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The dielectric properties of 15 vegetables and fruits were measured at 2450MHz from 5 to 130 8C. Equations were developed as a function of temperature, ash, and either moisture content or water activity, and compared to literature equations. Dielectric constant of vegetables and fruits decreased with temperature and ash content. However, ash was not a factor in the equations produced separately for fruits. Dielectric loss factor changed quadrically with increasing temperature: first decreasing and then increasing. This transition temperature decreased with ash content. Ash increased the dielectric loss factor. Garlic and potato gave unusual results, which could be explained by the behavior of solutions of inulin and potato starch, respectively.

The dielectric properties of 19 different ham samples with different moisture (38.2% to 68.9%) and ash contents (1.78% to 6.80%) were measured at -35 to 70 °C at 2450MHz. Equations were developed as a function of temperature, moisture, and ash, and compared to literature equations. The dielectric constant decreased with ash content and increased with moisture content. It increased instead of decreasing with temperature. The dielectric loss factor increased with moisture content for moisture contents lower than 60.7%, then decreased for higher moisture contents. Ash content and temperature increased dielectric loss factor. Frozen samples had low dielectric activity that was increased by ash content above -20 to -10 °C.

The dielectric properties of cod, perch, salmon, chicken breast, chicken thigh and beef were measured at 15 to 65 degrees C at 2450 MHz. The samples covered a moisture range of 68.9-81.2% and ash range of 0.96-1.20%. Equations were developed as a function of temperature, moisture, and ash, and compared to literature equations. The dielectric constant decreased with temperature and increased with moisture content. It was not affected by ash content. The dielectric loss factor increased with moisture content for moisture contents lower than 74.9%, then decreased for higher moisture contents. The dielectric-loss factor was quadratically related to temperature, decreasing to 30.2 degrees C then increasing. The dielectric loss factor increased with ash content. The effect of moisture content and temperature on the dielectric loss factor in the literature is reviewed to explain these results.

The dielectric properties of turkey meat at water activities of 0.84 to 0.98 were measured at 2450 and 915MHz. Equations were developed as a function of temperature, moisture, water activity, and ash, and compared to literature equations. Unexpected results were: as the water activity decreased or ash increased, the dielectric constant increased with temperature, and dielectric loss factor of reduced moisture samples was determined by moisture not ash. It is theorized that the effect of temperature on dielectric constant is a function of the ratio of bound to free water. Glycerol did not affect the dielectric properties, while lactic acid decreases them by promoting water loss during protein denaturation.

In the present study, pumpkin (Cucurbita Pepo L.) was grown under water stress to determine its effects on the chemical composition of the seeds (i.e., oil, protein, fatty acids and vitamin E), in Kayseri, Turkey. Irrigation treatments were designed to supply different portions of depleted moisture within the efficient root zone of the plants (60 cm). The treatments were arranged as supplying 100% (I100), 80% (I80), 60% (I60), 40% (I40), 20% (I20) and 0% (I0) of depleted moisture through a drip irrigation system. The effects of irrigation levels on the oil content of pumpkin seeds were found to be significant (p < 0.01). The oil contents of irrigation treatments varied between 26% (I0, dry) and 64% (I100, full irrigation). However, the effects of deficit irrigation on protein, fatty acids and vitamin E contents were not found to be significant. The vitamin E contents varied from 41.6 – 55.3 mg/100 g; while the protein contents varied from 28.5–37.7%. Six different fatty acids (linolenic, linoleic, oleic, stearic, palmitic and myristic acid) were examined. The average concentration of palmitic, stearic, oleic and linoleic acids ranged from 10.7–12.6%, 6.4–10.4%, 39.6–48.9% and 32.4–35%, respectively. Myristic and linolenic acids were not detected in the pumpkin seeds.

ÖzBu çalışmanın amacı ayva işlemede infrared kurutma sisteminde ön işlem olarak ultrases ile düşük metoksil pektin ve sodyum aljinat kaplama uygulamalarının kurutulmuş ayvaların fiziko-kimyasal kalitesi üzerine etkisinin belirlenmesidir. Kurutma öncesi ayva örnekleri (2 cm x 2 cm x 0.5 cm) 70 ºC'de etüvde 24 saat ve 105 ºC'de infrared kurutma cihazında kurutulmuştur. Beş farklı yöntem ile kurutulan ayvaların fizikokimyasal özellikleri (nem, kül, titrasyon asitliği, suda çözünebilir kuru madde, yağ ve protein) tespit edilmiş; pH, su aktivitesi, çekme oranı, rehidrasyon kapasitesi, renk, toplam fenolik, toplam flavonoid içerikleri, antioksidan kapasiteleri (TEAC ve DPPH) ve tekstürel özellikleri karşılaştırılmıştır. Düşük metoksil pektin ve sodyum aljinat kaplama işlemi örneklerin fenolik ve antioksidatif bileşiklerin kaybını azaltmıştır. Infrared kurutma işlemi ayvaların fenolik, antioksidatif ve flavanoid bileşiklerini koruduğu tespit edilmiştir. Ultrases ön işlemi uygulanıp infrared kurutulan örneklerin fenolik, antioksidatif ve flavanoid bileşiklerin miktarında bir artış gözlenmiştir. Infrared kurutma işleminde L değerinde artış meydana gelmiştir. L değerinde görülen artış esmerleşme reaksiyonlarının azaldığının göstergesidir. Düşük metoksil pektin kaplama uygulanıp infrared kurutulan örneklerde L ve b* değerinde artış, a* değerinde azalış tespit edilmiştir. Ultrases ve kaplama ön işlemleri uygulanıp infrared kurutulan ayvaların renginin korunduğu tespit edilmiştir. Ayva örneklerinin sertlik özellikleri tekstür analizi ile incelenmiştir. Etüv kurutmada görülen kurutma süresi artışının, ürün sertlik değeri üzerinde artırıcı etkisi olduğu tespit edilmiştir. Çalışmalar infrared sistemde kurutma işleminin ayva örneklerinin aşırı sertleşmesini önleyen bir yöntem olduğunu göstermiştir. Sonuç olarak, ayva meyvesinin antioksidan aktivite, toplam fenolik bileşik, toplam flavanoid ve tekstürel özelliklerini korumak için sodyum aljinat ve düşük metoksil pektin kaplamaların yenilebilir kaplamalar olarak kullanılabileceği, ultrases ve kaplama ön işlemlerinin infrared kurutulmuş ayva örneklerinde kuruma verimini ve kalitesini artırmada etkin bir yöntem olduğunu göstermiştir.