil furfural, preservatives in fruit juices
(sorbic acid and its salts)
Spectrophotometry: Carotenoid, total/individual
group.
Capillary gas chromatography: Cellobiose.
Scott titration or distillation and direct volumen
determination: Essential oils
Centrifugation % value: Centrifugagle pulp
Potentiometric titration: Formol number
Liquid chromatography Free amino acids
Potentiometry: pH value
Precipitation / photometry Pectin
Photometric determination: Phosphorus /
phosphate, Proline by photometry.
Colorimetric: Starch
Digestion/Titration: Total nitrogen
Microfluorometry: vitamin C (dehydroascorbic
and ascorbic acid)
A.I.J.N. Reference Guidelines
Fruit juices manufactured and sold in the EU have to comply with the provisions
in the existing EU legislation applicable to foodstuffs in general and to fruit juices
in particular.
The European Fruit Juice Association Reference Guidelines apply to both direct
fruit juices and reconstituted fruit juices placed on the market as well as to their
raw materials and are based on authentic juices without permitted ingredients
and/or additives.
Absolute quality
requirements
Relative density
For those products, which are usually produced as a juice a minimum relative density is determined as such
in relation to water at 20/20ºC. The corresponding Brix value is directly obtained from the IFU table no. 8 .
For those products, which are usually produced as a puree, only a minimum uncorrected refractometric Brix
reading (without correction of acid) is determined. In cases where a clarified puree/juice is used a minimum
relative density is taken.
Majority of fruit juices marketed are reconstituted from concentrate.The EU Directive requires reconstitution
to the original value. The values given are in line with Brix values commonly found in nature over the year.
Direct juices from defined origin and variety may have lower natural values as the respective minimum value
indicated. The indicated minimum values is justified in order to meet justified consumer expectations.
Direct juices low in natural extract must be blended with direct juices of higher natural extract in order to
come up to at least the minimum value. Correcting by adding concentrate is not permitted without the
appropriate labelling (from concentrate). Otherwise it is not permitted to dilute direct juices higher in natural
extract with water to a lower level.
Biogenic acids and ethanol
No volatile acids, lactic acid and ethanol in juices produced from suitable and
properly stored fruit. Larger amounts than mentioned indicate a lack of hygiene
in fruit handling or problems in plant sanitation.
As a rule, properly processed products should be clearly under the maximum
values given. Contents over the maximum values given will be perceived as a
change in organoleptic quality
Other problems with fruit quality and/or sanitation may also result in undesired
mycotoxins (Patulin)
Arsenic and heavy metals
Environmental contaminants to be avoided
The maximum values given in the reference guidelines comply with
the current recommendations of the public health authorities.
Products in metal containers may contain higher values for iron and
tin, but should not exceed official limits.
Hydroxymethylfurfural (HMF)
In fruit juices processed according to “Good Manufacturing Practice” (GMP) only traces of HMF
are found.
Higher values can be expected in cases of excessive thermal treatment during processing or
filling as well as inappropriate storage conditions and/or times.
Packed juices should under normal storage conditions not exceed the maximum values indicated
before the end of the indicated shelf life.
Usually, with increasing HMF values, a loss of L-ascorbic acid, colour and other sensorial
characteristics may be observed.
Changes made in the A-criteria of a Reference Guideline become applicable 12 months after
publication of the adopted change(s) on the Code of Practice website.
Water for reconstitution
The new Fruit Juice Directive (2012/12) stipulates that the water used for the reconstitution of fruit juice
concentrates has to comply with the EU Potable Water Directive (98/89) (Codex Standard 247 2005 for
fruit juices). The components include such substances as: – heavy metals, pesticides, halocarbons,
acrylamide, halides, nitrate, nitrite, cyanide, benzo(a)pyrene, PAHs and pathogenic microorganisms. If
using water from a commercial supply, conformance with the Directive should be guaranteed by the
supplier.
The water used for reconstitution should be free from off tastes and aromas.
The sodium and nitrate values of the water used for reconstitution be kept as low as possible.
Reference guidelines refers only to the natural concentrations seen in the juice/purée. The water used for
the reconstitution of concentrate should not influence.
In the Potable Water Directive (no limit set for Na and the level permitted for nitrate (50 mg/l) is above the
values seen in most fruits. The concentrations of these parameters and calcium and magnesium
influenced by the composition of the water.
Water used for processing fruit juices
Used for in line extraction of the pulp or for treating products during further
processing
Should either be potable water or have the appropriate characteristics,
particular from a chemical, microbiological and sensorial point of view, to
maintain the requirements of the original juice.
ISOTOPIC ANALYSIS
DETECTION OF WATER ADITION TO DIRECT JUICES
Oxygen isotopic analysis (delta 18O)
ADITION OF SUGARS ( C4 DERIVED,CANE OR CORN), ACIDS, POLYMERIC
STABILISERS
Carbon isotopic analysis (isotope ratio mass spectrometry)
- on the bulk or on isolated components (sugars, acids, pectins)
- Addition of beet derived sugars (Deuterium-NMR {(D/H)1})
- Sugars from pineapple (quantitative 13C-NMR after fermentation)
GENERAL ISOTOPIC ANALYSIS
The use of hydrogen, carbon and oxygen isotopes, have been used for many years to detect adulteration
of juices.
Detection limits for the isotopic methods have been improved by the use of internal isotopic ratioin.
Individual compounds from the same sample e.g. the glucose, fructose and sucrose are separated and
the carbon isotope ratios are measured. Authentic samples have ratios, for the individual compounds,
that fall within known limits. Similarly it is possible to measure the carbon isotope ratios of different sites
within the same molecule e.g. malic acid. Natural malic acid has differing ratios than malic acid from a
synthetic source which allows its detection.
The proportions of the metal ions in a sample could be use for the detection of the origin of juices.
Some examples:
- The use of Ba and Rb to confirm a juice to be Floridian rather than one from Brazil for instance.
- The use of some of the heavy isotopes, such as 87Sr, has been found to be extremely useful at
confirming the country of origin. This element is found at relatively higher levels in samples grown in
areas where the rocks are old such as in Brazil whereas in other regions where the rocks are much
younger the level of this element is lower.
D-MALTOSE IN CLEAR JUICES
CITRUS JUICES do not contain significant levels of maltose above the limit of quantification (LOQ).
STARCH naturally present. Treatment with amylase during processing (produces maltose) Detection with
GC, HPLC-linked with an electrochemical detector (e.g. HPAEC-PAD) or HPLC-linked with a light scattering
detector.
Clear apple and pear juices less than 100 mg/l maltose (on a single strength basis). Higher levels(unripe
fruits or addition of sugar syrups derived from starch)
Maltose naturally present in In some juices/purées (guava purée less than 50 mg/kg, mango purées
the levels are normally less than 100 mg/kg.)
Isomaltose is a natural component of pineapple juice unusual in others. normally associated with the
presence of added sugar syrup derived from starch, such as HFCS. If both maltose and isomaltose are
detected in a pineapple juice, the product should be examined very closely for the presence of syrup
derived from starch, as maltose is not normally seen in this juice, quantitative 13C-NMR is a suitable
procedure to use here.
The Cap-GC method, detailed in IFU recommendation 4 (IFU rec # 4) is a good procedure to detect both
maltose and isomaltose in juices.
Oligosaccharide profile
The pattern of peaks after derivatisation in the Capillary Gas Chromatography
(Cap-GC ). IFU recommendation number 4.
Sample adulterated with a sugar derived from a starch or inulin source,
characteristic peaks will be present (different from the two maltose peaks by
amylase treatment of fruits that naturally contain low levels of starch).
Samples adulterated with partial or total invert syrups can also identified by
the presence of specific “invert marker peaks”. However in high acid juices in
particular, heating also influences the size of these peaks and caution should be
exercised as false results can be produced.
Presence of cellobiose, which is used as a marker for the action of a cellulose
(prohibited by the EU fruit juice directive).
Anthocyanin profile
Evaluation of red/black fruit juices and purees, such as raspberry. Reverse phase HPLC method, such
as IFU No. 71. The pattern of peaks is then compared with a reference sample of the fruit or with the
profiles given in the IFU method.
Pattern characteristic of the fruit (differentiate between different varieties of the same fruit):
A particular fruit or fruit variety will contain a number of anthocyanins that are specific to that fruit.
Presence of extra or unusual peaks indicative of the addition of undeclared fruit and/or colour.
The enzymes used during processing can remove or distort the relative sizes of some of these peaks
A reduction in the size of all the peaks can be indicative of dilution of the product or poor and/or
extended storage.
If the analysis is correctly performed the baseline of the profile is normally flat. If a pronounced
hump is present this is also an indication of poor and /or extended storage that has caused the
anthocyanin materials to degrade (polymerise).
Polyphenol profiles and polymethoxyflavones
Detection of the presence of one type of fruit in another (separation of the compounds by
reverse phase HPLC)
Pattern of peaks that can be compared with a reference sample of fruit.
Examples of the use of these methods are:
Differentiation of citrus juices
The detection of mixtures of citrus juices such as sweet (C. sinensis) and sour (C. aurantium)
orange
The presence of grapefruit in orange
Differentiation of lime from lemon.
Differentiation of apple and pear or mixtures thereof
Profile of volatile flavour compounds
The pattern of volatile compounds seen in the Cap-GC profile of a sample should be characteristic of that fruit.
Chiral-GC analysis: Natural flavour compounds often exist in specific spatial forms known as enatiomers, D & L
or (+) & (-) forms. Chiral analysis is able to separate these 2 forms and thereby provide valuable evidence of
the presence of synthetic flavour compounds. For example, if a particular flavour compound is known only to
occur naturally in the “L” form then the presence of the “D “ form in a juice indicates adulteration.
The compound occurs naturally in both forms (the “normal/expected ratio of the “L” and the “D” are known)
The most difficult situation when the natural ratio is close to 1:1 (ratio found in synthetic flavours). Apply
isotopic techniques.
GC-IRMS: Isotopic analysis of flavour compounds if the flavour of interest does not occur in (D/L)forms. The
compounds of interest are first separated on a GC and then individually analysed by isotope ratio mass
spectrometer (IRMS). Here the carbon isotope ratios of the individual flavour compounds are measured.
The carbon isotopic ratios of naturally occurring flavour compounds are known. If synthetic flavour
compounds are present the carbon isotopic ratios will be altered and hence the adulteration can be identified
THANK YOU FOR YOUR ATTENTION