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What are the key evaluation criteria for fruit and vegetable juices regarding nutritional value?
Technological methods, sensory analyses (colour, flavour, taste), shelf-life tests, pH value, weight ratio, presence of preservatives.
What aspects are assessed in sensory analyses of fruit and vegetable juices?
Colour/appearance, flavour/odour, and taste.
What are the components used to evaluate the carbohydrate content in fruit juices?
Glucose, fructose, sucrose, sugar free extract, sorbitol, and fibre.
What is the definition of fruit juice according to the lecture?
The fermentable but unfermented product obtained from sound and ripe fruit, having the characteristic colour, flavour, and taste typical of the fruit.
What is the significance of the pH value in fruit juice evaluation?
It indicates the acidity and potential degradation of the fruit juice.
What testing method can determine the presence of sulfurous acid in fruit juices?
Chemical distillation with methanol and titration with NaOH.
How can one identify adulterations in fruit juices?
By analyzing phenolic substances and their stability, particularly flavonoid-glycosides.
What are the two types of sugars that can be distinguished by Fehling's solution?
Reducing sugars and Non-Reducing Sugars such as glucose and sucrose.
What factors influence the oxidation of ascorbic acid in food products?
Temperature, pH value, oxygen, oxidizing enzymes, and bivalent cations.
What is the purpose of using HPLC in the analysis of fruit and vegetable juices?
To achieve high-resolution separation of non-volatile or thermally unstable substance mixtures.
What can a high peroxide value in fats indicate?
A degree of oxidation of the fat, suggesting potential spoilage.
What is the role of antioxidants in fats?
They inhibit autoxidation by acting as radical scavengers.
What is the significance of hydrocyanic acid presence in fruits?
It can be an indicator of toxicity, especially in certain stone fruits.
What analytical method is used for determining amino acid presence in fruit juices?
Thin layer chromatography (TLC) and gas chromatography (GC) after derivatization.
What type of chromatography is used to separate volatile compounds?
Gas chromatography (GC).
What are the major detection methods for protein content in foods?
Bradford protein assay and nitrogen quantification via Kjeldahl method.
What determines the esterification degree of pectin?
The number of carboxyl groups esterified with methanol relative to the total number of carboxyl groups.
What is the consequence of high esterification in pectin?
It affects gelling ability and results in different textures in fruit preserves.
What is the impact of light on the lipids in food?
It can promote photo-oxidation of lipids, leading to rancidity.
What are the common storage conditions to prevent lipid oxidation?
Reducing storage temperature, eliminating light exposure, and using inert gases.
What does the term 'titratable acidity' refer to in food analysis?
It refers to the total acidity of a food product as measured by titration.
What is the importance of the relative density in juice quality assessment?
It helps determine the concentration of juice and presence of additives.
