Marjan Simčič

Biological Variance, Burden or Benefit

Based on theoretical considerations, a new approach to deal with the variation in properties and quality attributes inherently occurring in all products and batches is presented. It leads to a better understanding of the processes involved and enables the mathematical description and modelling of the observed phenomena. The effect of variation in harvest maturity on the composition of batches drawn from a larger population is used as an example to elucidate the effects of external conditions. These external conditions include the rate constant of the process (directly linked to temperature and controlled atmosphere (CA) conditions), the magnitude of the variation in the larger population and the size of the batches. These theoretical examples show that the standard advice of statisticians to increase the number of individuals in a batch or sample does indeed increase the reliability of data analysis based on mean values. It also shows that the so obtained estimate may well give a complete false picture of the real value. An overview is given for ways to avoid the generation of biological variance, as well as ways to decrease the effects of biological variance already present. This new approach shows how biological variance should be tackled, and even possibly turned into a benefit. A number of practical examples is provided and described briefly to underpin the validity of the approach presented. These examples relate to sources of variation (sweetening of potatoes), to the behaviour of variation during postharvest treatment (colour of apples, keeping quality of cucumbers) and to sophisticated means of dealing with biological variance without too much explicit knowledge of the mechanisms involved (dynamic control system, soil irrigation).

Effect of location in the canopy on the colour development of three apple cultivars during growth

BACKGROUND Homogeneity in appearance is one of the quality aspects asked for in the supply chain. Decreasing the biological variation in batches of harvested apples (cultivars Braeburn, Fuji and Gala) becomes increasingly important. Skin colour is one of the aspects that determine both optimal harvest and stage of development. Skin colour is affected by location in the canopy. The rules of development of biological variation are now established and will be used on skin colour data. RESULTS The Minolta colour aspects a*, b* and L* measured before commercial harvest change in a sigmoidal fashion and can be analysed including the biological variation, with a logistic model in indexed nonlinear regression, obtaining explained parts of above 90%. The mechanism of colour change is not affected by state of development or location in the canopy. The location in the canopy affects the intensity of both red and green colouring compounds. The variation in colouration is not affected by the location in the canopy. CONCLUSION The red-coloured apple cultivar (Gala) depends more on the location in the canopy than the less-coloured cultivars (Fuji and Braeburn). The colour development in Fuji apples is considerably slower, with a much larger variation in stage of development. The location in the canopy affects all aspects of biological variation (biological shift factor and asymptotic starting level of colouration) for all three colour aspects L*, a* and b*, but only the mean value, not the standard deviation. The biological shift factors per colour aspects are linearly related. Once induced, variation remains constant during development.

School nutrition guidelines: overview of the implementation and evaluation

OBJECTIVE To holistically evaluate the extent of implementation of dietary guidelines in schools and present various monitoring systems. DESIGN The study comprises three methods: (i) a cross-sectional survey (process evaluation); (ii) an indicator-based evaluation (menu quality); and (iii) a 5 d weighed food record of school lunches (output evaluation). SETTING Slovenian primary schools. SUBJECTS A total 234 food-service managers from 488 schools completed a self-administrated questionnaire for process evaluation; 177 out of 194 randomly selected schools provided menus for menu quality evaluation; and 120 school lunches from twenty-four schools were measured and nutritionally analysed for output evaluation. RESULTS The survey among food-service managers revealed high levels of implementation at almost all process evaluation areas of the guidelines. An even more successful implementation of these guidelines was found in relation to organization cultural issues as compared with technical issues. Differences found in some process evaluation areas were related to location, size and socio-economic characteristics of schools. Evaluation of school menu quality demonstrated that score values followed a normal distribution. Higher (better) nutrition scores were found in larger-sized schools and corresponding municipalities with higher socio-economic status. School lunches did not meet minimum recommendations for energy, carbohydrates or dietary fibre intake, nor for six vitamins and three (macro, micro and trace) elements. CONCLUSIONS The implementation of the guidelines was achieved differently at distinct levels. The presented multilevel evaluation suggests that different success in implementation might be attributed to different characteristics of individual schools. System changes might also be needed to support and improve implementation of the guidelines.

Influence of Cultivar and Storage Time on the Content of Higher Fatty Acids in Apple Cuticle

Influence of Cultivar and Storage Time on the Content of Higher Fatty Acids in Apple Cuticle The main objective was to determine the fatty acid composition on the surface of apple peel and in seeds. 7 apple cultivars were used: Elstar, Fuji, Gloster, Idared, Jonagold, Pink Lady and Golden Delicious. Apple seeds contain from 8.4% to 15% of water and from 17.1% to 28.0% (f.w.) of fat. The fatty acid content in seeds ranged as follows: linoleic (55.9-62.3), oleic (23.9-30.7%), palmitic (7.1-9.3%), stearic (1.6-2.3%), arachidic (1.2-1.6%), linolenic (0.4-0.7%. Linolic acid is prevalent fatty acid on peel as well. Ratio of linolenic acid on peel is up to 30 fold higher than in seeds. Saturated palmitic and stearic fatty acid ratio is considerably higher in peel than in seeds while is the ratio of oleic acid nearly the same as in seeds. During storage of apples the ratio of palmitic and oleic acid increases, while ratio of linoleic acid considerably decreases. Wpływ Odmiany I Długości Okresu Przechowania Na Zawartość Wyższych Kwasów Tłuszczowych W Epidermie Jabłka Celem badań było określenie zawartości kwasów tłuszczowych w skórce i nasionach jabłka. Testy wykonywano na 7 odmianach jabłek: Elstar, Fuji, Gloster, Idared, Jonagold, Pink Lady i Golden Delicious. Nasiona jabłek zawierały od 8,4 do 15% wody i od 17,1 do 28,0% tłuszczów (w świeżej masie). Stwierdzono następujące zawartości poszczególnych kwasów tłuszczowych w nasionach: kwas linolowy (55,9-62,3%), kwas oleinowy (23,9-30,7%), kwas palmitynowy (7,1-9,3%), kwas stearynowy (1,6-2,3%), kwas arachidowy (1,2-1,6%), kwas linolenowy (0,4-0,7%). Kwas linolowy jest dominującym kwasem tłuszczowym również w skórce. Zawartość kwasu linolenowego jest do 30 razy wyższa w skórce niż w nasionach. Zawartość nasyconych kwasów tłuszczowych: palmitynowego i stearynowego, jest znacznie wyższa w skórce niż w nasionach, podczas gdy zawartość kwasu oleinowego jest zbliżona w skórce i nasionach. W czasie przechowywania jabłek, zawartość kwasu palmitynowego i oleinowego wzrasta natomiast kwasu linolowego znacznie obniża się.

Modelling the Colour of Strawberry Spread During Storage, Including Effects of Technical Variations

Abstract The colour of freshly processed strawberry spread changes relatively rapidly from a bright red to a dull red, which then makes its appearance generally less acceptable for consumers. The colours of strawberry spreads following several processing conditions were measured under different storage conditions. Additional sugar and colorant had only slight effects on the colour decay, while exclusion of oxygen and daylight did not affect this process. The only condition that clearly maintained the freshly processed appearance was storage at 4°C. Hexagonal bottles were filled with the strawberry spreads and their colour was repeatedly measured at the six sides of the bottles, using a Minolta chroma meter. Data were analysed using non-linear indexed regression analysis based on a logistic function for the three colour aspect of a*, b* and L*. This technology allowed the determination of the variation in these data in terms of improved reliability (R2adj, >90%). It also allowed better interpretation of the processes involved. All variations in the data could be attributed to technical variation.

Similarities between quality and health promoting compounds as a result to stress.

Similarities Between Quality and Health Promoting Compounds as a Result to Stress Antioxidants are produce by plants as a defence mechanism against stress. It is not unlikely that quality related properties are related to that stress induced production system (secondary metabolites). Based on purely theoretical considerations and on scarce information from literature and experts, a highly speculative model was developed to investigate the possible importance of stress levels on the production of health promoting compounds and quality related properties. Simulations with that model, using completely arbitrary parameter values showed that a relation exist between applied stress and production of these beneficiary compounds. Zależności Pomiędzy Jakością a Prozdrowotnymi Składnikami Jako Wynik Stresu Antyutleniacze są produkowane przez rośliny na skutek uruchamiania mechanizmu obronnego przeciwko stresowi. Jest niewykluczone, że cechy odpowiedzialne za jakość są związane z tym mechanizmem, indukowanym przez stres. Opierając się na czysto teoretycznych rozważaniach i na nielicznych doniesieniach z literatury, stworzono wysoce spekulatywny model w celu sprawdzenia możliwość wpływu różnych poziomów stresu na produkcję prozdrowotnych składników przez rośliny. Symulacje modelowe wskazują, że istnieje zależność pomiędzy zadanym stresem a produkcją korzystnych dla zdrowia człowieka składników.