Quality attributes of pomegranate fruit and co-products relevant to processing and nutrition

Ampem, Gilbert (2017-03)

Thesis (MSc Food Sc)--Stellenbosch University, 2017.

Thesis

ENGLISH SUMMARY: Pomegranate fruit, owing to its health benefits, has served several important applications in industrial processing and nutrition. However, knowledge of the physico-chemical and textural properties of the fruit relevant to processing and nutrition remains critical. Presently, the South African pomegranate industry has great concerns on key issues governing pomegranate fruit processing. These issues are centered on understanding how pomegranate fruit properties influence prospect for value addition, processing and nutrition; what extent do cultivar differences influence the ease of processing and suitability as a raw material in food processing; and how to classify pomegranates based on their potential as source of raw materials for health-promoting compounds. Based on these, the overall aim of the study was to add value to commercially cultivated pomegranate (‘Wonderful’, ‘Acco’ and ‘Herskovitz’) in South Africa by evaluating their physical, textural and chemical properties, including the nutritional and mineral compositions, and quality attributes and functional properties of the kernels and oil constituents of these cultivars with emphasis on processing. Investigation of the physical properties of ‘Wonderful’, ‘Acco’ and ‘Herskovitz’ showed no significant differences in whole fruit weight, length, diameter, geometric mean diameter, surface area and volume of oblate spheroid among the cultivars. However, Wonderful and Herskovitz fruit cultivars had the highest (61.62%) and lowest (56.98%) edible portion, respectively. In addition, the arils of ‘Acco’ yielded the highest juice volume (74.05 mL/100 g arils i.e. 74.05%). Furthermore, juice extracted from ‘Wonderful’ contained the highest total soluble solids (15.93°Brix) while ‘Herskovitz’ fruit juice was characterised by high titratable acidity (1.32% citric acid). The textural properties in terms of maximum forces to cut, puncture and compress the fruit, distinguished ‘Wonderful’ whole fruit from the other cultivars. These textural tests characterised Wonderful cultivar as the hardest and therefore would require higher mechanical energy than the other cultivars during processing. The physical and textural properties of fresh and dried arils and kernels relevant to processing and nutrition were also investigated. As expected, the loss of moisture in fresh arils and kernels resulted in a significant reduction in weight and lineal dimensions. However, kernel index, shape index as well as compressibility characteristics of both arils and kernels increased for the cultivars after drying. From value-addition viewpoint, the kernels of Acco cultivar contained the highest oil yield (27.39%), proteins (18.73%), energy (1655.60 kJ/100 g), moisture (0.24%), ash (3.55%) and dietary minerals. On the other hand, kernels of ‘Wonderful’ and ‘Herskovitz’ were rich in carbohydrate (30.65%) and dietary fibre (36.48%), respectively. In addition, dietary mineral profiling of pomegranate kernel was in the order of Nitrogen (2453.00 – 3047.00 mg/100g) > Potassium (846.67 – 1646.00 mg/100g) > Phosphorus (380.33 – 500.67 mg/100g) > Magnesium (144.33 – 204.67 mg/100g) > Calcium (138.33 – 152.67 mg/100g) > Sodium (10.67 – 21.55 mg/100g) > Iron (5.28 – 5.72 mg/100g) > Zinc (2.91 – 3.94 mg/100g) > Copper (1.89 – 2.58 mg/100g) > Manganese (1.40 – 1.99 mg/100g) > Boron (0.96 – 1.82 mg/100g). These amounts are within the Recommended Daily Allowance (RDA) proposed by European Union and United States of America. These findings may therefore help processors and nutritionists to improve food formulations with pomegranate kernels. The study was further extended with special interest on pomegranate kernel oil (PKO). The yield of PKO ranged between 16.59 – 27.39% and were in the order ‘Acco’ > ‘Herskovitz’ > ‘Wonderful’, regardless of extraction solvent. Acetone extracted PKO with light yellow colour and also, with high amounts of phenolics, tocol, α- and γ-linolenic acids and para-anisidine value. However, among the cultivars, PKO of ‘Herskovitz’ had the highest para-anisidine value suggesting its weak resistance to oxidation. Punicic acid, a unique conjugated linolenic acid in PKO, ranged between 59.90 – 69.85% and were in the order of petroleum ether > n-hexane > acetone. In addition, the investigated PKO exhibited high (89.50 – 91.60%) radical scavenging activity, regardless of cultivar and extraction solvent. In terms of oil stability, storage temperature and duration affected properties of PKO. In comparison with oil stored at 25ºC, a remarkable reduction in punicic acid and increase in α- and γ-linolenic acids were observed in PKO stored at 60°C. This study showed that PKO of ‘Wonderful’, ‘Acco’ and ‘Herskovitz’ could potentially serve as good source of bioactive oil. Overall, this study presents scientific background on how pomegranate cultivars could influence the ease of processing, and their suitability as sources of raw materials for health-promoting compounds in nutraceutical industries.

AFRIKAANSE OPSOMMING: Granate, met sy gesondheidsvoordele, het belangrike toepassings in die industriele proseseering en voedingstowwe. Alhoewel die kennis van die fisio-chemiese en tekstuur eienskappe van die relevante vrugte relevant is tot die nutriente, bly die na-oes prosseseering steeds krieties. Tans, die Suid-Afrikaanse granaat bedryf het 'n groot kommer oor belangrike kwessies regerende granaatboom vrugte verwerking. Hierdie kwessies is gesentreer op die begrip van hoe granaatboom vrugte eienskappe beïnvloed vooruitsig vir waardetoevoeging, verwerking en voeding; watter mate stem kultivar verskille beïnvloed die gemak van die verwerking en geskiktheid as 'n rou materiaal in die voedsel verwerking; en hoe om granate te klassifiseer op grond van hul potensiaal as bron van grondstowwe vir gesondheidsbevorderende verbindings. Gebasseer op die bogenoemde is die doel van die studie om waarde by te voeg tot komersiële gekultiveerde granate (‘Wonderful’, ‘Acco’ en ‘Herskovitz’) in Suid-Afrika deur die fisiese, tekstuur en chemise aspekte, insluitend die nutrient en mineral samestellings, kwaliteit en funksionele eienskappe van die kern en olie samestellings van die kultivars met beklemtoning om prossesseering te evalueer. Met ondersoek van die fisieke eienskappe van die ‘Wonderful’, ‘Acco’ en ‘Herskovitz’ het daar geen beduidende verskille in die vrug se gewig, lengte, diameter, geometriese gemiddelde diameter, oppervlak area of volume van die sfere voorgekom nie. Alhoewel, die ‘Wonderful’ en ‘Herskovitz’ granaat kultivars het die hoogste (61.62%) en die laagste (56.98%) eetbare porsie. Daareenbenewens het die saad van die ‘Acco’ ekstraksie die hoogste volume sap (75.05 mL/100 g m.a.w. 74.05%) gelewer. Verde het die sap ekstraksie van die ‘Wonderful’ granaat die hoogdte totaal oplosbare soliede bevat (15.93°Brix) terwyl ‘Herskovotz’ vrugtesap geklasifiseer is deur sy hoë titreerbare suurheid (1.32% sitroensuur). Die tekstuur eienskappe in term van die maksimum kragte om die granaat te sny, kneus en die vrugte te prosseseer het veroorsaak dat dit die ‘Wonderful’ vrug van die ander kultivars skei. Hierdie tekstuur toetse het die ‘Wonderful’ kultivar geklasifiseer as die hardste vrug en benodig meer meganiese energie as die ander kultivars gedurende prosseseering. Die fisiese en tekstuur eienskappe van die vars en gedroogde saad en kern relevant tot die proseseering en nutriente was ook geondersoek. Soos verwag het die verlies van vog in vars saad en kern ‘n beduidende verlies in massa en liniëre dimensies veroorsaak. Alhoewel, die kern en vorm indeks asook die kompressie eienskappe van beide saad het toegeneem vir elke kultivars na drooging. Van ‘n waarde toevoeging oogpunt het die kern van die ‘Acco’ kultivar die hoogste olie opberengs gelewer (27.39%), proteïene (18.73%), energie (1655.60 kJ/100g), vog (0.24%) en minerale. Aan die ander kant, die kern van die ‘Wonderful’ en ‘Herskovitz’ was ryk in die koolhidrate (30.65%) en vesel (36.48%). Die klasifiseering van die granaatkern was gedoen met die hulp van Stikstof (2453.00 – 3047.00 mg/100g) > Kalium (846.67 – 1646.00 mg/100g) > Fosfor (380.33 – 500.67 mg/100g) > Magnesium (144.33 – 204.67 mg/100g) > Kalsium (138.33 – 152.67 mg/100g) > Natrium (10.67 – 21.55 mg/100g) > Yster (5.28 – 5.72 mg/100g) > Sink (2.91 – 3.94 mg/100g) > Koper (1.89 – 2.58 mg/100g) > Mangaan (1.40 – 1.99 mg/100g) > Boron (0.96 – 1.82 mg/100g). Hierdie hoeveelhede is binne die voorgeskere RDA (Recommended Daily Allowance) voorgeskryf deur die Europese Unie van die Verenigde State van Amerika. Hierdie bevindings kan dus proseseerders en dietkundiges help om die voedsel formulasies van die granaat kern te verbeter. Die studie was verder uitgebrei met spesiale aandag op die granaat kern olie (GKO). Die opberengs van die GKO het gevarieer tussen 16.59 – 27.39% en in die volgorde ‘Acco’ > ‘Herskovitz’ > ‘Wonderful’, afgesien van die ekstraksie oplosmiddel. Asetoon geekstraeerde GKO met ‘n ligte geel kleur met hoë hoeveelhede van fenoliese verbindings, tacol, α- en γ- linoleensuur en para anisidien waarde het gely tot swak weerstand tot oksidasie. Punicic suur, ‘n unieke gekonjugeerde linoleensuur in GKO het gevarieer tussen 59.90 – 69.85% en was in die orde: petroleum-eter > n-heksaan > asetoon. Die ondersoekte GKO het hoë (89.50 – 91.60%) radikale soekende aktiwiteit afgesien van die kultivar en ekstraksie oplosmiddel. In terme van olie stabiliteit, stoor temperatuur en tyd geaffekteer deur die eienskappe van GKO. In vergelyking met die olie wat gestoor word teen 25°C, ‘n merkwaardige afname in punicic suur en ‘n toename in α- en - linoleensuur was geobserveer in GKO wat gestoor is teen ‘n temperatuur van 60°C. Hierdie studie het getoon dat die ‘Wonderful’, ‘Acco’ en ‘Herskovitz’ potensieel kan dien as goeie bron van bioaktiewe olie. Hierdie studie verteenwoordig algehele wetenskaplike agtergrond oor hoe om die granaat kultivars te gebruik om proseseering te vergemaklik en die geskiktheid van die rou material vir gesondheid bevorderingde stowwe in die voeding industrië.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101380
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